和load()过程类似，最终Glide.with(context).load(url).into(imageView).的into()方法也调用的是GenericRequestBuilder类里面的into()方法。
GenericRequestBuilder类里面的into()方法
public Target<TranscodeType> into(ImageView view) {
Util.assertMainThread();
if (view == null) {
throw new IllegalArgumentException("You must pass in a non null View");
}
if (!isTransformationSet && view.getScaleType() != null) {
switch (view.getScaleType()) {
case CENTER_CROP:
applyCenterCrop();
break;
case FIT_CENTER:
case FIT_START:
case FIT_END:
applyFitCenter();
break;
//$CASES-OMITTED$
default:
// Do nothing.
}
}
//调用了重载的into()方法，在重载的into()方法中传入的是Target对象
return into(glide.buildImageViewTarget(view, transcodeClass));
}
先说一下这个Target接口。
- Target接口：继承自LifecycleListener接口，Glide获取资源之后资源作用的目标，是一个回调接口，在Glide做完所有的加载和处理之后返回结果。在into()过程中，Glide会一直跟踪Target，并在图片加载处理之后更新Target内部的资源引用，在Target中我们可以获得加载的图片资源。
继承关系
Target接口->BaseTarget抽象类->ViewTarget抽象类(11)->ImageViewTarget抽象类(该抽象类还实现了GlideAnimation.ViewAdapter接口)->GlideDrawableImageViewTarget实现类/BitmapImageViewTarget实现类/DrawableImageViewTarget实现类
11ViewTarget抽象类中还包括了一个SizeDeterminer内部类
Target接口->BaseTarget抽象类->SimpleTarget抽象类->AppWidgetTarget实现类/NotificationTarget实现类
继承了Target接口的SimpleTarget抽象类和ViewTarget抽象类用于自定义抽象类
自定义Target:SimpleTarget和ViewTarget
继承自LifecycleListener接口就很眼熟吧，对吧，继承自LifecycleListener接口后的生命周期就可以被RequestManager所监控，被ActivityFragmentLifeCycle所回调。
看一下glide.buildImageViewTarget(view, transcodeClass);这行代码。
Glide类中
public class Glide {
......
private final ImageViewTargetFactory imageViewTargetFactory = new ImageViewTargetFactory();
<R> Target<R> buildImageViewTarget(ImageView imageView, Class<R> transcodedClass) {
return imageViewTargetFactory.buildTarget(imageView, transcodedClass);
}
glide.buildImageViewTarget(view, transcodeClass);这行代码调用了Glide类中的buildImageViewTarget()方法，在这个方法中，调用了imageViewTargetFactory.buildTarget(imageView, transcodedClass);
来看一下ImageViewTargetFactory 类的buildTarget()方法。
ImageViewTargetFactory类中
public class ImageViewTargetFactory {
@SuppressWarnings("unchecked")
public <Z> Target<Z> buildTarget(ImageView view, Class<Z> clazz) {
if (GlideDrawable.class.isAssignableFrom(clazz)) {
return (Target<Z>) new GlideDrawableImageViewTarget(view);
} else if (Bitmap.class.equals(clazz)) {
return (Target<Z>) new BitmapImageViewTarget(view);
} else if (Drawable.class.isAssignableFrom(clazz)) {
return (Target<Z>) new DrawableImageViewTarget(view);
} else {
throw new IllegalArgumentException("Unhandled class: " + clazz
+ ", try .as*(Class).transcode(ResourceTranscoder)");
}
}
}
在ImageViewTargetFactory类中的buildTarget()方法中会根据传入的class参数来构建不同的Target对象，这个class参数其实基本上只有两种情况，如果你在使用Glide加载图片的时候调用了asBitmap()方法，那么这里就会构建出BitmapImageViewTarget对象，否则的话构建的都是GlideDrawableImageViewTarget对象。那么imageViewTargetFactory.buildTarget(imageView, transcodedClass);返回的将是GlideDrawableImageViewTarget对象。
接着看重载的into()方法
public <Y extends Target<TranscodeType>> Y into(Y target) {
Util.assertMainThread();
if (target == null) {
throw new IllegalArgumentException("You must pass in a non null Target");
}
if (!isModelSet) {
throw new IllegalArgumentException("You must first set a model (try #load())");
}
//target.getRequest()的过程(对应ViewTarget抽象类中的一系列方法)，先判断该View的Target是否有之前的Request，有的话则释放
Request previous = target.getRequest();
if (previous != null) {
previous.clear();
requestTracker.removeRequest(previous);
previous.recycle();
}
//1.
Request request = buildRequest(target);
//将新生成的Request设置到Target中
target.setRequest(request);
//将target加入到ActivityFragmentLifeCycle的LifeCycleListener集合中，进行生命周期管理
lifecycle.addListener(target);
//2.
requestTracker.runRequest(request);
return target;
}
分析一下1过程
这个buildRequest(target)方法是GenericRequestBuilder类中的方法。
GenericRequestBuilder类中的buildRequest(target)方法
private Request buildRequest(Target<TranscodeType> target) {
if (priority == null) {
priority = Priority.NORMAL;
}
return buildRequestRecursive(target, null);
}
在GenericRequestBuilder类中的buildRequest(target)方法又调用了GenericRequestBuilder类中的buildRequestRecursive(target, null);方法
private GenericRequestBuilder<?, ?, ?, TranscodeType> thumbnailRequestBuilder;
public GenericRequestBuilder<ModelType, DataType, ResourceType, TranscodeType> thumbnail(
GenericRequestBuilder<?, ?, ?, TranscodeType> thumbnailRequest) {
if (this.equals(thumbnailRequest)) {
throw new IllegalArgumentException("You cannot set a request as a thumbnail for itself. Consider using "
+ "clone() on the request you are passing to thumbnail()");
}
this.thumbnailRequestBuilder = thumbnailRequest;
return this;
}
private Request buildRequestRecursive(Target<TranscodeType> target, ThumbnailRequestCoordinator parentCoordinator) {
if (thumbnailRequestBuilder != null) {
if (isThumbnailBuilt) {
throw new IllegalStateException("You cannot use a request as both the main request and a thumbnail, "
+ "consider using clone() on the request(s) passed to thumbnail()");
}
if (thumbnailRequestBuilder.animationFactory.equals(NoAnimation.getFactory())) {
thumbnailRequestBuilder.animationFactory = animationFactory;
}
if (thumbnailRequestBuilder.priority == null) {
thumbnailRequestBuilder.priority = getThumbnailPriority();
}
if (Util.isValidDimensions(overrideWidth, overrideHeight)
&& !Util.isValidDimensions(thumbnailRequestBuilder.overrideWidth,
thumbnailRequestBuilder.overrideHeight)) {
thumbnailRequestBuilder.override(overrideWidth, overrideHeight);
}
ThumbnailRequestCoordinator coordinator = new ThumbnailRequestCoordinator(parentCoordinator);
Request fullRequest = obtainRequest(target, sizeMultiplier, priority, coordinator);
// Guard against infinite recursion.
isThumbnailBuilt = true;
// Recursively generate thumbnail requests.
Request thumbRequest = thumbnailRequestBuilder.buildRequestRecursive(target, coordinator);
isThumbnailBuilt = false;
coordinator.setRequests(fullRequest, thumbRequest);
return coordinator;
} else if (thumbSizeMultiplier != null) {
// Base case: thumbnail multiplier generates a thumbnail request, but cannot recurse.
ThumbnailRequestCoordinator coordinator = new ThumbnailRequestCoordinator(parentCoordinator);
Request fullRequest = obtainRequest(target, sizeMultiplier, priority, coordinator);
Request thumbnailRequest = obtainRequest(target, thumbSizeMultiplier, getThumbnailPriority(), coordinator);
coordinator.setRequests(fullRequest, thumbnailRequest);
return coordinator;
} else {
return obtainRequest(target, sizeMultiplier, priority, parentCoordinator);
}
}
在buildRequestRecursive()方法中，首先对缩略图及是否对Target设置参数的判断(是否使用了thumbnail()方法和sizeMultiplier()方法)，如果有使用thunmnail()方法，则生成原始图片和缩略图的请求，并由ThumbnailRequestCoordinator对象来协调管理，使用了sizeMultiplier()方法，则同样的处理(前者递归的获得缩略图的Request，后者不递归)，否则就只生成原始图片的请求，生成的请求Request是GenericRequest对象。
- ThumbnailRequestCoordinator对象也是一个Request，用来协调管理缩略图和原始图片的请求。
获取Requst是在obtainRequest()方法中，看一下这个方法。
GenericRequestBuilder类的obtainRequest()
private Request obtainRequest(Target<TranscodeType> target, float sizeMultiplier, Priority priority,
RequestCoordinator requestCoordinator) {
return GenericRequest.obtain(
loadProvider,
model,
signature,
context,
priority,
target,
sizeMultiplier,
placeholderDrawable,
placeholderId,
errorPlaceholder,
errorId,
fallbackDrawable,
fallbackResource,
requestListener,
requestCoordinator,
glide.getEngine(),
transformation,
transcodeClass,
isCacheable,
animationFactory,
overrideWidth,
overrideHeight,
diskCacheStrategy);
}
看到在这个方法中得到了GenericRequest对象。这个GenericRequest继承了Request接口。
回到重载的into()方法，1过程得到Request的过程分析结束。
接下来2过程。
requestTracker.runRequest(request);,来先看一下RequestTracker类的runRequest()方法。
RequestTracker类的runRequest()方法
public void runRequest(Request request) {
requests.add(request);
if (!isPaused) {
request.begin();
} else {
pendingRequests.add(request);
}
}
看到了是调用了request.begin()，这个request就是刚刚分析的过程中得到的GenericRequest类型的request。
进入GenericRequest类中。
GenericRequest类中的begin()方法
public void begin() {
startTime = LogTime.getLogTime();
//如果model即load()方法中传入的String字符串为空
if (model == null) {
//1.
onException(null);
return;
}
status = Status.WAITING_FOR_SIZE;
//用override()方法设置了大小，直接进入onSizeReady()方法
if (Util.isValidDimensions(overrideWidth, overrideHeight)) {
//2.
onSizeReady(overrideWidth, overrideHeight);
} else {
//在这个方法进行一系列的计算后还是会调用onSizeReady()方法
target.getSize(this);
}
if (!isComplete() && !isFailed() && canNotifyStatusChanged()) {
target.onLoadStarted(getPlaceholderDrawable());
}
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logV("finished run method in " + LogTime.getElapsedMillis(startTime));
}
}
分析1过程，先看一下GenericRequest类的onException(null)方法。
GenericRequest类的onException(null)方法
public void onException(Exception e) {
if (Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(TAG, "load failed", e);
}
status = Status.FAILED;
if (requestListener == null || !requestListener.onException(e, model, target, isFirstReadyResource())) {
setErrorPlaceholder(e);
}
}
如果你在使用Glide的时候使用了GenericRequestBuilder的listener()方法，在这个listener()方法传入的是一个RequestListener接口，如下例所示；
Glide.with(this).load(url).listener(new RequestListener<String, GlideDrawable>() {
@Override
public boolean onException(Exception e, String model, Target<GlideDrawable> target, boolean isFirstResource) {
return false;
}
@Override
public boolean onResourceReady(GlideDrawable resource, String model, Target<GlideDrawable> target, boolean isFromMemoryCache, boolean isFirstResource) {
return false;
}
}).into(imageView);
这个RequestListener接口中有两个方法，分别是 onException()和onResourceReady()方法。
在进行到GenericRequest类的onException(null)方法时，在这个方法中，requestListener指向的是我们自己指定的RequestListener接口，在自己指定的requestListener为null或自己指定的requestListener的onException()方法返回为false时会调用GenericRequest类的setErrorPlaceholder()方法。
GenericRequest类的setErrorPlaceholder()方法
private void setErrorPlaceholder(Exception e) {
if (!canNotifyStatusChanged()) {
return;
}
Drawable error = model == null ? getFallbackDrawable() : null;
if (error == null) {
error = getErrorDrawable();
}
if (error == null) {
error = getPlaceholderDrawable();
}
target.onLoadFailed(e, error);
}
private Drawable getFallbackDrawable() {
if (fallbackDrawable == null && fallbackResourceId > 0) {
fallbackDrawable = context.getResources().getDrawable(fallbackResourceId);
}
return fallbackDrawable;
}
private Drawable getErrorDrawable() {
if (errorDrawable == null && errorResourceId > 0) {
errorDrawable = context.getResources().getDrawable(errorResourceId);
}
return errorDrawable;
}
在这个setErrorPlaceholder()方法中，model为null时,则会显示fallback()方法中设置的drawable，如果没有设置fallback()方法，则会显示error()方法中设置的Drawable，如果没有设置error()方法，则会显示placeHolder()方法中设置的Drawable。
设置drawable时调用Target.onLoadFailed()方法，onLoadFailed()方法是Target接口中设置的方法，在ImageViewTarget抽象类中进行了实现，在ImageViewTarget抽象类的onLoadFailed()方法中，就会进行调用view.setImageDrawable()方法，将Drawable设置到View中。
1过程分析完了，接着进行2过程分析。
GenericRequest类的onSizeReady()方法
public void onSizeReady(int width, int height) {
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logV("Got onSizeReady in " + LogTime.getElapsedMillis(startTime));
}
if (status != Status.WAITING_FOR_SIZE) {
return;
}
status = Status.RUNNING;
width = Math.round(sizeMultiplier * width);
height = Math.round(sizeMultiplier * height);
//loadProvider指向的是ChildLoadProvider类型，最后得到的是ImageVideoModelLoader类型的
ModelLoader<A, T> modelLoader = loadProvider.getModelLoader();
//ImageVideoModelLoader类的getResourceFetcher()最后得到ImageVideoFetcher类型的dataFetcher
final DataFetcher<T> dataFetcher = modelLoader.getResourceFetcher(model, width, height);
if (dataFetcher == null) {
onException(new Exception("Failed to load model: \'" + model + "\'"));
return;
}
//得到GifBitmapWrapperDrawableTranscoder类型对象
ResourceTranscoder<Z, R> transcoder = loadProvider.getTranscoder();
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logV("finished setup for calling load in " + LogTime.getElapsedMillis(startTime));
}
loadedFromMemoryCache = true;
//将上面得到的参数传入到Engine类的load()方法中
loadStatus = engine.load(signature, width, height, dataFetcher, loadProvider, transformation, transcoder,
priority, isMemoryCacheable, diskCacheStrategy, this);
loadedFromMemoryCache = resource != null;
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logV("finished onSizeReady in " + LogTime.getElapsedMillis(startTime));
}
}
上面的注释中已经很明白了，在上一篇GequestRequestBuilder类的分析中已经知道loadProvider指向的是ChildLoadProvider类型。ChildLoadProvider构造器中又传入了FixedLoadProvider对象，FixedLoadProvider对象中传入了ImageVideoModelLoader对象等。，在上一篇文中已经分析过了，过程中的一些初始化的过程以及实例变量的意义及来源。Glide中很早的初始化一些东西，很早初始化的这些东西又传入到后面的方法中，这个要注意。
好滴，onSizeReady()方法中最重要的就是调用了Engine的load()方法，进入这个方法看看。
Engine的load()方法
private final EngineJobFactory engineJobFactory;
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) {
Util.assertMainThread();
long startTime = LogTime.getLogTime();
final String id = fetcher.getId();
EngineKey key = keyFactory.buildKey(id, signature, width, height, loadProvider.getCacheDecoder(),
loadProvider.getSourceDecoder(), transformation, loadProvider.getEncoder(),
transcoder, loadProvider.getSourceEncoder());
//从缓存中获取图片资源
EngineResource<?> cached = loadFromCache(key, isMemoryCacheable);
if (cached != null) {
cb.onResourceReady(cached);
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logWithTimeAndKey("Loaded resource from cache", startTime, key);
}
return null;
}
EngineResource<?> active = loadFromActiveResources(key, isMemoryCacheable);
if (active != null) {
cb.onResourceReady(active);
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logWithTimeAndKey("Loaded resource from active resources", startTime, key);
}
return null;
}
EngineJob current = jobs.get(key);
if (current != null) {
current.addCallback(cb);
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logWithTimeAndKey("Added to existing load", startTime, key);
}
return new LoadStatus(cb, current);
}
//生成EngineJob
EngineJob engineJob = engineJobFactory.build(key, isMemoryCacheable);
//这个fetcher就是在GenericRequest类中得到的ImageVideoFetcher类型的
DecodeJob<T, Z, R> decodeJob = new DecodeJob<T, Z, R>(key, width, height, fetcher, loadProvider, transformation,
transcoder, diskCacheProvider, diskCacheStrategy, priority);
EngineRunnable runnable = new EngineRunnable(engineJob, decodeJob, priority);
jobs.put(key, engineJob);
engineJob.addCallback(cb);
engineJob.start(runnable);
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logWithTimeAndKey("Started new load", startTime, key);
}
return new LoadStatus(cb, engineJob);
}
- Engine类：任务创建，发起，回调，管理存活和缓存的资源，Engine类的实例对象是在GildeBuilder类中初始化的。
- EngineJob类：实现了EngineRunnable.EngineRunnableManager接口。这个类的主要作用就是用来开启线程的，为后面的异步加载图片做准备。
- EngineJobFactory类：是Engine类的静态内部类，里面有一个build()方法用来生成EngineJob对象，生成EngineJob对象时传入的EngineListener接口的实现是在Engine类中实现的。
- DecodeJob类：用来对图片解码的
- EngineRunnable类：实现Runnable接口
看到在这个方法的参数中ResourceCallback cb参数是从GenericRequest类中传入的，GenericRequest类实现了ResourceCallback这个接口。load()方法中进行先是进行判断是否有内存缓存，如果有的话就会调用cb.onResourceReady(cached);,从缓存中加载图片。如果缓存中没有，就会创建EngineJob来开启新的线程来进行异步加载图片。
在这个方法中在最后调用了engineJob.start(runnable);，来看一下这个EngineJob的start()方法
EngineJob的start()方法
public void start(EngineRunnable engineRunnable) {
this.engineRunnable = engineRunnable;
future = diskCacheService.submit(engineRunnable);
}
这就会开启异步线程，来加载图片。来看一下EngineRunnable的run()方法。
EngineRunnable的run()方法
public void run() {
if (isCancelled) {
return;
}
Exception exception = null;
Resource<?> resource = null;
try {
//1.
resource = decode();
} catch (Exception e) {
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "Exception decoding", e);
}
exception = e;
}
if (isCancelled) {
if (resource != null) {
resource.recycle();
}
return;
}
if (resource == null) {
onLoadFailed(exception);
} else {
onLoadComplete(resource);
}
}
进入EngineRunnable的decode()方法
EngineRunnable的decode()方法
private Resource<?> decode() throws Exception {
if (isDecodingFromCache()) {
//这个方法会从缓存中取图片
return decodeFromCache();
} else {
return decodeFromSource();
}
}
private Resource<?> decodeFromSource() throws Exception {
//decodeJob是在Engine的load()方法中创建EngineRunnable对象时传入的DecodeJob对象
return decodeJob.decodeFromSource();
}
DecodeJob的decodeFromSource()方法
public Resource<Z> decodeFromSource() throws Exception {
Resource<T> decoded = decodeSource();
return transformEncodeAndTranscode(decoded);
}
先看这个DecodeJob的decodeSource()方法
DecodeJob的 decodeSource()方法
private Resource<T> decodeSource() throws Exception {
Resource<T> decoded = null;
try {
long startTime = LogTime.getLogTime();
//1.这个fetcher就是就是在GenericRequest类中得到的ImageVideoFetcher类型的对象并传入Engine类并之后传入DecodeJob中
final A data = fetcher.loadData(priority);
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logWithTimeAndKey("Fetched data", startTime);
}
if (isCancelled) {
return null;
}
decoded = decodeFromSourceData(data);
} finally {
fetcher.cleanup();
}
return decoded;
}
在1处调用了fetcher.loadData(priority);这个fetcher是ImageVideoFetcher类型的，来看看这个ImageVideoFetcher类的load()方法。
ImageVideoFetcher类
static class ImageVideoFetcher implements DataFetcher<ImageVideoWrapper> {
private final DataFetcher<InputStream> streamFetcher;
private final DataFetcher<ParcelFileDescriptor> fileDescriptorFetcher;
public ImageVideoFetcher(DataFetcher<InputStream> streamFetcher,
DataFetcher<ParcelFileDescriptor> fileDescriptorFetcher) {
this.streamFetcher = streamFetcher;
this.fileDescriptorFetcher = fileDescriptorFetcher;
}
@SuppressWarnings("resource")
// @see ModelLoader.loadData
@Override
public ImageVideoWrapper loadData(Priority priority) throws Exception {
InputStream is = null;
if (streamFetcher != null) {
try {
//1.之前已经分析过了这个streamFetcher是HttpUrlFetcher类型
is = streamFetcher.loadData(priority);
} catch (Exception e) {
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "Exception fetching input stream, trying ParcelFileDescriptor", e);
}
if (fileDescriptorFetcher == null) {
throw e;
}
}
}
ParcelFileDescriptor fileDescriptor = null;
if (fileDescriptorFetcher != null) {
try {
fileDescriptor = fileDescriptorFetcher.loadData(priority);
} catch (Exception e) {
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "Exception fetching ParcelFileDescriptor", e);
}
if (is == null) {
throw e;
}
}
}
return new ImageVideoWrapper(is, fileDescriptor);
}
}
}
进入HttpUrlFetcher类的load()方法看看。
HttpUrlFetcher类的load()方法
public InputStream loadData(Priority priority) throws Exception {
return loadDataWithRedirects(glideUrl.toURL(), 0 /*redirects*/, null /*lastUrl*/, glideUrl.getHeaders());
}
private InputStream loadDataWithRedirects(URL url, int redirects, URL lastUrl, Map<String, String> headers)
throws IOException {
if (redirects >= MAXIMUM_REDIRECTS) {
throw new IOException("Too many (> " + MAXIMUM_REDIRECTS + ") redirects!");
} else {
// Comparing the URLs using .equals performs additional network I/O and is generally broken.
// See http://michaelscharf.blogspot.com/2006/11/javaneturlequals-and-hashcode-make.html.
try {
if (lastUrl != null && url.toURI().equals(lastUrl.toURI())) {
throw new IOException("In re-direct loop");
}
} catch (URISyntaxException e) {
// Do nothing, this is best effort.
}
}
urlConnection = connectionFactory.build(url);
for (Map.Entry<String, String> headerEntry : headers.entrySet()) {
urlConnection.addRequestProperty(headerEntry.getKey(), headerEntry.getValue());
}
urlConnection.setConnectTimeout(2500);
urlConnection.setReadTimeout(2500);
urlConnection.setUseCaches(false);
urlConnection.setDoInput(true);
// Connect explicitly to avoid errors in decoders if connection fails.
urlConnection.connect();
if (isCancelled) {
return null;
}
final int statusCode = urlConnection.getResponseCode();
if (statusCode / 100 == 2) {
return getStreamForSuccessfulRequest(urlConnection);
} else if (statusCode / 100 == 3) {
String redirectUrlString = urlConnection.getHeaderField("Location");
if (TextUtils.isEmpty(redirectUrlString)) {
throw new IOException("Received empty or null redirect url");
}
URL redirectUrl = new URL(url, redirectUrlString);
return loadDataWithRedirects(redirectUrl, redirects + 1, url, headers);
} else {
if (statusCode == -1) {
throw new IOException("Unable to retrieve response code from HttpUrlConnection.");
}
throw new IOException("Request failed " + statusCode + ": " + urlConnection.getResponseMessage());
}
}
发现了吧，在这里面发生了网络请求。最后返回的是InputStream流。
回到ImageVideoFetcher的loadData()方法中，发现最后将这个InputStream流包装生成了ImageVideoWrapper对象。
ImageVideoFetcher的loadData()方法结束了，回到DecodeJob的 decodeSource()方法中，又调用了decodeFromSourceData(data);方法。并将刚刚从ImageVideoFetcher的loadData()方法中得到的ImageVideoWrapper对象传入这个decodeFromSourceData(data);方法。
DecodeJob的decodeFromSourceData(data)方法
private Resource<T> decodeFromSourceData(A data) throws IOException {
final Resource<T> decoded;
if (diskCacheStrategy.cacheSource()) {
decoded = cacheAndDecodeSourceData(data);
} else {
long startTime = LogTime.getLogTime();
decoded = loadProvider.getSourceDecoder().decode(data, width, height);
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logWithTimeAndKey("Decoded from source", startTime);
}
}
return decoded;
}
这个方法中着重看一下decoded = loadProvider.getSourceDecoder().decode(data, width, height);这行代码。
首先这个loadProvider之前已经分析过了，loadProvider.getSourceDecoder().最终会得到FixedLoadProvider类的构造器中传入的ImageVideoGifDrawableLoadProvider类getSourceDecoder()方法所返回的结果，最后得到的是GifBitmapWrapperResourceDecoder对象。所以最终loadProvider.getSourceDecoder().decode(data, width, height);这句代码会调用GifBitmapWrapperResourceDecoder对象的decode()方法。
GifBitmapWrapperResourceDecoder的decode()方法
public Resource<GifBitmapWrapper> decode(ImageVideoWrapper source, int width, int height) throws IOException {
ByteArrayPool pool = ByteArrayPool.get();
byte[] tempBytes = pool.getBytes();
GifBitmapWrapper wrapper = null;
try {
wrapper = decode(source, width, height, tempBytes);
} finally {
pool.releaseBytes(tempBytes);
}
return wrapper != null ? new GifBitmapWrapperResource(wrapper) : null;
}
private GifBitmapWrapper decode(ImageVideoWrapper source, int width, int height, byte[] bytes) throws IOException {
final GifBitmapWrapper result;
if (source.getStream() != null) {
result = decodeStream(source, width, height, bytes);
} else {
//对于普通的静态图的处理
result = decodeBitmapWrapper(source, width, height);
}
return result;
}
GifBitmapWrapperResourceDecoder的decodeBitmapWrapper()方法
private final ResourceDecoder<ImageVideoWrapper, Bitmap> bitmapDecoder;
private GifBitmapWrapper decodeBitmapWrapper(ImageVideoWrapper toDecode, int width, int height) throws IOException {
GifBitmapWrapper result = null;
Resource<Bitmap> bitmapResource = bitmapDecoder.decode(toDecode, width, height);
if (bitmapResource != null) {
result = new GifBitmapWrapper(bitmapResource, null);
}
return result;
}
在这个GifBitmapWrapperResourceDecoder的decodeBitmapWrapper()方法中会调用ImageVideoBitmapDecoder类中的decode()方法。
ImageVideoBitmapDecoder类中的decode()方法
public Resource<Bitmap> decode(ImageVideoWrapper source, int width, int height) throws IOException {
private final ResourceDecoder<InputStream, Bitmap> streamDecoder;
Resource<Bitmap> result = null;
InputStream is = source.getStream();
if (is != null) {
try {
result = streamDecoder.decode(is, width, height);
} catch (IOException e) {
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "Failed to load image from stream, trying FileDescriptor", e);
}
}
}
if (result == null) {
ParcelFileDescriptor fileDescriptor = source.getFileDescriptor();
if (fileDescriptor != null) {
result = fileDescriptorDecoder.decode(fileDescriptor, width, height);
}
}
return result;
}
在这个ImageVideoBitmapDecoder类中的decode()方法中会调用StreamBitmapDecoder类的decode()方法。
StreamBitmapDecoder类的decode()方法
public Resource<Bitmap> decode(InputStream source, int width, int height) {
private final Downsampler downsampler;
Bitmap bitmap = downsampler.decode(source, bitmapPool, width, height, decodeFormat);
return BitmapResource.obtain(bitmap, bitmapPool);
}
在这个StreamBitmapDecoder类的decode()方法中会调用Downsampler类的decode()方法。
Downsampler类的decode()方法
public Bitmap decode(InputStream is, BitmapPool pool, int outWidth, int outHeight, DecodeFormat decodeFormat) {
final ByteArrayPool byteArrayPool = ByteArrayPool.get();
final byte[] bytesForOptions = byteArrayPool.getBytes();
final byte[] bytesForStream = byteArrayPool.getBytes();
final BitmapFactory.Options options = getDefaultOptions();
MarkEnforcingInputStream invalidatingStream = new MarkEnforcingInputStream(exceptionStream);
try {
exceptionStream.mark(MARK_POSITION);
int orientation = 0;
try {
orientation = new ImageHeaderParser(exceptionStream).getOrientation();
} catch (IOException e) {
if (Log.isLoggable(TAG, Log.WARN)) {
Log.w(TAG, "Cannot determine the image orientation from header", e);
}
} finally {
try {
exceptionStream.reset();
} catch (IOException e) {
if (Log.isLoggable(TAG, Log.WARN)) {
Log.w(TAG, "Cannot reset the input stream", e);
}
}
}
options.inTempStorage = bytesForOptions;
final int[] inDimens = getDimensions(invalidatingStream, bufferedStream, options);
final int inWidth = inDimens[0];
final int inHeight = inDimens[1];
final int degreesToRotate = TransformationUtils.getExifOrientationDegrees(orientation);
final int sampleSize = getRoundedSampleSize(degreesToRotate, inWidth, inHeight, outWidth, outHeight);
final Bitmap downsampled =
downsampleWithSize(invalidatingStream, bufferedStream, options, pool, inWidth, inHeight, sampleSize,
decodeFormat);
if (streamException != null) {
throw new RuntimeException(streamException);
}
Bitmap rotated = null;
if (downsampled != null) {
rotated = TransformationUtils.rotateImageExif(downsampled, pool, orientation);
if (!downsampled.equals(rotated) && !pool.put(downsampled)) {
downsampled.recycle();
}
}
return rotated;
} finally {
byteArrayPool.releaseBytes(bytesForOptions);
byteArrayPool.releaseBytes(bytesForStream);
exceptionStream.release();
releaseOptions(options);
}
}
在这个Downsampler类的decode()方法中j进行InputStream的读取，以及对图片的加载全都在这里了，最后会返回一个Bitmap对象。
回到StreamBitmapDecoder类的decode()方法方法中，这个方法会将Downsampler类的decode()方法返回的Bitmap对象包装成BitmapResource对象。
回到ImageVideoBitmapDecoder类中的decode()方法中，这个方法继续返回BitmapResource对象给GifBitmapWrapperResourceDecoder类中的decodeBitmapWrapper()方法。
回到GifBitmapWrapperResourceDecoder类中的decodeBitmapWrapper(方法，在这个方法中会将返回的BitmapResource对象包装成GifBitmapWrapper对象，最后回到GifBitmapWrapperResourceDecoder类中的decode()方法，该方法将decodeBitmapWrapper()方法中返回的GifBitmapWrapper对象包装成GifBitmapWrapperResource对象。
loadProvider.getSourceDecoder().decode(data, width, height);这句代码的过程分析结束了，最后得到了GifBitmapWrapperResource()对象，这个对象对象里面包含要加载的Bitmap对象。(BitmapResource对象里面包装的是Bitmap对象，GifBitmapWrapper对象里面包装的是BitmapResource对象，GifBitmapWrapperResource对象里面包装的是GifBitmapWrapper对象)。
回到DecodeJob的decodeFromSourceData()方法中，执行完loadProvider.getSourceDecoder().decode();后返回GifBitmapWrapperResource对象到decodeSource()方法，最后回到decodeFromSource()方法中，执行transformEncodeAndTranscode()方法。
DecodeJob的transformEncodeAndTranscode()方法
private Resource<Z> transformEncodeAndTranscode(Resource<T> decoded) {
long startTime = LogTime.getLogTime();
Resource<T> transformed = transform(decoded);
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logWithTimeAndKey("Transformed resource from source", startTime);
}
writeTransformedToCache(transformed);
startTime = LogTime.getLogTime();
Resource<Z> result = transcode(transformed);
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logWithTimeAndKey("Transcoded transformed from source", startTime);
}
return result;
}
private Resource<Z> transcode(Resource<T> transformed) {
if (transformed == null) {
return null;
}
//这个transcoder指向了在Engine中创建DecodeJob对象时传入的GifBitmapWrapperDrawableTranscoder类
return transcoder.transcode(transformed);
}
进入GifBitmapWrapperDrawableTranscoder对象的transcode(transformed)方法。
GifBitmapWrapperDrawableTranscoder对象的transcode(transformed)方法
public Resource<GlideDrawable> transcode(Resource<GifBitmapWrapper> toTranscode) {
private final ResourceTranscoder<Bitmap, GlideBitmapDrawable> bitmapDrawableResourceTranscoder;
//得到GifBitmapWrapper对象
GifBitmapWrapper gifBitmap = toTranscode.get();
//从GifBitmapWrapper中取出Bitmap对象
Resource<Bitmap> bitmapResource = gifBitmap.getBitmapResource();
final Resource<? extends GlideDrawable> result;
//bitmapResource为null说明为Gif类型
if (bitmapResource != null) {
//新建GlideBitmapDrawableTranscoder对象，将Bitmap进行
result =
bitmapDrawableResourceTranscoder.transcode(bitmapResource);
} else {
result = gifBitmap.getGifResource();
}
return (Resource<GlideDrawable>) result;
}
进入GlideBitmapDrawableTranscoder的transcode()方法。
GlideBitmapDrawableTranscoder的transcode()方法
public Resource<GlideBitmapDrawable> transcode(Resource<Bitmap> toTranscode) {
GlideBitmapDrawable drawable = new GlideBitmapDrawable(resources, toTranscode.get());
return new GlideBitmapDrawableResource(drawable, bitmapPool);
}
在GlideBitmapDrawableTranscoder的transcode()方法中将Bitemap对象保存在GlideBitmapDrawableResource中。
一路返回到EngineRunnable的run()方法中，EngineRunnable的run()方法
中的1过程分析结束了，最后的到了GlideBitmapDrawableResource对象，里面保存了要展示的Bitmp。再贴一下EngineRunnable的run()方法。
EngineRunnable的run()方法
public void run() {
if (isCancelled) {
return;
}
Exception exception = null;
Resource<?> resource = null;
try {
//1.
resource = decode();
} catch (Exception e) {
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "Exception decoding", e);
}
exception = e;
}
if (isCancelled) {
if (resource != null) {
resource.recycle();
}
return;
}
if (resource == null) {
onLoadFailed(exception);
} else {
onLoadComplete(resource);
}
}
可以看到得到Resource后，调用了EngineRunnable的onLoadComplete(resource)方法。
EngineRunnable的onLoadComplete(resource)方法
private void onLoadComplete(Resource resource) {
manager.onResourceReady(resource);
}
这个manager指向的是EngineRunnable的构造器中传来的EngineRunnableManager参数，这个EngineRunnableManager被EngineJob实现。
进入EngineJob类中。
EngineJob类中的方法
private static final Handler MAIN_THREAD_HANDLER = new Handler(Looper.getMainLooper(), new MainThreadCallback());
public void onResourceReady(final Resource<?> resource) {
this.resource = resource;
//通过Handler发送了一条消息，切换到主线程，准备进行UI的修改
MAIN_THREAD_HANDLER.obtainMessage(MSG_COMPLETE, this).sendToTarget();
}
private void handleResultOnMainThread() {
if (isCancelled) {
resource.recycle();
return;
} else if (cbs.isEmpty()) {
throw new IllegalStateException("Received a resource without any callbacks to notify");
}
engineResource = engineResourceFactory.build(resource, isCacheable);
hasResource = true;
engineResource.acquire();
listener.onEngineJobComplete(key, engineResource);
//这个ResourceCallback前面已经分析过了，GenericRequest类实现了，在for()循环中处理ResourceCallback接口
for (ResourceCallback cb : cbs) {
if (!isInIgnoredCallbacks(cb)) {
engineResource.acquire();
cb.onResourceReady(engineResource);
}
}
engineResource.release();
}
private static class MainThreadCallback implements Handler.Callback {
@Override
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;
}
}
处理ResourceCallback接口时，会调用GenericRequest中的实现了ResourceCallback接口的方法。
进入GenericRequest类中。
GenericRequest类中
public void onResourceReady(Resource<?> resource) {
if (resource == null) {
onException(new Exception("Expected to receive a Resource<R> with an object of " + transcodeClass
+ " inside, but instead got null."));
return;
}
Object received = resource.get();
if (received == null || !transcodeClass.isAssignableFrom(received.getClass())) {
releaseResource(resource);
onException(new Exception("Expected to receive an object of " + transcodeClass
+ " but instead got " + (received != null ? received.getClass() : "") + "{" + received + "}"
+ " inside Resource{" + resource + "}."
+ (received != null ? "" : " "
+ "To indicate failure return a null Resource object, "
+ "rather than a Resource object containing null data.")
));
return;
}
if (!canSetResource()) {
releaseResource(resource);
// We can't set the status to complete before asking canSetResource().
status = Status.COMPLETE;
return;
}
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);
//调用Target来展示图片
target.onResourceReady(result, animation);
}
notifyLoadSuccess();
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logV("Resource ready in " + LogTime.getElapsedMillis(startTime) + " size: "
+ (resource.getSize() * TO_MEGABYTE) + " fromCache: " + loadedFromMemoryCache);
}
}
GlideDrawableImageViewTarget类中
public void onResourceReady(GlideDrawable resource, GlideAnimation<? super GlideDrawable> animation) {
if (!resource.isAnimated()) {
float viewRatio = view.getWidth() / (float) view.getHeight();
float drawableRatio = resource.getIntrinsicWidth() / (float) resource.getIntrinsicHeight();
if (Math.abs(viewRatio - 1f) <= SQUARE_RATIO_MARGIN
&& Math.abs(drawableRatio - 1f) <= SQUARE_RATIO_MARGIN) {
resource = new SquaringDrawable(resource, view.getWidth());
}
}
super.onResourceReady(resource, animation);
this.resource = resource;
resource.setLoopCount(maxLoopCount);
resource.start();
}
protected void setResource(GlideDrawable resource) {
//这个view就是我们之前into()中传进来的ImageView
view.setImageDrawable(resource);
}
最后图片就显示出来了。
