android.graphics
Class Canvas

java.lang.Object
  android.graphics.Canvas

public class Canvas
extends Object

The Canvas class holds the "draw" calls. To draw something, you need 4 basic components: A Bitmap to hold the pixels, a Canvas to host the draw calls (writing into the bitmap), a drawing primitive (e.g. Rect, Path, text, Bitmap), and a paint (to describe the colors and styles for the drawing).

Nested Class Summary

static class	Canvas.EdgeType
static class	Canvas.VertexMode

Field Summary

static int	ALL_SAVE_FLAG restore everything when restore() is called
static int	CLIP_SAVE_FLAG restore the current clip when restore() is called
static int	CLIP_TO_LAYER_SAVE_FLAG clip against the layer's bounds
static int	FULL_COLOR_LAYER_SAVE_FLAG the layer needs to 8-bits per color component
static int	HAS_ALPHA_LAYER_SAVE_FLAG the layer needs to per-pixel alpha
static int	MATRIX_SAVE_FLAG restore the current matrix when restore() is called
(package private) int	mNativeCanvas

Constructor Summary

Canvas()
Construct an empty raster canvas.

Canvas(Bitmap bitmap)
Construct a canvas with the specified bitmap to draw into.

Canvas(GL gl)
Construct a canvas with the specified gl context.

Canvas(int nativeCanvas)

Method Summary

boolean	clipPath(Path path) Intersect the current clip with the specified path.
boolean	clipPath(Path path, Region.Op op) Modify the current clip with the specified path.
boolean	clipRect(float left, float top, float right, float bottom) Intersect the current clip with the specified rectangle, which is expressed in local coordinates.
boolean	clipRect(float left, float top, float right, float bottom, Region.Op op) Modify the current clip with the specified rectangle, which is expressed in local coordinates.
boolean	clipRect(int left, int top, int right, int bottom) Intersect the current clip with the specified rectangle, which is expressed in local coordinates.
boolean	clipRect(Rect rect) Intersect the current clip with the specified rectangle, which is expressed in local coordinates.
boolean	clipRect(RectF rect) Intersect the current clip with the specified rectangle, which is expressed in local coordinates.
boolean	clipRect(RectF rect, Region.Op op) Modify the current clip with the specified rectangle.
boolean	clipRect(Rect rect, Region.Op op) Modify the current clip with the specified rectangle, which is expressed in local coordinates.
boolean	clipRegion(Region region) Intersect the current clip with the specified region.
boolean	clipRegion(Region region, Region.Op op) Modify the current clip with the specified region.
void	concat(Matrix matrix) Preconcat the current matrix with the specified matrix.
void	drawArc(RectF oval, float startAngle, float sweepAngle, boolean useCenter, Paint paint) Draw the specified arc, which will be scaled to fit inside the specified oval.
void	drawARGB(int a, int r, int g, int b) Fill the entire canvas' bitmap (restricted to the current clip) with the specified ARGB color, using srcover porterduff mode.
void	drawBitmap(Bitmap bitmap, float left, float top, Paint paint) Draw the specified bitmap, with its top/left corner at (x,y), using the specified paint, transformed by the current matrix.
void	drawBitmap(Bitmap bitmap, Matrix matrix, Paint paint) Draw the bitmap using the specified matrix.
void	drawBitmap(Bitmap bitmap, Rect src, RectF dst, Paint paint) Draw the specified bitmap, scaling/translating automatically to fill the destination rectangle.
void	drawBitmap(Bitmap bitmap, Rect src, Rect dst, Paint paint) Draw the specified bitmap, scaling/translating automatically to fill the destination rectangle.
void	drawBitmap(int[] colors, int offset, int stride, int x, int y, int width, int height, boolean hasAlpha, Paint paint) Treat the specified array of colors as a bitmap, and draw it.
void	drawBitmapMesh(Bitmap bitmap, int meshWidth, int meshHeight, float[] verts, int vertOffset, int[] colors, int colorOffset, Paint paint) Draw the bitmap through the mesh, where mesh vertices are evenly distributed across the bitmap.
void	drawCircle(float cx, float cy, float radius, Paint paint) Draw the specified circle using the specified paint.
void	drawColor(int color) Fill the entire canvas' bitmap (restricted to the current clip) with the specified color, using srcover porterduff mode.
void	drawColor(int color, PorterDuff.Mode mode) Fill the entire canvas' bitmap (restricted to the current clip) with the specified color and porter-duff xfermode.
void	drawLine(float startX, float startY, float stopX, float stopY, Paint paint) Draw a line segment with the specified start and stop x,y coordinates, using the specified paint.
void	drawLines(float[] pts, int offset, int count, Paint paint) Draw a series of lines.
void	drawLines(float[] pts, Paint paint)
void	drawOval(RectF oval, Paint paint) Draw the specified oval using the specified paint.
void	drawPaint(Paint paint) Fill the entire canvas' bitmap (restricted to the current clip) with the specified paint.
void	drawPath(Path path, Paint paint) Draw the specified path using the specified paint.
void	drawPicture(Picture picture) Save the canvas state, draw the picture, and restore the canvas state.
void	drawPicture(Picture picture, Rect dst) Draw the picture, stretched to fit into the dst rectangle.
void	drawPicture(Picture picture, RectF dst) Draw the picture, stretched to fit into the dst rectangle.
void	drawPoint(float x, float y, Paint paint) Helper for drawPoints() for drawing a single point.
void	drawPoints(float[] pts, int offset, int count, Paint paint) Draw a series of points.
void	drawPoints(float[] pts, Paint paint) Helper for drawPoints() that assumes you want to draw the entire array
void	drawPosText(char[] text, int index, int count, float[] pos, Paint paint) Draw the text in the array, with each character's origin specified by the pos array.
void	drawPosText(String text, float[] pos, Paint paint) Draw the text in the array, with each character's origin specified by the pos array.
void	drawRect(float left, float top, float right, float bottom, Paint paint) Draw the specified Rect using the specified paint.
void	drawRect(RectF rect, Paint paint) Draw the specified Rect using the specified paint.
void	drawRect(Rect r, Paint paint) Draw the specified Rect using the specified Paint.
void	drawRGB(int r, int g, int b) Fill the entire canvas' bitmap (restricted to the current clip) with the specified RGB color, using srcover porterduff mode.
void	drawRoundRect(RectF rect, float rx, float ry, Paint paint) Draw the specified round-rect using the specified paint.
void	drawText(char[] text, int index, int count, float x, float y, Paint paint) Draw the text, with origin at (x,y), using the specified paint.
void	drawText(CharSequence text, int start, int end, float x, float y, Paint paint) Draw the specified range of text, specified by start/end, with its origin at (x,y), in the specified Paint.
void	drawText(String text, float x, float y, Paint paint) Draw the text, with origin at (x,y), using the specified paint.
void	drawText(String text, int start, int end, float x, float y, Paint paint) Draw the text, with origin at (x,y), using the specified paint.
void	drawTextOnPath(char[] text, int index, int count, Path path, float hOffset, float vOffset, Paint paint) Draw the text, with origin at (x,y), using the specified paint, along the specified path.
void	drawTextOnPath(String text, Path path, float hOffset, float vOffset, Paint paint) Draw the text, with origin at (x,y), using the specified paint, along the specified path.
void	drawVertices(Canvas.VertexMode mode, int vertexCount, float[] verts, int vertOffset, float[] texs, int texOffset, int[] colors, int colorOffset, short[] indices, int indexOffset, int indexCount, Paint paint) Draw the array of vertices, interpreted as triangles (based on mode).
protected void	finalize() Called by the virtual machine when there are no longer any (non-weak) references to the receiver.
static void	freeGlCaches() Call this to free up OpenGL resources that may be cached or allocated on behalf of the Canvas.
Rect	getClipBounds() Retrieve the clip bounds.
boolean	getClipBounds(Rect bounds) Retrieve the clip bounds, returning true if they are non-empty.
DrawFilter	getDrawFilter()
GL	getGL() Return the GL object associated with this canvas, or null if it is not backed by GL.
int	getHeight() Returns the height of the current drawing layer
Matrix	getMatrix() Return a new matrix with a copy of the canvas' current transformation matrix.
void	getMatrix(Matrix ctm) Return, in ctm, the current transformation matrix.
int	getSaveCount() Returns the number of matrix/clip states on the Canvas' private stack.
int	getWidth() Returns the width of the current drawing layer
boolean	isOpaque() Return true if the device that the current layer draws into is opaque (i.e.
boolean	quickReject(float left, float top, float right, float bottom, Canvas.EdgeType type) Return true if the specified rectangle, after being transformed by the current matrix, would lie completely outside of the current clip.
boolean	quickReject(Path path, Canvas.EdgeType type) Return true if the specified path, after being transformed by the current matrix, would lie completely outside of the current clip.
boolean	quickReject(RectF rect, Canvas.EdgeType type) Return true if the specified rectangle, after being transformed by the current matrix, would lie completely outside of the current clip.
void	restore() This call balances a previous call to save(), and is used to remove all modifications to the matrix/clip state since the last save call.
void	restoreToCount(int saveCount) Efficient way to pop any calls to save() that happened after the save count reached saveCount.
void	rotate(float degrees) Preconcat the current matrix with the specified rotation.
void	rotate(float degrees, float px, float py) Preconcat the current matrix with the specified rotation.
int	save() Saves the current matrix and clip onto a private stack.
int	save(int saveFlags) Based on saveFlags, can save the current matrix and clip onto a private stack.
int	saveLayer(float left, float top, float right, float bottom, Paint paint, int saveFlags) Helper version of saveLayer() that takes 4 values rather than a RectF.
int	saveLayer(RectF bounds, Paint paint, int saveFlags) This behaves the same as save(), but in addition it allocates an offscreen bitmap.
int	saveLayerAlpha(float left, float top, float right, float bottom, int alpha, int saveFlags) Helper for saveLayerAlpha() that takes 4 values instead of a RectF.
int	saveLayerAlpha(RectF bounds, int alpha, int saveFlags) This behaves the same as save(), but in addition it allocates an offscreen bitmap.
void	scale(float sx, float sy) Preconcat the current matrix with the specified scale.
void	scale(float sx, float sy, float px, float py) Preconcat the current matrix with the specified scale.
void	setBitmap(Bitmap bitmap) Specify a bitmap for the canvas to draw into.
void	setDrawFilter(DrawFilter filter)
void	setMatrix(Matrix matrix) Completely replace the current matrix with the specified matrix.
void	setViewport(int width, int height) Set the viewport dimensions if this canvas is GL based.
void	skew(float sx, float sy) Preconcat the current matrix with the specified skew.
void	translate(float dx, float dy) Preconcat the current matrix with the specified translation

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

mNativeCanvas

final int mNativeCanvas

MATRIX_SAVE_FLAG

public static final int MATRIX_SAVE_FLAG

restore the current matrix when restore() is called

See Also:

Constant Field Values

CLIP_SAVE_FLAG

public static final int CLIP_SAVE_FLAG

restore the current clip when restore() is called

See Also:

Constant Field Values

HAS_ALPHA_LAYER_SAVE_FLAG

public static final int HAS_ALPHA_LAYER_SAVE_FLAG

the layer needs to per-pixel alpha

See Also:

Constant Field Values

FULL_COLOR_LAYER_SAVE_FLAG

public static final int FULL_COLOR_LAYER_SAVE_FLAG

the layer needs to 8-bits per color component

See Also:

Constant Field Values

CLIP_TO_LAYER_SAVE_FLAG

public static final int CLIP_TO_LAYER_SAVE_FLAG

clip against the layer's bounds

See Also:

Constant Field Values

ALL_SAVE_FLAG

public static final int ALL_SAVE_FLAG

restore everything when restore() is called

See Also:

Constant Field Values

Constructor Detail

Canvas

public Canvas()

Construct an empty raster canvas. Use setBitmap() to specify a bitmap to draw into.

Canvas

public Canvas(Bitmap bitmap)

Construct a canvas with the specified bitmap to draw into. The bitmap must be mutable.

Parameters:

bitmap - Specifies a mutable bitmap for the canvas to draw into.

Canvas

Canvas(int nativeCanvas)

Canvas

public Canvas(GL gl)

Construct a canvas with the specified gl context. All drawing through this canvas will be redirected to OpenGL. Note: some features may not be supported in this mode (e.g. some GL implementations may not support antialiasing or certain effects like ColorMatrix or certain Xfermodes). However, no exception will be thrown in those cases.

Method Detail

getGL

public GL getGL()

Return the GL object associated with this canvas, or null if it is not backed by GL.

freeGlCaches

public static void freeGlCaches()

Call this to free up OpenGL resources that may be cached or allocated on behalf of the Canvas. Any subsequent drawing with a GL-backed Canvas will have to recreate those resources.

setBitmap

public void setBitmap(Bitmap bitmap)

Specify a bitmap for the canvas to draw into.

Parameters:

bitmap - Specifies a mutable bitmap for the canvas to draw into.

setViewport

public void setViewport(int width,
                        int height)

Set the viewport dimensions if this canvas is GL based. If it is not, this method is ignored and no exception is thrown.

Parameters:

width - The width of the viewport

height - The height of the viewport

isOpaque

public boolean isOpaque()

Return true if the device that the current layer draws into is opaque (i.e. does not support per-pixel alpha).

Returns:

true if the device that the current layer draws into is opaque

getWidth

public int getWidth()

Returns the width of the current drawing layer

Returns:

the width of the current drawing layer

getHeight

public int getHeight()

Returns the height of the current drawing layer

Returns:

the height of the current drawing layer

save

public int save()

Saves the current matrix and clip onto a private stack. Subsequent calls to translate,scale,rotate,skew,concat or clipRect,clipPath will all operate as usual, but when the balancing call to restore() is made, those calls will be forgotten, and the settings that existed before the save() will be reinstated.

Returns:

The value to pass to restoreToCount() to balance this save()

save

public int save(int saveFlags)

Based on saveFlags, can save the current matrix and clip onto a private stack. Subsequent calls to translate,scale,rotate,skew,concat or clipRect,clipPath will all operate as usual, but when the balancing call to restore() is made, those calls will be forgotten, and the settings that existed before the save() will be reinstated.

Parameters:

saveFlags - flag bits that specify which parts of the Canvas state to save/restore

Returns:

The value to pass to restoreToCount() to balance this save()

saveLayer

public int saveLayer(RectF bounds,
                     Paint paint,
                     int saveFlags)

This behaves the same as save(), but in addition it allocates an offscreen bitmap. All drawing calls are directed there, and only when the balancing call to restore() is made is that offscreen transfered to the canvas (or the previous layer). Subsequent calls to translate, scale, rotate, skew, concat or clipRect, clipPath all operate on this copy. When the balancing call to restore() is made, this copy is deleted and the previous matrix/clip state is restored.

Parameters:

bounds - May be null. The maximum size the offscreen bitmap needs to be (in local coordinates)

paint - This is copied, and is applied to the offscreen when restore() is called.

saveFlags - see _SAVE_FLAG constants

Returns:

value to pass to restoreToCount() to balance this save()

saveLayer

public int saveLayer(float left,
                     float top,
                     float right,
                     float bottom,
                     Paint paint,
                     int saveFlags)

Helper version of saveLayer() that takes 4 values rather than a RectF.

saveLayerAlpha

public int saveLayerAlpha(RectF bounds,
                          int alpha,
                          int saveFlags)

This behaves the same as save(), but in addition it allocates an offscreen bitmap. All drawing calls are directed there, and only when the balancing call to restore() is made is that offscreen transfered to the canvas (or the previous layer). Subsequent calls to translate, scale, rotate, skew, concat or clipRect, clipPath all operate on this copy. When the balancing call to restore() is made, this copy is deleted and the previous matrix/clip state is restored.

Parameters:

bounds - The maximum size the offscreen bitmap needs to be (in local coordinates)

alpha - The alpha to apply to the offscreen when when it is drawn during restore()

saveFlags - see _SAVE_FLAG constants

Returns:

value to pass to restoreToCount() to balance this call

saveLayerAlpha

public int saveLayerAlpha(float left,
                          float top,
                          float right,
                          float bottom,
                          int alpha,
                          int saveFlags)

Helper for saveLayerAlpha() that takes 4 values instead of a RectF.

restore

public void restore()

This call balances a previous call to save(), and is used to remove all modifications to the matrix/clip state since the last save call. It is an error to call restore() more times than save() was called.

getSaveCount

public int getSaveCount()

Returns the number of matrix/clip states on the Canvas' private stack. This will equal # save() calls - # restore() calls.

restoreToCount

public void restoreToCount(int saveCount)

Efficient way to pop any calls to save() that happened after the save count reached saveCount. It is an error for saveCount to be less than 1. Example: int count = canvas.save(); ... // more calls potentially to save() canvas.restoreToCount(count); // now the canvas is back in the same state it was before the initial // call to save().

Parameters:

saveCount - The save level to restore to.

translate

public void translate(float dx,
                      float dy)

Preconcat the current matrix with the specified translation

Parameters:

dx - The distance to translate in X

dy - The distance to translate in Y

scale

public void scale(float sx,
                  float sy)

Preconcat the current matrix with the specified scale.

Parameters:

sx - The amount to scale in X

sy - The amount to scale in Y

scale

public final void scale(float sx,
                        float sy,
                        float px,
                        float py)

Preconcat the current matrix with the specified scale.

Parameters:

sx - The amount to scale in X

sy - The amount to scale in Y

px - The x-coord for the pivot point (unchanged by the rotation)

py - The y-coord for the pivot point (unchanged by the rotation)

rotate

public void rotate(float degrees)

Preconcat the current matrix with the specified rotation.

Parameters:

degrees - The amount to rotate, in degrees

rotate

public final void rotate(float degrees,
                         float px,
                         float py)

Preconcat the current matrix with the specified rotation.

Parameters:

degrees - The amount to rotate, in degrees

px - The x-coord for the pivot point (unchanged by the rotation)

py - The y-coord for the pivot point (unchanged by the rotation)

skew

public void skew(float sx,
                 float sy)

Preconcat the current matrix with the specified skew.

Parameters:

sx - The amount to skew in X

sy - The amount to skew in Y

concat

public void concat(Matrix matrix)

Preconcat the current matrix with the specified matrix.

Parameters:

matrix - The matrix to preconcatenate with the current matrix

setMatrix

public void setMatrix(Matrix matrix)

Completely replace the current matrix with the specified matrix. If the matrix parameter is null, then the current matrix is reset to identity.

Parameters:

matrix - The matrix to replace the current matrix with. If it is null, set the current matrix to identity.

getMatrix

public void getMatrix(Matrix ctm)

Return, in ctm, the current transformation matrix. This does not alter the matrix in the canvas, but just returns a copy of it.

getMatrix

public final Matrix getMatrix()

Return a new matrix with a copy of the canvas' current transformation matrix.

clipRect

public boolean clipRect(RectF rect,
                        Region.Op op)

Modify the current clip with the specified rectangle.

Parameters:

rect - The rect to intersect with the current clip

op - How the clip is modified

Returns:

true if the resulting clip is non-empty

clipRect

public boolean clipRect(Rect rect,
                        Region.Op op)

Modify the current clip with the specified rectangle, which is expressed in local coordinates.

Parameters:

rect - The rectangle to intersect with the current clip.

op - How the clip is modified

Returns:

true if the resulting clip is non-empty

clipRect

public boolean clipRect(RectF rect)

Intersect the current clip with the specified rectangle, which is expressed in local coordinates.

Parameters:

rect - The rectangle to intersect with the current clip.

Returns:

true if the resulting clip is non-empty

clipRect

public boolean clipRect(Rect rect)

Intersect the current clip with the specified rectangle, which is expressed in local coordinates.

Parameters:

rect - The rectangle to intersect with the current clip.

Returns:

true if the resulting clip is non-empty

clipRect

public boolean clipRect(float left,
                        float top,
                        float right,
                        float bottom,
                        Region.Op op)

Modify the current clip with the specified rectangle, which is expressed in local coordinates.

Parameters:

left - The left side of the rectangle to intersect with the current clip

top - The top of the rectangle to intersect with the current clip

right - The right side of the rectangle to intersect with the current clip

bottom - The bottom of the rectangle to intersect with the current clip

op - How the clip is modified

Returns:

true if the resulting clip is non-empty

clipRect

public boolean clipRect(float left,
                        float top,
                        float right,
                        float bottom)

Intersect the current clip with the specified rectangle, which is expressed in local coordinates.

Parameters:

left - The left side of the rectangle to intersect with the current clip

top - The top of the rectangle to intersect with the current clip

right - The right side of the rectangle to intersect with the current clip

bottom - The bottom of the rectangle to intersect with the current clip

Returns:

true if the resulting clip is non-empty

clipRect

public boolean clipRect(int left,
                        int top,
                        int right,
                        int bottom)

Intersect the current clip with the specified rectangle, which is expressed in local coordinates.

Parameters:

left - The left side of the rectangle to intersect with the current clip

top - The top of the rectangle to intersect with the current clip

right - The right side of the rectangle to intersect with the current clip

bottom - The bottom of the rectangle to intersect with the current clip

Returns:

true if the resulting clip is non-empty

clipPath

public boolean clipPath(Path path,
                        Region.Op op)

Modify the current clip with the specified path.

Parameters:

path - The path to operate on the current clip

op - How the clip is modified

Returns:

true if the resulting is non-empty

clipPath

public boolean clipPath(Path path)

Intersect the current clip with the specified path.

Parameters:

path - The path to intersect with the current clip

Returns:

true if the resulting is non-empty

clipRegion

public boolean clipRegion(Region region,
                          Region.Op op)

Modify the current clip with the specified region. Note that unlike clipRect() and clipPath() which transform their arguments by the current matrix, clipRegion() assumes its argument is already in the coordinate system of the current layer's bitmap, and so not transformation is performed.

Parameters:

region - The region to operate on the current clip, based on op

op - How the clip is modified

Returns:

true if the resulting is non-empty

clipRegion

public boolean clipRegion(Region region)

Intersect the current clip with the specified region. Note that unlike clipRect() and clipPath() which transform their arguments by the current matrix, clipRegion() assumes its argument is already in the coordinate system of the current layer's bitmap, and so not transformation is performed.

Parameters:

region - The region to operate on the current clip, based on op

Returns:

true if the resulting is non-empty

getDrawFilter

public DrawFilter getDrawFilter()

setDrawFilter

public void setDrawFilter(DrawFilter filter)

quickReject

public boolean quickReject(RectF rect,
                           Canvas.EdgeType type)

Return true if the specified rectangle, after being transformed by the current matrix, would lie completely outside of the current clip. Call this to check if an area you intend to draw into is clipped out (and therefore you can skip making the draw calls).

Parameters:

rect - the rect to compare with the current clip

type - specifies how to treat the edges (BW or antialiased)

Returns:

true if the rect (transformed by the canvas' matrix) does not intersect with the canvas' clip

quickReject

public boolean quickReject(Path path,
                           Canvas.EdgeType type)

Return true if the specified path, after being transformed by the current matrix, would lie completely outside of the current clip. Call this to check if an area you intend to draw into is clipped out (and therefore you can skip making the draw calls). Note: for speed it may return false even if the path itself might not intersect the clip (i.e. the bounds of the path intersects, but the path does not).

Parameters:

path - The path to compare with the current clip

type - true if the path should be considered antialiased, since that means it may affect a larger area (more pixels) than non-antialiased.

Returns:

true if the path (transformed by the canvas' matrix) does not intersect with the canvas' clip

quickReject

public boolean quickReject(float left,
                           float top,
                           float right,
                           float bottom,
                           Canvas.EdgeType type)

Return true if the specified rectangle, after being transformed by the current matrix, would lie completely outside of the current clip. Call this to check if an area you intend to draw into is clipped out (and therefore you can skip making the draw calls).

Parameters:

left - The left side of the rectangle to compare with the current clip

top - The top of the rectangle to compare with the current clip

right - The right side of the rectangle to compare with the current clip

bottom - The bottom of the rectangle to compare with the current clip

type - true if the rect should be considered antialiased, since that means it may affect a larger area (more pixels) than non-antialiased.

Returns:

true if the rect (transformed by the canvas' matrix) does not intersect with the canvas' clip

getClipBounds

public boolean getClipBounds(Rect bounds)

Retrieve the clip bounds, returning true if they are non-empty.

Parameters:

bounds - Return the clip bounds here. If it is null, ignore it but still return true if the current clip is non-empty.

Returns:

true if the current clip is non-empty.

getClipBounds

public final Rect getClipBounds()

Retrieve the clip bounds.

Returns:

the clip bounds, or [0, 0, 0, 0] if the clip is empty.

drawRGB

public void drawRGB(int r,
                    int g,
                    int b)

Fill the entire canvas' bitmap (restricted to the current clip) with the specified RGB color, using srcover porterduff mode.

Parameters:

r - red component (0..255) of the color to draw onto the canvas

g - green component (0..255) of the color to draw onto the canvas

b - blue component (0..255) of the color to draw onto the canvas

drawARGB

public void drawARGB(int a,
                     int r,
                     int g,
                     int b)

Fill the entire canvas' bitmap (restricted to the current clip) with the specified ARGB color, using srcover porterduff mode.

Parameters:

a - alpha component (0..255) of the color to draw onto the canvas

r - red component (0..255) of the color to draw onto the canvas

g - green component (0..255) of the color to draw onto the canvas

b - blue component (0..255) of the color to draw onto the canvas

drawColor

public void drawColor(int color)

Fill the entire canvas' bitmap (restricted to the current clip) with the specified color, using srcover porterduff mode.

Parameters:

color - the color to draw onto the canvas

drawColor

public void drawColor(int color,
                      PorterDuff.Mode mode)

Fill the entire canvas' bitmap (restricted to the current clip) with the specified color and porter-duff xfermode.

Parameters:

color - the color to draw with

mode - the porter-duff mode to apply to the color

drawPaint

public void drawPaint(Paint paint)

Fill the entire canvas' bitmap (restricted to the current clip) with the specified paint. This is equivalent (but faster) to drawing an infinitely large rectangle with the specified paint.

Parameters:

paint - The paint used to draw onto the canvas

drawPoints

public void drawPoints(float[] pts,
                       int offset,
                       int count,
                       Paint paint)

Draw a series of points. Each point is centered at the coordinate specified by pts[], and its diameter is specified by the paint's stroke width (as transformed by the canvas' CTM), with special treatment for a stroke width of 0, which always draws exactly 1 pixel (or at most 4 if antialiasing is enabled). The shape of the point is controlled by the paint's Cap type. The shape is a square, unless the cap type is Round, in which case the shape is a circle.

Parameters:

pts - Array of points to draw [x0 y0 x1 y1 x2 y2 ...]

offset - Number of values to skip before starting to draw.

count - The number of values to process, after skipping offset of them. Since one point uses two values, the number of "points" that are drawn is really (count >> 1).

paint - The paint used to draw the points

drawPoints

public void drawPoints(float[] pts,
                       Paint paint)

Helper for drawPoints() that assumes you want to draw the entire array

drawPoint

public void drawPoint(float x,
                      float y,
                      Paint paint)

Helper for drawPoints() for drawing a single point.

drawLine

public void drawLine(float startX,
                     float startY,
                     float stopX,
                     float stopY,
                     Paint paint)

Draw a line segment with the specified start and stop x,y coordinates, using the specified paint. NOTE: since a line is always "framed", the Style is ignored in the paint.

Parameters:

startX - The x-coordinate of the start point of the line

startY - The y-coordinate of the start point of the line

paint - The paint used to draw the line

drawLines

public void drawLines(float[] pts,
                      int offset,
                      int count,
                      Paint paint)

Draw a series of lines. Each line is taken from 4 consecutive values in the pts array. Thus to draw 1 line, the array must contain at least 4 values. This is logically the same as drawing the array as follows: drawLine(pts[0], pts[1], pts[2], pts[3]) followed by drawLine(pts[4], pts[5], pts[6], pts[7]) and so on.

Parameters:

pts - Array of points to draw [x0 y0 x1 y1 x2 y2 ...]

offset - Number of values in the array to skip before drawing.

count - The number of values in the array to process, after skipping "offset" of them. Since each line uses 4 values, the number of "lines" that are drawn is really (count >> 2).

paint - The paint used to draw the points

drawLines

public void drawLines(float[] pts,
                      Paint paint)

drawRect

public void drawRect(RectF rect,
                     Paint paint)

Draw the specified Rect using the specified paint. The rectangle will be filled or framed based on the Style in the paint.

Parameters:

rect - The rect to be drawn

paint - The paint used to draw the rect

drawRect

public void drawRect(Rect r,
                     Paint paint)

Draw the specified Rect using the specified Paint. The rectangle will be filled or framed based on the Style in the paint.

Parameters:

r - The rectangle to be drawn.

paint - The paint used to draw the rectangle

drawRect

public void drawRect(float left,
                     float top,
                     float right,
                     float bottom,
                     Paint paint)

Draw the specified Rect using the specified paint. The rectangle will be filled or framed based on the Style in the paint.

Parameters:

left - The left side of the rectangle to be drawn

top - The top side of the rectangle to be drawn

right - The right side of the rectangle to be drawn

bottom - The bottom side of the rectangle to be drawn

paint - The paint used to draw the rect

drawOval

public void drawOval(RectF oval,
                     Paint paint)

Draw the specified oval using the specified paint. The oval will be filled or framed based on the Style in the paint.

Parameters:

oval - The rectangle bounds of the oval to be drawn

drawCircle

public void drawCircle(float cx,
                       float cy,
                       float radius,
                       Paint paint)

Draw the specified circle using the specified paint. If radius is <= 0, then nothing will be drawn. The circle will be filled or framed based on the Style in the paint.

Parameters:

cx - The x-coordinate of the center of the cirle to be drawn

cy - The y-coordinate of the center of the cirle to be drawn

radius - The radius of the cirle to be drawn

paint - The paint used to draw the circle

drawArc

public void drawArc(RectF oval,
                    float startAngle,
                    float sweepAngle,
                    boolean useCenter,
                    Paint paint)

Draw the specified arc, which will be scaled to fit inside the specified oval. If the sweep angle is >= 360, then the oval is drawn completely. Note that this differs slightly from SkPath::arcTo, which treats the sweep angle mod 360.

Parameters:

oval - The bounds of oval used to define the shape and size of the arc

startAngle - Starting angle (in degrees) where the arc begins

sweepAngle - Sweep angle (in degrees) measured clockwise

useCenter - If true, include the center of the oval in the arc, and close it if it is being stroked. This will draw a wedge

paint - The paint used to draw the arc

drawRoundRect

public void drawRoundRect(RectF rect,
                          float rx,
                          float ry,
                          Paint paint)

Draw the specified round-rect using the specified paint. The roundrect will be filled or framed based on the Style in the paint.

Parameters:

rect - The rectangular bounds of the roundRect to be drawn

rx - The x-radius of the oval used to round the corners

ry - The y-radius of the oval used to round the corners

paint - The paint used to draw the roundRect

drawPath

public void drawPath(Path path,
                     Paint paint)

Draw the specified path using the specified paint. The path will be filled or framed based on the Style in the paint.

Parameters:

path - The path to be drawn

paint - The paint used to draw the path

drawBitmap

public void drawBitmap(Bitmap bitmap,
                       float left,
                       float top,
                       Paint paint)

Draw the specified bitmap, with its top/left corner at (x,y), using the specified paint, transformed by the current matrix. Note: if the paint contains a maskfilter that generates a mask which extends beyond the bitmap's original width/height (e.g. BlurMaskFilter), then the bitmap will be drawn as if it were in a Shader with CLAMP mode. Thus the color outside of the original width/height will be the edge color replicated.

Parameters:

bitmap - The bitmap to be drawn

left - The position of the left side of the bitmap being drawn

top - The position of the top side of the bitmap being drawn

paint - The paint used to draw the bitmap (may be null)

drawBitmap

public void drawBitmap(Bitmap bitmap,
                       Rect src,
                       RectF dst,
                       Paint paint)

Draw the specified bitmap, scaling/translating automatically to fill the destination rectangle. If the source rectangle is not null, it specifies the subset of the bitmap to draw. Note: if the paint contains a maskfilter that generates a mask which extends beyond the bitmap's original width/height (e.g. BlurMaskFilter), then the bitmap will be drawn as if it were in a Shader with CLAMP mode. Thus the color outside of the original width/height will be the edge color replicated.

Parameters:

bitmap - The bitmap to be drawn

src - May be null. The subset of the bitmap to be drawn

dst - The rectangle that the bitmap will be scaled/translated to fit into

paint - May be null. The paint used to draw the bitmap

drawBitmap

public void drawBitmap(Bitmap bitmap,
                       Rect src,
                       Rect dst,
                       Paint paint)

Draw the specified bitmap, scaling/translating automatically to fill the destination rectangle. If the source rectangle is not null, it specifies the subset of the bitmap to draw. Note: if the paint contains a maskfilter that generates a mask which extends beyond the bitmap's original width/height (e.g. BlurMaskFilter), then the bitmap will be drawn as if it were in a Shader with CLAMP mode. Thus the color outside of the original width/height will be the edge color replicated.

Parameters:

bitmap - The bitmap to be drawn

src - May be null. The subset of the bitmap to be drawn

dst - The rectangle that the bitmap will be scaled/translated to fit into

paint - May be null. The paint used to draw the bitmap

drawBitmap

public void drawBitmap(int[] colors,
                       int offset,
                       int stride,
                       int x,
                       int y,
                       int width,
                       int height,
                       boolean hasAlpha,
                       Paint paint)

Treat the specified array of colors as a bitmap, and draw it. This gives the same result as first creating a bitmap from the array, and then drawing it, but this method avoids explicitly creating a bitmap object which can be more efficient if the colors are changing often.

Parameters:

colors - Array of colors representing the pixels of the bitmap

offset - Offset into the array of colors for the first pixel

stride - The number of of colors in the array between rows (must be >= width or <= -width).

x - The X coordinate for where to draw the bitmap

y - The Y coordinate for where to draw the bitmap

width - The width of the bitmap

height - The height of the bitmap

hasAlpha - True if the alpha channel of the colors contains valid values. If false, the alpha byte is ignored (assumed to be 0xFF for every pixel).

paint - May be null. The paint used to draw the bitmap

drawBitmap

public void drawBitmap(Bitmap bitmap,
                       Matrix matrix,
                       Paint paint)

Draw the bitmap using the specified matrix.

Parameters:

bitmap - The bitmap to draw

matrix - The matrix used to transform the bitmap when it is drawn

paint - May be null. The paint used to draw the bitmap

drawBitmapMesh

public void drawBitmapMesh(Bitmap bitmap,
                           int meshWidth,
                           int meshHeight,
                           float[] verts,
                           int vertOffset,
                           int[] colors,
                           int colorOffset,
                           Paint paint)

Draw the bitmap through the mesh, where mesh vertices are evenly distributed across the bitmap. There are meshWidth+1 vertices across, and meshHeight+1 vertices down. The verts array is accessed in row-major order, so that the first meshWidth+1 vertices are distributed across the top of the bitmap from left to right. A more general version of this methid is drawVertices().

Parameters:

bitmap - The bitmap to draw using the mesh

meshWidth - The number of columns in the mesh. Nothing is drawn if this is 0

meshHeight - The number of rows in the mesh. Nothing is drawn if this is 0

verts - Array of x,y pairs, specifying where the mesh should be drawn. There must be at least (meshWidth+1) * (meshHeight+1) * 2 + meshOffset values in the array

vertOffset - Number of verts elements to skip before drawing

colors - May be null. Specifies a color at each vertex, which is interpolated across the cell, and whose values are multiplied by the corresponding bitmap colors. If not null, there must be at least (meshWidth+1) * (meshHeight+1) + colorOffset values in the array.

colorOffset - Number of color elements to skip before drawing

paint - May be null. The paint used to draw the bitmap

drawVertices

public void drawVertices(Canvas.VertexMode mode,
                         int vertexCount,
                         float[] verts,
                         int vertOffset,
                         float[] texs,
                         int texOffset,
                         int[] colors,
                         int colorOffset,
                         short[] indices,
                         int indexOffset,
                         int indexCount,
                         Paint paint)

Draw the array of vertices, interpreted as triangles (based on mode). The verts array is required, and specifies the x,y pairs for each vertex. If texs is non-null, then it is used to specify the coordinate in shader coordinates to use at each vertex (the paint must have a shader in this case). If there is no texs array, but there is a color array, then each color is interpolated across its corresponding triangle in a gradient. If both texs and colors arrays are present, then they behave as before, but the resulting color at each pixels is the result of multiplying the colors from the shader and the color-gradient together. The indices array is optional, but if it is present, then it is used to specify the index of each triangle, rather than just walking through the arrays in order.

Parameters:

mode - How to interpret the array of vertices

vertexCount - The number of values in the vertices array (and corresponding texs and colors arrays if non-null). Each logical vertex is two values (x, y), vertexCount must be a multiple of 2.

verts - Array of vertices for the mesh

vertOffset - Number of values in the verts to skip before drawing.

texs - May be null. If not null, specifies the coordinates to sample into the current shader (e.g. bitmap tile or gradient)

texOffset - Number of values in texs to skip before drawing.

colors - May be null. If not null, specifies a color for each vertex, to be interpolated across the triangle.

colorOffset - Number of values in colors to skip before drawing.

indices - If not null, array of indices to reference into the vertex (texs, colors) array.

indexCount - number of entries in the indices array (if not null).

paint - Specifies the shader to use if the texs array is non-null.

drawText

public void drawText(char[] text,
                     int index,
                     int count,
                     float x,
                     float y,
                     Paint paint)

Draw the text, with origin at (x,y), using the specified paint. The origin is interpreted based on the Align setting in the paint.

Parameters:

text - The text to be drawn

x - The x-coordinate of the origin of the text being drawn

y - The y-coordinate of the origin of the text being drawn

paint - The paint used for the text (e.g. color, size, style)

drawText

public void drawText(String text,
                     float x,
                     float y,
                     Paint paint)

Draw the text, with origin at (x,y), using the specified paint. The origin is interpreted based on the Align setting in the paint.

Parameters:

text - The text to be drawn

x - The x-coordinate of the origin of the text being drawn

y - The y-coordinate of the origin of the text being drawn

paint - The paint used for the text (e.g. color, size, style)

drawText

public void drawText(String text,
                     int start,
                     int end,
                     float x,
                     float y,
                     Paint paint)

Draw the text, with origin at (x,y), using the specified paint. The origin is interpreted based on the Align setting in the paint.

Parameters:

text - The text to be drawn

start - The index of the first character in text to draw

end - (end - 1) is the index of the last character in text to draw

x - The x-coordinate of the origin of the text being drawn

y - The y-coordinate of the origin of the text being drawn

paint - The paint used for the text (e.g. color, size, style)

drawText

public void drawText(CharSequence text,
                     int start,
                     int end,
                     float x,
                     float y,
                     Paint paint)

Draw the specified range of text, specified by start/end, with its origin at (x,y), in the specified Paint. The origin is interpreted based on the Align setting in the Paint.

Parameters:

text - The text to be drawn

start - The index of the first character in text to draw

end - (end - 1) is the index of the last character in text to draw

x - The x-coordinate of origin for where to draw the text

y - The y-coordinate of origin for where to draw the text

paint - The paint used for the text (e.g. color, size, style)

drawPosText

public void drawPosText(char[] text,
                        int index,
                        int count,
                        float[] pos,
                        Paint paint)

Draw the text in the array, with each character's origin specified by the pos array.

Parameters:

text - The text to be drawn

index - The index of the first character to draw

count - The number of characters to draw, starting from index.

pos - Array of [x,y] positions, used to position each character

paint - The paint used for the text (e.g. color, size, style)

drawPosText

public void drawPosText(String text,
                        float[] pos,
                        Paint paint)

Draw the text in the array, with each character's origin specified by the pos array.

Parameters:

text - The text to be drawn

pos - Array of [x,y] positions, used to position each character

paint - The paint used for the text (e.g. color, size, style)

drawTextOnPath

public void drawTextOnPath(char[] text,
                           int index,
                           int count,
                           Path path,
                           float hOffset,
                           float vOffset,
                           Paint paint)

Draw the text, with origin at (x,y), using the specified paint, along the specified path. The paint's Align setting determins where along the path to start the text.

Parameters:

text - The text to be drawn

path - The path the text should follow for its baseline

hOffset - The distance along the path to add to the text's starting position

vOffset - The distance above(-) or below(+) the path to position the text

paint - The paint used for the text (e.g. color, size, style)

drawTextOnPath

public void drawTextOnPath(String text,
                           Path path,
                           float hOffset,
                           float vOffset,
                           Paint paint)

Draw the text, with origin at (x,y), using the specified paint, along the specified path. The paint's Align setting determins where along the path to start the text.

Parameters:

text - The text to be drawn

path - The path the text should follow for its baseline

hOffset - The distance along the path to add to the text's starting position

vOffset - The distance above(-) or below(+) the path to position the text

paint - The paint used for the text (e.g. color, size, style)

drawPicture

public void drawPicture(Picture picture)

Save the canvas state, draw the picture, and restore the canvas state. This differs from picture.draw(canvas), which does not perform any save/restore.

Parameters:

picture - The picture to be drawn

drawPicture

public void drawPicture(Picture picture,
                        RectF dst)

Draw the picture, stretched to fit into the dst rectangle.

drawPicture

public void drawPicture(Picture picture,
                        Rect dst)

Draw the picture, stretched to fit into the dst rectangle.

finalize

protected void finalize()
                 throws Throwable

Description copied from class: Object

Called by the virtual machine when there are no longer any (non-weak) references to the receiver. Subclasses can use this facility to guarantee that any associated resources are cleaned up before the receiver is garbage collected. Uncaught exceptions which are thrown during the running of the method cause it to terminate immediately, but are otherwise ignored.

Note: The virtual machine assumes that the implementation in class Object is empty.

Overrides:

finalize in class Object

Throws:

Throwable - The virtual machine ignores any exceptions which are thrown during finalization.