Glide源码解析05-onLoadComplete

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本文深入解析Glide中图片加载成功的流程，从EngineRunnable#onLoadComplete开始，通过Handler发送消息，EngineJob处理主线程结果，最终调用ImageViewTarget#onResourceReady完成图片展示。

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Glide源码解析05-onLoadComplete

在Glide源码解析03中我们以及看到Glide调用了EngineRunnable#onLoadFailed或者EngineRunnable#onLoadComplete来调用失败或成功的结果。
这里我们来详细看下onLoadComplete，onLoadFailed也是同样的逻辑。

    if (resource == null) {
        onLoadFailed(exception);
    } else {
        onLoadComplete(resource);
    }

5.0 Handler.obtainMessage(MSG_COMPLETE)

在onLoadComplete中调用了EngineRunnableManager#onResourceReady()，其内部调用Handler发送了MSG_COMPLETE的消息。

public void onResourceReady(final Resource<?> resource) {
    this.resource = resource;
    MAIN_THREAD_HANDLER.obtainMessage(MSG_COMPLETE, this).sendToTarget();
}

5.1 Handler.handleMessage

在handleMessage中，调用了EngineJob#handleResultOnMainThread()

public boolean handleMessage(Message message) {
    if (MSG_COMPLETE == message.what || MSG_EXCEPTION == message.what) {
        EngineJob job = (EngineJob) message.obj;
        if (MSG_COMPLETE == message.what) {
            job.handleResultOnMainThread();
        } else {
            job.handleExceptionOnMainThread();
        }
        return true;
    }

    return false;
}

5.2 EngineJob#handleResultOnMainThread

在这里，会去遍历ResourceCallback集合，并调用其onResourceReady()，这里的cb是GenericRequest对象。

private void handleResultOnMainThread() {
    //...

    for (ResourceCallback cb : cbs) {
        if (!isInIgnoredCallbacks(cb)) {
            engineResource.acquire();
            cb.onResourceReady(engineResource);
        }
    }
    //...
}

5.3 GenericRequest#onResourceReady ####

在这里会去调用target#onResourceReady()，target可以是ImageViewTarget的子类GlideDrawableImageViewTarget、DrawableImageViewTarget、BitmapImageViewTarget。
具体构建的地方在Glide电泳into方法时，使用ImageViewTargetFactory.buildTarget创建的target对象。

public void onResourceReady(Resource<?> resource) {
    //...
    onResourceReady(resource, (R) received);
}

private void onResourceReady(Resource<?> resource, R result) {
    boolean isFirstResource = isFirstReadyResource();
    status = Status.COMPLETE;
    this.resource = resource;

    if (requestListener == null || !requestListener.onResourceReady(result, model, target, loadedFromMemoryCache,
            isFirstResource)) {
        GlideAnimation<R> animation = animationFactory.build(loadedFromMemoryCache, isFirstResource);
        target.onResourceReady(result, animation);
    }

    notifyLoadSuccess();
    //...
}

5.4 ImageViewTarget#onResourceReady

ImageViewTarget的子类，调用onResourceReady时，最终都会调用setResource()，比如DrawableImageViewTarget

public class DrawableImageViewTarget extends ImageViewTarget<Drawable> {
    public DrawableImageViewTarget(ImageView view) {
        super(view); //父类调用了setResource方法
    }

    @Override
    protected void setResource(Drawable resource) {
       view.setImageDrawable(resource);
    }
}

至此，图片加载成功。

PS:cb.onResourceReady

在5.2中，调用的cb.onResourceReady，cb为什么是GenericRequest对象对象呢? 这要看调用GenericRequest#onSizeReady()的时候

//GenericRequest#onSizeReady()
public void onSizeReady(int width, int height) {
    //...
    loadStatus = engine.load(signature, width, height, dataFetcher, loadProvider, transformation, transcoder,
            priority, isMemoryCacheable, diskCacheStrategy, this);
    loadedFromMemoryCache = resource != null;
    //...
}

//Engine#load()  
public <T, Z, R> LoadStatus load(Key signature, int width, int height, DataFetcher<T> fetcher,
        DataLoadProvider<T, Z> loadProvider, Transformation<Z> transformation, ResourceTranscoder<Z, R> transcoder,
        Priority priority, boolean isMemoryCacheable, DiskCacheStrategy diskCacheStrategy, ResourceCallback cb) {
    //...

    EngineJob engineJob = engineJobFactory.build(key, isMemoryCacheable);
    //...
    EngineRunnable runnable = new EngineRunnable(engineJob, decodeJob, priority);
    jobs.put(key, engineJob);

    //将cb添加到EngineJob中，而cb就是GenericRequest调用engine.load时传入的this参数。
    engineJob.addCallback(cb);
    engineJob.start(runnable);

    return new LoadStatus(cb, engineJob);
}

Glide源码解析01-with
Glide源码解析02-load
Glide源码解析03-into
Glide源码解析04-decode
Glide源码解析05-onLoadComplete
Glide源码解析06-Glide流程图