Glide 4.8.0 版本源码分析-1

简单使用

   Glide.with(this).load(url).into(imageView);

首先看with

   @NonNull
  public static RequestManager with(@NonNull FragmentActivity activity) {
    return getRetriever(activity).get(activity);
  }

  @NonNull
  private static RequestManagerRetriever getRetriever(@Nullable Context context) {
    // Context could be null for other reasons (ie the user passes in null), but in practice it will
    // only occur due to errors with the Fragment lifecycle.
    Preconditions.checkNotNull(
        context,
        "You cannot start a load on a not yet attached View or a Fragment where getActivity() "
            + "returns null (which usually occurs when getActivity() is called before the Fragment "
            + "is attached or after the Fragment is destroyed).");
   // glide的get方法         
    return Glide.get(context).getRequestManagerRetriever();
  }
// DCL 单例模式
  public static Glide get(@NonNull Context context) {
    if (glide == null) {
      synchronized (Glide.class) {
        if (glide == null) {
          checkAndInitializeGlide(context);
        }
      }
    }

    return glide;
  }
	
  private static void checkAndInitializeGlide(@NonNull Context context) {
    // In the thread running initGlide(), one or more classes may call Glide.get(context).
    // Without this check, those calls could trigger infinite recursion.
    if (isInitializing) {
      throw new IllegalStateException("You cannot call Glide.get() in registerComponents(),"
          + " use the provided Glide instance instead");
    }
    isInitializing = true;
    // 初始化对象
    initializeGlide(context);
    isInitializing = false;
  }
//glide对象的创建 建造者模式构建
//glideModule对象主要用于配置各种参数的，
private static void initializeGlide(@NonNull Context context, @NonNull GlideBuilder builder) {
    Context applicationContext = context.getApplicationContext();
    GeneratedAppGlideModule annotationGeneratedModule = getAnnotationGeneratedGlideModules();
    List<com.bumptech.glide.module.GlideModule> manifestModules = Collections.emptyList();
    if (annotationGeneratedModule == null || annotationGeneratedModule.isManifestParsingEnabled()) {
      manifestModules = new ManifestParser(applicationContext).parse();
    }

    if (annotationGeneratedModule != null
        && !annotationGeneratedModule.getExcludedModuleClasses().isEmpty()) {
      Set<Class<?>> excludedModuleClasses =
          annotationGeneratedModule.getExcludedModuleClasses();
      Iterator<com.bumptech.glide.module.GlideModule> iterator = manifestModules.iterator();
      while (iterator.hasNext()) {
        com.bumptech.glide.module.GlideModule current = iterator.next();
        if (!excludedModuleClasses.contains(current.getClass())) {
          continue;
        }
        if (Log.isLoggable(TAG, Log.DEBUG)) {
          Log.d(TAG, "AppGlideModule excludes manifest GlideModule: " + current);
        }
        iterator.remove();
      }
    }

    if (Log.isLoggable(TAG, Log.DEBUG)) {
      for (com.bumptech.glide.module.GlideModule glideModule : manifestModules) {
        Log.d(TAG, "Discovered GlideModule from manifest: " + glideModule.getClass());
      }
    }

    RequestManagerRetriever.RequestManagerFactory factory =
        annotationGeneratedModule != null
            ? annotationGeneratedModule.getRequestManagerFactory() : null;
    builder.setRequestManagerFactory(factory);
    for (com.bumptech.glide.module.GlideModule module : manifestModules) {
      module.applyOptions(applicationContext, builder);
    }
    if (annotationGeneratedModule != null) {
      annotationGeneratedModule.applyOptions(applicationContext, builder);
    }
	//build方法
    Glide glide = builder.build(applicationContext);
    for (com.bumptech.glide.module.GlideModule module : manifestModules) {
      module.registerComponents(applicationContext, glide, glide.registry);
    }
    if (annotationGeneratedModule != null) {
      annotationGeneratedModule.registerComponents(applicationContext, glide, glide.registry);
    }
    applicationContext.registerComponentCallbacks(glide);
    Glide.glide = glide;
 }
进入build方法
 Glide build(@NonNull Context context) {
    if (sourceExecutor == null) {
    //执行网络操作的线程池对象
      sourceExecutor = GlideExecutor.newSourceExecutor();
    }

    if (diskCacheExecutor == null) {
    //disk 磁盘缓存线程池对象
      diskCacheExecutor = GlideExecutor.newDiskCacheExecutor();
    }

    if (animationExecutor == null) {
    // 执行动画的线程池对象
      animationExecutor = GlideExecutor.newAnimationExecutor();
    }

    if (memorySizeCalculator == null) {
    // 执行内存计算的对象
      memorySizeCalculator = new MemorySizeCalculator.Builder(context).build();
    }

    if (connectivityMonitorFactory == null) {
    // 监听网络状态的连接工厂对象
      connectivityMonitorFactory = new DefaultConnectivityMonitorFactory();
    }

    if (bitmapPool == null) {
      int size = memorySizeCalculator.getBitmapPoolSize();
      if (size > 0) {
      //内部使用链表存储的map 缓存对象
        bitmapPool = new LruBitmapPool(size);
      } else {
        bitmapPool = new BitmapPoolAdapter();
      }
    }

    if (arrayPool == null) {
    //类似linkedHashmap的缓存对象
      arrayPool = new LruArrayPool(memorySizeCalculator.getArrayPoolSizeInBytes());
    }

    if (memoryCache == null) {
    //内存缓存的处理
      memoryCache = new LruResourceCache(memorySizeCalculator.getMemoryCacheSize());
    }

    if (diskCacheFactory == null) {
   // 磁盘缓存处理
      diskCacheFactory = new InternalCacheDiskCacheFactory(context);
    }

    if (engine == null) {
    // 负责加载资源和取消资源加载
      engine =
          new Engine(
              memoryCache,
              diskCacheFactory,
              diskCacheExecutor,
              sourceExecutor,
              GlideExecutor.newUnlimitedSourceExecutor(),
              GlideExecutor.newAnimationExecutor(),
              isActiveResourceRetentionAllowed);
    }

    RequestManagerRetriever requestManagerRetriever =
        new RequestManagerRetriever(requestManagerFactory);

//创建glide对象
    return new Glide(
        context,
        engine,
        memoryCache,
        bitmapPool,
        arrayPool,
        requestManagerRetriever,
        connectivityMonitorFactory,
        logLevel,
        defaultRequestOptions.lock(),
        defaultTransitionOptions);
  }
}

with: 多个重载方法，传入不同的上下文,不同的上下文有不同的生命周期，根据上下文对象生命周期的方法来去管理glide的生命周期。

    public static RequestManager with(FragmentActivity activity) {
        RequestManagerRetriever retriever = RequestManagerRetriever.get();
        // 注意get方法
        return retriever.get(activity);
    }
 	public static RequestManager with(Activity activity) {
   
    public static RequestManager with(FragmentActivity activity) {
     
    public static RequestManager with(android.app.Fragment fragment) {
      
 	public static RequestManager with(Fragment fragment) {
       


		//get方法，以 参数activity为例。

	     @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    public RequestManager get(Activity activity) {
    	不是主线程
        if (Util.isOnBackgroundThread() || Build.VERSION.SDK_INT < Build.VERSION_CODES.HONEYCOMB) {
        	// 通过不同的context 获取RequestManager
            return get(activity.getApplicationContext());
        } else {
            assertNotDestroyed(activity);
            android.app.FragmentManager fm = activity.getFragmentManager();
            //通过fragmentmanager处理
            return fragmentGet(activity, fm);
        }
    }

    public RequestManager get(Context context) {
        if (context == null) {
            throw new IllegalArgumentException("You cannot start a load on a null Context");
        } else if (Util.isOnMainThread() && !(context instanceof Application)) {
            if (context instanceof FragmentActivity) {
                return get((FragmentActivity) context);
            } else if (context instanceof Activity) {
                return get((Activity) context);
            } else if (context instanceof ContextWrapper) {
                return get(((ContextWrapper) context).getBaseContext());
            }
        }
	
        return getApplicationManager(context);
    }


    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    RequestManager fragmentGet(Context context, android.app.FragmentManager fm) {
    	//从管理器获取fragment,否则创建fragmetn。用它来监听activity的
    	//生命周期状态，便于glide回收资源。
        RequestManagerFragment current = getRequestManagerFragment(fm);
        
        RequestManager requestManager = current.getRequestManager();
        if (requestManager == null) {
            requestManager = new RequestManager(context, current.getLifecycle(), current.getRequestManagerTreeNode());
            current.setRequestManager(requestManager);
        }
        return requestManager;
    }