详解Glide4.0集成及使用注意事项

Glide 4.0由Google的各种团队内部使用，4.0被认为是内部稳定的。但外部用户可能会发现内部尚未发现的问题。因此，将此作为RC发布。如果没有发现稳定性或API中的重大问题，预计不久之后就会发布非RC版本。

一、集成

1、project gradle

 repositories {
    mavenLocal()
 }

2、app gradle

compile 'com.android.support:support-v4:25.3.1'
compile 'com.github.bumptech.glide:glide:4.0.0'
annotationProcessor 'com.github.bumptech.glide:compiler:4.0.0'

3、混淆

#glide4.0
-keep public class * implements com.bumptech.glide.module.GlideModule
-keep public class * extends com.bumptech.glide.AppGlideModule
-keep public enum com.bumptech.glide.load.resource.bitmap.ImageHeaderParser$** {
 **[] $VALUES;
 public *;
}

# for DexGuard only
-keepresourcexmlelements manifest/application/meta-data@value=GlideModule

# 从glide4.0开始，GifDrawable没有提供getDecoder()方法，
# 需要通过反射获取gifDecoder字段值，所以需要保持GifframeLoader和GifState类不被混淆
-keep class com.bumptech.glide.load.resource.gif.GifDrawable$GifState{*;}
-keep class com.bumptech.glide.load.resource.gif.GifframeLoader {*;}

4、在4.0中不用像3.X需要在AndroidManifest.xml配置GlideModule，而是通过注解继承AppGlideModule的子类来配置。

@GlideModule
public class GlideConfiguration extends AppGlideModule {
  @Override
  public void applyOptions(Context context, GlideBuilder builder) {
    //自定义缓存目录，磁盘缓存给150M 另外一种设置缓存方式
    builder.setDiskCache(new InternalCacheDiskCacheFactory(context, "GlideImgCache", 150 * 1024 * 1024));
    //配置图片缓存格式 默认格式为8888
    builder.setDefaultRequestOptions(RequestOptions.formatOf(DecodeFormat.PREFER_ARGB_8888));
    ViewTarget.setTagId(R.id.glide_tag_id);
  }

  
  @Override
  public boolean isManifestParsingEnabled() {
    return false;
  }

}

二、使用注意事项

1、使用GlideApp代替Glide，asBitmap、asGif、asDrawable、asFile都要放到load之前（glide3.7.0都是要在load之后调用）。

public static void loadImg(Context context,String url, ImageView imageView){
    GlideApp.with(context)
 .asBitmap()
 .load(url)
 .placeholder(R.drawable.placeholder) //设置资源加载过程中的占位符
 .into(imageView);
  }

2、占位符.placeholder(R.drawable.placeholder)不能用.9图，占位图片和加载的目标图片会同时显示，只是目标图片会先显示缩略图，然后显示正常。fallback和error还没测试过，有兴趣的可以测试看看。

3、加载gif图时，若调用dontAnimate()移除所有动画，gif就会加载失败。

4、计算gif播放一次的动画时长。

glide 3.7.0你可以这样获取动画时长：

 public void loadGif(Context context,ImageView mIvGif,int url){
    Glide.with(context)
 .load(url)
 .listener(new RequestListener() {
   @Override
   public boolean onException(Exception e, Integer model, Target target, boolean isFirstResource) {
     return false;
   }

   @Override
   public boolean onResourceReady(GlideDrawable resource, Integer model, Target target, boolean isFromMemoryCache, boolean isFirstResource) {
     try {
int duration = 0;
GifDrawable gifDrawable = (GifDrawable) resource;
GifDecoder decoder = gifDrawable.getDecoder();
for (int i = 0; i < gifDrawable.getframeCount(); i++) {
  duration += decoder.getDelay(i);
}
Log.e("Glide3.7.0","gif播放一次动画时长duration:"+duration);
     } catch (Throwable e) {
     }
     return false;
   }
 })
 .into(new GlideDrawableImageViewTarget(mIvGif, 1));
  }

glide4.0中GifDrawable没有提供getDecoder()方法并且还去掉了decoder这个成员变量。除此之外，glide4.0还去掉了GlideDrawableImageViewTarget类，那我们该如何来计算gif播放一次的时长呢？只能从源码中找答案了。

（1）寻找decoder

glide3.7.0 GifDrawable中我们可以发现decoder最终于会传入GifframeLoader类中并赋值给gifDecoder变量。

//源码
//glide 3.7.0 GifDrawable.java
 GifDrawable(GifState state) {
    if (state == null) {
      throw new NullPointerException("GifState must not be null");
    }

    this.state = state;
    this.decoder = new GifDecoder(state.bitmapProvider);
    this.paint = new Paint();
    decoder.setData(state.gifHeader, state.data);
    frameLoader = new GifframeLoader(state.context, this, decoder, state.targetWidth, state.targetHeight);
    frameLoader.setframeTransformation(state.frameTransformation);
  }

//glide 3.7.0 GifframeLoader.java
private final GifDecoder gifDecoder;//私有属性
public GifframeLoader(Context context, frameCallback callback, GifDecoder gifDecoder, int width, int height) {
    this(callback, gifDecoder, null,
 getRequestBuilder(context, gifDecoder, width, height, Glide.get(context).getBitmapPool()));
 }

  GifframeLoader(frameCallback callback, GifDecoder gifDecoder, Handler handler,
      GenericRequestBuilder requestBuilder) {
    if (handler == null) {
      handler = new Handler(Looper.getMainLooper(), new frameLoaderCallback());
    }
    this.callback = callback;
    //看这里
    this.gifDecoder = gifDecoder;
    this.handler = handler;
    this.requestBuilder = requestBuilder;
  }

glide4.0 GifDrawable类的构造中我们可以看到有一个gifDecoder的参数，这个参数的解释是解码器用于解码GIF数据（The decoder to use to decode GIF data）。继续看这个构造，发现gifDecoder最终也是被传到GifframeLoader类中并赋值给gifDecoder变量。所以glide3.7.0中的decoder其实就是4.0中的gifDecoder。

//源码
//glide 4.0 GifDrawable.java
private final GifState state;

 public GifDrawable(Context context, GifDecoder gifDecoder, BitmapPool bitmapPool,
   Transformation frameTransformation, int targetframeWidth, int targetframeHeight,
   Bitmap firstframe) {
  this(
    new GifState(
      bitmapPool,
      new GifframeLoader(
 // TODO(b/27524013): Factor out this call to Glide.get()
 Glide.get(context),
 gifDecoder,
 targetframeWidth,
 targetframeHeight,
 frameTransformation,
 firstframe)));
 }

//glide4.0 GifframeLoader.java
private final GifDecoder gifDecoder;//私有属性
 public GifframeLoader(
   Glide glide,
   GifDecoder gifDecoder,
   int width,
   int height,
   Transformation transformation,
   Bitmap firstframe) {
  this(
    glide.getBitmapPool(),
    Glide.with(glide.getContext()),
    gifDecoder,
    null ,
    getRequestBuilder(Glide.with(glide.getContext()), width, height),
    transformation,
    firstframe);
 }

 @SuppressWarnings("PMD.ConstructorCallsOverridableMethod")
 GifframeLoader(
   BitmapPool bitmapPool,
   RequestManager requestManager,
   GifDecoder gifDecoder,
   Handler handler,
   RequestBuilder requestBuilder,
   Transformation transformation,
   Bitmap firstframe) {
  this.requestManager = requestManager;
  if (handler == null) {
   handler = new Handler(Looper.getMainLooper(), new frameLoaderCallback());
  }
  this.bitmapPool = bitmapPool;
  this.handler = handler;
  this.requestBuilder = requestBuilder;

  //看这里
  this.gifDecoder = gifDecoder;

  setframeTransformation(transformation, firstframe);
 }

（2）获取decoder

从上面Glide4.0的GifDrawable构造中可以看到gifDecoder被传递到GifframeLoader中赋值给私有属性gifDecoder;，而GifframeLoader又被传入GifState中并被赋值给它的成员变量frameLoader，那要怎么获取frameLoader？

从源码中，可以看到GifDrawable提供了getConstantState()方法来获取state变量（这个变量的类型就是GifState），但是GifState并没有get方法获取frameLoader，frameLoader对象中的gifDecoder也是私有，也没有提供get方法来获取，那么我们只能通过反射来获取了。

//源码
//glide4.0 GifDrawable.java
private final GifState state;
 @Override
 public ConstantState getConstantState() {
  return state;
 }
 static class GifState extends ConstantState {
  static final int GRAVITY = Gravity.FILL;
  final BitmapPool bitmapPool;
  final GifframeLoader frameLoader;

  public GifState(BitmapPool bitmapPool, GifframeLoader frameLoader) {
   this.bitmapPool = bitmapPool;
   this.frameLoader = frameLoader;
  }

  @Override
  public Drawable newDrawable(Resources res) {
   return newDrawable();
  }

  @Override
  public Drawable newDrawable() {
   return new GifDrawable(this);
  }

  @Override
  public int getChangingConfigurations() {
   return 0;
  }
 }

通过反射来获取获取decoder

.listener(new RequestListener() {
   @Override
   public boolean onLoadFailed(@Nullable GlideException e, Object model, Target target, boolean isFirstResource) {
     return false;
   }

   @Override
   public boolean onResourceReady(GifDrawable gifDrawable, Object model, Target target, DataSource dataSource, boolean isFirstResource) {
     try {
int duration = 0;
// 计算动画时长
//GifDecoder decoder = gifDrawable.getDecoder();//4.0开始没有这个方法了
Drawable.ConstantState state = gifDrawable.getConstantState();
if(state!=null){
  //不能混淆GifframeLoader和GifState类
  Object gifframeLoader = getValue(state,"frameLoader");
  if(gifframeLoader!=null){
    Object decoder = getValue(gifframeLoader,"gifDecoder");
    if(decoder!=null && decoder instanceof GifDecoder){
      for (int i = 0; i < gifDrawable.getframeCount(); i++) {
 duration += ((GifDecoder) decoder).getDelay(i);
      }
    }
  }
  Log.e("Glide4.0","gif播放动画时长duration:"+duration);
}
     } catch (Throwable e) {
     }
     return false;
   }
 })



  public static Object getValue(Object object, String fieldName) throws Exception {
    if (object == null) {
      return null;
    }
    if (TextUtils.isEmpty(fieldName)) {
      return null;
    }
    Field field = null;
    Class clazz = object.getClass();
    for (; clazz != Object.class; clazz = clazz.getSuperclass()) {
      try {
 field = clazz.getDeclaredField(fieldName);
 field.setAccessible(true);
 return field.get(object);
      } catch (Exception e) {
 //这里甚么都不要做！并且这里的异常必须这样写，不能抛出去。
 //如果这里的异常打印或者往外抛，则就不会执行clazz = clazz.getSuperclass(),最后就不会进入到父类中了
      }
    }

    return null;
  }

(3)设置gif循环播放次数

glide4.0中没有GlideDrawableImageViewTarget类，那么怎么设置循环播放次数呢？

从glide3.7.0源码可以发现GlideDrawableImageViewTarget是通过GlideDrawable的setLoopCount方法来设置循环播放次数的，查看setLoopCount具体实现地方是在GifDrawable，所以这里调用的其实是GifDrawable的setLoopCount方法。glide4.0中没有GlideDrawable类和GlideDrawableImageViewTarget类，但是仍然有GifDrawable类，并且onResourceReady方法中第一个参数就是GifDrawable，所以可以直接调用GifDrawable的setLoopCount(loopCount)来设置播放次数。

//源码
//3.7.0 GlideDrawableImageViewTarget.java
 public GlideDrawableImageViewTarget(ImageView view, int maxLoopCount) {
    super(view);
    this.maxLoopCount = maxLoopCount;
 }
  @Override
  public void onResourceReady(GlideDrawable resource, GlideAnimation animation) {
    if (!resource.isAnimated()) {
      //TODO: Try to generalize this to other sizes/shapes.
      // This is a dirty hack that tries to make loading square thumbnails and then square full images less costly
      // by forcing both the smaller thumb and the larger version to have exactly the same intrinsic dimensions.
      // If a drawable is replaced in an ImageView by another drawable with different intrinsic dimensions,
      // the ImageView requests a layout. Scrolling rapidly while replacing thumbs with larger images triggers
      // lots of these calls and causes significant amounts of jank.
      float viewRatio = view.getWidth() / (float) view.getHeight();
      float drawableRatio = resource.getIntrinsicWidth() / (float) resource.getIntrinsicHeight();
      if (Math.abs(viewRatio - 1f) <= SQUARE_RATIO_MARGIN
   && Math.abs(drawableRatio - 1f) <= SQUARE_RATIO_MARGIN) {
 resource = new SquaringDrawable(resource, view.getWidth());
      }
    }
    super.onResourceReady(resource, animation);
    this.resource = resource;
    /
//源码 RequestOptions.java
private DiskCacheStrategy diskCacheStrategy = DiskCacheStrategy.AUTOMATIC;

7、占位符、错误图片设置

glide4.0 若into中设置的是target，占位符（placeholder、error）需要在回调中再次设置，否则无效。

 public static void loadImg(String url, ImageView imageView) {
    //into中用Target，占位符（placeholder、error）需要在回调中设置
    GlideApp.with(FanhuanApplication.getInstance().getApplication())
 .asBitmap()
 .load(url)
 .placeholder(drawbleId) //设置资源加载过程中的占位符
 .fallback(drawbleId)
 .error(drawbleId)
 .diskCacheStrategy(DiskCacheStrategy.ALL)
 .into(new SimpleTarget() {
   @Override
   public void onResourceReady(Bitmap resource, Transition transition) {
     imageView.setImageBitmap(resource);   
  }

   @Override
   public void onLoadFailed(@Nullable Drawable errorDrawable) {
     super.onLoadFailed(errorDrawable);
      if(errorDrawable!=null){
imageView.setImageDrawable(errorDrawable);
     }  
   }

   @Override
   public void onLoadStarted(@Nullable Drawable placeholder) {
     super.onLoadStarted(placeholder);
     if(placeholder!=null){
imageView.setImageDrawable(placeholder);
     }
   }
 });
  }

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