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
public abstract class AbstractCursor.SelfContentObserver Cursors use this class to track changes others make to their URI. 
Fields
protected boolean mClosed
protected ContentResolver mContentResolver
protected Long mCurrentRowID
protected int mPos
protected int mRowIdColumnIndex 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 This HashMap contains a mapping from Long rowIDs to another Map that maps from String column names to new values.
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)
Copy data from cursor to CursorWindow
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.
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.
boolean getWantsAllOnMoveCalls()
onMove() will only be called across processes if this method returns true.
CursorWindow getWindow()
returns a pre-filled window, return NULL if no such window
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()
Is called before the object's memory is being reclaimed by the VM.
Object getUpdatedField(int columnIndex)
This function returns the uncommitted updated value for the field at columnIndex.
boolean isFieldUpdated(int columnIndex)
This function returns true if the field has been updated and is used in conjunction with getUpdatedField(int) to allow subclasses to support reading uncommitted updates.
void onChange(boolean selfChange)
Subclasses must call this method when they finish committing updates to notify all observers.
[Expand]
Inherited Methods
From class java.lang.Object
From interface android.database.CrossProcessCursor
From interface android.database.Cursor

Fields

protected boolean mClosed

protected ContentResolver mContentResolver

protected Long mCurrentRowID

protected int mPos

protected int mRowIdColumnIndex

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

This HashMap contains a mapping from Long rowIDs to another Map that maps from String column names to new values. A NULL value means to remove an existing value, and all numeric values are in their class forms, i.e. Integer, Long, Float, etc.

Public Constructors

public AbstractCursor ()

Public Methods

public void close ()

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)

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 ()

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)

Copy data from cursor to CursorWindow

Parameters
position start position of data

public byte[] getBlob (int column)

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

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

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

public int getColumnCount ()

Return total number of columns

Returns
  • number of columns

public int getColumnIndex (String columnName)

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)

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)

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 ()

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 ()

Returns the numbers of rows in the cursor.

Returns
  • the number of rows in the cursor.

public abstract double getDouble (int column)

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).

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

public Bundle getExtras ()

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.EMTPY if there are no values. Never null.

public abstract float getFloat (int column)

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).

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)

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).

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)

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).

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

public final int getPosition ()

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)

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).

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)

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).

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

public boolean getWantsAllOnMoveCalls ()

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 ()

returns a pre-filled window, return NULL if no such window

public final boolean isAfterLast ()

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 ()

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 ()

return true if the cursor is closed

Returns
  • true if the cursor is closed.

public final boolean isFirst ()

Returns whether the cursor is pointing to the first row.

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

public final boolean isLast ()

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)

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)

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 ()

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 ()

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 ()

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)

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 ()

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)

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)

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)

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 ()

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

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

public Bundle respond (Bundle extras)

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.EMTPY. Never null.
Returns
  • extra values, or Bundle.EMTPY. Never null.

public void setNotificationUri (ContentResolver cr, Uri notifyUri)

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)

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)

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 ()

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 ()

Is called before the object's memory is being reclaimed by the VM. This can only happen once the VM has detected, during a run of the garbage collector, that the object is no longer reachable by any thread of the running application.

The method can be used to free system resources or perform other cleanup before the object is garbage collected. The default implementation of the method is empty, which is also expected by the VM, but subclasses can override finalize() as required. Uncaught exceptions which are thrown during the execution of this method cause it to terminate immediately but are otherwise ignored.

Note that the VM does guarantee that finalize() is called at most once for any object, but it doesn't guarantee when (if at all) finalize() will be called. For example, object B's finalize() can delay the execution of object A's finalize() method and therefore it can delay the reclamation of A's memory. To be safe, use a ReferenceQueue, because it provides more control over the way the VM deals with references during garbage collection.

protected Object getUpdatedField (int columnIndex)

This function returns the uncommitted updated value for the field at columnIndex. NOTE: This function and isFieldUpdated(int) should be called together inside of a block synchronized on mUpdatedRows.

Parameters
columnIndex the column index of the field to retrieve
Returns
  • the updated value

protected boolean isFieldUpdated (int columnIndex)

This function returns true if the field has been updated and is used in conjunction with getUpdatedField(int) to allow subclasses to support reading uncommitted updates. NOTE: This function and getUpdatedField(int) should be called together inside of a block synchronized on mUpdatedRows.

Parameters
columnIndex the column index of the field to check
Returns
  • true if the field has been updated, false otherwise

protected void onChange (boolean selfChange)

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