Fresco學(xué)習(xí)中文地址：Fresco中文學(xué)習(xí)

Fresco Javadoc地址：Javadoc

Fresco初始化分析：

在Application中加入：

Fresco.initialize(this);

請(qǐng)看我的注釋：

/*
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

package com.facebook.drawee.backends.pipeline;

import *

/**
 * Fresco entry point.(總體入口點(diǎn))
 *
 * <p/> You must initialize this class before use. The simplest way is to just do
 * {#code Fresco.initialize(Context)}.
 * （指明了一個(gè)簡(jiǎn)單例子）
 */
public class Fresco {
  private static PipelineDraweeControllerBuilderSupplier sDraweeControllerBuilderSupplier; //業(yè)務(wù)邏輯工廠

  private Fresco() {}

  /** Initializes Fresco with the default config. */
  public static void initialize(Context context) {
    ImagePipelineFactory.initialize(context); // 關(guān)系圖片下載邏輯處理和緩存處理
    initializeDrawee(context);
  }

  /** Initializes Fresco with the specified config. */
  public static void initialize(Context context, ImagePipelineConfig imagePipelineConfig) {
    ImagePipelineFactory.initialize(imagePipelineConfig); // 關(guān)系圖片下載邏輯處理和緩存處理
    initializeDrawee(context);
  }

  private static void initializeDrawee(Context context) {
    sDraweeControllerBuilderSupplier = new PipelineDraweeControllerBuilderSupplier(context);
    SimpleDraweeView.initialize(sDraweeControllerBuilderSupplier); // 這個(gè)SimpleDraweeView是在布局中使用的代理Imageview辛孵，掛在一堆轉(zhuǎn)換邏輯
  }

  /** Gets the supplier of Fresco Drawee controller builders. */
  public static PipelineDraweeControllerBuilderSupplier getDraweeControllerBuilderSupplier() {
    return sDraweeControllerBuilderSupplier; // 這貨給外部使用，看需求而定
  }

  /** Returns a new instance of Fresco Drawee controller builder. */
  public static PipelineDraweeControllerBuilder newDraweeControllerBuilder() {
    return sDraweeControllerBuilderSupplier.get(); // 給外部需求所用，拿到一個(gè)新的業(yè)務(wù)邏輯工廠對(duì)象
  }

  public static ImagePipelineFactory getImagePipelineFactory() {
    return ImagePipelineFactory.getInstance(); // 外部使用的管道類踢故，這貨檢查是否初始化
  }

  /** Gets the image pipeline instance. */
  public static ImagePipeline getImagePipeline() {
    return getImagePipelineFactory().getImagePipeline();// 外部使用的管道類，這貨檢查是否初始化嗤栓，沒(méi)有給你個(gè)新的佑刷，工廠模式
  }

  /** Shuts Fresco down. */
  public static void shutDown() { //Application 退出調(diào)用，避免內(nèi)存泄露
    sDraweeControllerBuilderSupplier = null;
    SimpleDraweeView.shutDown();
    ImagePipelineFactory.shutDown();
  }
}

初始化翻譯就這樣：

Fresco.initialize() ===> Fresco.initializeDrawee() ===> SimpleDraweeView.initialize();

請(qǐng)繼續(xù)看我的注釋：

/*
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */

package com.facebook.drawee.view;

import *

/**
 * This view takes a uri as input and internally builds and sets a controller.(這個(gè)類就是掛載url和control準(zhǔn)備)
 *
 * <p>This class must be statically initialized in order to be used. If you are using the Fresco
 * image pipeline, use {@link com.facebook.drawee.backends.pipeline.Fresco#initialize} to do this.
 * （官方教育你钝计，先初始化Fresco.initialize）
 */
public class SimpleDraweeView extends GenericDraweeView { // 這個(gè)繼承有點(diǎn)深恋博，慢慢來(lái)，最終爸爸肯定是ImageView私恬，但每個(gè)繼承做了深度定制

  private static Supplier<? extends SimpleDraweeControllerBuilder> sDraweeControllerBuilderSupplier;// 這貨就是前面初始化進(jìn)來(lái)的業(yè)務(wù)邏輯提供者

  /** Initializes {@link SimpleDraweeView} with supplier of Drawee controller builders. */
  public static void initialize( // 初始化傳值
      Supplier<? extends SimpleDraweeControllerBuilder> draweeControllerBuilderSupplier) {
    sDraweeControllerBuilderSupplier = draweeControllerBuilderSupplier;
  }

  /** Shuts {@link SimpleDraweeView} down. */
  public static void shutDown() { // 關(guān)閉
    sDraweeControllerBuilderSupplier = null;
  }

  private SimpleDraweeControllerBuilder mSimpleDraweeControllerBuilder; // 真正的業(yè)務(wù)邏輯對(duì)象债沮，從sDraweeControllerBuilderSupplier拿出

  public SimpleDraweeView(Context context, GenericDraweeHierarchy hierarchy) {
    super(context, hierarchy);
    init(context, null);
  }

  public SimpleDraweeView(Context context) {
    super(context);
    init(context, null);
  }

  public SimpleDraweeView(Context context, AttributeSet attrs) {
    super(context, attrs);
    init(context, attrs);
  }

  public SimpleDraweeView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    init(context, attrs);
  }

  @TargetApi(Build.VERSION_CODES.LOLLIPOP)
  public SimpleDraweeView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
    super(context, attrs, defStyleAttr, defStyleRes);
    init(context, attrs);
  }

  private void init(Context context, @Nullable AttributeSet attrs) {
    if (isInEditMode()) { // 來(lái)自view，是否控件可以編輯
      return;
    }
    Preconditions.checkNotNull(
        sDraweeControllerBuilderSupplier,
        "SimpleDraweeView was not initialized!"); // 檢查sDraweeControllerBuilderSupplier
    mSimpleDraweeControllerBuilder = sDraweeControllerBuilderSupplier.get(); // 拿到對(duì)應(yīng)的業(yè)務(wù)邏輯（正常來(lái)說(shuō)都是PipelineDraweeControllerBuilder本鸣，如果自己沒(méi)有外部定制需求）

    // 拿布局屬性疫衩，基本無(wú)用，可以是個(gè)默認(rèn)圖uri
    if (attrs != null) {
      TypedArray gdhAttrs = context.obtainStyledAttributes(
          attrs,
          R.styleable.SimpleDraweeView);
      try {
        if (gdhAttrs.hasValue(R.styleable.SimpleDraweeView_actualImageUri)) {
          setImageURI(Uri.parse(gdhAttrs.getString(R.styleable.SimpleDraweeView_actualImageUri)), null);
        }
      } finally {
        gdhAttrs.recycle();
      }
    }
  }

  protected SimpleDraweeControllerBuilder getControllerBuilder() { // 給外部使用荣德，沒(méi)有什么好說(shuō)的
    return mSimpleDraweeControllerBuilder;
  }

  /**
   * Displays an image given by the uri.
   *
   * @param uri uri of the image
   * @undeprecate
   */
  @Override
  public void setImageURI(Uri uri) { // 定制網(wǎng)絡(luò)圖片url
    setImageURI(uri, null);
  }

  /**
   * Displays an image given by the uri string.
   *
   * @param uriString uri string of the image
   */
  public void setImageURI(@Nullable String uriString) {
    setImageURI(uriString, 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) { // builder模式建立DraweeController 
    DraweeController controller = mSimpleDraweeControllerBuilder
        .setCallerContext(callerContext)// 這貨如果沒(méi)有指定闷煤，都是null，一直傳到所有的生產(chǎn)者中
        .setUri(uri)
        .setOldController(getController())// 這貨首次是null
        .build();
    setController(controller);
  }

  /**
   * Displays an image given by the uri string.
   *
   * @param uriString uri string of the image
   * @param callerContext caller context
   */
  public void setImageURI(@Nullable String uriString, @Nullable Object callerContext) { // 多態(tài)
    Uri uri = (uriString != null) ? Uri.parse(uriString) : null;
    setImageURI(uri, callerContext);
  }
}

SimpleDraweeView 的繼承先不看命爬，控件處理而已曹傀，先看完關(guān)心request流程。

流程：SimpleDraweeView.setImageURI() ===> PipelineDraweeControllerBuilder.build(),然后SimpleDraweeView 再持有PipelineDraweeController這個(gè)對(duì)象

接著看注釋饲宛，這個(gè)build類：

package com.facebook.drawee.backends.pipeline;

import *

/**
 * Concrete implementation of ImagePipeline Drawee controller builder. （業(yè)務(wù)邏輯實(shí)現(xiàn)類）
 * <p/> See {@link AbstractDraweeControllerBuilder} for more details.
 */
public class PipelineDraweeControllerBuilder extends AbstractDraweeControllerBuilder<
    PipelineDraweeControllerBuilder,
    ImageRequest,
    CloseableReference<CloseableImage>,
    ImageInfo> { // 很多實(shí)現(xiàn)在基類AbstractDraweeControllerBuilder完成皆愉，如果你需要定制自己DraweeController，繼承這個(gè)基類

  private final ImagePipeline mImagePipeline; // 各種緩存和策略艇抠，維護(hù)臟活的就是它
  private final PipelineDraweeControllerFactory mPipelineDraweeControllerFactory;// 這貨持有uiThread幕庐，用來(lái)回掉更新，配合ImagePipeline 完成請(qǐng)求

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

  @Override
  public PipelineDraweeControllerBuilder setUri(Uri uri) { // 轉(zhuǎn)換成一個(gè)ImageRequest
    return super.setImageRequest(ImageRequest.fromUri(uri));
  }

  @Override
  public PipelineDraweeControllerBuilder setUri(@Nullable String uriString) { // 轉(zhuǎn)換成一個(gè)ImageRequest
    return super.setImageRequest(ImageRequest.fromUri(uriString));
  }

// 這個(gè)函數(shù)來(lái)自SimpleDraweeView:setImageURI():PipelineDraweeControllerBuilder.build()
  @Override
  protected PipelineDraweeController obtainController() { // 父類會(huì)回掉家淤，首次會(huì)走else异剥，為了重復(fù)使用，把新數(shù)據(jù)更新到controller中
    DraweeController oldController = getOldController(); 
    PipelineDraweeController controller;
    if (oldController instanceof PipelineDraweeController) {
      controller = (PipelineDraweeController) oldController;
      controller.initialize(
          obtainDataSourceSupplier(),
          generateUniqueControllerId(),
          getCacheKey(),
          getCallerContext());
    } else {
      controller = mPipelineDraweeControllerFactory.newController(
          obtainDataSourceSupplier(),
          generateUniqueControllerId(),
          getCacheKey(),
          getCallerContext());
    }
    return controller;
  }

  private CacheKey getCacheKey() { // 根據(jù)imageRequest 拿到對(duì)應(yīng)的Cache策略絮重，這貨從ImagePipeline 拿到Cache
    final ImageRequest imageRequest = getImageRequest();
    final CacheKeyFactory cacheKeyFactory = mImagePipeline.getCacheKeyFactory();
    CacheKey cacheKey = null;
    if (cacheKeyFactory != null && imageRequest != null) {
      if (imageRequest.getPostprocessor() != null) {
        cacheKey = cacheKeyFactory.getPostprocessedBitmapCacheKey(
            imageRequest,
            getCallerContext());
      } else {
        cacheKey = cacheKeyFactory.getBitmapCacheKey(
            imageRequest,
            getCallerContext());
      }
    }
    return cacheKey;
  }

 // 數(shù)據(jù)Bean冤寿，帶有回掉數(shù)據(jù)接口（成功或者失敗）,利用執(zhí)行ImagePipeline request
  @Override
  protected DataSource<CloseableReference<CloseableImage>> getDataSourceForRequest(
      ImageRequest imageRequest,
      Object callerContext,
      boolean bitmapCacheOnly) {
    if (bitmapCacheOnly) {
      return mImagePipeline.fetchImageFromBitmapCache(imageRequest, callerContext);
    } else {
      return mImagePipeline.fetchDecodedImage(imageRequest, callerContext);
    }
  }
    
    .......
}

好了大致知道了Cache類和Executor類了青伤，都來(lái)自ImagePipeline督怜。

ImagePipeline 負(fù)責(zé)圖片的獲取和管理。圖片可以來(lái)自遠(yuǎn)程服務(wù)器狠角，本地文件号杠，或者Content Provider，本地資源。壓縮后的文件緩存在本地存儲(chǔ)中姨蟋，Bitmap數(shù)據(jù)緩存在內(nèi)存中屉凯。

obtainController(),這個(gè)函數(shù)比較重要，構(gòu)造了業(yè)務(wù)邏輯眼溶，有點(diǎn)像MVC悠砚，這里創(chuàng)建后生成回掉，給后面view偷仿，addWindow()后哩簿，收集WMS和IMS(WindowManagerService和InputeManagerService)產(chǎn)生的生命周期回掉或者輸入事件綁定。

在5.0系統(tǒng)以下酝静，Image Pipeline 使用 pinned purgeables 將Bitmap數(shù)據(jù)避開(kāi)Java堆內(nèi)存节榜，存在ashmem中。這要求圖片不使用時(shí)别智，要顯式地釋放內(nèi)存宗苍。
SimpleDraweeView自動(dòng)處理了這個(gè)釋放過(guò)程，所以沒(méi)有特殊情況薄榛，盡量使用SimpleDraweeView讳窟，在特殊的場(chǎng)合，如果有需要敞恋，也可以直接控制Image Pipeline丽啡。

Paste_Image.png

那執(zhí)行Requst代碼在哪硬猫，在前面SimpleDraweeView.setImageURI()里面是執(zhí)行

package com.facebook.drawee.backends.pipeline;

import *

/**
 * Drawee controller that bridges the image pipeline with {@link SettableDraweeHierarchy}. <p> The
 * hierarchy's actual image is set to the image(s) obtained by the provided data source. The data
 * source is automatically obtained and closed based on attach / detach calls.
 */
public class PipelineDraweeController
    extends AbstractDraweeController<CloseableReference<CloseableImage>, ImageInfo> {

  // Components
  private final Resources mResources;
  private final AnimatedDrawableFactory mAnimatedDrawableFactory;

  private @Nullable MemoryCache<CacheKey, CloseableImage> mMemoryCache;

  private static Experiment sExperiment; // 這貨相當(dāng)于一個(gè)對(duì)象鎖

  private CacheKey mCacheKey;

  // Constant state (non-final because controllers can be reused)
  private Supplier<DataSource<CloseableReference<CloseableImage>>> mDataSourceSupplier;

  public PipelineDraweeController( // 初始化和傳值一堆补箍，為了基類使用
      Resources resources,
      DeferredReleaser deferredReleaser,
      AnimatedDrawableFactory animatedDrawableFactory,
      Executor uiThreadExecutor,
      MemoryCache<CacheKey, CloseableImage> memoryCache,
      Supplier<DataSource<CloseableReference<CloseableImage>>> dataSourceSupplier,
      String id,
      CacheKey cacheKey,
      Object callerContext) {
      super(deferredReleaser, uiThreadExecutor, id, callerContext);
    mResources = resources;
    mAnimatedDrawableFactory = animatedDrawableFactory;
    mMemoryCache = memoryCache;
    mCacheKey = cacheKey;
    init(dataSourceSupplier);
  }

  public void initialize(
      Supplier<DataSource<CloseableReference<CloseableImage>>> dataSourceSupplier,
      String id,
      CacheKey cacheKey,
      Object callerContext) {
    super.initialize(id, callerContext);
    init(dataSourceSupplier);
    mCacheKey = cacheKey;
  }

  private void init(Supplier<DataSource<CloseableReference<CloseableImage>>> dataSourceSupplier) {
    mDataSourceSupplier = dataSourceSupplier;
  }

// 這個(gè)函數(shù)比較重要，利用DataSourceSupplier提供model接口數(shù)據(jù)接口（MVC模式）
  @Override
  protected DataSource<CloseableReference<CloseableImage>> getDataSource() { // 更新數(shù)據(jù)的接口，有成功和失敗
    if (FLog.isLoggable(FLog.VERBOSE)) {
      FLog.v(TAG, "controller %x: getDataSource", System.identityHashCode(this));
    }
    return mDataSourceSupplier.get();
  }

  @Override
  protected Drawable createDrawable(CloseableReference<CloseableImage> image) {// 創(chuàng)建Drawable的策略回掉
    Preconditions.checkState(CloseableReference.isValid(image));
    CloseableImage closeableImage = image.get();
    if (closeableImage instanceof CloseableStaticBitmap) {
      CloseableStaticBitmap closeableStaticBitmap = (CloseableStaticBitmap) closeableImage;
      Drawable bitmapDrawable = new BitmapDrawable(
        mResources,
        closeableStaticBitmap.getUnderlyingBitmap());
      if (closeableStaticBitmap.getRotationAngle() == 0 ||
          closeableStaticBitmap.getRotationAngle() == EncodedImage.UNKNOWN_ROTATION_ANGLE) {
        return bitmapDrawable;
      } else {
        return new OrientedDrawable(bitmapDrawable, closeableStaticBitmap.getRotationAngle());
      }
    } else if (mAnimatedDrawableFactory != null) {
      return mAnimatedDrawableFactory.create(closeableImage);
    } else {
      throw new UnsupportedOperationException("Unrecognized image class: " + closeableImage);
    }
  }
       .......

  @Override
  protected void releaseImage(@Nullable CloseableReference<CloseableImage> image) { // 釋放引用策略
    CloseableReference.closeSafely(image);
  }

  @Override
  protected void releaseDrawable(@Nullable Drawable drawable) { // 釋放引用策略
    if (drawable instanceof DrawableWithCaches) {
      ((DrawableWithCaches) drawable).dropCaches();
    }
  }

  @Override 
  protected CloseableReference<CloseableImage> getCachedImage() { // 關(guān)閉引用策略
    if (!getExperiment().mIsFastCheckEnabled) {
      return null;
    }
    if (mMemoryCache == null || mCacheKey == null) {
      return null;
    }
    // We get the CacheKey
    CloseableReference<CloseableImage> closeableImage = mMemoryCache.get(mCacheKey);
    if (closeableImage != null && !closeableImage.get().getQualityInfo().isOfFullQuality()) {
      closeableImage.close();
      return null;
    }
    return closeableImage;
  }

  /**
   * @return The Experiment object
   */
  protected static Experiment getExperiment() {
    if (sExperiment == null) {
      sExperiment = new Experiment();
    }
    return sExperiment;
  }

  protected static class Experiment { // 檢查類

    private boolean mIsFastCheckEnabled;

    public Experiment setFastCheckEnabled(final boolean fastCheckEnabled) {
      mIsFastCheckEnabled = fastCheckEnabled;
      return this;
    }
  }
}

上面只是實(shí)力類，真正調(diào)用在基類, 比較重要的就是getDataSource()和createDrawable()的實(shí)現(xiàn)了读规，其它都是釋放資源和回收，后面再講這個(gè)資源回收和回掉過(guò)程

接下來(lái)看基類指明干活

package com.facebook.drawee.controller;

import *

/**
 * Abstract Drawee controller that implements common functionality
 * regardless of the backend used to fetch the image.
 *
 * All methods should be called on the main UI thread.
 *
 */
@NotThreadSafe
public abstract class AbstractDraweeController<T, INFO> implements
    DraweeController,
    DeferredReleaser.Releasable,
    GestureDetector.ClickListener {

  /**
   * This class is used to allow an optimization of not creating a ForwardingControllerListener
   * when there is only a single controller listener.
   * 這貨也比較重要裹粤，但尼瑪你沒(méi)有定制自己controllistener，默認(rèn)為null蜂林，沒(méi)有什么卵用
   */
  private static class InternalForwardingListener<INFO> extends ForwardingControllerListener<INFO> { 
    public static <INFO> InternalForwardingListener<INFO> createInternal(
        ControllerListener<? super INFO> listener1,
        ControllerListener<? super INFO> listener2) {
      InternalForwardingListener<INFO> forwarder = new InternalForwardingListener<INFO>();
      forwarder.addListener(listener1);
      forwarder.addListener(listener2);
      return forwarder;
    }
  }

  // Components
  private final DraweeEventTracker mEventTracker = DraweeEventTracker.newInstance(); // 日志追蹤
  private final DeferredReleaser mDeferredReleaser; // 賴加載遥诉，延遲安排任務(wù)
  private final Executor mUiThreadImmediateExecutor; // ui線程從PipelineDraweeControllerBuilder ：PipelineDraweeControllerFactory 來(lái)的

  // Optional components
  private @Nullable RetryManager mRetryManager; // 重試機(jī)制
  private @Nullable GestureDetector mGestureDetector; // 手勢(shì)
  private @Nullable ControllerListener<INFO> mControllerListener; // 業(yè)務(wù)邏輯回掉監(jiān)聽(tīng)

  // Hierarchy
  private @Nullable SettableDraweeHierarchy mSettableDraweeHierarchy; // view對(duì)象樹(shù)， 用于組織和維護(hù)最終繪制和呈現(xiàn)的 Drawable 對(duì)象
  private @Nullable Drawable mControllerOverlay; // view對(duì)象

  // Constant state (non-final because controllers can be reused)
  private String mId;
  private Object mCallerContext;

  // Mutable state
  private boolean mIsAttached; // 是否view添加到window上
  private boolean mIsRequestSubmitted; // 是否已經(jīng)開(kāi)始request
  private boolean mHasFetchFailed;// 當(dāng)前request更新失敗flag
  private boolean mRetainImageOnFailure;// 設(shè)置是否顯示最新的可用的圖片（默認(rèn)圖）噪叙，在失敗的時(shí)候
  private @Nullable String mContentDescription; // 描述
  private @Nullable DataSource<T> mDataSource; // 子類data策略
  private @Nullable T mFetchedImage; // 獲取到當(dāng)前image
  private @Nullable Drawable mDrawable; // 圖片資源

  public AbstractDraweeController(
      DeferredReleaser deferredReleaser,
      Executor uiThreadImmediateExecutor,
      String id,
      Object callerContext) {
    mDeferredReleaser = deferredReleaser;
    mUiThreadImmediateExecutor = uiThreadImmediateExecutor;
    init(id, callerContext, true);
  }

  protected void initialize(String id, Object callerContext) {
    init(id, callerContext, false);
  }

  private void init(String id, Object callerContext, boolean justConstructed) {
    mEventTracker.recordEvent(Event.ON_INIT_CONTROLLER);
    // cancel deferred release
    if (!justConstructed && mDeferredReleaser != null) {
      mDeferredReleaser.cancelDeferredRelease(this);
    }
    // reinitialize mutable state (fetch state)
    mIsAttached = false;
    releaseFetch();
    mRetainImageOnFailure = false;
    // reinitialize optional components
    if (mRetryManager != null) {
      mRetryManager.init();
    }
    if (mGestureDetector != null) {
      mGestureDetector.init();
      mGestureDetector.setClickListener(this);
    }
    if (mControllerListener instanceof InternalForwardingListener) {
      ((InternalForwardingListener) mControllerListener).clearListeners();
    } else {
      mControllerListener = null;
    }
    // clear hierarchy and controller overlay
    if (mSettableDraweeHierarchy != null) {
      mSettableDraweeHierarchy.reset();
      mSettableDraweeHierarchy.setControllerOverlay(null);
      mSettableDraweeHierarchy = null;
    }
    mControllerOverlay = null;
    // reinitialize constant state
    if (FLog.isLoggable(FLog.VERBOSE)) {
      FLog.v(TAG, "controller %x %s -> %s: initialize", System.identityHashCode(this), mId, id);
    }
    mId = id;
    mCallerContext = callerContext;
  }

  @Override
  public void release() {
    mEventTracker.recordEvent(Event.ON_RELEASE_CONTROLLER);
    if (mRetryManager != null) {
      mRetryManager.reset();
    }
    if (mGestureDetector != null) {
      mGestureDetector.reset();
    }
    if (mSettableDraweeHierarchy != null) {
      mSettableDraweeHierarchy.reset();
    }
    releaseFetch();
  }

  private void releaseFetch() { // 釋放hold的image和data突那，為request做準(zhǔn)備
    boolean wasRequestSubmitted = mIsRequestSubmitted;
    mIsRequestSubmitted = false;
    mHasFetchFailed = false;
    if (mDataSource != null) {
      mDataSource.close();
      mDataSource = null;
    }
    if (mDrawable != null) {
      releaseDrawable(mDrawable);
    }
    if (mContentDescription != null) {
      mContentDescription = null;
    }
    mDrawable = null;
    if (mFetchedImage != null) {
      logMessageAndImage("release", mFetchedImage);
      releaseImage(mFetchedImage);
      mFetchedImage = null;
    }
    if (wasRequestSubmitted) {
      getControllerListener().onRelease(mId);
    }
  }

  public Object getCallerContext() { // 默認(rèn)情況都是null，基本無(wú)卵用构眯，如果你有特殊要求，這個(gè)上下文能起到很大重要早龟，如惫霸，日志追蹤
    return mCallerContext;
  }

  protected @Nullable RetryManager getRetryManager() { // 重試機(jī)制
    return mRetryManager;
  }

      .......

  /** Gets gesture detector. */
  protected @Nullable GestureDetector getGestureDetector() {
    return mGestureDetector;
  }

  /** Sets gesture detector. */
  protected void setGestureDetector(@Nullable GestureDetector gestureDetector) {
    mGestureDetector = gestureDetector;
    if (mGestureDetector != null) {
      mGestureDetector.setClickListener(this);
    }
  }

// 這貨有意思了猫缭，這貨給你個(gè)flag，需要set進(jìn)來(lái)壹店，作用是你下載完后猜丹，失敗需要重新下載標(biāo)志
  protected void setRetainImageOnFailure(boolean enabled) {
    mRetainImageOnFailure = enabled;
  }

      .......

 // 基本無(wú)用，默認(rèn)是null硅卢，為了完成你自己定制的回掉監(jiān)聽(tīng)設(shè)置
  /** Adds controller listener. */
  public void addControllerListener(ControllerListener<? super INFO> controllerListener) {
    Preconditions.checkNotNull(controllerListener);
    if (mControllerListener instanceof InternalForwardingListener) {
      ((InternalForwardingListener<INFO>) mControllerListener).addListener(controllerListener);
      return;
    }
    if (mControllerListener != null) {
      mControllerListener = InternalForwardingListener.createInternal(
          mControllerListener,
          controllerListener);
      return;
    }
    // Listener only receives <INFO>, it never produces one.
    // That means if it can accept <? super INFO>, it can very well accept <INFO>.
    mControllerListener = (ControllerListener<INFO>) controllerListener;
  }

      .......

  /** Gets controller listener for internal use. */
  protected ControllerListener<INFO> getControllerListener() {
    if (mControllerListener == null) {
      return BaseControllerListener.getNoOpListener();
    }
    return mControllerListener;
  }

  /** Gets the hierarchy */
  @Override
  public @Nullable
  DraweeHierarchy getHierarchy() {
    return mSettableDraweeHierarchy;
  }

  // 這函數(shù)比較屌射窒，維護(hù)view樹(shù)，以后再講
  @Override
  public void setHierarchy(@Nullable DraweeHierarchy hierarchy) {
    if (FLog.isLoggable(FLog.VERBOSE)) {
      FLog.v(
          TAG,
          "controller %x %s: setHierarchy: %s",
          System.identityHashCode(this),
          mId,
          hierarchy);
    }
    mEventTracker.recordEvent(
        (hierarchy != null) ? Event.ON_SET_HIERARCHY : Event.ON_CLEAR_HIERARCHY);
    // force release in case request was submitted
    if (mIsRequestSubmitted) {
      mDeferredReleaser.cancelDeferredRelease(this);
      release();
    }
    // clear the existing hierarchy
    if (mSettableDraweeHierarchy != null) {
      mSettableDraweeHierarchy.setControllerOverlay(null);
      mSettableDraweeHierarchy = null;
    }
    // set the new hierarchy
    if (hierarchy != null) {
      Preconditions.checkArgument(hierarchy instanceof SettableDraweeHierarchy);
      mSettableDraweeHierarchy = (SettableDraweeHierarchy) hierarchy;
      mSettableDraweeHierarchy.setControllerOverlay(mControllerOverlay);
    }
  }

  /** Sets the controller overlay */
  protected void setControllerOverlay(@Nullable Drawable controllerOverlay) {
    mControllerOverlay = controllerOverlay;
    if (mSettableDraweeHierarchy != null) {
      mSettableDraweeHierarchy.setControllerOverlay(mControllerOverlay);
    }
  }

  /** Gets the controller overlay */
  protected @Nullable Drawable getControllerOverlay() {
    return mControllerOverlay;
  }

  @Override
  public void onAttach() { // 回調(diào)
    if (FLog.isLoggable(FLog.VERBOSE)) {
      FLog.v(
          TAG,
          "controller %x %s: onAttach: %s",
          System.identityHashCode(this),
          mId,
          mIsRequestSubmitted ? "request already submitted" : "request needs submit");
    }
    mEventTracker.recordEvent(Event.ON_ATTACH_CONTROLLER);
    Preconditions.checkNotNull(mSettableDraweeHierarchy);
    mDeferredReleaser.cancelDeferredRelease(this);
    mIsAttached = true;
    if (!mIsRequestSubmitted) {
      submitRequest();
    }
  }

  @Override
  public void onDetach() { // 回調(diào)
    if (FLog.isLoggable(FLog.VERBOSE)) {
      FLog.v(TAG, "controller %x %s: onDetach", System.identityHashCode(this), mId);
    }
    mEventTracker.recordEvent(Event.ON_DETACH_CONTROLLER);
    mIsAttached = false;
    mDeferredReleaser.scheduleDeferredRelease(this);
  }

  @Override
  public boolean onTouchEvent(MotionEvent event) { // 回調(diào)
    if (FLog.isLoggable(FLog.VERBOSE)) {
      FLog.v(TAG, "controller %x %s: onTouchEvent %s", System.identityHashCode(this), mId, event);
    }
    if (mGestureDetector == null) {
      return false;
    }
    if (mGestureDetector.isCapturingGesture() || shouldHandleGesture()) {
      mGestureDetector.onTouchEvent(event);
      return true;
    }
    return false;
  }

  /** Returns whether the gesture should be handled by the controller */
  protected boolean shouldHandleGesture() {
    return shouldRetryOnTap();
  }

  private boolean shouldRetryOnTap() {
    // We should only handle touch event if we are expecting some gesture.
    // For example, we expect click when fetch fails and tap-to-retry is enabled.
    return mHasFetchFailed && mRetryManager != null && mRetryManager.shouldRetryOnTap(); // shouldRetryOnTap 判斷是否超過(guò)重新的最大值（MAX：4次）
  }

  @Override
  public boolean onClick() {// 回調(diào)
    if (FLog.isLoggable(FLog.VERBOSE)) {
      FLog.v(TAG, "controller %x %s: onClick", System.identityHashCode(this), mId);
    }
    if (shouldRetryOnTap()) { // mRetryManager去通知重新request準(zhǔn)備
      mRetryManager.notifyTapToRetry();
      mSettableDraweeHierarchy.reset();
      submitRequest();
      return true;
    }
    return false;
  }

  protected void submitRequest() { // 這貨就是干活的
    final T closeableImage = getCachedImage(); // 拿到子類的Cache圖片
    if (closeableImage != null) { // 如果有将塑，直接刷新成功
      mDataSource = null;
      mIsRequestSubmitted = true;
      mHasFetchFailed = false;
      mEventTracker.recordEvent(Event.ON_SUBMIT_CACHE_HIT);
      getControllerListener().onSubmit(mId, mCallerContext);
      onNewResultInternal(mId, mDataSource, closeableImage, 1.0f, true, true);
      return;
    }
    mEventTracker.recordEvent(Event.ON_DATASOURCE_SUBMIT); // 日志
    getControllerListener().onSubmit(mId, mCallerContext); // 給監(jiān)聽(tīng)器去干活脉顿，一個(gè)id一個(gè)坑
    mSettableDraweeHierarchy.setProgress(0, true);// 對(duì)象樹(shù)準(zhǔn)備
    mIsRequestSubmitted = true;// 已經(jīng)提交
    mHasFetchFailed = false;// 重置
    mDataSource = getDataSource(); // 獲取子類data策略
    if (FLog.isLoggable(FLog.VERBOSE)) {
      FLog.v(
          TAG,
          "controller %x %s: submitRequest: dataSource: %x",
          System.identityHashCode(this),
          mId,
          System.identityHashCode(mDataSource));
    }
    final String id = mId;
    final boolean wasImmediate = mDataSource.hasResult();
    final DataSubscriber<T> dataSubscriber =
        new BaseDataSubscriber<T>() {
          @Override
          public void onNewResultImpl(DataSource<T> dataSource) {
            // isFinished must be obtained before image, otherwise we might set intermediate result
            // as final image.
            boolean isFinished = dataSource.isFinished();
            float progress = dataSource.getProgress();
            T image = dataSource.getResult();
            if (image != null) {
              onNewResultInternal(id, dataSource, image, progress, isFinished, wasImmediate);
            } else if (isFinished) {
              onFailureInternal(id, dataSource, new NullPointerException(), /* isFinished */ true);
            }
          }
          @Override
          public void onFailureImpl(DataSource<T> dataSource) {
            onFailureInternal(id, dataSource, dataSource.getFailureCause(), /* isFinished */ true);
          }
          @Override
          public void onProgressUpdate(DataSource<T> dataSource) {
            boolean isFinished = dataSource.isFinished();
            float progress = dataSource.getProgress();
            onProgressUpdateInternal(id, dataSource, progress, isFinished);
          }
        };
    mDataSource.subscribe(dataSubscriber, mUiThreadImmediateExecutor); // 在ui線程訂閱，開(kāi)始刷新
  }

  private void onNewResultInternal( // 成功
      String id,
      DataSource<T> dataSource,
      @Nullable T image,
      float progress,
      boolean isFinished,
      boolean wasImmediate) {
    // ignore late callbacks (data source that returned the new result is not the one we expected)
    if (!isExpectedDataSource(id, dataSource)) { // 略過(guò)老data
      logMessageAndImage("ignore_old_datasource @ onNewResult", image);
      releaseImage(image);
      dataSource.close();
      return;
    }
    mEventTracker.recordEvent( // 日志追蹤
        isFinished ? Event.ON_DATASOURCE_RESULT : Event.ON_DATASOURCE_RESULT_INT);
    // create drawable
    Drawable drawable;
    try {
      drawable = createDrawable(image); //調(diào)用子類策略創(chuàng)建drawable 
    } catch (Exception exception) { // 失敗打印和釋放資源
      logMessageAndImage("drawable_failed @ onNewResult", image);
      releaseImage(image);
      onFailureInternal(id, dataSource, exception, isFinished);
      return;
    }
    T previousImage = mFetchedImage; // 完成新老數(shù)據(jù)交換
    Drawable previousDrawable = mDrawable;
    mFetchedImage = image; // 給hold的當(dāng)前image進(jìn)行策略釋放
    mDrawable = drawable;
    try {
      // set the new image
      if (isFinished) { // 完成后点寥，刷新艾疟，監(jiān)聽(tīng)回掉，改干嘛干嘛
        logMessageAndImage("set_final_result @ onNewResult", image);
        mDataSource = null;
        mSettableDraweeHierarchy.setImage(drawable, 1f, wasImmediate);
        getControllerListener().onFinalImageSet(id, getImageInfo(image), getAnimatable());
        // IMPORTANT: do not execute any instance-specific code after this point
      } else {
        logMessageAndImage("set_intermediate_result @ onNewResult", image);
        mSettableDraweeHierarchy.setImage(drawable, progress, wasImmediate);
        getControllerListener().onIntermediateImageSet(id, getImageInfo(image));
        // IMPORTANT: do not execute any instance-specific code after this point
      }
    } finally { // 釋放當(dāng)前請(qǐng)求資源
      if (previousDrawable != null && previousDrawable != drawable) {
        releaseDrawable(previousDrawable);
      }
      if (previousImage != null && previousImage != image) {
        logMessageAndImage("release_previous_result @ onNewResult", previousImage);
        releaseImage(previousImage);
      }
    }
  }

  private void onFailureInternal( // 更新失敗數(shù)據(jù)
      String id,
      DataSource<T> dataSource,
      Throwable throwable,
      boolean isFinished) {
    // ignore late callbacks (data source that failed is not the one we expected)
    if (!isExpectedDataSource(id, dataSource)) { // 判斷是否是自己感興趣的data
      logMessageAndFailure("ignore_old_datasource @ onFailure", throwable);
      dataSource.close();
      return;
    }
    mEventTracker.recordEvent( // 日志追蹤
        isFinished ? Event.ON_DATASOURCE_FAILURE : Event.ON_DATASOURCE_FAILURE_INT);
    // fail only if the data source is finished
    if (isFinished) { //刷新失敗流程
      logMessageAndFailure("final_failed @ onFailure", throwable);
      mDataSource = null;
      mHasFetchFailed = true;
      // Set the previously available image if available.
      if (mRetainImageOnFailure && mDrawable != null) {
        mSettableDraweeHierarchy.setImage(mDrawable, 1f, true);
      } else if (shouldRetryOnTap()) {
        mSettableDraweeHierarchy.setRetry(throwable);
      } else {
        mSettableDraweeHierarchy.setFailure(throwable);
      }
      getControllerListener().onFailure(mId, throwable);
      // IMPORTANT: do not execute any instance-specific code after this point
    } else {
      logMessageAndFailure("intermediate_failed @ onFailure", throwable);
      getControllerListener().onIntermediateImageFailed(mId, throwable);
      // IMPORTANT: do not execute any instance-specific code after this point
    }
  }

  private void onProgressUpdateInternal( // 更新實(shí)時(shí)數(shù)據(jù)
      String id,
      DataSource<T> dataSource,
      float progress,
      boolean isFinished) {
    // ignore late callbacks (data source that failed is not the one we expected)
    if (!isExpectedDataSource(id, dataSource)) {
      logMessageAndFailure("ignore_old_datasource @ onProgress", null);
      dataSource.close();
      return;
    }
    if (!isFinished) {
      mSettableDraweeHierarchy.setProgress(progress, false);
    }
  }

  private boolean isExpectedDataSource(String id, DataSource<T> dataSource) { // 判斷當(dāng)前提交狀態(tài)的dataSource 釋放為新的敢辩，持有id老dataSource 不再感興趣
    if (dataSource == null && mDataSource == null) {
      // DataSource is null when we use directly the Bitmap from the MemoryCache. In this case
      // we don't have to close the DataSource.
      return true;
    }
    // There are several situations in which an old data source might return a result that we are no
    // longer interested in. To verify that the result is indeed expected, we check several things:
    return id.equals(mId) && dataSource == mDataSource && mIsRequestSubmitted;
  }

     ........

  @Override
  public @Nullable Animatable getAnimatable() {
    return (mDrawable instanceof Animatable) ? (Animatable) mDrawable : null;
  }

 // 下面都是回掉子類接口 PipelineDraweeController

  protected abstract DataSource<T> getDataSource();

  protected abstract Drawable createDrawable(T image);

  protected abstract @Nullable INFO getImageInfo(T image);

  protected String getImageClass(@Nullable T image) {
    return (image != null) ? image.getClass().getSimpleName() : "<null>";
  }

  protected int getImageHash(@Nullable T image) {
    return System.identityHashCode(image);
  }

  protected abstract void releaseImage(@Nullable T image);

  protected abstract void releaseDrawable(@Nullable Drawable drawable);

     ........

}

屬性：SettableDraweeHierarchy 你可以認(rèn)為這貨就是你的drawable的修飾類所需要維護(hù)的樹(shù)形結(jié)構(gòu)蔽莱，相當(dāng)于drawable是衣服的話，DraweeHierarchy就是衣服上的線條結(jié)構(gòu)和底色配色戚长，和XML中布局默認(rèn)屬性差不多

這個(gè)類比較長(zhǎng)盗冷，所有request是從attach開(kāi)始submit，onDetach停止和釋放資源維護(hù)同廉。

attach和onDetach事件來(lái)自于DraweeHierarchy中toplevel仪糖，Drawable的DraweeHold，它實(shí)現(xiàn)了監(jiān)聽(tīng)和派發(fā)回掉

好了你大致也看懂了submit這個(gè)函數(shù)中恤溶，先準(zhǔn)備一些flag乓诽，然后給Listener去實(shí)現(xiàn)submit，然后自己訂閱回掉在ui線程咒程，開(kāi)始刷新界面鸠天。

這個(gè)大多數(shù)人都有個(gè)誤區(qū)，認(rèn)為L(zhǎng)istener是實(shí)現(xiàn)提交請(qǐng)求帐姻，其實(shí)不是稠集，這貨只是監(jiān)聽(tīng)回調(diào)，真正在跑網(wǎng)絡(luò)數(shù)據(jù)得是這個(gè)訂閱得datasrouce,而這個(gè)datasrouce來(lái)自getDataSource(),這個(gè)來(lái)自AbstractDraweeControllerBuilder:getDataSourceSupplierForRequest(),一路追蹤最后來(lái)自PipelineDraweeControllerBuilder:getDataSourceForRequest(),好了這個(gè)主線來(lái)了饥瓷，ImagePipeline要開(kāi)始干活了剥纷，往上面翻，自己再總結(jié)理解下呢铆。

接著看：Fresco源碼分析（二）