Fresco 源码分析(二) Fresco客户端与服务端交互(2) Fresco.initializeDrawee()分析续

4.2.1.2 Fresco.initializeDrawee()的过程续

继续上篇博客的分析Fresco.initializeDrawee()

    sDraweeControllerBuilderSupplier = new PipelineDraweeControllerBuilderSupplier(context);

    SimpleDraweeView.initialize(sDraweeControllerBuilderSupplier);

初始化了一个sDraweeControllerBuilderSupplier
将此sDraweeControllerBuilderSupplier用于初始化SimpleDraweeView

还是老的分析思路：一步一步分析

4.2.1.2.1 sDraweeControllerBuilderSupplier初始化的过程

public PipelineDraweeControllerBuilderSupplier(Context context) {

    this(context, ImagePipelineFactory.getInstance());

  }

  public PipelineDraweeControllerBuilderSupplier(

      Context context,

      ImagePipelineFactory imagePipelineFactory) {

    this(context, imagePipelineFactory, null);

  }

  public PipelineDraweeControllerBuilderSupplier(

      Context context,

      ImagePipelineFactory imagePipelineFactory,

      Set<ControllerListener> boundControllerListeners) {

    mContext = context;

    mImagePipeline = imagePipelineFactory.getImagePipeline();

    mPipelineDraweeControllerFactory = new PipelineDraweeControllerFactory(

        context.getResources(),

        DeferredReleaser.getInstance(),

        imagePipelineFactory.getAnimatedDrawableFactory(),

        UiThreadImmediateExecutorService.getInstance());

    mBoundControllerListeners = boundControllerListeners;

  }

构造方法，相互调用，总结过程

获取到了ImagePipelineFactory的实例，经过查看源码，只是将Fresco第一步初始化中的ImagePipelineFactory,获取到了这个实例,这里采用了单例的形式
获取到ImagePipleline，并且保存在这个Supplier中,这个里面代码看似只有这么几行，但是包涵的内容很多，还是先从广度看，然后再从深度看（这个方面作为遗留的Q2，一会儿再看）

*** ImagePipelineFactory.getImagePipeline（）源码 ***

public ImagePipeline getImagePipeline() {

if (mImagePipeline == null) {

mImagePipeline =

new ImagePipeline(

getProducerSequenceFactory(),

mConfig.getRequestListeners(),

mConfig.getIsPrefetchEnabledSupplier(),

getBitmapMemoryCache(),

getEncodedMemoryCache(),

mConfig.getCacheKeyFactory());

}

return mImagePipeline;

}

在获取ImagePipeline（）中，如果为空，创建了一个

3. 创建了一个PipelineDraweeControllerFactory，并且保存到这个Supplier中

看到这里，我们先继续的广度分析，就是继续的分析SimpleDraweeView.initialize(sDraweeControllerBuilderSupplier)的过程

4.2.1.2.2 SimpleDraweeView.initialize(sDraweeControllerBuilderSupplier)的过程

在上面的分析，我们已经看到sDraweeControllerBuilderSupplier使用的是PipelineDraweeControllerBuilderSupplier

接下来，我们就看SimpleDraweeView.initialize(sDraweeControllerBuilderSupplier)的过程

从下面的代码，我们看到sDraweeControllerBuilderSupplier保存在了SimpleDraweeView中，SimpleDraweeView能够很简单的使用，是因为Fresco帮助我们在这里初始化了很多东西

  private static Supplier<? extends SimpleDraweeControllerBuilder> sDraweeControllerBuilderSupplier;

  /** Initializes {@link SimpleDraweeView} with supplier of Drawee controller builders. */

  public static void initialize(

      Supplier<? extends SimpleDraweeControllerBuilder> draweeControllerBuilderSupplier) {

    sDraweeControllerBuilderSupplier = draweeControllerBuilderSupplier;

  }

接着，以SimpleDraweeView的xml解析的方式来分析初始化的过程，我们发现，这里调用了我们的sDraweeControllerBuilderSupplier的get方法

*** SimpleDraweeView 的xml构造方式源码分析 ***

  public SimpleDraweeView(Context context, AttributeSet attrs) {

    super(context, attrs);

    init();

  }

  private void init() {

    if (isInEditMode()) {

      return;

    }

    Preconditions.checkNotNull(

        sDraweeControllerBuilderSupplier,

        "SimpleDraweeView was not initialized!");

    mSimpleDraweeControllerBuilder = sDraweeControllerBuilderSupplier.get();

  }

先别着急，我们再接着看，在使用xml解析的方式，我们还用到了一个setImageUri方法，再接着看这个方法，在setImageUri中，创建了一个DraweeController，然后设置给了自身，在构造DraweeController的时候，我们发现，调用了mSimpleDraweeControllerBuilder的build()方法

*** setImageURI（Uri）的源码分析 ***

  /**

   * Displays an image given by the uri.

   *

   * @param uri uri of the image

   * @undeprecate

   */

  @Override

  public void setImageURI(Uri uri) {

    setImageURI(uri, null);

  }

  /**

   * Displays an image given by the uri.

   *

   * @param uri uri of the image

   * @param callerContext caller context

   */

  public void setImageURI(Uri uri, @Nullable Object callerContext) {

    DraweeController controller = mSimpleDraweeControllerBuilder

        .setCallerContext(callerContext)

        .setUri(uri)

        .setOldController(getController())

        .build();

    setController(controller);

  }

到这里，我们先总结一下：

SimpleDraweeView中的sDraweeControllerBuilderSupplier是PipelineDraweeControllerBuilderSupplier
SimpleDraweeView中的controller是什么呢？那么这里就需要看看sDraweeControllerBuilderSupplier的get到什么ControllerBuilder？
对应的ControllerBuilder，build出什么controller
controller又是怎么样将提交请求的
遗留的Q2问题什么时候可以分析

看到这几个问题，我们发现，我们的分析，任重而道远

4.2.1.2.3 PipelineDraweeControllerBuilderSupplier的get()分析

这里只是创建了一个PipelineDraweeControllerBuilder，并且这个builder保存了imagePipeline和mPipelineDraweeControllerFactory

*** PipelineDraweeControllerBuilder.get()分析 ***

@Override

public PipelineDraweeControllerBuilder get() {

return new PipelineDraweeControllerBuilder(

mContext,

mPipelineDraweeControllerFactory,

mImagePipeline,

mBoundControllerListeners);

}

*** PipelineDraweeControllerBuilder的构造方法 ***

在这里，我们看不到什么，那么就继续看build()方法吧

public PipelineDraweeControllerBuilder(

Context context,

PipelineDraweeControllerFactory pipelineDraweeControllerFactory,

ImagePipeline imagePipeline,

Set boundControllerListeners) {

super(context, boundControllerListeners);

mImagePipeline = imagePipeline;

mPipelineDraweeControllerFactory = pipelineDraweeControllerFactory;

}

查看build方法时，便已经看到了这个PipelineDraweeControllerBuilder的继承结构

AbstractDraweeControllerBuilder

--| VolleyDraweeControllerBuilder

--|　PipelineDraweeControllerBuilder

Volley相关的我们就不看了，这个是和Vollery框架结合使用的，有兴趣可以自己研究下，大同小异

这次直接从方法调用来看即可，这次我们就要看到请求到底是如何产生的了

*** AbstractDraweeControllerBuilder.build()方法源码分析 ***

非核心代码，这次就忽略了，我们主要目的是要看到如何发送请求的，到后面请求如何反馈到前台，我们再详细分析其他代码

在build中，最关键的是buildController（），而在buildController中，最核心的是obtainController()，然后其他的是设置请求的一些信息，比如说设置请求的ImageRequest，其他的是设置重试等等

  /** Builds the specified controller. */

  @Override

  public AbstractDraweeController build() {

    validate();

    // if only a low-res request is specified, treat it as a final request.

    if (mImageRequest == null && mMultiImageRequests == null && mLowResImageRequest != null) {

      mImageRequest = mLowResImageRequest;

      mLowResImageRequest = null;

    }

    return buildController();

  }

  /** Builds a regular controller. */

  protected AbstractDraweeController buildController() {

    AbstractDraweeController controller = obtainController();

    maybeBuildAndSetRetryManager(controller);

    maybeAttachListeners(controller);

    return controller;

  }

  /** Concrete builder classes should override this method to return a new controller. */

  protected abstract AbstractDraweeController obtainController();

而在这里，发现obtainController（）是抽象方法，那么就是找子类呗

*** PipelineDraweeControllerBuilder.obtainController()源码分析 ***

在获取controller的方法中，我们还是以第一次初始化为例，那么就是else的部分，这里就是用mPipelineDraweeControllerFactory创建了一个newController

@Override

protected PipelineDraweeController obtainController() {

DraweeController oldController = getOldController();

PipelineDraweeController controller;

if (oldController instanceof PipelineDraweeController) {

controller = (PipelineDraweeController) oldController;

controller.initialize(

obtainDataSourceSupplier(),

generateUniqueControllerId(),

getCallerContext());

} else {

controller = mPipelineDraweeControllerFactory.newController(

obtainDataSourceSupplier(),

generateUniqueControllerId(),

getCallerContext());

}

return controller;

}

这块要关键的分析了，因为已经到了重点了

  controller = mPipelineDraweeControllerFactory.newController(

      obtainDataSourceSupplier(),

      generateUniqueControllerId(),

      getCallerContext());

我们一步一步看

obtainDataSourceSupplier()获取到了一个DataSourceSupplier
然后mPipelineDraweeControllerFactory类new了一个controller

这也没看出来什么，是吧，我们下节就得来点插叙，结合DraweeController和这里的获取Supplier直接的关系，那么基本的请求流程，我们算基本分析结束

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