Picture
public
class
Picture
extends Object
java.lang.Object | |
↳ | android.graphics.Picture |
A Picture records drawing calls (via the canvas returned by beginRecording)
and can then play them back into Canvas (via Picture#draw(Canvas)
or
Canvas#drawPicture(Picture)
).For most content (e.g. 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
method-call overhead.
Note: Prior to API level 23 a picture cannot be replayed on a hardware accelerated canvas.
Summary
Public constructors | |
---|---|
Picture()
Creates an empty picture that is ready to record. |
|
Picture(Picture src)
Create a picture by making a copy of what has already been recorded in src. |
Public methods | |
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Canvas
|
beginRecording(int width, int height)
To record a picture, call beginRecording() and then draw into the Canvas that is returned. |
void
|
draw(Canvas canvas)
Draw this picture on the canvas. |
void
|
endRecording()
Call endRecording when the picture is built. |
int
|
getHeight()
Get the height of the picture as passed to beginRecording. |
int
|
getWidth()
Get the width of the picture as passed to beginRecording. |
boolean
|
requiresHardwareAcceleration()
Indicates whether or not this Picture contains recorded commands that only work when drawn to a hardware-accelerated canvas. |
Protected methods | |
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void
|
finalize()
Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. |
Inherited methods | |
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Public constructors
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.
Parameters | |
---|---|
src |
Picture |
Public methods
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. Canvas#drawRect(Rect, Paint)
) will be recorded.
To stop recording, call endRecording(). After endRecording() the Canvas
that was returned must no longer be used, and nothing should be drawn
into it.
Parameters | |
---|---|
width |
int |
height |
int |
Returns | |
---|---|
Canvas |
This value cannot be null . |
draw
public void draw (Canvas canvas)
Draw this picture on the canvas.
Prior to Build.VERSION_CODES.LOLLIPOP
, this call could
have the side effect of changing the matrix and clip of the canvas
if this picture had imbalanced saves/restores.
Note: This forces the picture to internally call
Picture#endRecording()
in order to prepare for playback.
Parameters | |
---|---|
canvas |
Canvas : The picture is drawn to this canvas
This value cannot be null . |
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 used anymore. This is automatically called if Picture#draw
or Canvas#drawPicture(Picture)
is called.
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.
Returns | |
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int |
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.
Returns | |
---|---|
int |
requiresHardwareAcceleration
public boolean requiresHardwareAcceleration ()
Indicates whether or not this Picture contains recorded commands that only work when
drawn to a hardware-accelerated canvas. If this returns true then this Picture can only
be drawn to another Picture or to a Canvas where canvas.isHardwareAccelerated() is true.
Note this value is only updated after recording has finished by a call to
endRecording()
. Prior to that it will be the default value of false.
Returns | |
---|---|
boolean |
true if the Picture can only be drawn to a hardware-accelerated canvas, false otherwise. |
Protected methods
finalize
protected void finalize ()
Called by the garbage collector on an object when garbage collection
determines that there are no more references to the object.
A subclass overrides the finalize
method to dispose of
system resources or to perform other cleanup.
The general contract of finalize
is that it is invoked
if and when the Java virtual
machine has determined that there is no longer any
means by which this object can be accessed by any thread that has
not yet died, except as a result of an action taken by the
finalization of some other object or class which is ready to be
finalized. The finalize
method may take any action, including
making this object available again to other threads; the usual purpose
of finalize
, however, is to perform cleanup actions before
the object is irrevocably discarded. For example, the finalize method
for an object that represents an input/output connection might perform
explicit I/O transactions to break the connection before the object is
permanently discarded.
The finalize
method of class Object
performs no
special action; it simply returns normally. Subclasses of
Object
may override this definition.
The Java programming language does not guarantee which thread will
invoke the finalize
method for any given object. It is
guaranteed, however, that the thread that invokes finalize will not
be holding any user-visible synchronization locks when finalize is
invoked. If an uncaught exception is thrown by the finalize method,
the exception is ignored and finalization of that object terminates.
After the finalize
method has been invoked for an object, no
further action is taken until the Java virtual machine has again
determined that there is no longer any means by which this object can
be accessed by any thread that has not yet died, including possible
actions by other objects or classes which are ready to be finalized,
at which point the object may be discarded.
The finalize
method is never invoked more than once by a Java
virtual machine for any given object.
Any exception thrown by the finalize
method causes
the finalization of this object to be halted, but is otherwise
ignored.
Throws | |
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Throwable |