需求：

近段时间正好有一个需求，是要实现Gif图只加载播放一次，并且要在Gif播放完毕后回调给系统的需求。

因为Glide 3系列的API与4系列还是有很大差距的，这里我们针对Glide 3.x和Glide 4.x的分别进行实现方案的说明。

解决方案：

在Glide3.x的解决方案：

Glide.with(this).load("xxxurl").listener(new RequestListener<Integer, GlideDrawable>() {@Overridepublic boolean onException(Exception arg0, Integer arg1,Target<GlideDrawable> arg2, boolean arg3) {return false;}@Overridepublic boolean onResourceReady(GlideDrawable resource,Integer model, Target<GlideDrawable> target,boolean isFromMemoryCache, boolean isFirstResource) {// 计算动画时长GifDrawable drawable = (GifDrawable) resource;GifDecoder decoder = drawable.getDecoder();for (int i = 0; i < drawable.getFrameCount(); i++) {duration += decoder.getDelay(i);}//发送延时消息，通知动画结束handler.sendEmptyMessageDelayed(MESSAGE_SUCCESS,duration);return false;}}) //仅仅加载一次gif动画.into(new GlideDrawableImageViewTarget(imageview, 1));

在Glide4.x的解决方案：

在Glide4.x中，我们没法再直接获取GifDecoder对象了，原因是因为GlideDrawable不再提供这个方法了。需要采用反射的方法获取到GifDecoder变量，具体代码如下：

public static void loadOneTimeGif(Context context, Object model, final ImageView imageView, final GifListener gifListener) {Glide.with(context).asGif().load(model).listener(new RequestListener<GifDrawable>() {@Overridepublic boolean onLoadFailed(@Nullable GlideException e, Object model, Target<GifDrawable> target, boolean isFirstResource) {return false;}@Overridepublic boolean onResourceReady(GifDrawable resource, Object model, Target<GifDrawable> target, DataSource dataSource, boolean isFirstResource) {try {Field gifStateField = GifDrawable.class.getDeclaredField("state");gifStateField.setAccessible(true);Class gifStateClass = Class.forName("com.bumptech.glide.load.resource.gif.GifDrawable$GifState");Field gifFrameLoaderField = gifStateClass.getDeclaredField("frameLoader");gifFrameLoaderField.setAccessible(true);Class gifFrameLoaderClass = Class.forName("com.bumptech.glide.load.resource.gif.GifFrameLoader");Field gifDecoderField = gifFrameLoaderClass.getDeclaredField("gifDecoder");gifDecoderField.setAccessible(true);Class gifDecoderClass = Class.forName("com.bumptech.glide.gifdecoder.GifDecoder");Object gifDecoder = gifDecoderField.get(gifFrameLoaderField.get(gifStateField.get(resource)));Method getDelayMethod = gifDecoderClass.getDeclaredMethod("getDelay", int.class);getDelayMethod.setAccessible(true);//设置只播放一次resource.setLoopCount(1);//获得总帧数int count = resource.getFrameCount();int delay = 0;for (int i = 0; i < count; i++) {//计算每一帧所需要的时间进行累加delay += (int) getDelayMethod.invoke(gifDecoder, i);}imageView.postDelayed(new Runnable() {@Overridepublic void run() {if (gifListener != null) {gifListener.gifPlayComplete();}}}, delay);} catch (NoSuchFieldException e) {e.printStackTrace();}catch (ClassNotFoundException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();} catch (NoSuchMethodException e) {e.printStackTrace();} catch (InvocationTargetException e) {e.printStackTrace();}return false;}}).into(imageView);}/*** Gif播放完毕回调*/public interface GifListener {void gifPlayComplete();}

同时，因为采用的是反射，所以别忘了proguard-rules.pro中加上Glide的反混淆规则：

#Glide
-keep class com.bumptech.glide.** {*;}