java.lang.Object | |
↳ | android.database.AbstractCursor |
Known Direct Subclasses |
Known Indirect Subclasses |
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.
Nested Classes | |||||||||||
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AbstractCursor.SelfContentObserver | Cursors use this class to track changes others make to their URI. |
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Inherited Constants | |||||||||||
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From interface
android.database.Cursor
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Fields | |||||||||||
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mClosed | |||||||||||
mContentResolver | |||||||||||
mCurrentRowID | This field was deprecated in API level 16. This field should not be used. | ||||||||||
mPos | |||||||||||
mRowIdColumnIndex | This field was deprecated in API level 16. This field should not be used. | ||||||||||
mUpdatedRows | This field was deprecated in API level 11. This is never updated by this class and should not be used |
Public Constructors | |||||||||||
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Public Methods | |||||||||||
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Closes the Cursor, releasing all of its resources and making it completely invalid.
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Retrieves the requested column text and stores it in the buffer provided.
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Deactivates the Cursor, making all calls on it fail until
requery() is called. | |||||||||||
Copies cursor data into the window.
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Returns the value of the requested column as a byte array.
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Return total number of columns
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Returns the zero-based index for the given column name, or -1 if the column doesn't exist.
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Returns the zero-based index for the given column name, or throws
IllegalArgumentException if the column doesn't exist. | |||||||||||
Returns the column name at the given zero-based column index.
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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.
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Returns the numbers of rows in the cursor.
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Returns the value of the requested column as a double.
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Returns a bundle of extra values.
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Returns the value of the requested column as a float.
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Returns the value of the requested column as an int.
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Returns the value of the requested column as a long.
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Return the URI at which notifications of changes in this Cursor's data
will be delivered, as previously set by
setNotificationUri(ContentResolver, Uri) . | |||||||||||
Returns the current position of the cursor in the row set.
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Returns the value of the requested column as a short.
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Returns the value of the requested column as a String.
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Returns data type of the given column's value.
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onMove() will only be called across processes if this method returns true.
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If the cursor is backed by a
CursorWindow , returns a pre-filled
window with the contents of the cursor, otherwise null. | |||||||||||
Returns whether the cursor is pointing to the position after the last
row.
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Returns whether the cursor is pointing to the position before the first
row.
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return true if the cursor is closed
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Returns whether the cursor is pointing to the first row.
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Returns whether the cursor is pointing to the last row.
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Returns
true if the value in the indicated column is null. | |||||||||||
Move the cursor by a relative amount, forward or backward, from the
current position.
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Move the cursor to the first row.
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Move the cursor to the last row.
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Move the cursor to the next row.
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Move the cursor to an absolute position.
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Move the cursor to the previous row.
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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.
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Register an observer that is called when changes happen to the content backing this cursor.
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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() . | |||||||||||
Performs the query that created the cursor again, refreshing its
contents.
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This is an out-of-band way for the the user of a cursor to communicate with the cursor.
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Specifies a content URI to watch for changes.
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Unregister an observer that has previously been registered with this
cursor via
registerContentObserver(ContentObserver) . | |||||||||||
Unregister an observer that has previously been registered with this
cursor via
registerContentObserver(ContentObserver) . |
Protected Methods | |||||||||||
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This function throws CursorIndexOutOfBoundsException if
the cursor position is out of bounds.
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Invoked when the garbage collector has detected that this instance is no longer reachable.
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This method was deprecated
in API level 11.
Always returns null since Cursors do not support updating rows
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This method was deprecated
in API level 11.
Always returns false since Cursors do not support updating rows
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Subclasses must call this method when they finish committing updates to notify all
observers.
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Inherited Methods | |||||||||||
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From class
java.lang.Object
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From interface
android.database.CrossProcessCursor
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From interface
android.database.Cursor
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From interface
java.io.Closeable
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From interface
java.lang.AutoCloseable
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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.
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.
This field was deprecated
in API level 11.
This is never updated by this class and should not be used
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.
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
columnIndex | the zero-based index of the target column. if the target column is null, return buffer |
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buffer | the buffer to copy the text into. |
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.
position | The zero-based index of the first row to copy into the window. |
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window | The window to fill. |
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.
column | the zero-based index of the target column. |
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Return total number of columns
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.
columnName | the name of the target column. |
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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.
columnName | the name of the target column. |
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Returns the column name at the given zero-based column index.
columnIndex | the zero-based index of the target column. |
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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 numbers of rows in the 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.
column | the zero-based index of the target column. |
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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.
Bundle.EMPTY
if there
are no values. Never null
.
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.
column | the zero-based index of the target column. |
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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.
column | the zero-based index of the target column. |
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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.
column | the zero-based index of the target column. |
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Return the URI at which notifications of changes in this Cursor's data
will be delivered, as previously set by setNotificationUri(ContentResolver, Uri)
.
ContentResolver.registerContentObserver
to find out about changes to this Cursor's
data. May be null if no notification URI has been set.
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 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.
column | the zero-based index of the target column. |
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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.
column | the zero-based index of the target column. |
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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
column | the zero-based index of the target column. |
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onMove() will only be called across processes if this method returns true.
If the cursor is backed by a CursorWindow
, returns a pre-filled
window with the contents of the cursor, otherwise null.
Returns whether the cursor is pointing to the position after the last row.
Returns whether the cursor is pointing to the position before the first row.
return true if the cursor is closed
Returns whether the cursor is pointing to the first row.
Returns whether the cursor is pointing to the last row.
Returns true
if the value in the indicated column is null.
column | the zero-based index of the target column. |
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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.
offset | the offset to be applied from the current position. |
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Move the cursor to the first row.
This method will return false if the cursor is empty.
Move the cursor to the last row.
This method will return false if the cursor is empty.
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.
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.
position | the zero-based position to move to. |
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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.
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.
oldPosition | the position that we're moving from |
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newPosition | the position that we're moving to |
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.
observer | the object that gets notified when the content backing the cursor changes. |
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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()
.
observer | the object that gets notified when the cursors data set changes. |
---|
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.
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.
extras | extra values, or Bundle.EMPTY .
Never null . |
---|
Bundle.EMPTY
.
Never null
.
Specifies a content URI to watch for changes.
cr | The content resolver from the caller's context. |
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notifyUri | The URI to watch for changes. This can be a specific row URI, or a base URI for a whole class of content. |
Unregister an observer that has previously been registered with this
cursor via registerContentObserver(ContentObserver)
.
observer | the object to unregister. |
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Unregister an observer that has previously been registered with this
cursor via registerContentObserver(ContentObserver)
.
observer | the object to unregister. |
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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.
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.
This method was deprecated
in API level 11.
Always returns null since Cursors do not support updating rows
This method was deprecated
in API level 11.
Always returns false since Cursors do not support updating rows
Subclasses must call this method when they finish committing updates to notify all observers.