Android 自定义 View 播放 Gif 动画，ffmpeg 音视频开发实战 6 下载

public void setGifResource(int movieResourceId, OnPlayListener onPlayListener) {mOnPlayListener = onPlayListener;movie = Movie.decodeStream(getResources().openRawResource(movieResourceId));if (movie == null) {//如果 movie 为空，那么就不是 gif 文件，尝试转换为 bitmap 显示 Bitmap bitmap = BitmapFactory.decodeResource(getResources(), movieResourceId);if (bitmap != null) {setImageBitmap(bitmap);return;}}movieDuration = movie.duration() == 0 ? DEFAULT_DURATION : movie.duration();requestLayout();}

调用 requestLayout 重新计算 View 大小，并重新绘制。如果是 gif 格式则 View 宽高等于 movie 的宽高，不是则调用父类的测量方法。

@Overrideprotected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {if (movie != null) {int movieWidth = movie.width();int movieHeight = movie.height();setMeasuredDimension(movieWidth, movieHeight);} else {super.onMeasure(widthMeasureSpec, heightMeasureSpec);}}

开始播放，其实就是调用 invalidate 从而调用 onDraw 方法就行 UI 绘制：

public void play(int counts) {this.counts = counts;reset();if (mOnPlayListener != null) {mOnPlayListener.onPlayStart();}invalidate();}

不断调用 onDraw 方法来绘制 Gif 当前时间的图片帧（同样需要判断是否是 gif 格式，不是则调用父类的绘制方法）：

@Overrideprotected void onDraw(Canvas canvas) {if (movie != null) {if (!mPaused && hasStart) {drawMovieFrame(canvas);invalidateView();} else {drawMovieFrame(canvas);}} else {super.onDraw(canvas);}}/**

• 画出 gif 帧*/private void drawMovieFrame(Canvas canvas) {movie.setTime(getCurrentFrameTime());movie.draw(canvas, 0.0f, 0.0f);}

最核心的方法就是计算当前时间需要绘制处于 movie 中的对应时间的图片帧。

private int getCurrentFrameTime() {if (movieDuration == 0)return 0;//因为有暂停，所以需要减去暂停时间 long

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now = SystemClock.uptimeMillis() - dealyTime;int nowCount = (int) ((now - mMovieStart) / movieDuration);if (counts != -1 && nowCount >= counts) {hasStart = false;if (mOnPlayListener != null) {mOnPlayListener.onPlayEnd();}}int currentTime = (int) ((now - mMovieStart) % movieDuration);int percent = currentTime * 100 / movieDuration;if (mOnPlayListener != null && hasStart) {mOnPlayListener.onPlaying(percent);}return currentTime;}

暂停 Gif 播放：

public void pause() {if (movie != null && !mPaused && hasStart) {mPaused = true;invalidate();mMoviePauseTime = SystemClock.uptimeMillis();if (mOnPlayListener != null) {mOnPlayListener.onPlayPause(true);}} else {if (mOnPlayListener != null) {mOnPlayListener.onPlayPause(false);}}}

继续 Gif 播放：

if (mPaused && mMoviePauseTime > 0) {mPaused = false;dealyTime = dealyTime + SystemClock.uptimeMillis() - mMoviePauseTime;invalidate();if (mOnPlayListener != null) {mOnPlayListener.onPlayRestart();}}

经过这些处理，我们就能更好地控制 Gif 的播放流程了。下面简单看下成品图：

进阶