Android APIs
public abstract class

AbstractCursor

extends Object
implements CrossProcessCursor
java.lang.Object
   ↳ android.database.AbstractCursor
Known Direct Subclasses
Known Indirect Subclasses

Class Overview

This is an abstract cursor class that handles a lot of the common code that all cursors need to deal with and is provided for convenience reasons.

Summary

Nested Classes
class AbstractCursor.SelfContentObserver Cursors use this class to track changes others make to their URI. 
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Inherited Constants
From interface android.database.Cursor
Fields
protected boolean mClosed
protected ContentResolver mContentResolver
protected Long mCurrentRowID This field was deprecated in API level 16. This field should not be used.
protected int mPos
protected int mRowIdColumnIndex This field was deprecated in API level 16. This field should not be used.
protected HashMap<LongMap<StringObject>> mUpdatedRows This field was deprecated in API level 11. This is never updated by this class and should not be used
Public Constructors
AbstractCursor()
Public Methods
void close()
Closes the Cursor, releasing all of its resources and making it completely invalid.
void copyStringToBuffer(int columnIndex, CharArrayBuffer buffer)
Retrieves the requested column text and stores it in the buffer provided.
void deactivate()
Deactivates the Cursor, making all calls on it fail until requery() is called.
void fillWindow(int position, CursorWindow window)
Copies cursor data into the window.
byte[] getBlob(int column)
Returns the value of the requested column as a byte array.
int getColumnCount()
Return total number of columns
int getColumnIndex(String columnName)
Returns the zero-based index for the given column name, or -1 if the column doesn't exist.
int getColumnIndexOrThrow(String columnName)
Returns the zero-based index for the given column name, or throws IllegalArgumentException if the column doesn't exist.
String getColumnName(int columnIndex)
Returns the column name at the given zero-based column index.
abstract 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.
abstract int getCount()
Returns the numbers of rows in the cursor.
abstract double getDouble(int column)
Returns the value of the requested column as a double.
Bundle getExtras()
Returns a bundle of extra values.
abstract float getFloat(int column)
Returns the value of the requested column as a float.
abstract int getInt(int column)
Returns the value of the requested column as an int.
abstract long getLong(int column)
Returns the value of the requested column as a long.
Uri getNotificationUri()
Return the URI at which notifications of changes in this Cursor's data will be delivered, as previously set by setNotificationUri(ContentResolver, Uri).
final int getPosition()
Returns the current position of the cursor in the row set.
abstract short getShort(int column)
Returns the value of the requested column as a short.
abstract 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 getWantsAllOnMoveCalls()
onMove() will only be called across processes if this method returns true.
CursorWindow getWindow()
If the cursor is backed by a CursorWindow, returns a pre-filled window with the contents of the cursor, otherwise null.
final boolean isAfterLast()
Returns whether the cursor is pointing to the position after the last row.
final boolean isBeforeFirst()
Returns whether the cursor is pointing to the position before the first row.
boolean isClosed()
return true if the cursor is closed
final boolean isFirst()
Returns whether the cursor is pointing to the first row.
final boolean isLast()
Returns whether the cursor is pointing to the last row.
abstract boolean isNull(int column)
Returns true if the value in the indicated column is null.
final boolean move(int offset)
Move the cursor by a relative amount, forward or backward, from the current position.
final boolean moveToFirst()
Move the cursor to the first row.
final boolean moveToLast()
Move the cursor to the last row.
final boolean moveToNext()
Move the cursor to the next row.
final boolean moveToPosition(int position)
Move the cursor to an absolute position.
final boolean moveToPrevious()
Move the cursor to the previous row.
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 requery(), deactivate(), or close().
boolean requery()
Performs the query that created the cursor again, refreshing its contents.
Bundle respond(Bundle extras)
This is an out-of-band way for the the user of a cursor to communicate with the cursor.
void setNotificationUri(ContentResolver cr, Uri notifyUri)
Specifies a content URI to watch for changes.
void unregisterContentObserver(ContentObserver observer)
Unregister an observer that has previously been registered with this cursor via registerContentObserver(ContentObserver).
void unregisterDataSetObserver(DataSetObserver observer)
Unregister an observer that has previously been registered with this cursor via registerContentObserver(ContentObserver).
Protected Methods
void checkPosition()
This function throws CursorIndexOutOfBoundsException if the cursor position is out of bounds.
void finalize()
Invoked when the garbage collector has detected that this instance is no longer reachable.
Object getUpdatedField(int columnIndex)
boolean isFieldUpdated(int columnIndex)
void onChange(boolean selfChange)
Subclasses must call this method when they finish committing updates to notify all observers.
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Inherited Methods
From class java.lang.Object
From interface android.database.CrossProcessCursor
From interface android.database.Cursor
From interface java.io.Closeable
From interface java.lang.AutoCloseable

Fields

protected boolean mClosed

Added in API level 1

protected ContentResolver mContentResolver

Added in API level 1

protected Long mCurrentRowID

Added in API level 1

This field was deprecated in API level 16.
This field should not be used.

If mRowIdColumnIndex is not -1 this contains contains the value of the column at mRowIdColumnIndex for the current row this cursor is pointing at.

protected int mPos

Added in API level 1

protected int mRowIdColumnIndex

Added in API level 1

This field was deprecated in API level 16.
This field should not be used.

This must be set to the index of the row ID column by any subclass that wishes to support updates.

protected HashMap<LongMap<StringObject>> mUpdatedRows

Added in API level 1

This field was deprecated in API level 11.
This is never updated by this class and should not be used

Public Constructors

public AbstractCursor ()

Added in API level 1

Public Methods

public void close ()

Added in API level 1

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

public void copyStringToBuffer (int columnIndex, CharArrayBuffer buffer)

Added in API level 1

Retrieves the requested column text and stores it in the buffer provided. If the buffer size is not sufficient, a new char buffer will be allocated and assigned to CharArrayBuffer.data

Parameters
columnIndex the zero-based index of the target column. if the target column is null, return buffer
buffer the buffer to copy the text into.

public void deactivate ()

Added in API level 1

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

public void fillWindow (int position, CursorWindow window)

Added in API level 1

Copies cursor data into the window.

Clears the window and fills it with data beginning at the requested row position until all of the data in the cursor is exhausted or the window runs out of space.

The filled window uses the same row indices as the original cursor. For example, if you fill a window starting from row 5 from the cursor, you can query the contents of row 5 from the window just by asking it for row 5 because there is a direct correspondence between the row indices used by the cursor and the window.

The current position of the cursor, as returned by getPosition(), is not changed by this method.

Parameters
position The zero-based index of the first row to copy into the window.
window The window to fill.

public byte[] getBlob (int column)

Added in API level 1

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.

Parameters
column the zero-based index of the target column.
Returns
  • the value of that column as a byte array.

public int getColumnCount ()

Added in API level 1

Return total number of columns

Returns
  • number of columns

public int getColumnIndex (String columnName)

Added in API level 1

Returns the zero-based index for the given column name, or -1 if the column doesn't exist. If you expect the column to exist use getColumnIndexOrThrow(String) instead, which will make the error more clear.

Parameters
columnName the name of the target column.
Returns
  • the zero-based column index for the given column name, or -1 if the column name does not exist.

public int getColumnIndexOrThrow (String columnName)

Added in API level 1

Returns the zero-based index for the given column name, or throws IllegalArgumentException if the column doesn't exist. If you're not sure if a column will exist or not use getColumnIndex(String) and check for -1, which is more efficient than catching the exceptions.

Parameters
columnName the name of the target column.
Returns
  • the zero-based column index for the given column name

public String getColumnName (int columnIndex)

Added in API level 1

Returns the column name at the given zero-based column index.

Parameters
columnIndex the zero-based index of the target column.
Returns
  • the column name for the given column index.

public abstract String[] getColumnNames ()

Added in API level 1

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.

Returns
  • the names of the columns returned in this query.

public abstract int getCount ()

Added in API level 1

Returns the numbers of rows in the cursor.

Returns
  • the number of rows in the cursor.

public abstract double getDouble (int column)

Added in API level 1

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.

Parameters
column the zero-based index of the target column.
Returns
  • the value of that column as a double.

public Bundle getExtras ()

Added in API level 1

Returns a bundle of extra values. This is an optional way for cursors to provide out-of-band metadata to their users. One use of this is for reporting on the progress of network requests that are required to fetch data for the cursor.

These values may only change when requery is called.

Returns
  • cursor-defined values, or Bundle.EMPTY if there are no values. Never null.

public abstract float getFloat (int column)

Added in API level 1

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.

Parameters
column the zero-based index of the target column.
Returns
  • the value of that column as a float.

public abstract int getInt (int column)

Added in API level 1

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.

Parameters
column the zero-based index of the target column.
Returns
  • the value of that column as an int.

public abstract long getLong (int column)

Added in API level 1

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.

Parameters
column the zero-based index of the target column.
Returns
  • the value of that column as a long.

public Uri getNotificationUri ()

Added in API level 11

Return the URI at which notifications of changes in this Cursor's data will be delivered, as previously set by setNotificationUri(ContentResolver, Uri).

Returns

public final int getPosition ()

Added in API level 1

Returns the current position of the cursor in the row set. The value is zero-based. When the row set is first returned the cursor will be at positon -1, which is before the first row. After the last row is returned another call to next() will leave the cursor past the last entry, at a position of count().

Returns
  • the current cursor position.

public abstract short getShort (int column)

Added in API level 1

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.

Parameters
column the zero-based index of the target column.
Returns
  • the value of that column as a short.

public abstract String getString (int column)

Added in API level 1

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.

Parameters
column the zero-based index of the target column.
Returns
  • the value of that column as a String.

public int getType (int column)

Added in API level 11

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 getInt(int), getFloat(int) etc.

Returned column types are

Parameters
column the zero-based index of the target column.
Returns
  • column value type

public boolean getWantsAllOnMoveCalls ()

Added in API level 1

onMove() will only be called across processes if this method returns true.

Returns
  • whether all cursor movement should result in a call to onMove().

public CursorWindow getWindow ()

Added in API level 1

If the cursor is backed by a CursorWindow, returns a pre-filled window with the contents of the cursor, otherwise null.

Returns
  • The pre-filled window that backs this cursor, or null if none.

public final boolean isAfterLast ()

Added in API level 1

Returns whether the cursor is pointing to the position after the last row.

Returns
  • whether the cursor is after the last result.

public final boolean isBeforeFirst ()

Added in API level 1

Returns whether the cursor is pointing to the position before the first row.

Returns
  • whether the cursor is before the first result.

public boolean isClosed ()

Added in API level 1

return true if the cursor is closed

Returns
  • true if the cursor is closed.

public final boolean isFirst ()

Added in API level 1

Returns whether the cursor is pointing to the first row.

Returns
  • whether the cursor is pointing at the first entry.

public final boolean isLast ()

Added in API level 1

Returns whether the cursor is pointing to the last row.

Returns
  • whether the cursor is pointing at the last entry.

public abstract boolean isNull (int column)

Added in API level 1

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

Parameters
column the zero-based index of the target column.
Returns
  • whether the column value is null.

public final boolean move (int offset)

Added in API level 1

Move the cursor by a relative amount, forward or backward, from the current position. Positive offsets move forwards, negative offsets move backwards. If the final position is outside of the bounds of the result set then the resultant position will be pinned to -1 or count() depending on whether the value is off the front or end of the set, respectively.

This method will return true if the requested destination was reachable, otherwise, it returns false. For example, if the cursor is at currently on the second entry in the result set and move(-5) is called, the position will be pinned at -1, and false will be returned.

Parameters
offset the offset to be applied from the current position.
Returns
  • whether the requested move fully succeeded.

public final boolean moveToFirst ()

Added in API level 1

Move the cursor to the first row.

This method will return false if the cursor is empty.

Returns
  • whether the move succeeded.

public final boolean moveToLast ()

Added in API level 1

Move the cursor to the last row.

This method will return false if the cursor is empty.

Returns
  • whether the move succeeded.

public final boolean moveToNext ()

Added in API level 1

Move the cursor to the next row.

This method will return false if the cursor is already past the last entry in the result set.

Returns
  • whether the move succeeded.

public final boolean moveToPosition (int position)

Added in API level 1

Move the cursor to an absolute position. The valid range of values is -1 <= position <= count.

This method will return true if the request destination was reachable, otherwise, it returns false.

Parameters
position the zero-based position to move to.
Returns
  • whether the requested move fully succeeded.

public final boolean moveToPrevious ()

Added in API level 1

Move the cursor to the previous row.

This method will return false if the cursor is already before the first entry in the result set.

Returns
  • whether the move succeeded.

public boolean onMove (int oldPosition, int newPosition)

Added in API level 1

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.

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

public void registerContentObserver (ContentObserver observer)

Added in API level 1

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

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

public void registerDataSetObserver (DataSetObserver observer)

Added in API level 1

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 requery(), deactivate(), or close().

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

public boolean requery ()

Added in API level 1

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

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

public Bundle respond (Bundle extras)

Added in API level 1

This is an out-of-band way for the the user of a cursor to communicate with the cursor. The structure of each bundle is entirely defined by the cursor.

One use of this is to tell a cursor that it should retry its network request after it reported an error.

Parameters
extras extra values, or Bundle.EMPTY. Never null.
Returns

public void setNotificationUri (ContentResolver cr, Uri notifyUri)

Added in API level 1

Specifies a content URI to watch for changes.

Parameters
cr The content resolver from the caller's context.
notifyUri The URI to watch for changes. This can be a specific row URI, or a base URI for a whole class of content.

public void unregisterContentObserver (ContentObserver observer)

Added in API level 1

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

Parameters
observer the object to unregister.

public void unregisterDataSetObserver (DataSetObserver observer)

Added in API level 1

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

Parameters
observer the object to unregister.

Protected Methods

protected void checkPosition ()

Added in API level 1

This function throws CursorIndexOutOfBoundsException if the cursor position is out of bounds. Subclass implementations of the get functions should call this before attempting to retrieve data.

protected void finalize ()

Added in API level 1

Invoked when the garbage collector has detected that this instance is no longer reachable. The default implementation does nothing, but this method can be overridden to free resources.

Note that objects that override finalize are significantly more expensive than objects that don't. Finalizers may be run a long time after the object is no longer reachable, depending on memory pressure, so it's a bad idea to rely on them for cleanup. Note also that finalizers are run on a single VM-wide finalizer thread, so doing blocking work in a finalizer is a bad idea. A finalizer is usually only necessary for a class that has a native peer and needs to call a native method to destroy that peer. Even then, it's better to provide an explicit close method (and implement Closeable), and insist that callers manually dispose of instances. This works well for something like files, but less well for something like a BigInteger where typical calling code would have to deal with lots of temporaries. Unfortunately, code that creates lots of temporaries is the worst kind of code from the point of view of the single finalizer thread.

If you must use finalizers, consider at least providing your own ReferenceQueue and having your own thread process that queue.

Unlike constructors, finalizers are not automatically chained. You are responsible for calling super.finalize() yourself.

Uncaught exceptions thrown by finalizers are ignored and do not terminate the finalizer thread. See Effective Java Item 7, "Avoid finalizers" for more.

protected Object getUpdatedField (int columnIndex)

Added in API level 1

This method was deprecated in API level 11.
Always returns null since Cursors do not support updating rows

protected boolean isFieldUpdated (int columnIndex)

Added in API level 1

This method was deprecated in API level 11.
Always returns false since Cursors do not support updating rows

protected void onChange (boolean selfChange)

Added in API level 1

Subclasses must call this method when they finish committing updates to notify all observers.