Choreographer

Class Overview

Coordinates the timing of animations, input and drawing.

The choreographer receives timing pulses (such as vertical synchronization) from the display subsystem then schedules work to occur as part of rendering the next display frame.

Applications typically interact with the choreographer indirectly using higher level abstractions in the animation framework or the view hierarchy. Here are some examples of things you can do using the higher-level APIs.

• To post an animation to be processed on a regular time basis synchronized with display frame rendering, use start() .
• To post a Runnable to be invoked once at the beginning of the next display frame, use postOnAnimation(Runnable) .
• To post a Runnable to be invoked once at the beginning of the next display frame after a delay, use postOnAnimationDelayed(Runnable, long) .
• To post a call to invalidate() to occur once at the beginning of the next display frame, use postInvalidateOnAnimation() or postInvalidateOnAnimation(int, int, int, int) .
• To ensure that the contents of a View scroll smoothly and are drawn in sync with display frame rendering, do nothing. This already happens automatically. onDraw(Canvas) will be called at the appropriate time.

However, there are a few cases where you might want to use the functions of the choreographer directly in your application. Here are some examples.

• If your application does its rendering in a different thread, possibly using GL, or does not use the animation framework or view hierarchy at all and you want to ensure that it is appropriately synchronized with the display, then use postFrameCallback(Choreographer.FrameCallback) .
• ... and that's about it.

Each Looper thread has its own choreographer. Other threads can post callbacks to run on the choreographer but they will run on the Looper to which the choreographer belongs.

Summary

[Expand] Inherited Methods

From class java.lang.Object Object clone () Creates and returns a copy of this Object . boolean equals ( Object o) Compares this instance with the specified object and indicates if they are equal. void finalize () Invoked when the garbage collector has detected that this instance is no longer reachable. final Class <?> getClass () Returns the unique instance of Class that represents this object's class. int hashCode () Returns an integer hash code for this object. final void notify () Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up. final void notifyAll () Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up. String toString () Returns a string containing a concise, human-readable description of this object. final void wait () Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object. final void wait (long millis, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires. final void wait (long millis) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.