接上文《Fresco图片框架实现原理（一）》文末

private static void initializeDrawee(
      Context context,
      @Nullable DraweeConfig draweeConfig) {
    sDraweeControllerBuilderSupplier =
        new PipelineDraweeControllerBuilderSupplier(context, draweeConfig);
    SimpleDraweeView.initialize(sDraweeControllerBuilderSupplier);  }

在研究正真的PipelineDraweeController之前，先来看看PipelineDraweeControllerBuilder在Fresco中的构造原理和过程

从上面的函数我们一个一个往里面点

image.png

PipelineDraweeControllerBuilder.png

AbstractDraweeControllerBuilder.png

SimpleDraweeControllerBuilder接口.png

这下继承关系清除了：

继承关系图.png

SimpleDraweeControllerBuilder

/**
 * Interface for simple Drawee controller builders.
 */
   simple Drawee controller builders的接口
public interface SimpleDraweeControllerBuilder {

  /** Sets the caller context. */
  设置调用者上下文
  SimpleDraweeControllerBuilder setCallerContext(Object callerContext);

  /** Sets the uri. */
  设置图像Uri
  SimpleDraweeControllerBuilder setUri(Uri uri);

  /** Sets the uri from a string. */
   设置图像Uri
  SimpleDraweeControllerBuilder setUri(@Nullable String uriString);

  /** Sets the old controller to be reused if possible. */
   
 如果有可能，设置旧的controller 用以重用
  SimpleDraweeControllerBuilder setOldController(@Nullable DraweeController oldController);

  /** Builds the specified controller. */
  构建具体的DraweeController  
  DraweeController build();
}

AbstractDraweeControllerBuilder 源码

/**
 * Base implementation for Drawee controller builders.
 */
public abstract class AbstractDraweeControllerBuilder <
    BUILDER extends AbstractDraweeControllerBuilder<BUILDER, REQUEST, IMAGE, INFO>,
    REQUEST,
    IMAGE,
    INFO>
    implements SimpleDraweeControllerBuilder {

  private static final ControllerListener<Object> sAutoPlayAnimationsListener =
      new BaseControllerListener<Object>() {
        @Override
        public void onFinalImageSet(String id, @Nullable Object info, @Nullable Animatable anim) {
          if (anim != null) {
            anim.start();
          }
        }
      };

  private static final NullPointerException NO_REQUEST_EXCEPTION =
      new NullPointerException("No image request was specified!");

  // components
  private final Context mContext;
  private final Set<ControllerListener> mBoundControllerListeners;

  // builder parameters
  private @Nullable Object mCallerContext;
  图片请求 ImageRequest
  private @Nullable REQUEST mImageRequest;
  底分辨率图片请求
  private @Nullable REQUEST mLowResImageRequest;
  多图片请求
  private @Nullable REQUEST[] mMultiImageRequests;
  private boolean mTryCacheOnlyFirst;
  数据源提供者
  private @Nullable Supplier<DataSource<IMAGE>> mDataSourceSupplier;
  private @Nullable ControllerListener<? super INFO> mControllerListener;
  private @Nullable ControllerViewportVisibilityListener mControllerViewportVisibilityListener;
  是否可点击重试
  private boolean mTapToRetryEnabled;
 是否需要自动播放动画
  private boolean mAutoPlayAnimations;
  private boolean mRetainImageOnFailure;
  private String mContentDescription;
  // old controller to reuse
  这个变量重要 重用的DraweeController ，其具体的对象，就给子类去构建
  private @Nullable DraweeController mOldController;

  private static final AtomicLong sIdCounter = new AtomicLong();

  protected AbstractDraweeControllerBuilder(
      Context context,
      Set<ControllerListener> boundControllerListeners) {
    mContext = context;
    mBoundControllerListeners = boundControllerListeners;
    init();
  }

  /** Initializes this builder. */
  private void init() {
    mCallerContext = null;
    mImageRequest = null;
    mLowResImageRequest = null;
    mMultiImageRequests = null;
    mTryCacheOnlyFirst = true;
    mControllerListener = null;
    mControllerViewportVisibilityListener = null;
    默认false
    mTapToRetryEnabled = false;
    默认不自动播放
    mAutoPlayAnimations = false;
    mOldController = null;
    mContentDescription = null;
  }
   ....其他方法
   /** Builds a regular controller. */
   构建一个常规的controller
  protected AbstractDraweeController buildController() {
    AbstractDraweeController controller = obtainController();
    controller.setRetainImageOnFailure(getRetainImageOnFailure());
    controller.setContentDescription(getContentDescription());
    controller.setControllerViewportVisibilityListener(getControllerViewportVisibilityListener());
    maybeBuildAndSetRetryManager(controller);
    maybeAttachListeners(controller);
    return controller;
  }
   /** Concrete builder classes should override this method to return a new controller. */
   这个抽象类的唯一抽象方法，又子类去实现构造具体的类
  protected abstract AbstractDraweeController obtainController();
   ...其他方法

AbstractDraweeControllerBuilder 的作用其实就是提供DraweeControllerBuilder所需要的所有成员变量，然后具体的变量值交给子类PipelineDraweeControllerBuilder去获取实现，并设置这些成员变量
PipelineDraweeControllerBuilder源码：

/**
 * Concrete implementation of ImagePipeline Drawee controller builder.
 * <p/> See {@link AbstractDraweeControllerBuilder} for more details.
 */
ImagePipeline Drawee controller builder.的具体实现

public class PipelineDraweeControllerBuilder extends AbstractDraweeControllerBuilder<
    PipelineDraweeControllerBuilder,
    ImageRequest,
    CloseableReference<CloseableImage>,
    ImageInfo> {
   
  重要的成员变量图像管道，final类型，初始化一遍不在变化，上篇文章中提到可以从ImagePipelineFactory中获取
  private final ImagePipeline mImagePipeline;

  重要的成员变量 PipelineDraweeControllerFactory是PipelineDraweeController工厂
  private final PipelineDraweeControllerFactory mPipelineDraweeControllerFactory;

  @Nullable
  private ImmutableList<DrawableFactory> mCustomDrawableFactories;

  public PipelineDraweeControllerBuilder(
      Context context,
      PipelineDraweeControllerFactory pipelineDraweeControllerFactory,
      ImagePipeline imagePipeline,
      Set<ControllerListener> boundControllerListeners) {
    super(context, boundControllerListeners);
    mImagePipeline = imagePipeline;
    mPipelineDraweeControllerFactory = pipelineDraweeControllerFactory;
  }

  @Override
  public PipelineDraweeControllerBuilder setUri(@Nullable Uri uri) {
    if (uri == null) {
      return super.setImageRequest(null);
    }
    设置图片Uri的的本质是： 用此Uri构建图像请求ImageRequest，实际上Fresco加载图片，都是构造ImageRequest
    ImageRequest imageRequest = ImageRequestBuilder.newBuilderWithSource(uri)
        .setRotationOptions(RotationOptions.autoRotateAtRenderTime())
        .build();
    return super.setImageRequest(imageRequest);
  }

  @Override
  public PipelineDraweeControllerBuilder setUri(@Nullable String uriString) {
    if (uriString == null || uriString.isEmpty()) {
      return super.setImageRequest(ImageRequest.fromUri(uriString));
    }
    return setUri(Uri.parse(uriString));
  }
  ...其他方法

  父级抽象类的抽象方法，重要方法  obtainController。
  @Override
  protected PipelineDraweeController obtainController() {
    先获取之前设置的OldController
    DraweeController oldController = getOldController();
    PipelineDraweeController controller;
    
    if (oldController instanceof PipelineDraweeController) {
     如果oldController 是PipelineDraweeController的实例 ，就在从controller的实例上修改一些需要的值，不用再实例化一个controller
      controller = (PipelineDraweeController) oldController;
      controller.initialize(
          obtainDataSourceSupplier(),
          generateUniqueControllerId(),
          getCacheKey(),
          getCallerContext(),
          mCustomDrawableFactories);
    } else {
      如果oldcontroller ==null 使用PipelineDraweeControllerFactory重新生成一个新的controller
      controller = mPipelineDraweeControllerFactory.newController(
          obtainDataSourceSupplier(),
          generateUniqueControllerId(),
          getCacheKey(),
          getCallerContext(),
          mCustomDrawableFactories);
    }
    return controller;
  }
 ...其他方法
}

这个类主要是为了设置一些builder所需要的值，并且构造除乐具体的controller。PipelineDraweeController的实例
PipelineDraweeController这个类是真正的DraweeController，这个下一章在分析。
PipelineDraweeControllerFactory是PipelineDraweeController的工厂类。用于常见controller实例。

/**
 * Default implementation of {@link PipelineDraweeControllerFactory}.
 */
public class PipelineDraweeControllerFactory {

  private Resources mResources;
  private DeferredReleaser mDeferredReleaser;
  private DrawableFactory mAnimatedDrawableFactory;
  private Executor mUiThreadExecutor;
  private MemoryCache<CacheKey, CloseableImage> mMemoryCache;
  @Nullable
  private ImmutableList<DrawableFactory> mDrawableFactories;
  @Nullable
  private Supplier<Boolean> mDebugOverlayEnabledSupplier;

  public void init(
      Resources resources,
      DeferredReleaser deferredReleaser,
      DrawableFactory animatedDrawableFactory,
      Executor uiThreadExecutor,
      MemoryCache<CacheKey, CloseableImage> memoryCache,
      @Nullable ImmutableList<DrawableFactory> drawableFactories,
      @Nullable Supplier<Boolean> debugOverlayEnabledSupplier) {
    mResources = resources;
    mDeferredReleaser = deferredReleaser;
    mAnimatedDrawableFactory = animatedDrawableFactory;
    mUiThreadExecutor = uiThreadExecutor;
    mMemoryCache = memoryCache;
    mDrawableFactories = drawableFactories;
    mDebugOverlayEnabledSupplier = debugOverlayEnabledSupplier;
  }

  public PipelineDraweeController newController(
      Supplier<DataSource<CloseableReference<CloseableImage>>> dataSourceSupplier,
      String id,
      CacheKey cacheKey,
      Object callerContext) {
    return newController(dataSourceSupplier, id, cacheKey, callerContext, null);
  }

  public PipelineDraweeController newController(
      Supplier<DataSource<CloseableReference<CloseableImage>>> dataSourceSupplier,
      String id,
      CacheKey cacheKey,
      Object callerContext,
      @Nullable ImmutableList<DrawableFactory> customDrawableFactories) {
    Preconditions.checkState(mResources != null, "init() not called");
    // Field values passed as arguments so that any subclass of PipelineDraweeControllerFactory
    // can simply override internalCreateController() and return a custom Drawee controller
    PipelineDraweeController controller = internalCreateController(
        mResources,
        mDeferredReleaser,
        mAnimatedDrawableFactory,
        mUiThreadExecutor,
        mMemoryCache,
        mDrawableFactories,
        customDrawableFactories,
        dataSourceSupplier,
        id,
        cacheKey,
        callerContext);
    if (mDebugOverlayEnabledSupplier != null) {
      controller.setDrawDebugOverlay(mDebugOverlayEnabledSupplier.get());
    }
    return controller;
  }
  内部创建PipelineDraweeController ，创建一个controller需要这么多参数，所以需要上面讲的重用controller的实例，只改变其中的几个成员变量值就行了。
  protected PipelineDraweeController internalCreateController(
      Resources resources,
      DeferredReleaser deferredReleaser,
      DrawableFactory animatedDrawableFactory,
      Executor uiThreadExecutor,
      MemoryCache<CacheKey, CloseableImage> memoryCache,
      @Nullable ImmutableList<DrawableFactory> globalDrawableFactories,
      @Nullable ImmutableList<DrawableFactory> customDrawableFactories,
      Supplier<DataSource<CloseableReference<CloseableImage>>> dataSourceSupplier,
      String id,
      CacheKey cacheKey,
      Object callerContext) {
    PipelineDraweeController controller = new PipelineDraweeController(
        resources,
        deferredReleaser,
        animatedDrawableFactory,
        uiThreadExecutor,
        memoryCache,
        dataSourceSupplier,
        id,
        cacheKey,
        callerContext,
        globalDrawableFactories);
    controller.setCustomDrawableFactories(customDrawableFactories);
    return controller;
  }
}