android.database
Class MergeCursor

java.lang.Object
  android.database.AbstractCursor
      android.database.MergeCursor

All Implemented Interfaces:

CrossProcessCursor, Cursor

public class MergeCursor
extends AbstractCursor

A convience class that lets you present an array of Cursors as a single linear Cursor. The schema of the cursors presented is entirely up to the creator of the MergeCursor, and may be different if that is desired. Calls to getColumns, getColumnIndex, etc will return the value for the row that the MergeCursor is currently pointing at.

Nested Class Summary

Nested classes/interfaces inherited from class android.database.AbstractCursor

AbstractCursor.SelfContentObserver

Field Summary

Fields inherited from class android.database.AbstractCursor

mClosed, mContentObservable, mContentResolver, mCurrentRowID, mDataSetObservable, mPos, mRowIdColumnIndex, mUpdatedRows

Constructor Summary

MergeCursor(Cursor[] cursors)

Method Summary

void	close() Closes the Cursor, releasing all of its resources and making it completely invalid.
boolean	commitUpdates() Deprecated.
void	deactivate() Deactivates the Cursor, making all calls on it fail until Cursor.requery() is called.
boolean	deleteRow() Deprecated.
byte[]	getBlob(int column) Returns the value of the requested column as a byte array.
String[]	getColumnNames() Returns a string array holding the names of all of the columns in the result set in the order in which they were listed in the result.
int	getCount() Returns the numbers of rows in the cursor.
double	getDouble(int column) Returns the value of the requested column as a double.
float	getFloat(int column) Returns the value of the requested column as a float.
int	getInt(int column) Returns the value of the requested column as an int.
long	getLong(int column) Returns the value of the requested column as a long.
short	getShort(int column) Returns the value of the requested column as a short.
String	getString(int column) Returns the value of the requested column as a String.
boolean	isNull(int column) Returns true if the value in the indicated column is null.
boolean	onMove(int oldPosition, int newPosition) This function is called every time the cursor is successfully scrolled to a new position, giving the subclass a chance to update any state it may have.
void	registerContentObserver(ContentObserver observer) Register an observer that is called when changes happen to the content backing this cursor.
void	registerDataSetObserver(DataSetObserver observer) Register an observer that is called when changes happen to the contents of the this cursors data set, for example, when the data set is changed via Cursor.requery(), Cursor.deactivate(), or Cursor.close().
boolean	requery() Performs the query that created the cursor again, refreshing its contents.
void	unregisterContentObserver(ContentObserver observer) Unregister an observer that has previously been registered with this cursor via Cursor.registerContentObserver(android.database.ContentObserver).
void	unregisterDataSetObserver(DataSetObserver observer) Unregister an observer that has previously been registered with this cursor via Cursor.registerContentObserver(android.database.ContentObserver).

Methods inherited from class android.database.AbstractCursor

abortUpdates, checkPosition, commitUpdates, copyStringToBuffer, deactivateInternal, fillWindow, finalize, getColumnCount, getColumnIndex, getColumnIndexOrThrow, getColumnName, getDataSetObservable, getExtras, getPosition, getUpdatedField, getWantsAllOnMoveCalls, getWindow, hasUpdates, isAfterLast, isBeforeFirst, isClosed, isFieldUpdated, isFirst, isLast, move, moveToFirst, moveToLast, moveToNext, moveToPosition, moveToPrevious, notifyDataSetChange, onChange, respond, setNotificationUri, supportsUpdates, update, updateBlob, updateDouble, updateFloat, updateInt, updateLong, updateShort, updateString, updateToNull

Methods inherited from class java.lang.Object

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

Constructor Detail

MergeCursor

public MergeCursor(Cursor[] cursors)

Method Detail

getCount

public int getCount()

Description copied from interface: Cursor

Returns the numbers of rows in the cursor.

Specified by:

getCount in interface Cursor

Specified by:

getCount in class AbstractCursor

Returns:

the number of rows in the cursor.

onMove

public boolean onMove(int oldPosition,
                      int newPosition)

Description copied from class: AbstractCursor

This function is called every time the cursor is successfully scrolled to a new position, giving the subclass a chance to update any state it may have. If it returns false the move function will also do so and the cursor will scroll to the beforeFirst position.

Specified by:

onMove in interface CrossProcessCursor

Overrides:

onMove in class AbstractCursor

Parameters:

oldPosition - the position that we're moving from

newPosition - the position that we're moving to

Returns:

true if the move is successful, false otherwise

deleteRow

public boolean deleteRow()

Deprecated.

Description copied from interface: Cursor

Removes the row at the current cursor position from the underlying data store. After this method returns the cursor will be pointing to the row after the row that is deleted. This has the side effect of decrementing the result of count() by one.

The query must have the row ID column in its selection, otherwise this call will fail.

Specified by:

deleteRow in interface Cursor

Overrides:

deleteRow in class AbstractCursor

Returns:

whether the record was successfully deleted.

commitUpdates

public boolean commitUpdates()

Deprecated.

Description copied from interface: Cursor

Atomically commits all updates to the backing store. After completion, this method leaves the data in an inconsistent state and you should call Cursor.requery() before reading data from the cursor again.

Specified by:

commitUpdates in interface Cursor

Overrides:

commitUpdates in class AbstractCursor

Returns:

whether the operation succeeded.

getString

public String getString(int column)

Description copied from interface: Cursor

Returns the value of the requested column as a String.

If the native content of that column is not text the result will be the result of passing the column value to String.valueOf(x).

Specified by:

getString in interface Cursor

Specified by:

getString in class AbstractCursor

Parameters:

column - the zero-based index of the target column.

Returns:

the value of that column as a String.

getShort

public short getShort(int column)

Description copied from interface: Cursor

Returns the value of the requested column as a short.

If the native content of that column is not numeric the result will be the result of passing the column value to Short.valueOf(x).

Specified by:

getShort in interface Cursor

Specified by:

getShort in class AbstractCursor

Parameters:

column - the zero-based index of the target column.

Returns:

the value of that column as a short.

getInt

public int getInt(int column)

Description copied from interface: Cursor

Returns the value of the requested column as an int.

If the native content of that column is not numeric the result will be the result of passing the column value to Integer.valueOf(x).

Specified by:

getInt in interface Cursor

Specified by:

getInt in class AbstractCursor

Parameters:

column - the zero-based index of the target column.

Returns:

the value of that column as an int.

getLong

public long getLong(int column)

Description copied from interface: Cursor

Returns the value of the requested column as a long.

If the native content of that column is not numeric the result will be the result of passing the column value to Long.valueOf(x).

Specified by:

getLong in interface Cursor

Specified by:

getLong in class AbstractCursor

Parameters:

column - the zero-based index of the target column.

Returns:

the value of that column as a long.

getFloat

public float getFloat(int column)

Description copied from interface: Cursor

Returns the value of the requested column as a float.

If the native content of that column is not numeric the result will be the result of passing the column value to Float.valueOf(x).

Specified by:

getFloat in interface Cursor

Specified by:

getFloat in class AbstractCursor

Parameters:

column - the zero-based index of the target column.

Returns:

the value of that column as a float.

getDouble

public double getDouble(int column)

Description copied from interface: Cursor

Returns the value of the requested column as a double.

If the native content of that column is not numeric the result will be the result of passing the column value to Double.valueOf(x).

Specified by:

getDouble in interface Cursor

Specified by:

getDouble in class AbstractCursor

Parameters:

column - the zero-based index of the target column.

Returns:

the value of that column as a double.

isNull

public boolean isNull(int column)

Description copied from interface: Cursor

Returns true if the value in the indicated column is null.

Specified by:

isNull in interface Cursor

Specified by:

isNull in class AbstractCursor

Parameters:

column - the zero-based index of the target column.

Returns:

whether the column value is null.

getBlob

public byte[] getBlob(int column)

Description copied from interface: Cursor

Returns the value of the requested column as a byte array.

If the native content of that column is not blob exception may throw

Specified by:

getBlob in interface Cursor

Overrides:

getBlob in class AbstractCursor

Parameters:

column - the zero-based index of the target column.

Returns:

the value of that column as a byte array.

getColumnNames

public String[] getColumnNames()

Description copied from interface: Cursor

Returns a string array holding the names of all of the columns in the result set in the order in which they were listed in the result.

Specified by:

getColumnNames in interface Cursor

Specified by:

getColumnNames in class AbstractCursor

Returns:

the names of the columns returned in this query.

deactivate

public void deactivate()

Description copied from interface: Cursor

Deactivates the Cursor, making all calls on it fail until Cursor.requery() is called. Inactive Cursors use fewer resources than active Cursors. Calling Cursor.requery() will make the cursor active again.

Specified by:

deactivate in interface Cursor

Overrides:

deactivate in class AbstractCursor

close

public void close()

Description copied from interface: Cursor

Closes the Cursor, releasing all of its resources and making it completely invalid. Unlike Cursor.deactivate() a call to Cursor.requery() will not make the Cursor valid again.

Specified by:

close in interface Cursor

Overrides:

close in class AbstractCursor

registerContentObserver

public void registerContentObserver(ContentObserver observer)

Description copied from interface: Cursor

Register an observer that is called when changes happen to the content backing this cursor. Typically the data set won't change until Cursor.requery() is called.

Specified by:

registerContentObserver in interface Cursor

Overrides:

registerContentObserver in class AbstractCursor

Parameters:

observer - the object that gets notified when the content backing the cursor changes.

See Also:

Cursor.unregisterContentObserver(ContentObserver)

unregisterContentObserver

public void unregisterContentObserver(ContentObserver observer)

Description copied from interface: Cursor

Unregister an observer that has previously been registered with this cursor via Cursor.registerContentObserver(android.database.ContentObserver).

Specified by:

unregisterContentObserver in interface Cursor

Overrides:

unregisterContentObserver in class AbstractCursor

Parameters:

observer - the object to unregister.

See Also:

Cursor.registerContentObserver(ContentObserver)

registerDataSetObserver

public void registerDataSetObserver(DataSetObserver observer)

Description copied from interface: Cursor

Register an observer that is called when changes happen to the contents of the this cursors data set, for example, when the data set is changed via Cursor.requery(), Cursor.deactivate(), or Cursor.close().

Specified by:

registerDataSetObserver in interface Cursor

Overrides:

registerDataSetObserver in class AbstractCursor

Parameters:

observer - the object that gets notified when the cursors data set changes.

See Also:

Cursor.unregisterDataSetObserver(DataSetObserver)

unregisterDataSetObserver

public void unregisterDataSetObserver(DataSetObserver observer)

Description copied from interface: Cursor

Unregister an observer that has previously been registered with this cursor via Cursor.registerContentObserver(android.database.ContentObserver).

Specified by:

unregisterDataSetObserver in interface Cursor

Overrides:

unregisterDataSetObserver in class AbstractCursor

Parameters:

observer - the object to unregister.

See Also:

Cursor.registerDataSetObserver(DataSetObserver)

requery

public boolean requery()

Description copied from interface: Cursor

Performs the query that created the cursor again, refreshing its contents. This may be done at any time, including after a call to Cursor.deactivate().

Specified by:

requery in interface Cursor

Overrides:

requery in class AbstractCursor

Returns:

true if the requery succeeded, false if not, in which case the cursor becomes invalid.