| java.lang.Object | |
| ↳ | android.graphics.Picture |
A picture records drawing calls (via the canvas returned by beginRecording) and can then play them back (via picture.draw(canvas) or canvas.drawPicture). The picture's contents can also be written to a stream, and then later restored to a new picture (via writeToStream / createFromStream). For most content (esp. text, lines, rectangles), drawing a sequence from a picture can be faster than the equivalent API calls, since the picture performs its playback without incurring any java-call overhead.
| Public Constructors | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Create a picture by making a copy of what has already been recorded in
src.
| |||||||||||
| Public Methods | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
To record a picture, call beginRecording() and then draw into the Canvas
that is returned.
| |||||||||||
Create a new picture (already recorded) from the data in the stream.
| |||||||||||
Draw this picture on the canvas.
| |||||||||||
Call endRecording when the picture is built.
| |||||||||||
Get the height of the picture as passed to beginRecording.
| |||||||||||
Get the width of the picture as passed to beginRecording.
| |||||||||||
Write the picture contents to a stream.
| |||||||||||
| Protected Methods | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Invoked when the garbage collector has detected that this instance is no longer reachable.
| |||||||||||
|
[Expand]
Inherited Methods | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
From class
java.lang.Object
| |||||||||||
Create a picture by making a copy of what has already been recorded in src. The contents of src are unchanged, and if src changes later, those changes will not be reflected in this picture.
To record a picture, call beginRecording() and then draw into the Canvas that is returned. Nothing we appear on screen, but all of the draw commands (e.g. drawRect(...)) will be recorded. To stop recording, call endRecording(). At this point the Canvas that was returned must no longer be referenced, and nothing should be drawn into it.
Create a new picture (already recorded) from the data in the stream. This data was generated by a previous call to writeToStream(). Note: a picture created from an input stream cannot be replayed on a hardware accelerated canvas.
Draw this picture on the canvas. The picture may have the side effect of changing the matrix and clip of the canvas.
| canvas | The picture is drawn to this canvas |
|---|
Call endRecording when the picture is built. After this call, the picture may be drawn, but the canvas that was returned by beginRecording must not be referenced anymore. This is automatically called if Picture.draw() or Canvas.drawPicture() is called.
Get the height of the picture as passed to beginRecording. This does not reflect (per se) the content of the picture.
Get the width of the picture as passed to beginRecording. This does not reflect (per se) the content of the picture.
Write the picture contents to a stream. The data can be used to recreate the picture in this or another process by calling createFromStream. Note: a picture created from an input stream cannot be replayed on a hardware accelerated canvas.
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.
| Throwable |
|---|