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Android Reference

Picture


android.graphics

Class Picture



  • public class Picture
    extends Object
    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.
    • Field Detail

      • createdFromStream

        public final boolean createdFromStream
    • Constructor Detail

      • Picture

        public Picture()
      • Picture

        public Picture(Picture src)
        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.
    • Method Detail

      • beginRecording

        public Canvas beginRecording(int width,
                            int height)
        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.
      • endRecording

        public void endRecording()
        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.
      • getWidth

        public int getWidth()
        Get the width of the picture as passed to beginRecording. This does not reflect (per se) the content of the picture.
      • getHeight

        public int getHeight()
        Get the height of the picture as passed to beginRecording. This does not reflect (per se) the content of the picture.
      • draw

        public void draw(Canvas canvas)
        Draw this picture on the canvas. The picture may have the side effect of changing the matrix and clip of the canvas.
        Parameters:
        canvas - The picture is drawn to this canvas
      • createFromStream

        public static Picture createFromStream(InputStream stream)
        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.
        See Also:
        writeToStream(java.io.OutputStream)
      • writeToStream

        public void writeToStream(OutputStream stream)
        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.
        See Also:
        createFromStream(java.io.InputStream)
      • finalize

        protected void finalize()
                         throws Throwable
        Description copied from class: Object
        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.

        Overrides:
        finalize in class Object
        Throws:
        Throwable


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