功能介紹

    使用文章介紹以及和Picasso的對(duì)比分析請(qǐng)參考Introduction to Glide, Image Loader Library for Android, recommended by Google

    由于這篇文章使用glide的老版本，因此有些使用方法可能不太一致了，

Android Glide源碼解析

    本文基于github上Glide最新代碼4.0.0版本做解析。

    最基本的使用方式如下：

<code avrasm="" class="hljs">Glide.with(this)                .asDrawable()                .load(http://i6.topit.me/6/5d/45/1131907198420455d6o.jpg)                .apply(fitCenterTransform(this))                .apply(placeholderOf(R.drawable.skyblue_logo_wechatfavorite_checked))                .into(imageView);</code>

    Glide使用了現(xiàn)在非常流行的流氏編碼方式，方便了開(kāi)發(fā)者的使用，簡(jiǎn)明、扼要。

    接下來(lái)主要對(duì)上面這一段流氏操作做拆分。

Glide 主入口

    這個(gè)類(lèi)有點(diǎn)像門(mén)臉模式的統(tǒng)一代理入口，不過(guò)實(shí)際作用在4.0.0中很多功能都被放到后面的其他類(lèi)中，此類(lèi)關(guān)注的點(diǎn)就很少了。雖然整個(gè)libray的所有需要的組建都在這個(gè)類(lèi)中，但是實(shí)際也只是一個(gè)統(tǒng)一初始化的地方。

RequestManager（Glide.with(…)）

    這個(gè)類(lèi)主要用于管理和啟動(dòng)Glide的所有請(qǐng)求，可以使用activity，fragment或者連接生命周期的事件去智能的停止，啟動(dòng)，和重啟請(qǐng)求。也可以檢索或者通過(guò)實(shí)例化一個(gè)新的對(duì)象，或者使用靜態(tài)的Glide去利用構(gòu)建在Activity和Fragment生命周期處理中。它的方法跟你的Fragment和Activity的是同步的。

RequestBuilder

    通用類(lèi)，可以處理設(shè)置選項(xiàng)，并啟動(dòng)負(fù)載的通用資源類(lèi)型。

    在這個(gè)類(lèi)中，主要是應(yīng)用請(qǐng)求的很多選項(xiàng)(如下的選項(xiàng)從字面都能看出具體的用處，在ImageView控件中經(jīng)常也能看到，另外之前版本可不是這么使用的)：

<code class="hljs" php="">public final class RequestOptions extends BaseRequestOptions<requestoptions>{  private static RequestOptions skipMemoryCacheTrueOptions;  private static RequestOptions skipMemoryCacheFalseOptions;  private static RequestOptions fitCenterOptions;  private static RequestOptions centerCropOptions;  private static RequestOptions circleCropOptions;  private static RequestOptions noTransformOptions;  private static RequestOptions noAnimationOptions;  // ...省略...}</requestoptions></code>

    RequestBuilder transition(TransitionOptions transitionOptions){} 這個(gè)方法主要是用于加載對(duì)象從占位符（placeholder）或者縮略圖（thumbnail）到真正對(duì)象加載完成的轉(zhuǎn)場(chǎng)動(dòng)畫(huà)。

    RequestBuilder load(…){}多太方法中，這里可以加載很多類(lèi)型的數(shù)據(jù)對(duì)象，可以是String，Uri，F(xiàn)ile，resourceId，byte[]這些。當(dāng)然這些后面對(duì)應(yīng)的編碼方式也是不一樣的。

    Target into(…){}這個(gè)方法是觸發(fā)Request真正啟動(dòng)的地方，在上邊的示例中最后就是調(diào)用這個(gè)方法發(fā)起請(qǐng)求。

    不得不說(shuō)的registry域，這個(gè)域掛載了很多元件，該注冊(cè)器中囊括了模塊加載器（ModelLoader）、編碼器（Encoder）、資源解碼器（ResourceDecoder）、資源編碼器（ResourceEncoder）、數(shù)據(jù)回轉(zhuǎn)器（DataRewinder）、轉(zhuǎn)碼器（Transcoder）。這些都是Glide在對(duì)資源編解碼中既是基礎(chǔ)又是核心功能。

代碼結(jié)構(gòu)

    這里主要列舉一下一些重要的組件以及他們的結(jié)構(gòu)關(guān)系：

    ModelLoader

    DataFetcher

    Target

    Resource

    ResourceTransformation

    Pool

    Cache

    Decoder

    Encoder

    把這些組件代碼結(jié)構(gòu)列舉出來(lái)主要是為了讓讀者和使用者一目了然的看到自己需要的一些功能。

執(zhí)行流程

1、根據(jù)不同版本的Fragment創(chuàng)建RequestManagerFragment或者SupportRequestManagerFragment，并加入到對(duì)應(yīng)的FragmentManager中。這兩種Fragment是不帶有任何界面的，主要是用于同步生命周期。具體實(shí)現(xiàn)如下：

<code avrasm="" class="hljs">public static RequestManager with(Context context) {    RequestManagerRetriever retriever = RequestManagerRetriever.get();    return retriever.get(context);  }// RequestManagerRetriever.get(...)  @TargetApi(Build.VERSION_CODES.HONEYCOMB)  public RequestManager get(Activity activity) {    if (Util.isOnBackgroundThread() || Build.VERSION.SDK_INT < Build.VERSION_CODES.HONEYCOMB) {      return get(activity.getApplicationContext());    } else {      assertNotDestroyed(activity);      android.app.FragmentManager fm = activity.getFragmentManager();      return fragmentGet(activity, fm, null);    }  }  @TargetApi(Build.VERSION_CODES.HONEYCOMB)  RequestManager fragmentGet(Context context, android.app.FragmentManager fm,      android.app.Fragment parentHint) {    RequestManagerFragment current = getRequestManagerFragment(fm, parentHint);    RequestManager requestManager = current.getRequestManager();    if (requestManager == null) {      requestManager =          new RequestManager(context, current.getLifecycle(), current.getRequestManagerTreeNode());      current.setRequestManager(requestManager);    }    return requestManager;  }  @TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR1)  RequestManagerFragment getRequestManagerFragment(      final android.app.FragmentManager fm, 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);        fm.beginTransaction().add(current, FRAGMENT_TAG).commitAllowingStateLoss();        handler.obtainMessage(ID_REMOVE_FRAGMENT_MANAGER, fm).sendToTarget();      }    }    return current;  }</code>

2、創(chuàng)建一個(gè)RequestBuilder，并添加一個(gè)DrawableTransitionOptions類(lèi)型的轉(zhuǎn)場(chǎng)動(dòng)畫(huà)

<code class="hljs" cs="">public RequestBuilder<drawable>asDrawable() {    return as(Drawable.class).transition(new DrawableTransitionOptions());  }</drawable></code>

3、加載對(duì)象（model域）

<code class="hljs" cs="">public RequestBuilder<transcodetype>load(@Nullable Object model) {    return loadGeneric(model);  }private RequestBuilder<transcodetype>loadGeneric(@Nullable Object model) {    this.model = model;    isModelSet = true;    return this;  }</transcodetype></transcodetype></code>

4、裝載對(duì)象（包含請(qǐng)求的發(fā)起點(diǎn)）。

<code class="hljs" cs="">public<y extends="" transcodetype="">> Y into(@NonNull Y target) {    Util.assertMainThread();    Preconditions.checkNotNull(target);    if (!isModelSet) {      throw new IllegalArgumentException(You must call #load() before calling #into());    }    Request previous = target.getRequest();    if (previous != null) {      requestManager.clear(target);    }    requestOptions.lock();    Request request = buildRequest(target);    target.setRequest(request);    requestManager.track(target, request);    return target;  }</y></code>

    一般而言，大部分使用者都是用來(lái)裝載圖片的，因此都會(huì)調(diào)用如下這個(gè)方法：

<code class="hljs" cs="">public Target<transcodetype>into(ImageView view) {    Util.assertMainThread();    Preconditions.checkNotNull(view);    if (!requestOptions.isTransformationSet()        && requestOptions.isTransformationAllowed()        && view.getScaleType() != null) {      if (requestOptions.isLocked()) {        requestOptions = requestOptions.clone();      }      switch (view.getScaleType()) {        case CENTER_CROP:          requestOptions.optionalCenterCrop(context);          break;        case FIT_CENTER:        case FIT_START:        case FIT_END:          requestOptions.optionalFitCenter(context);          break;        //$CASES-OMITTED$        default:          // Do nothing.      }    }    return into(context.buildImageViewTarget(view, transcodeClass));  }</transcodetype></code>

    這里針對(duì)ImageView的填充方式做了篩選并對(duì)應(yīng)設(shè)置到requestOptions上。最終的是通過(guò)ImageView和轉(zhuǎn)碼類(lèi)型（transcodeClass）創(chuàng)建不通過(guò)的Target（例如Bitmap對(duì)應(yīng)的BitmapImageViewTarget和Drawable對(duì)應(yīng)的DrawableImageViewTarget）

    4.1 Request的創(chuàng)建buildRequest(target)。

    在Request的創(chuàng)建中會(huì)針對(duì)是否有縮略圖來(lái)創(chuàng)建不同尺寸的請(qǐng)求，縮略圖方法可以使用RequestBuilder.thumbnail(…)方法來(lái)添加上。

    Glide中的Request都是使用了SingleRequest類(lèi)，當(dāng)然縮略圖采用的是ThumbnailRequestCoordinator類(lèi)：

<code class="hljs" cs="">private Request obtainRequest(Target<transcodetype>target,      BaseRequestOptionsrequestOptions, RequestCoordinator requestCoordinator,      TransitionOptionstransitionOptions, Priority priority,      int overrideWidth, int overrideHeight) {    requestOptions.lock();    return SingleRequest.obtain(        context,        model,        transcodeClass,        requestOptions,        overrideWidth,        overrideHeight,        priority,        target,        requestListener,        requestCoordinator,        context.getEngine(),        transitionOptions.getTransitionFactory());  }</transcodetype></code>

    比較值得推崇的是SingleRequest.obtain寫(xiě)法，個(gè)人認(rèn)為比new關(guān)鍵字更簡(jiǎn)潔明了吧。

    target.setRequest(request)也是一個(gè)比較值得注意的地方，如果target是ViewTarget，那么request會(huì)被設(shè)置到View的tag上。這樣其實(shí)是有一個(gè)好處，每一個(gè)View有一個(gè)自己的Request，如果有重復(fù)請(qǐng)求，那么都會(huì)先去拿到上一個(gè)已經(jīng)綁定的Request，并且從RequestManager中清理回收掉。這應(yīng)該是去重的功能。

    4.2 requestManager.track(target, request)

    這個(gè)方法非常的復(fù)雜，主要用于觸發(fā)請(qǐng)求、編解碼、裝載和緩存這些功能。下面就一步一步來(lái)看吧：

    4.2.1 緩存target，并啟動(dòng)Request

<code class="hljs" java="">void track(Targettarget, Request request) {    targetTracker.track(target);    requestTracker.runRequest(request);  }  /**   * Starts tracking the given request.   */  public void runRequest(Request request) {    requests.add(request); //添加內(nèi)存緩存    if (!isPaused) {      request.begin(); // 開(kāi)始    } else {      pendingRequests.add(request); // 掛起請(qǐng)求    }  }</code>

    繼續(xù)看一下SingleRequest中的begin方法：

<code class="hljs" java="">@Override  public void begin() {    stateVerifier.throwIfRecycled();    startTime = LogTime.getLogTime();    // 如果model空的，那么是不能執(zhí)行的。 這里的model就是前面提到的RequestBuilder中的model    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;    }    status = Status.WAITING_FOR_SIZE;    // 如果當(dāng)前的View尺寸已經(jīng)加載獲取到了，那么就會(huì)進(jìn)入真正的加載流程。    if (Util.isValidDimensions(overrideWidth, overrideHeight)) {      onSizeReady(overrideWidth, overrideHeight);    } else {    // 反之，當(dāng)前View還沒(méi)有畫(huà)出來(lái)，那么是沒(méi)有尺寸的。    // 這里會(huì)調(diào)用到ViewTreeObserver.addOnPreDrawListener。    // 等待View的尺寸都o(jì)k，才會(huì)繼續(xù)      target.getSize(this);    }    // 如果等待和正在執(zhí)行狀態(tài)，那么當(dāng)前會(huì)加載占位符Drawable    if ((status == Status.RUNNING || status == Status.WAITING_FOR_SIZE)        && canNotifyStatusChanged()) {      target.onLoadStarted(getPlaceholderDrawable());    }    if (Log.isLoggable(TAG, Log.VERBOSE)) {      logV(finished run method in  + LogTime.getElapsedMillis(startTime));    }  }</code>

    接下來(lái)是target.getSize(this)方法。這里主要說(shuō)一下尺寸未加載出來(lái)的情況(ViewTarget.java)：

<code class="hljs" java="">void getSize(SizeReadyCallback cb) {      int currentWidth = getViewWidthOrParam();      int currentHeight = getViewHeightOrParam();      if (isSizeValid(currentWidth) && isSizeValid(currentHeight)) {        cb.onSizeReady(currentWidth, currentHeight);      } else {        // We want to notify callbacks in the order they were added and we only expect one or two        // callbacks to        // be added a time, so a List is a reasonable choice.        if (!cbs.contains(cb)) {          cbs.add(cb);        }        if (layoutListener == null) {          final ViewTreeObserver bserver = view.getViewTreeObserver();          layoutListener = new SizeDeterminerLayoutListener(this);          // 繪畫(huà)之前加入尺寸的監(jiān)聽(tīng)。這一點(diǎn)我想大部分Android開(kāi)發(fā)同學(xué)應(yīng)該都知道。          // 接下來(lái)在看看系統(tǒng)觸發(fā)該Listener時(shí)target又干了些什么。          observer.addOnPreDrawListener(layoutListener);        }      }    }private static class SizeDeterminerLayoutListener implements ViewTreeObserver        .OnPreDrawListener {        // 注意這里是弱引用      private final WeakReference<sizedeterminer>sizeDeterminerRef;      public SizeDeterminerLayoutListener(SizeDeterminer sizeDeterminer) {        sizeDeterminerRef = new WeakReference<>(sizeDeterminer);      }      @Override      public boolean onPreDraw() {        if (Log.isLoggable(TAG, Log.VERBOSE)) {          Log.v(TAG, OnGlobalLayoutListener called listener= + this);        }        SizeDeterminer sizeDeterminer = sizeDeterminerRef.get();        if (sizeDeterminer != null) {         // 通知SizeDeterminer去重新檢查尺寸，并觸發(fā)后續(xù)操作。         // SizeDeterminer有點(diǎn)像工具類(lèi)，又作為尺寸回調(diào)的檢測(cè)接口          sizeDeterminer.checkCurrentDimens();        }        return true;      }    }</sizedeterminer></code>

    ok，繼續(xù)回到SingleRequest.onSizeReady方法,主要就是Engine發(fā)起load操作

<code avrasm="" class="hljs">public void onSizeReady(int width, int height) {    stateVerifier.throwIfRecycled();    if (Log.isLoggable(TAG, Log.VERBOSE)) {      logV(Got onSizeReady in  + LogTime.getElapsedMillis(startTime));    }    if (status != Status.WAITING_FOR_SIZE) {      return;    }    status = Status.RUNNING;    float sizeMultiplier = requestOptions.getSizeMultiplier();    this.width = Math.round(sizeMultiplier * width);    this.height = Math.round(sizeMultiplier * height);    if (Log.isLoggable(TAG, Log.VERBOSE)) {      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.getOptions(),        requestOptions.isMemoryCacheable(),        this);    if (Log.isLoggable(TAG, Log.VERBOSE)) {      logV(finished onSizeReady in  + LogTime.getElapsedMillis(startTime));    }  }</code>

    特別的，所有的操作都是來(lái)之唯一一個(gè)Engine，它的創(chuàng)建是來(lái)至于Glide的初始化。如果有需要修改緩存配置的同學(xué)可以繼續(xù)看一下diskCacheFactory的創(chuàng)建：

<code class="hljs" cs="">if (engine == null) {      engine = new Engine(memoryCache, diskCacheFactory, diskCacheExecutor, sourceExecutor);    }</code>

    繼續(xù)看一下Engine.load的詳細(xì)過(guò)程：

<code class="hljs" lasso="">public<r>LoadStatus load(      GlideContext glideContext,      Object model,      Key signature,      int width,      int height,      ClassresourceClass,      Class<r>transcodeClass,      Priority priority,      DiskCacheStrategy diskCacheStrategy,      Map<class<?>, Transformation> transformations,      boolean isTransformationRequired,      Options options,      boolean isMemoryCacheable,      ResourceCallback cb) {    Util.assertMainThread();    long startTime = LogTime.getLogTime();    // 創(chuàng)建key，這是給每次加載資源的唯一標(biāo)示，
電腦資料
《Android Glide源碼解析》(http://www.oriental01.com)。    EngineKey key = keyFactory.buildKey(model, signature, width, height, transformations,        resourceClass, transcodeClass, options);    // 通過(guò)key查找緩存資源 （PS 這里的緩存主要是內(nèi)存中的緩存，切記,可以查看MemoryCache）    EngineResourcecached = loadFromCache(key, isMemoryCacheable);    if (cached != null) {     // 如果有，那么直接利用當(dāng)前緩存的資源。      cb.onResourceReady(cached, DataSource.MEMORY_CACHE);      if (Log.isLoggable(TAG, Log.VERBOSE)) {        logWithTimeAndKey(Loaded resource from cache, startTime, key);      }      return null;    }    // 這是一個(gè)二級(jí)內(nèi)存的緩存引用，很簡(jiǎn)單用了一個(gè)Map<key,>>>裝載起來(lái)的。    // 這個(gè)緩存主要是誰(shuí)來(lái)放進(jìn)去呢？ 可以參考上面一級(jí)內(nèi)存緩存loadFromCache方法。    EngineResourceactive = loadFromActiveResources(key, isMemoryCacheable);    if (active != null) {      cb.onResourceReady(active, DataSource.MEMORY_CACHE);      if (Log.isLoggable(TAG, Log.VERBOSE)) {        logWithTimeAndKey(Loaded resource from active resources, startTime, key);      }      return null;    }    // 根據(jù)key獲取緩存的job。    EngineJob current = jobs.get(key);    if (current != null) {      current.addCallback(cb); // 給當(dāng)前job添加上回調(diào)Callback      if (Log.isLoggable(TAG, Log.VERBOSE)) {        logWithTimeAndKey(Added to existing load, startTime, key);      }      return new LoadStatus(cb, current);    }    // 創(chuàng)建job    EngineJob<r>engineJob = engineJobFactory.build(key, isMemoryCacheable);    DecodeJob<r>decodeJob = decodeJobFactory.build(        glideContext,        model,        key,        signature,        width,        height,        resourceClass,        transcodeClass,        priority,        diskCacheStrategy,        transformations,        isTransformationRequired,        options,        engineJob);    jobs.put(key, engineJob);    engineJob.addCallback(cb);    // 放入線(xiàn)程池，執(zhí)行    engineJob.start(decodeJob);    if (Log.isLoggable(TAG, Log.VERBOSE)) {      logWithTimeAndKey(Started new load, startTime, key);    }    return new LoadStatus(cb, engineJob);  }</r></r></key,></class<?></r></r></code>

    上面有一些值得注意的地方：

<code class="hljs" cs="">private void runWrapped() {     switch (runReason) {      case INITIALIZE:        // 初始化 獲取下一個(gè)階段狀態(tài)        stage = getNextStage(Stage.INITIALIZE);        currentGenerator = getNextGenerator();        // 運(yùn)行        runGenerators();        break;      case SWITCH_TO_SOURCE_SERVICE:        runGenerators();        break;      case DECODE_DATA:        decodeFromRetrievedData();        break;      default:        throw new IllegalStateException(Unrecognized run reason:  + runReason);    }  }// 這里的階段策略首先是從resource中尋找，然后再是data，，再是sourceprivate Stage getNextStage(Stage current) {    switch (current) {      case INITIALIZE:       // 根據(jù)定義的緩存策略來(lái)回去下一個(gè)狀態(tài)      // 緩存策略來(lái)之于RequestBuilder的requestOptions域      // 如果你有自定義的策略，可以調(diào)用RequestBuilder.apply方法即可      // 詳細(xì)的可用緩存策略請(qǐng)參看DiskCacheStrategy.java        return diskCacheStrategy.decodeCachedResource()            ? Stage.RESOURCE_CACHE : getNextStage(Stage.RESOURCE_CACHE);      case RESOURCE_CACHE:        return diskCacheStrategy.decodeCachedData()            ? Stage.DATA_CACHE : getNextStage(Stage.DATA_CACHE);      case DATA_CACHE:        return Stage.SOURCE;      case SOURCE:      case FINISHED:        return Stage.FINISHED;      default:        throw new IllegalArgumentException(Unrecognized stage:  + current);    }// 根據(jù)Stage找到數(shù)據(jù)抓取生成器。private DataFetcherGenerator getNextGenerator() {    switch (stage) {      case RESOURCE_CACHE:       // 產(chǎn)生含有降低采樣/轉(zhuǎn)換資源數(shù)據(jù)緩存文件的DataFetcher。        return new ResourceCacheGenerator(decodeHelper, this);      case DATA_CACHE:       // 產(chǎn)生包含原始未修改的源數(shù)據(jù)緩存文件的DataFetcher。        return new DataCacheGenerator(decodeHelper, this);      case SOURCE:      // 生成使用注冊(cè)的ModelLoader和加載時(shí)提供的Model獲取源數(shù)據(jù)規(guī)定的DataFetcher。      // 根據(jù)不同的磁盤(pán)緩存策略，源數(shù)據(jù)可首先被寫(xiě)入到磁盤(pán)，然后從緩存文件中加載，而不是直接返回。        return new SourceGenerator(decodeHelper, this);      case FINISHED:        return null;      default:        throw new IllegalStateException(Unrecognized stage:  + stage);    }  }</code>

<code class="hljs" java="">public boolean startNext() {    if (dataToCache != null) {      Object data = dataToCache;      dataToCache = null;      cacheData(data);    }    if (sourceCacheGenerator != null && sourceCacheGenerator.startNext()) {      return true;    }    sourceCacheGenerator = null;    loadData = null;    boolean started = false;    // 查找ModelLoader    while (!started && hasNextModelLoader()) {      loadData = helper.getLoadData().get(loadDataListIndex++);      if (loadData != null          && (helper.getDiskCacheStrategy().isDataCacheable(loadData.fetcher.getDataSource())          || helper.hasLoadPath(loadData.fetcher.getDataClass()))) {        started = true;        根據(jù)model的fetcher加載數(shù)據(jù)        loadData.fetcher.loadData(helper.getPriority(), this);      }    }    return started;  }</code>

<code class="hljs" lasso="">public void onDataReady(Object data) {    DiskCacheStrategy diskCacheStrategy = helper.getDiskCacheStrategy();    if (data != null && diskCacheStrategy.isDataCacheable(loadData.fetcher.getDataSource())) {      dataToCache = data;      // We might be being called back on someone else's thread. Before doing anything, we should      // reschedule to get back onto Glide's thread.      cb.reschedule();    } else {      cb.onDataFetcherReady(loadData.sourceKey, data, loadData.fetcher,          loadData.fetcher.getDataSource(), originalKey);    }  }</code>

<code class="hljs" cs="">public void reschedule() {    runReason = RunReason.SWITCH_TO_SOURCE_SERVICE;    callback.reschedule(this);  }</code>

<code class="hljs" cs="">public void reschedule(DecodeJobjob) {    if (isCancelled) {      MAIN_THREAD_HANDLER.obtainMessage(MSG_CANCELLED, this).sendToTarget();    } else {      sourceExecutor.execute(job);    }  }</code>

<code class="hljs" cs="">private void cacheData(Object dataToCache) {    long startTime = LogTime.getLogTime();    try {    // 根據(jù)不同的數(shù)據(jù)獲取注冊(cè)的不同Encoder      Encoder<object>encoder = helper.getSourceEncoder(dataToCache);      DataCacheWriter<object>writer =          new DataCacheWriter<>(encoder, dataToCache, helper.getOptions());      riginalKey = new DataCacheKey(loadData.sourceKey, helper.getSignature());      // 這里的DiskCache實(shí)現(xiàn)是Engine中LazyDiskCacheProvider提供的DiskCacheAdapter。      helper.getDiskCache().put(originalKey, writer);      if (Log.isLoggable(TAG, Log.VERBOSE)) {        Log.v(TAG, Finished encoding source to cache            + , key:  + originalKey            + , data:  + dataToCache            + , encoder:  + encoder            + , duration:  + LogTime.getElapsedMillis(startTime));      }    } finally {      loadData.fetcher.cleanup();    }    // 創(chuàng)建針對(duì)緩存的Generator    sourceCacheGenerator =        new DataCacheGenerator(Collections.singletonList(loadData.sourceKey), helper, this);  }</object></object></code>

<code class="hljs" cs="">public boolean startNext() {    while (modelLoaders == null || !hasNextModelLoader()) {      sourceIdIndex++;      if (sourceIdIndex >= cacheKeys.size()) {        return false;      }      Key sourceId = cacheKeys.get(sourceIdIndex);      Key riginalKey = new DataCacheKey(sourceId, helper.getSignature());      cacheFile = helper.getDiskCache().get(originalKey);      if (cacheFile != null) {        this.sourceKey = sourceId;        modelLoaders = helper.getModelLoaders(cacheFile);        modelLoaderIndex = 0;      }    }    loadData = null;    boolean started = false;    // 這里會(huì)通過(guò)model尋找注冊(cè)過(guò)的ModelLoader    while (!started && hasNextModelLoader()) {      ModelLoader<file,>modelLoader = modelLoaders.get(modelLoaderIndex++);      loadData =          modelLoader.buildLoadData(cacheFile, helper.getWidth(), helper.getHeight(),              helper.getOptions());      // 通過(guò)FileLoader繼續(xù)加載數(shù)據(jù)      if (loadData != null && helper.hasLoadPath(loadData.fetcher.getDataClass())) {        started = true;        loadData.fetcher.loadData(helper.getPriority(), this);      }    }    return started;  }</file,></code>

<code class="hljs" php="">public<model>List<modelloader<model,>> getModelLoaders(Model model) {    List<modelloader<model,>> result = modelLoaderRegistry.getModelLoaders(model);    if (result.isEmpty()) {      throw new NoModelLoaderAvailableException(model);    }    return result;  }</modelloader<model,></modelloader<model,></model></code>

<code class="hljs" lasso="">public void loadData(Priority priority, DataCallbackcallback) {        // 讀取文件數(shù)據(jù)      try {        data = opener.open(file);      } catch (FileNotFoundException e) {        if (Log.isLoggable(TAG, Log.DEBUG)) {          Log.d(TAG, Failed to open file, e);        }        //失敗        callback.onLoadFailed(e);        return;      }      // 成功      callback.onDataReady(data);    }</code>

<code class="hljs" haml="">-->DataCacheGenerator.onDataReady  -->SourceGenerator.onDataFetcherReady    -->DecodeJob.onDataFetcherReady    -->DecodeJob.decodeFromRetrievedData    -->DecodeJob.notifyEncodeAndRelease    -->DecodeJob.notifyComplete      -->EngineJob.onResourceReady</code>

<code class="hljs" haml="">-->EngineJob.handleResultOnMainThread        -->SingleRequest.onResourceReady          -->ImageViewTarget.onResourceReady          -->ImageViewTarget.setResource            -->ImageView.setImageDrawable/ImageView.setImageBitmap</code>

<code class="hljs" cs="">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);      exceptions.add(e);    }    if (resource != null) {      notifyEncodeAndRelease(resource, currentDataSource);    } else {      runGenerators();    }  }</r></code>

<code class="hljs" haml="">-->DecodeJob.decodeFromData-->DecodeJob.decodeFromFetcher-->DecodeJob.runLoadPath  -->LoadPath.load  -->LoadPath.loadWithExceptionList  -->LoadPath.decode  -->LoadPath.decodeResource  -->LoadPath.decodeResourceWithList    -->ResourceDecoder.handles    -->ResourceDecoder.decode</code>