Fresco源码阅读(一)

Android 源码分析 Volley 图片处理库 开源

---

初级

工程结构

1. drawe
2. drawee-pipeline
3. drawee-volley
4. fbcore
5. imagepipeline
6. imagepipeline-okhttp

基本代码统计

背景知识

接口

• DraweeController
  
  • getHierarchy/setHierarchy
  • onAttach/onDetach
  • onTouchEvent
  • getAnimatable
• DraweeHierarchy
  
  • getTopLevelDrawable
• SettableDraweeHierarchy
  SettableDraweeHierarchy in the given example has a FadeDrawable as its top level drawable. Top level drawable can be immediately put into view. Once the actual image is ready, it will be set to the hierarchy's SettableDrawable and fade animation between the placeholder and the actual image will be initiated. In case of failure, hierarchy will switch to failure image.
  All image branches are wrapped with ScaleType drawable which allows separate scale type to be applied on each.
  
  • reset
  • setImage、setProgress、setFailure、setRetry、setControllerOverlay
• SimpleDraweeControllerBuilder
  
  • setCallerContext
  • setUri
  • setOldController
  • build

分析入口

<com.facebook.drawee.view.SimpleDraweeView
    android:id="@+id/my_image_view"
    android:layout_width="20dp"
    android:layout_height="20dp"
    fresco:placeholderImage="@drawable/my_drawable"
  />

public class SimpleDraweeView extends GenericDraweeView {
//
public class GenericDraweeView extends DraweeView<GenericDraweeHierarchy> {
//
public class DraweeView<DH extends DraweeHierarchy> extends ImageView {
//
public class GenericDraweeHierarchy implements SettableDraweeHierarchy {
//
public interface DraweeHierarchy {
  public Drawable getTopLevelDrawable();
}
//
public interface SettableDraweeHierarchy extends DraweeHierarchy {

/**
 * A SettableDraweeHierarchy that displays placeholder image until the actual image is set.
 * If provided, failure image will be used in case of failure (placeholder otherwise).
 * If provided, retry image will be used in case of failure when retrying is enabled.
 * If provided, progressbar will be displayed until fully loaded.
 * Each image can be displayed with a different scale type (or no scaling at all).
 * Fading between the layers is supported.
 *
 * <p>
 * Example hierarchy with placeholder, retry, failure and one actual image:
 *  <pre>
 *     o FadeDrawable (top level drawable)
 *     |
 *     +--o ScaleTypeDrawable
 *     |  |
 *     |  +--o Drawable (placeholder image)
 *     |
 *     +--o ScaleTypeDrawable
 *     |  |
 *     |  +--o SettableDrawable
 *     |     |
 *     |     +--o Drawable (actual image)
 *     |
 *     +--o ScaleTypeDrawable
 *     |  |
 *     |  +--o Drawable (retry image)
 *     |
 *     +--o ScaleTypeDrawable
 *        |
 *        +--o Drawable (failure image)
 *  </pre>
 *
 * <p>
 */
public class GenericDraweeHierarchy implements SettableDraweeHierarchy {

设计模式入口

1. Facade : SimpleDraweeView、GenericDraweeView

2. Builder : GenericDraweeHierarchy、GenericDraweeHierarchyBuilder

3. Composite : GenericDraweeHierarchy、DraweeHolder、FadeDrawable

• Component
  
  • 为组合中的对象声明接口:
    SettableDraweeHierarchy extends DraweeHierarchy
  • 在适当的情况下，实现所有类共有接口的缺省行为: DraweeView
  • 声明一个接口用于访问和管理Component的子组件:VisibilityCallback
  • （可选）在递归结构中定义一个接口，用于访问一个父部件，并在合适的情况下实现它:DraweeHierarchy
    
    • Leaf : DraweeHolder
  • 在组合中表示叶节点对象，叶节点没有子节点
  • 在组合中定义图元对象的行为: onTouchEvent、onDraw
    
    • Composite : GenericDraweeHierarchy
  • 存储子部件 : mFadeDrawable
    mTopLevelDrawable、mEmptyPlaceholderDrawable、mActualImageSettableDrawable
  • 定义有子部件的那些部件的行为:
    private static class RootFadeDrawable
  • 在Component接口中实现与子部件有关的操作
    SettableDraweeHierarchy
• Client : GenericDraweeHierarchy

4. Chain of Responsibility : 职责链

事件流入口（MVP 模式）

1. Fresco.java 设置 PipelineDraweeControllerBuilderSupplier 以便初始化 SimpleDraweeView 得到 PipelineDraweeBuilder
   

   Fresco.initialize(context)
   |--- ImagePipelineFactory.initialize(context);
   |--- initializeDrawee(context);
   |-------- new PipelineDraweeControllerBuilderSupplier(context);
   |-------- SimpleDraweeView.initialize(sDraweeControllerBuilderSupplier);

2. SimpleDraweeView.java 配置 DraweeController （设置 DataSource 数据源，索引：getDataSource() ）
   |--- init() -> mSimpleDraweeControllerBuilder = sDraweeControllerBuilderSupplier.get();
   |--- setImageURI(Uri uri, @Nullable Object callerContext)
   |-------- .setUri()
   |-------- .build() -> AbstractDraweeControllerBuilder.java -> buildController() ->
   |-------------- PipelineDraweeControllerBuilder.java -> obtainController
   |-------- setController(controller) -> mDraweeHolder.setController(draweeController);
3. DraweeView.java 执行 onAttachedToWindow() -> DraweeController 执行 onAttach()
   |--- submitRequest()
   |-------- getControllerListener().onSubmit(mId, mCallerContext);
   |-------- getDataSource() -> ImagePipeline.java -> fetchImageFromBitmapCache()
   |------------- submitFetchRequest() -> CloseableProducerToDataSourceAdapter.create()
   |-------- new BaseDataSubscriber() -> mDataSource.subscribe();
4. 获取 DataSource 时，提交 request（索引：构造器 -> produceResults() ）
   |--- AbstractProducerToDataSourceAdapter.java（构造器）-> produceResults()
   |-------- createConsumer() -> AbstractDataSource.java -> setResult()
   |------------- setResultInternal() -> notifyDataSubscribers()

㊀ Model

ImagePipeline.java -> fetchImageFromBitmapCache()
FirstAvailableDataSourceSupplier.java -> AbstractDataSource.java

㊁ View Interface

DraweeHolder.java

㊂ View

SimpleDraweeView.java

㊃ Presenter

PipelineDraweeController.java -> AbstractDraweeController.java

补充

其它知识

Sample

Instrumentation : debug（模块化配置）

public class InstrumentedDraweeView extends SimpleDraweeView implements Instrumented {
  private Instrumentation mInstrumentation;
  private ControllerListener<Object> mListener;
  public InstrumentedDraweeView(Context context, GenericDraweeHierarchy hierarchy) {
    super(context, hierarchy);
    init();
  }
  public InstrumentedDraweeView(Context context) {
    super(context);
    init();
  }
  public InstrumentedDraweeView(Context context, AttributeSet attrs) {
    super(context, attrs);
    init();
  }
  public InstrumentedDraweeView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    init();
  }
  private void init() {
    mInstrumentation = new Instrumentation(this);
    mListener = new BaseControllerListener<Object>() {
      @Override
      public void onSubmit(String id, Object callerContext) {
        mInstrumentation.onStart();
      }
      @Override
      public void onFinalImageSet(
        String id,
        @Nullable Object imageInfo,
        @Nullable Animatable animatable) {
        mInstrumentation.onSuccess();
      }
      @Override
      public void onFailure(String id, Throwable throwable) {
        mInstrumentation.onFailure();
      }
      @Override
      public void onRelease(String id) {
        mInstrumentation.onCancellation();
      }
    };
  }
  @Override
  public void initInstrumentation(String tag, PerfListener perfListener) {
    mInstrumentation.init(tag, perfListener);
  }
  @Override
  public void onDraw(final Canvas canvas) {
    super.onDraw(canvas);
    mInstrumentation.onDraw(canvas);
  }
  @Override
  public void setImageURI(Uri uri, @Nullable Object callerContext) {
    SimpleDraweeControllerBuilder controllerBuilder = getControllerBuilder()
        .setUri(uri)
        .setCallerContext(callerContext)
        .setOldController(getController());
    if (controllerBuilder instanceof AbstractDraweeControllerBuilder) {
      ((AbstractDraweeControllerBuilder<?,?,?,?>) controllerBuilder)
          .setControllerListener(mListener);
    }
    setController(controllerBuilder.build());
  }
  public ControllerListener<Object> getListener() {
    return mListener;
  }
}