Glide 源码 4.12.0

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

with()

with() 方法是 Glide 类中的一组静态方法，可以传入 Activity Fragment Context View。每个 with()方法都是通过 getRetriever() 得到 RequestManagerRetriever 然后调用 RequestManagerRetriever 的 get() 方法获取 RequestManager 对象

RequestManagerRetriever 的 get() 和 with() 类似，有很多个方法，可以传入 Context Activity Fragment 等参数。这些可以分两种情况，即传入 Application 类型的参数，和非 Application 类型的参数。

传入 Application 参数的情况 :

在传入 Context 参数的方法中，通过判断 context 是否是 Application 并且是否在主线程，符合条件则直接通过 getApplicationManager() 来获取一个 RequestManager 对象，否则判断 context 类型调用其他 get() 方法。
因为 Application 对象的生命周期即应用程序的生命周期，因此 Glide 并不需要做什么特殊的处理，它自动就是和应用程序的生命周期是同步的，如果应用程序关闭的话，Glide 的加载也会同时终止。

传入非Application 参数的情况 :

如果在非主线程当中使用的 Glide 都当成传入 Application 参数的情况来处理。
会向当前的 Activity 当中添加一个隐藏的 Fragment 。
Glide 通过添加隐藏 Fragment 监听生命周期。例如 Activity 被销毁，Fragment 监听到，就可以停止图片加载。（或者有什么办法直接知道 Activity 的生命周期？）

RequestManager 实现 LifecycleListener 接口去监听生命周期，作出相应的处理

简单的说就是为了得到一个 RequestManager 对象，然后 Glide 会根据传入 with() 方法的参数来确定图片加载的生命周期

Glide 中的 with() ，getRetriever()

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  @NonNull
  public static RequestManager with(@NonNull Context context) {
    return getRetriever(context).get(context);
  }
  @NonNull
  public static RequestManager with(@NonNull Activity activity) {
    return getRetriever(activity).get(activity);
  }
  @NonNull
  public static RequestManager with(@NonNull FragmentActivity activity) {
    return getRetriever(activity).get(activity);
  }
  @NonNull
  public static RequestManager with(@NonNull Fragment fragment) {
    return getRetriever(fragment.getContext()).get(fragment);
  }
  @SuppressWarnings("deprecation")
  @Deprecated
  @NonNull
  public static RequestManager with(@NonNull android.app.Fragment fragment) {
    return getRetriever(fragment.getActivity()).get(fragment);
  }
  @NonNull
  public static RequestManager with(@NonNull View view) {
    return getRetriever(view.getContext()).get(view);
  }
  @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).");
    return Glide.get(context).getRequestManagerRetriever();
  }
  @NonNull
  public RequestManagerRetriever getRequestManagerRetriever() {
    return requestManagerRetriever;
  }

RequestManagerRetriever 的部分 get() 和添加 fragment 的地方

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  @NonNull
  public RequestManager get(@NonNull Context context) {
    if (context == null) {
      throw new IllegalArgumentException("You cannot start a load on a null Context");
      //判断是否在主线程；是否是 Application 类型，如果是直接通过 getApplicationManager() 来获取一个 RequestManager 对象
    } else if (Util.isOnMainThread() && !(context instanceof Application)) {
      //如果在非主线程当中使用的 Glide 都当成传入 Application 参数的情况来处理。否则才接着判断 context 类型
      if (context instanceof FragmentActivity) {
        return get((FragmentActivity) context);
      } else if (context instanceof Activity) {
        return get((Activity) context);
      } else if (context instanceof ContextWrapper
          // Only unwrap a ContextWrapper if the baseContext has a non-null application context.
          // Context#createPackageContext may return a Context without an Application instance,
          // in which case a ContextWrapper may be used to attach one.
          && ((ContextWrapper) context).getBaseContext().getApplicationContext() != null) {
        return get(((ContextWrapper) context).getBaseContext());
      }
    }

    return getApplicationManager(context);
  }

  @NonNull
  public RequestManager get(@NonNull FragmentActivity activity) {
    if (Util.isOnBackgroundThread()) {
      return get(activity.getApplicationContext());
    } else {
      assertNotDestroyed(activity);
      frameWaiter.registerSelf(activity);
      FragmentManager fm = activity.getSupportFragmentManager();
      return supportFragmentGet(activity, fm, /*parentHint=*/ null, isActivityVisible(activity));
    }
  }

  @NonNull
  public RequestManager get(@NonNull Fragment fragment) {
    Preconditions.checkNotNull(
        fragment.getContext(),
        "You cannot start a load on a fragment before it is attached or after it is destroyed");
    if (Util.isOnBackgroundThread()) {
      return get(fragment.getContext().getApplicationContext());
    } else {
      // In some unusual cases, it's possible to have a Fragment not hosted by an activity. There's
      // not all that much we can do here. Most apps will be started with a standard activity. If
      // we manage not to register the first frame waiter for a while, the consequences are not
      // catastrophic, we'll just use some extra memory.
      if (fragment.getActivity() != null) {
        frameWaiter.registerSelf(fragment.getActivity());
      }
      FragmentManager fm = fragment.getChildFragmentManager();
      return supportFragmentGet(fragment.getContext(), fm, fragment, fragment.isVisible());
    }
  }

  @SuppressWarnings("deprecation")
  @NonNull
  public RequestManager get(@NonNull Activity activity) {
    if (Util.isOnBackgroundThread()) {
      return get(activity.getApplicationContext());
    } else if (activity instanceof FragmentActivity) {
      return get((FragmentActivity) activity);
    } else {
      assertNotDestroyed(activity);
      frameWaiter.registerSelf(activity);
      android.app.FragmentManager fm = activity.getFragmentManager();
      return fragmentGet(activity, fm, /*parentHint=*/ null, isActivityVisible(activity));
    }
  }

  @SuppressWarnings("deprecation")
  @NonNull
  public RequestManager get(@NonNull View view) {
    if (Util.isOnBackgroundThread()) {
      return get(view.getContext().getApplicationContext());
    }

    Preconditions.checkNotNull(view);
    Preconditions.checkNotNull(
        view.getContext(), "Unable to obtain a request manager for a view without a Context");
    Activity activity = findActivity(view.getContext());
    // The view might be somewhere else, like a service.
    if (activity == null) {
      return get(view.getContext().getApplicationContext());
    }

    // Support Fragments.
    // Although the user might have non-support Fragments attached to FragmentActivity, searching
    // for non-support Fragments is so expensive pre O and that should be rare enough that we
    // prefer to just fall back to the Activity directly.
    if (activity instanceof FragmentActivity) {
      Fragment fragment = findSupportFragment(view, (FragmentActivity) activity);
      return fragment != null ? get(fragment) : get((FragmentActivity) activity);
    }

    // Standard Fragments.
    android.app.Fragment fragment = findFragment(view, activity);
    if (fragment == null) {
      return get(activity);
    }
    return get(fragment);
  }
  //activity 调用
  @SuppressWarnings({"deprecation", "DeprecatedIsStillUsed"})
  @Deprecated
  @NonNull
  private RequestManager fragmentGet(
      @NonNull Context context,
      @NonNull android.app.FragmentManager fm,
      @Nullable android.app.Fragment parentHint,
      boolean isParentVisible) {
        //这个方法中添加 fragment 往下看
    RequestManagerFragment current = getRequestManagerFragment(fm, parentHint);
    RequestManager requestManager = current.getRequestManager();
    if (requestManager == null) {
      // TODO(b/27524013): Factor out this Glide.get() call.
      Glide glide = Glide.get(context);
      requestManager =
          factory.build(
              glide, current.getGlideLifecycle(), current.getRequestManagerTreeNode(), context);
      // This is a bit of hack, we're going to start the RequestManager, but not the
      // corresponding Lifecycle. It's safe to start the RequestManager, but starting the
      // Lifecycle might trigger memory leaks. See b/154405040
      if (isParentVisible) {
        requestManager.onStart();
      }
      current.setRequestManager(requestManager);
    }
    return requestManager;
  }  
  @SuppressWarnings("deprecation")
  @NonNull
  private RequestManagerFragment getRequestManagerFragment(
      @NonNull final android.app.FragmentManager fm, @Nullable android.app.Fragment parentHint) {
    RequestManagerFragment current = (RequestManagerFragment) fm.findFragmentByTag(FRAGMENT_TAG);
    if (current == null) {
      current = pendingRequestManagerFragments.get(fm);
      if (current == null) {
        current = new RequestManagerFragment();
        current.setParentFragmentHint(parentHint);
        pendingRequestManagerFragments.put(fm, current);
        //添加 fragment
        fm.beginTransaction().add(current, FRAGMENT_TAG).commitAllowingStateLoss();
        handler.obtainMessage(ID_REMOVE_FRAGMENT_MANAGER, fm).sendToTarget();
      }
    }
    return current;
  }
  //Fragment 和 FragmentActivity 调用
  @NonNull
  private RequestManager supportFragmentGet(
      @NonNull Context context,
      @NonNull FragmentManager fm,
      @Nullable Fragment parentHint,
      boolean isParentVisible) {
        //这个方法中添加 fragment 往下看
    SupportRequestManagerFragment current = getSupportRequestManagerFragment(fm, parentHint);
    RequestManager requestManager = current.getRequestManager();
    if (requestManager == null) {
      // TODO(b/27524013): Factor out this Glide.get() call.
      Glide glide = Glide.get(context);
      requestManager =
          factory.build(
              glide, current.getGlideLifecycle(), current.getRequestManagerTreeNode(), context);
      // This is a bit of hack, we're going to start the RequestManager, but not the
      // corresponding Lifecycle. It's safe to start the RequestManager, but starting the
      // Lifecycle might trigger memory leaks. See b/154405040
      if (isParentVisible) {
        requestManager.onStart();
      }
      current.setRequestManager(requestManager);
    }
    return requestManager;
  }
  @NonNull
  private SupportRequestManagerFragment getSupportRequestManagerFragment(
      @NonNull final FragmentManager fm, @Nullable Fragment parentHint) {
    SupportRequestManagerFragment current =
        (SupportRequestManagerFragment) fm.findFragmentByTag(FRAGMENT_TAG);
    if (current == null) {
      current = pendingSupportRequestManagerFragments.get(fm);
      if (current == null) {
        current = new SupportRequestManagerFragment();
        current.setParentFragmentHint(parentHint);
        pendingSupportRequestManagerFragments.put(fm, current);
        //添加 fragment
        fm.beginTransaction().add(current, FRAGMENT_TAG).commitAllowingStateLoss();
        handler.obtainMessage(ID_REMOVE_SUPPORT_FRAGMENT_MANAGER, fm).sendToTarget();
      }
    }
    return current;
  }

load()

with() 返回 RequestManager 调用 load()，load() 也有多个，都是调用 asDrawable().load(xxx) 返回 RequestBuilder<Drawable>。

asDrawable() 返回 new RequestBuilder 并把 Drawable.class 作为参数传入 RequestBuilder 构造方法，最终在 RequestBuilder 执行 load() 方法。

RequestBuilder 中 load() 也有多个，都是根据上一步 asDrawable().load(xxx) 中的 xxx 参数类型，调用 loadGeneric(xxx)。

loadGeneric(xxx) 内容如下

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@NonNull
  private RequestBuilder<TranscodeType> loadGeneric(@Nullable Object model) {
    //如果开启isAutoCloneEnabled调用，默认关
    if (isAutoCloneEnabled()) {
      return clone().loadGeneric(model);
    }
    //赋值
    this.model = model;
    //告诉 RequestBuilder model 已经赋值，可以进行下一步
    isModelSet = true;
    //如果没有 lock 就返回 BaseRequestOptions
    return selfOrThrowIfLocked();
  }

apply()

loadGeneric() 最终返回 BaseRequestOptions ，apply() 方法在 RequestBuilder 中如下，重写了父类 BaseRequestOptions 的 apply() ，在 BaseRequestOptions 的 apply() 中最后和 loadGeneric() 一样，返回了 selfOrThrowIfLocked() 。apply() 可以设置一些参数，如错误时加载图片，占位图等。

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@NonNull
  @CheckResult
  @Override
  public RequestBuilder<TranscodeType> apply(@NonNull BaseRequestOptions<?> requestOptions) {
    Preconditions.checkNotNull(requestOptions);
    return super.apply(requestOptions);
  }

into()

RequestBuilder 调用 into() 设置数据到 Imageview 。这块代码有点多，包括请求失败，占位图，图片长宽等，就不全贴出来了。RequestBuilder 经过 buildRequest 一系列的调用最终 obtainRequest 方法进入到 SingleRequest 。

可以根据状态看执行相关操作，在构造方法中是 status = Status.PENDING; 在 onSizeReady 方法中 status = Status.RUNNING;

可以选择看 model 被做了什么，在 onSizeReady 有个 engine.load 方法把 model 等数据传入 Engine 然后在 waitForExistingOrStartNewJob 中被放入 DecodeJob<R> ，再由 EngineJob 处理 DecodeJob。

DecodeJob 实现了 Runable ， FetcherReadyCallback 等接口。在 DecodeJob 中 model 被赋值给 currentData 变量， run 方法和重写的 onDataFetcherReady 都会调用到 decodeFromRetrievedData()，在 decodeFromRetrievedData() 中调用 decodeFromData(currentFetcher, currentData, currentDataSource) ，在 decodeFromData 中调用 decodeFromFetcher(data, dataSource) ，最后调用 runLoadPath(data, dataSource, path)。

有点晕，直接着用 debug 的方式看 runLoadPath 方法，data 先是会被处理成 rewinder ，最终在 decodeResourceWithList 方法中通过 decoder.decode 获取到 InputStream 然后转成 Bitmap

大致流程如下：

RequestBuilder 中的 into 方法调用 buildRequest 由 obtainRequest 方法进入到 SingleRequest
SingleRequest 的 onSizeReady 中 engine.load 开始处理数据
Engine 运行 DecodeJob 做各种操作
完成后释放资源

SingleRequest 有多个工作状态，按流程执行
DataSource 数据来源，有本地，远程，缓存等
DataFetcher 数据获取接口？
DataRewinder 像是用来把要显示的图片资源接收为流数据？
DataRewinderRegistry 可以获取 DataRewinder

以下源码按顺序阅读

RequestBuilder 的 into() 和 obtainRequest

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@NonNull
  public ViewTarget<ImageView, TranscodeType> into(@NonNull ImageView view) {
    Util.assertMainThread();
    Preconditions.checkNotNull(view);

    BaseRequestOptions<?> requestOptions = this;
    if (!requestOptions.isTransformationSet()
        && requestOptions.isTransformationAllowed()
        && view.getScaleType() != null) {
      // Clone in this method so that if we use this RequestBuilder to load into a View and then
      // into a different target, we don't retain the transformation applied based on the previous
      // View's scale type.
      switch (view.getScaleType()) {
        case CENTER_CROP:
          requestOptions = requestOptions.clone().optionalCenterCrop();
          break;
        case CENTER_INSIDE:
          requestOptions = requestOptions.clone().optionalCenterInside();
          break;
        case FIT_CENTER:
        case FIT_START:
        case FIT_END:
          requestOptions = requestOptions.clone().optionalFitCenter();
          break;
        case FIT_XY:
          requestOptions = requestOptions.clone().optionalCenterInside();
          break;
        case CENTER:
        case MATRIX:
        default:
          // Do nothing.
      }
    }

    return into(
        glideContext.buildImageViewTarget(view, transcodeClass),
        /*targetListener=*/ null,
        requestOptions,
        Executors.mainThreadExecutor());
  }
  //上面 return into 进到下面这个 into
  private <Y extends Target<TranscodeType>> Y into(
      @NonNull Y target,
      @Nullable RequestListener<TranscodeType> targetListener,
      BaseRequestOptions<?> options,
      Executor callbackExecutor) {
    Preconditions.checkNotNull(target);
    //之前在 loadGeneric() 设置为 true
    if (!isModelSet) {
      throw new IllegalArgumentException("You must call #load() before calling #into()");
    }
    //  buildRequest 一系列的调用最终会调用到下面的 obtainRequest
    Request request = buildRequest(target, targetListener, options, callbackExecutor);

    Request previous = target.getRequest();
    if (request.isEquivalentTo(previous)
        && !isSkipMemoryCacheWithCompletePreviousRequest(options, previous)) {
      // If the request is completed, beginning again will ensure the result is re-delivered,
      // triggering RequestListeners and Targets. If the request is failed, beginning again will
      // restart the request, giving it another chance to complete. If the request is already
      // running, we can let it continue running without interruption.
      if (!Preconditions.checkNotNull(previous).isRunning()) {
        // Use the previous request rather than the new one to allow for optimizations like skipping
        // setting placeholders, tracking and un-tracking Targets, and obtaining View dimensions
        // that are done in the individual Request.
        previous.begin();
      }
      return target;
    }

    requestManager.clear(target);
    target.setRequest(request);
    requestManager.track(target, request);

    return target;
  }
  
  private Request obtainRequest(
      Object requestLock,
      Target<TranscodeType> target,
      RequestListener<TranscodeType> targetListener,
      BaseRequestOptions<?> requestOptions,
      RequestCoordinator requestCoordinator,
      TransitionOptions<?, ? super TranscodeType> transitionOptions,
      Priority priority,
      int overrideWidth,
      int overrideHeight,
      Executor callbackExecutor) {
    return SingleRequest.obtain(
        context,
        glideContext,
        requestLock,
        model,
        transcodeClass,
        requestOptions,
        overrideWidth,
        overrideHeight,
        priority,
        target,
        targetListener,
        requestListeners,
        requestCoordinator,
        glideContext.getEngine(),
        transitionOptions.getTransitionFactory(),
        callbackExecutor);
  }

SingleRequest 部分代码，由 obtainRequest 方法进入到 SingleRequest

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  public static <R> SingleRequest<R> obtain(
      Context context,
      GlideContext glideContext,
      Object requestLock,
      Object model,
      Class<R> transcodeClass,
      BaseRequestOptions<?> requestOptions,
      int overrideWidth,
      int overrideHeight,
      Priority priority,
      Target<R> target,
      RequestListener<R> targetListener,
      @Nullable List<RequestListener<R>> requestListeners,
      RequestCoordinator requestCoordinator,
      Engine engine,
      TransitionFactory<? super R> animationFactory,
      Executor callbackExecutor) {
    return new SingleRequest<>(
        context,
        glideContext,
        requestLock,
        model,
        transcodeClass,
        requestOptions,
        overrideWidth,
        overrideHeight,
        priority,
        target,
        targetListener,
        requestListeners,
        requestCoordinator,
        engine,
        animationFactory,
        callbackExecutor);
  }

@Override
  public void begin() {
    synchronized (requestLock) {
      assertNotCallingCallbacks();
      stateVerifier.throwIfRecycled();
      startTime = LogTime.getLogTime();
      if (model == null) {
        if (Util.isValidDimensions(overrideWidth, overrideHeight)) {
          width = overrideWidth;
          height = overrideHeight;
        }
        // Only log at more verbose log levels if the user has set a fallback drawable, because
        // fallback Drawables indicate the user expects null models occasionally.
        int logLevel = getFallbackDrawable() == null ? Log.WARN : Log.DEBUG;
        onLoadFailed(new GlideException("Received null model"), logLevel);
        return;
      }

      if (status == Status.RUNNING) {
        throw new IllegalArgumentException("Cannot restart a running request");
      }

      // If we're restarted after we're complete (usually via something like a notifyDataSetChanged
      // that starts an identical request into the same Target or View), we can simply use the
      // resource and size we retrieved the last time around and skip obtaining a new size, starting
      // a new load etc. This does mean that users who want to restart a load because they expect
      // that the view size has changed will need to explicitly clear the View or Target before
      // starting the new load.
      if (status == Status.COMPLETE) {
        onResourceReady(
            resource, DataSource.MEMORY_CACHE, /* isLoadedFromAlternateCacheKey= */ false);
        return;
      }

      // Restarts for requests that are neither complete nor running can be treated as new requests
      // and can run again from the beginning.

      status = Status.WAITING_FOR_SIZE;
      if (Util.isValidDimensions(overrideWidth, overrideHeight)) {
        onSizeReady(overrideWidth, overrideHeight);
      } else {
        target.getSize(this);
      }

      if ((status == Status.RUNNING || status == Status.WAITING_FOR_SIZE)
          && canNotifyStatusChanged()) {
        target.onLoadStarted(getPlaceholderDrawable());
      }
      if (IS_VERBOSE_LOGGABLE) {
        logV("finished run method in " + LogTime.getElapsedMillis(startTime));
      }
    }
  }

  @Override
  public void onSizeReady(int width, int height) {
    stateVerifier.throwIfRecycled();
    synchronized (requestLock) {
      if (IS_VERBOSE_LOGGABLE) {
        logV("Got onSizeReady in " + LogTime.getElapsedMillis(startTime));
      }
      if (status != Status.WAITING_FOR_SIZE) {
        return;
      }
      status = Status.RUNNING;

      float sizeMultiplier = requestOptions.getSizeMultiplier();
      this.width = maybeApplySizeMultiplier(width, sizeMultiplier);
      this.height = maybeApplySizeMultiplier(height, sizeMultiplier);

      if (IS_VERBOSE_LOGGABLE) {
        logV("finished setup for calling load in " + LogTime.getElapsedMillis(startTime));
      }
      loadStatus =
          engine.load(
              glideContext,
              model,
              requestOptions.getSignature(),
              this.width,
              this.height,
              requestOptions.getResourceClass(),
              transcodeClass,
              priority,
              requestOptions.getDiskCacheStrategy(),
              requestOptions.getTransformations(),
              requestOptions.isTransformationRequired(),
              requestOptions.isScaleOnlyOrNoTransform(),
              requestOptions.getOptions(),
              requestOptions.isMemoryCacheable(),
              requestOptions.getUseUnlimitedSourceGeneratorsPool(),
              requestOptions.getUseAnimationPool(),
              requestOptions.getOnlyRetrieveFromCache(),
              this,
              callbackExecutor);

      // This is a hack that's only useful for testing right now where loads complete synchronously
      // even though under any executor running on any thread but the main thread, the load would
      // have completed asynchronously.
      if (status != Status.RUNNING) {
        loadStatus = null;
      }
      if (IS_VERBOSE_LOGGABLE) {
        logV("finished onSizeReady in " + LogTime.getElapsedMillis(startTime));
      }
    }
  }

Engine 部分代码，由 SingleRequest 的 onSizeReady 中 engine.load 进入

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  public <R> LoadStatus load(
      GlideContext glideContext,
      Object model,
      Key signature,
      int width,
      int height,
      Class<?> resourceClass,
      Class<R> transcodeClass,
      Priority priority,
      DiskCacheStrategy diskCacheStrategy,
      Map<Class<?>, Transformation<?>> transformations,
      boolean isTransformationRequired,
      boolean isScaleOnlyOrNoTransform,
      Options options,
      boolean isMemoryCacheable,
      boolean useUnlimitedSourceExecutorPool,
      boolean useAnimationPool,
      boolean onlyRetrieveFromCache,
      ResourceCallback cb,
      Executor callbackExecutor) {
    long startTime = VERBOSE_IS_LOGGABLE ? LogTime.getLogTime() : 0;

    EngineKey key =
        keyFactory.buildKey(
            model,
            signature,
            width,
            height,
            transformations,
            resourceClass,
            transcodeClass,
            options);

    EngineResource<?> memoryResource;
    synchronized (this) {
      memoryResource = loadFromMemory(key, isMemoryCacheable, startTime);

      if (memoryResource == null) {
        return waitForExistingOrStartNewJob(
            glideContext,
            model,
            signature,
            width,
            height,
            resourceClass,
            transcodeClass,
            priority,
            diskCacheStrategy,
            transformations,
            isTransformationRequired,
            isScaleOnlyOrNoTransform,
            options,
            isMemoryCacheable,
            useUnlimitedSourceExecutorPool,
            useAnimationPool,
            onlyRetrieveFromCache,
            cb,
            callbackExecutor,
            key,
            startTime);
      }
    }

    // Avoid calling back while holding the engine lock, doing so makes it easier for callers to
    // deadlock.
    cb.onResourceReady(
        memoryResource, DataSource.MEMORY_CACHE, /* isLoadedFromAlternateCacheKey= */ false);
    return null;
  }

  private <R> LoadStatus waitForExistingOrStartNewJob(
      GlideContext glideContext,
      Object model,
      Key signature,
      int width,
      int height,
      Class<?> resourceClass,
      Class<R> transcodeClass,
      Priority priority,
      DiskCacheStrategy diskCacheStrategy,
      Map<Class<?>, Transformation<?>> transformations,
      boolean isTransformationRequired,
      boolean isScaleOnlyOrNoTransform,
      Options options,
      boolean isMemoryCacheable,
      boolean useUnlimitedSourceExecutorPool,
      boolean useAnimationPool,
      boolean onlyRetrieveFromCache,
      ResourceCallback cb,
      Executor callbackExecutor,
      EngineKey key,
      long startTime) {

    EngineJob<?> current = jobs.get(key, onlyRetrieveFromCache);
    if (current != null) {
      current.addCallback(cb, callbackExecutor);
      if (VERBOSE_IS_LOGGABLE) {
        logWithTimeAndKey("Added to existing load", startTime, key);
      }
      return new LoadStatus(cb, current);
    }

    EngineJob<R> engineJob =
        engineJobFactory.build(
            key,
            isMemoryCacheable,
            useUnlimitedSourceExecutorPool,
            useAnimationPool,
            onlyRetrieveFromCache);

    DecodeJob<R> decodeJob =
        decodeJobFactory.build(
            glideContext,
            model,
            key,
            signature,
            width,
            height,
            resourceClass,
            transcodeClass,
            priority,
            diskCacheStrategy,
            transformations,
            isTransformationRequired,
            isScaleOnlyOrNoTransform,
            onlyRetrieveFromCache,
            options,
            engineJob);

    jobs.put(key, engineJob);

    engineJob.addCallback(cb, callbackExecutor);
    engineJob.start(decodeJob);

    if (VERBOSE_IS_LOGGABLE) {
      logWithTimeAndKey("Started new load", startTime, key);
    }
    return new LoadStatus(cb, engineJob);
  }

DecodeJob 部分代码，由 engineJob.start(decodeJob) 进入

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  //实现 Runnable 的 run 方法
  @Override
  public void run() {
    // This should be much more fine grained, but since Java's thread pool implementation silently
    // swallows all otherwise fatal exceptions, this will at least make it obvious to developers
    // that something is failing.
    GlideTrace.beginSectionFormat("DecodeJob#run(model=%s)", model);
    // Methods in the try statement can invalidate currentFetcher, so set a local variable here to
    // ensure that the fetcher is cleaned up either way.
    DataFetcher<?> localFetcher = currentFetcher;
    try {
      if (isCancelled) {
        notifyFailed();
        return;
      }
      runWrapped();
    } catch (CallbackException e) {
      // If a callback not controlled by Glide throws an exception, we should avoid the Glide
      // specific debug logic below.
      throw e;
    } catch (Throwable t) {
      // Catch Throwable and not Exception to handle OOMs. Throwables are swallowed by our
      // usage of .submit() in GlideExecutor so we're not silently hiding crashes by doing this. We
      // are however ensuring that our callbacks are always notified when a load fails. Without this
      // notification, uncaught throwables never notify the corresponding callbacks, which can cause
      // loads to silently hang forever, a case that's especially bad for users using Futures on
      // background threads.
      if (Log.isLoggable(TAG, Log.DEBUG)) {
        Log.d(
            TAG,
            "DecodeJob threw unexpectedly" + ", isCancelled: " + isCancelled + ", stage: " + stage,
            t);
      }
      // When we're encoding we've already notified our callback and it isn't safe to do so again.
      if (stage != Stage.ENCODE) {
        throwables.add(t);
        notifyFailed();
      }
      if (!isCancelled) {
        throw t;
      }
      throw t;
    } finally {
      // Keeping track of the fetcher here and calling cleanup is excessively paranoid, we call
      // close in all cases anyway.
      if (localFetcher != null) {
        localFetcher.cleanup();
      }
      GlideTrace.endSection();
    }
  }

  private void runWrapped() {
    switch (runReason) {
      case INITIALIZE:
        stage = getNextStage(Stage.INITIALIZE);
        currentGenerator = getNextGenerator();
        runGenerators();
        break;
      case SWITCH_TO_SOURCE_SERVICE:
        runGenerators();
        break;
      case DECODE_DATA:
        decodeFromRetrievedData();
        break;
      default:
        throw new IllegalStateException("Unrecognized run reason: " + runReason);
    }
  }

  private void decodeFromRetrievedData() {
    if (Log.isLoggable(TAG, Log.VERBOSE)) {
      logWithTimeAndKey(
          "Retrieved data",
          startFetchTime,
          "data: "
              + currentData
              + ", cache key: "
              + currentSourceKey
              + ", fetcher: "
              + currentFetcher);
    }
    Resource<R> resource = null;
    try {
      resource = decodeFromData(currentFetcher, currentData, currentDataSource);
    } catch (GlideException e) {
      e.setLoggingDetails(currentAttemptingKey, currentDataSource);
      throwables.add(e);
    }
    if (resource != null) {
      notifyEncodeAndRelease(resource, currentDataSource, isLoadingFromAlternateCacheKey);
    } else {
      runGenerators();
    }
  }

  private <Data> Resource<R> decodeFromData(
      DataFetcher<?> fetcher, Data data, DataSource dataSource) throws GlideException {
    try {
      if (data == null) {
        return null;
      }
      long startTime = LogTime.getLogTime();
      Resource<R> result = decodeFromFetcher(data, dataSource);
      if (Log.isLoggable(TAG, Log.VERBOSE)) {
        logWithTimeAndKey("Decoded result " + result, startTime);
      }
      return result;
    } finally {
      fetcher.cleanup();
    }
  }

  private <Data> Resource<R> decodeFromFetcher(Data data, DataSource dataSource)
      throws GlideException {
    LoadPath<Data, ?, R> path = decodeHelper.getLoadPath((Class<Data>) data.getClass());
    return runLoadPath(data, dataSource, path);
  }

  private <Data, ResourceType> Resource<R> runLoadPath(
      Data data, DataSource dataSource, LoadPath<Data, ResourceType, R> path)
      throws GlideException {
    Options options = getOptionsWithHardwareConfig(dataSource);
    DataRewinder<Data> rewinder = glideContext.getRegistry().getRewinder(data);
    try {
      // ResourceType in DecodeCallback below is required for compilation to work with gradle.
      return path.load(
          rewinder, options, width, height, new DecodeCallback<ResourceType>(dataSource));
    } finally {
      rewinder.cleanup();
    }
  }

LoadPath 部分代码

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  public Resource<Transcode> load(
      DataRewinder<Data> rewinder,
      @NonNull Options options,
      int width,
      int height,
      DecodePath.DecodeCallback<ResourceType> decodeCallback)
      throws GlideException {
    List<Throwable> throwables = Preconditions.checkNotNull(listPool.acquire());
    try {
      return loadWithExceptionList(rewinder, options, width, height, decodeCallback, throwables);
    } finally {
      listPool.release(throwables);
    }
  }

  private Resource<Transcode> loadWithExceptionList(
      DataRewinder<Data> rewinder,
      @NonNull Options options,
      int width,
      int height,
      DecodePath.DecodeCallback<ResourceType> decodeCallback,
      List<Throwable> exceptions)
      throws GlideException {
    Resource<Transcode> result = null;
    //noinspection ForLoopReplaceableByForEach to improve perf
    for (int i = 0, size = decodePaths.size(); i < size; i++) {
      DecodePath<Data, ResourceType, Transcode> path = decodePaths.get(i);
      try {
        result = path.decode(rewinder, width, height, options, decodeCallback);
      } catch (GlideException e) {
        exceptions.add(e);
      }
      if (result != null) {
        break;
      }
    }

    if (result == null) {
      throw new GlideException(failureMessage, new ArrayList<>(exceptions));
    }

    return result;
  }

DecodePath 部分代码

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  public Resource<Transcode> decode(
      DataRewinder<DataType> rewinder,
      int width,
      int height,
      @NonNull Options options,
      DecodeCallback<ResourceType> callback)
      throws GlideException {
    Resource<ResourceType> decoded = decodeResource(rewinder, width, height, options);
    Resource<ResourceType> transformed = callback.onResourceDecoded(decoded);
    return transcoder.transcode(transformed, options);
  }

文章目录

with()

load()

apply()

into()