Package android.database

Class MergeCursor

java.lang.Object

android.database.AbstractCursor

android.database.MergeCursor

All Implemented Interfaces:

CrossProcessCursor, Cursor, Closeable, AutoCloseable

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.

Field Summary

Fields inherited from class android.database.AbstractCursor

mClosed, mCurrentRowID, mPos, mRowIdColumnIndex, mUpdatedRows

Fields inherited from interface android.database.Cursor

FIELD_TYPE_BLOB, FIELD_TYPE_FLOAT, FIELD_TYPE_INTEGER, FIELD_TYPE_NULL, FIELD_TYPE_STRING

Constructor Summary

Constructors

Constructor	Description
MergeCursor(Cursor[] cursors)

Method Summary

Modifier and Type	Method	Description
void	close()	Closes the Cursor, releasing all of its resources and making it completely invalid.
void	deactivate()	Deactivates the Cursor, making all calls on it fail until Cursor.requery() is called.
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.
int	getType(int column)	Returns data type of the given column's value.
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	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	unregisterDataSetObserver(DataSetObserver observer)	Unregister an observer that has previously been registered with this cursor via #registerContentObserver.

Methods inherited from class android.database.AbstractCursor

checkPosition, copyStringToBuffer, fillWindow, finalize, getColumnCount, getColumnIndex, getColumnIndexOrThrow, getColumnName, getExtras, getPosition, getUpdatedField, getWantsAllOnMoveCalls, getWindow, isAfterLast, isBeforeFirst, isClosed, isFieldUpdated, isFirst, isLast, move, moveToFirst, moveToLast, moveToNext, moveToPosition, moveToPrevious, onChange, onDeactivateOrClose, respond, setExtras

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

getString

public String getString(int column)

Description copied from interface: Cursor

Returns the value of the requested column as a String.

The result and whether this method throws an exception when the column value is null or the column type is not a string type is implementation-defined.

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.

The result and whether this method throws an exception when the column value is null, the column type is not an integral type, or the integer value is outside the range [Short.MIN_VALUE, Short.MAX_VALUE] is implementation-defined.

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.

The result and whether this method throws an exception when the column value is null, the column type is not an integral type, or the integer value is outside the range [Integer.MIN_VALUE, Integer.MAX_VALUE] is implementation-defined.

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.

The result and whether this method throws an exception when the column value is null, the column type is not an integral type, or the integer value is outside the range [Long.MIN_VALUE, Long.MAX_VALUE] is implementation-defined.

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.

The result and whether this method throws an exception when the column value is null, the column type is not a floating-point type, or the floating-point value is not representable as a float value is implementation-defined.

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.

The result and whether this method throws an exception when the column value is null, the column type is not a floating-point type, or the floating-point value is not representable as a double value is implementation-defined.

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.

getType

public int getType(int column)

Description copied from interface: Cursor

Returns data type of the given column's value. The preferred type of the column is returned but the data may be converted to other types as documented in the get-type methods such as Cursor.getInt(int), Cursor.getFloat(int) etc.

Returned column types are

• Cursor.FIELD_TYPE_NULL
• Cursor.FIELD_TYPE_INTEGER
• Cursor.FIELD_TYPE_FLOAT
• Cursor.FIELD_TYPE_STRING
• Cursor.FIELD_TYPE_BLOB

Specified by:

getType in interface Cursor

Overrides:

getType in class AbstractCursor

Parameters:

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

Returns:

column value type

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.

The result and whether this method throws an exception when the column value is null or the column type is not a blob type is implementation-defined.

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 AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in interface Cursor

Overrides:

close in class AbstractCursor

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 #registerContentObserver.

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(). Since this method could execute a query on the database and potentially take a while, it could cause ANR if it is called on Main (UI) thread. A warning is printed if this method is being executed on Main thread.

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.