Android AnimationDrawable并知道动画何时结束

Question

我想用几个图像文件制作一个动画，为此，AnimationDrawable效果很好。但是，我需要知道动画何时开始以及何时结束（即添加诸如Animation.AnimationListener之类的侦听器）。搜索答案后，我很难过AnimationDrawable不支持侦听器。有谁知道如何在Android上使用侦听器创建逐帧图像动画？

Answer 1

我需要知道一次完成的AnimationDrawable何时完成，而不必将AnimationDrawable子类化，因为我必须以XML设置动画列表。我写了这个课，并在Gingerbread和ICS上进行了测试。它可以很容易地扩展以在每个帧上提供回调。

/**

 * Provides a callback when a non-looping {@link AnimationDrawable} completes its animation sequence. More precisely,

 * {@link #onAnimationComplete()} is triggered when {@link View#invalidateDrawable(Drawable)} has been called on the

 * last frame.

 * 

 * @author Benedict Lau

 */

public abstract class AnimationDrawableCallback implements Callback {

    /**

     * The last frame of {@link Drawable} in the {@link AnimationDrawable}.

     */

    private Drawable mLastFrame;

    /**

     * The client's {@link Callback} implementation. All calls are proxied to this wrapped {@link Callback}

     * implementation after intercepting the events we need.

     */

    private Callback mWrappedCallback;

    /**

     * Flag to ensure that {@link #onAnimationComplete()} is called only once, since

     * {@link #invalidateDrawable(Drawable)} may be called multiple times.

     */

    private boolean mIsCallbackTriggered = false;

    /**

     * 

     * @param animationDrawable

     *            the {@link AnimationDrawable}.

     * @param callback

     *            the client's {@link Callback} implementation. This is usually the {@link View} the has the

     *            {@link AnimationDrawable} as background.

     */

    public AnimationDrawableCallback(AnimationDrawable animationDrawable, Callback callback) {

        mLastFrame = animationDrawable.getFrame(animationDrawable.getNumberOfFrames() - 1);

        mWrappedCallback = callback;

    }

    @Override

    public void invalidateDrawable(Drawable who) {

        if (mWrappedCallback != null) {

            mWrappedCallback.invalidateDrawable(who);

        }

        if (!mIsCallbackTriggered && mLastFrame != null && mLastFrame.equals(who.getCurrent())) {

            mIsCallbackTriggered = true;

            onAnimationComplete();

        }

    }

    @Override

    public void scheduleDrawable(Drawable who, Runnable what, long when) {

        if (mWrappedCallback != null) {

            mWrappedCallback.scheduleDrawable(who, what, when);

        }

    }

    @Override

    public void unscheduleDrawable(Drawable who, Runnable what) {

        if (mWrappedCallback != null) {

            mWrappedCallback.unscheduleDrawable(who, what);

        }

    }

    //

    // Public methods.

    //

    /**

     * Callback triggered when {@link View#invalidateDrawable(Drawable)} has been called on the last frame, which marks

     * the end of a non-looping animation sequence.

     */

    public abstract void onAnimationComplete();

}

这是使用方法。

AnimationDrawable countdownAnimation = (AnimationDrawable) mStartButton.getBackground();

countdownAnimation.setCallback(new AnimationDrawableCallback(countdownAnimation, mStartButton) {

    @Override

    public void onAnimationComplete() {

        // TODO Do something.

    }

});

countdownAnimation.start();

Answer 2

通过重写AnimationDrawable类中的selectDrawable方法，可以轻松跟踪动画结束。完整的代码如下：

public class AnimationDrawable2 extends AnimationDrawable

{

    public interface IAnimationFinishListener

    {

        void onAnimationFinished();

    }

    private boolean finished = false;

    private IAnimationFinishListener animationFinishListener;

    public IAnimationFinishListener getAnimationFinishListener()

    {

        return animationFinishListener;

    }

    public void setAnimationFinishListener(IAnimationFinishListener animationFinishListener)

    {

        this.animationFinishListener = animationFinishListener;

    }

    @Override

    public boolean selectDrawable(int idx)

    {

        boolean ret = super.selectDrawable(idx);

        if ((idx != 0) && (idx == getNumberOfFrames() - 1))

        {

            if (!finished)

            {

                finished = true;

                if (animationFinishListener != null) animationFinishListener.onAnimationFinished();

            }

        }

        return ret;

    }

}