和load()過程類似，最終Glide.with(context).load(url).into(imageView).的into()方法也調(diào)用的是GenericRequestBuilder類里面的into()方法。
GenericRequestBuilder類里面的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.
}
}
//調(diào)用了重載的into()方法，在重載的into()方法中傳入的是Target對象
return into(glide.buildImageViewTarget(view, transcodeClass));
}
先說一下這個Target接口。
- Target接口：繼承自LifecycleListener接口，Glide獲取資源之后資源作用的目標，是一個回調(diào)接口，在Glide做完所有的加載和處理之后返回結(jié)果。在into()過程中，Glide會一直跟蹤Target，并在圖片加載處理之后更新Target內(nèi)部的資源引用，在Target中我們可以獲得加載的圖片資源。
繼承關(guān)系
Target接口->BaseTarget抽象類->ViewTarget抽象類(11)->ImageViewTarget抽象類(該抽象類還實現(xiàn)了GlideAnimation.ViewAdapter接口)->GlideDrawableImageViewTarget實現(xiàn)類/BitmapImageViewTarget實現(xiàn)類/DrawableImageViewTarget實現(xiàn)類
11ViewTarget抽象類中還包括了一個SizeDeterminer內(nèi)部類
Target接口->BaseTarget抽象類->SimpleTarget抽象類->AppWidgetTarget實現(xiàn)類/NotificationTarget實現(xiàn)類
繼承了Target接口的SimpleTarget抽象類和ViewTarget抽象類用于自定義抽象類
自定義Target:SimpleTarget和ViewTarget
繼承自LifecycleListener接口就很眼熟吧，對吧，繼承自LifecycleListener接口后的生命周期就可以被RequestManager所監(jiān)控，被ActivityFragmentLifeCycle所回調(diào)。
看一下glide.buildImageViewTarget(view, transcodeClass);這行代碼。
Glide類中
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);這行代碼調(diào)用了Glide類中的buildImageViewTarget()方法，在這個方法中，調(diào)用了imageViewTargetFactory.buildTarget(imageView, transcodedClass);
來看一下ImageViewTargetFactory 類的buildTarget()方法。
ImageViewTargetFactory類中
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類中的buildTarget()方法中會根據(jù)傳入的class參數(shù)來構(gòu)建不同的Target對象，這個class參數(shù)其實基本上只有兩種情況，如果你在使用Glide加載圖片的時候調(diào)用了asBitmap()方法，那么這里就會構(gòu)建出BitmapImageViewTarget對象，否則的話構(gòu)建的都是GlideDrawableImageViewTarget對象。那么imageViewTargetFactory.buildTarget(imageView, transcodedClass);返回的將是GlideDrawableImageViewTarget對象。
接著看重載的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()的過程(對應(yīng)ViewTarget抽象類中的一系列方法)，先判斷該View的Target是否有之前的Request，有的話則釋放
Request previous = target.getRequest();
if (previous != null) {
previous.clear();
requestTracker.removeRequest(previous);
previous.recycle();
}
//1.
Request request = buildRequest(target);
//將新生成的Request設(shè)置到Target中
target.setRequest(request);
//將target加入到ActivityFragmentLifeCycle的LifeCycleListener集合中，進行生命周期管理
lifecycle.addListener(target);
//2.
requestTracker.runRequest(request);
return target;
}
分析一下1過程
這個buildRequest(target)方法是GenericRequestBuilder類中的方法。
GenericRequestBuilder類中的buildRequest(target)方法
private Request buildRequest(Target<TranscodeType> target) {
if (priority == null) {
priority = Priority.NORMAL;
}
return buildRequestRecursive(target, null);
}
在GenericRequestBuilder類中的buildRequest(target)方法又調(diào)用了GenericRequestBuilder類中的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，首先對縮略圖及是否對Target設(shè)置參數(shù)的判斷(是否使用了thumbnail()方法和sizeMultiplier()方法)，如果有使用thunmnail()方法，則生成原始圖片和縮略圖的請求，并由ThumbnailRequestCoordinator對象來協(xié)調(diào)管理，使用了sizeMultiplier()方法，則同樣的處理(前者遞歸的獲得縮略圖的Request，后者不遞歸)，否則就只生成原始圖片的請求，生成的請求Request是GenericRequest對象。
- ThumbnailRequestCoordinator對象也是一個Request，用來協(xié)調(diào)管理縮略圖和原始圖片的請求。
獲取Requst是在obtainRequest()方法中，看一下這個方法。
GenericRequestBuilder類的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);
}
看到在這個方法中得到了GenericRequest對象。這個GenericRequest繼承了Request接口。
回到重載的into()方法，1過程得到Request的過程分析結(jié)束。
接下來2過程。
requestTracker.runRequest(request);,來先看一下RequestTracker類的runRequest()方法。
RequestTracker類的runRequest()方法
public void runRequest(Request request) {
requests.add(request);
if (!isPaused) {
request.begin();
} else {
pendingRequests.add(request);
}
}
看到了是調(diào)用了request.begin()，這個request就是剛剛分析的過程中得到的GenericRequest類型的request。
進入GenericRequest類中。
GenericRequest類中的begin()方法
public void begin() {
startTime = LogTime.getLogTime();
//如果model即load()方法中傳入的String字符串為空
if (model == null) {
//1.
onException(null);
return;
}
status = Status.WAITING_FOR_SIZE;
//用override()方法設(shè)置了大小，直接進入onSizeReady()方法
if (Util.isValidDimensions(overrideWidth, overrideHeight)) {
//2.
onSizeReady(overrideWidth, overrideHeight);
} else {
//在這個方法進行一系列的計算后還是會調(diào)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過程，先看一下GenericRequest類的onException(null)方法。
GenericRequest類的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的時候使用了GenericRequestBuilder的listener()方法，在這個listener()方法傳入的是一個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);
這個RequestListener接口中有兩個方法，分別是 onException()和onResourceReady()方法。
在進行到GenericRequest類的onException(null)方法時，在這個方法中，requestListener指向的是我們自己指定的RequestListener接口，在自己指定的requestListener為null或自己指定的requestListener的onException()方法返回為false時會調(diào)用GenericRequest類的setErrorPlaceholder()方法。
GenericRequest類的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;
}
在這個setErrorPlaceholder()方法中，model為null時,則會顯示fallback()方法中設(shè)置的drawable，如果沒有設(shè)置fallback()方法，則會顯示error()方法中設(shè)置的Drawable，如果沒有設(shè)置error()方法，則會顯示placeHolder()方法中設(shè)置的Drawable。
設(shè)置drawable時調(diào)用Target.onLoadFailed()方法，onLoadFailed()方法是Target接口中設(shè)置的方法，在ImageViewTarget抽象類中進行了實現(xiàn)，在ImageViewTarget抽象類的onLoadFailed()方法中，就會進行調(diào)用view.setImageDrawable()方法，將Drawable設(shè)置到View中。
1過程分析完了，接著進行2過程分析。
GenericRequest類的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類型，最后得到的是ImageVideoModelLoader類型的
ModelLoader<A, T> modelLoader = loadProvider.getModelLoader();
//ImageVideoModelLoader類的getResourceFetcher()最后得到ImageVideoFetcher類型的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類型對象
ResourceTranscoder<Z, R> transcoder = loadProvider.getTranscoder();
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logV("finished setup for calling load in " + LogTime.getElapsedMillis(startTime));
}
loadedFromMemoryCache = true;
//將上面得到的參數(shù)傳入到Engine類的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));
}
}
上面的注釋中已經(jīng)很明白了，在上一篇GequestRequestBuilder類的分析中已經(jīng)知道loadProvider指向的是ChildLoadProvider類型。ChildLoadProvider構(gòu)造器中又傳入了FixedLoadProvider對象，F(xiàn)ixedLoadProvider對象中傳入了ImageVideoModelLoader對象等。，在上一篇文中已經(jīng)分析過了，過程中的一些初始化的過程以及實例變量的意義及來源。Glide中很早的初始化一些東西，很早初始化的這些東西又傳入到后面的方法中，這個要注意。
好滴，onSizeReady()方法中最重要的就是調(diào)用了Engine的load()方法，進入這個方法看看。
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());
//從緩存中獲取圖片資源
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);
//這個fetcher就是在GenericRequest類中得到的ImageVideoFetcher類型的
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類：任務(wù)創(chuàng)建，發(fā)起，回調(diào)，管理存活和緩存的資源，Engine類的實例對象是在GildeBuilder類中初始化的。
- EngineJob類：實現(xiàn)了EngineRunnable.EngineRunnableManager接口。這個類的主要作用就是用來開啟線程的，為后面的異步加載圖片做準備。
- EngineJobFactory類：是Engine類的靜態(tài)內(nèi)部類，里面有一個build()方法用來生成EngineJob對象，生成EngineJob對象時傳入的EngineListener接口的實現(xiàn)是在Engine類中實現(xiàn)的。
- DecodeJob類：用來對圖片解碼的
- EngineRunnable類：實現(xiàn)Runnable接口
看到在這個方法的參數(shù)中ResourceCallback cb參數(shù)是從GenericRequest類中傳入的，GenericRequest類實現(xiàn)了ResourceCallback這個接口。load()方法中進行先是進行判斷是否有內(nèi)存緩存，如果有的話就會調(diào)用cb.onResourceReady(cached);,從緩存中加載圖片。如果緩存中沒有，就會創(chuàng)建EngineJob來開啟新的線程來進行異步加載圖片。
在這個方法中在最后調(diào)用了engineJob.start(runnable);，來看一下這個EngineJob的start()方法
EngineJob的start()方法
public void start(EngineRunnable engineRunnable) {
this.engineRunnable = engineRunnable;
future = diskCacheService.submit(engineRunnable);
}
這就會開啟異步線程，來加載圖片。來看一下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);
}
}
進入EngineRunnable的decode()方法
EngineRunnable的decode()方法
private Resource<?> decode() throws Exception {
if (isDecodingFromCache()) {
//這個方法會從緩存中取圖片
return decodeFromCache();
} else {
return decodeFromSource();
}
}
private Resource<?> decodeFromSource() throws Exception {
//decodeJob是在Engine的load()方法中創(chuàng)建EngineRunnable對象時傳入的DecodeJob對象
return decodeJob.decodeFromSource();
}
DecodeJob的decodeFromSource()方法
public Resource<Z> decodeFromSource() throws Exception {
Resource<T> decoded = decodeSource();
return transformEncodeAndTranscode(decoded);
}
先看這個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.這個fetcher就是就是在GenericRequest類中得到的ImageVideoFetcher類型的對象并傳入Engine類并之后傳入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處調(diào)用了fetcher.loadData(priority);這個fetcher是ImageVideoFetcher類型的，來看看這個ImageVideoFetcher類的load()方法。
ImageVideoFetcher類
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.之前已經(jīng)分析過了這個streamFetcher是HttpUrlFetcher類型
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);
}
}
}
進入HttpUrlFetcher類的load()方法看看。
HttpUrlFetcher類的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());
}
}
發(fā)現(xiàn)了吧，在這里面發(fā)生了網(wǎng)絡(luò)請求。最后返回的是InputStream流。
回到ImageVideoFetcher的loadData()方法中，發(fā)現(xiàn)最后將這個InputStream流包裝生成了ImageVideoWrapper對象。
ImageVideoFetcher的loadData()方法結(jié)束了，回到DecodeJob的 decodeSource()方法中，又調(diào)用了decodeFromSourceData(data);方法。并將剛剛從ImageVideoFetcher的loadData()方法中得到的ImageVideoWrapper對象傳入這個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;
}
這個方法中著重看一下decoded = loadProvider.getSourceDecoder().decode(data, width, height);這行代碼。
首先這個loadProvider之前已經(jīng)分析過了，loadProvider.getSourceDecoder().最終會得到FixedLoadProvider類的構(gòu)造器中傳入的ImageVideoGifDrawableLoadProvider類getSourceDecoder()方法所返回的結(jié)果，最后得到的是GifBitmapWrapperResourceDecoder對象。所以最終loadProvider.getSourceDecoder().decode(data, width, height);這句代碼會調(diào)用GifBitmapWrapperResourceDecoder對象的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 {
//對于普通的靜態(tài)圖的處理
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;
}
在這個GifBitmapWrapperResourceDecoder的decodeBitmapWrapper()方法中會調(diào)用ImageVideoBitmapDecoder類中的decode()方法。
ImageVideoBitmapDecoder類中的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;
}
在這個ImageVideoBitmapDecoder類中的decode()方法中會調(diào)用StreamBitmapDecoder類的decode()方法。
StreamBitmapDecoder類的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);
}
在這個StreamBitmapDecoder類的decode()方法中會調(diào)用Downsampler類的decode()方法。
Downsampler類的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);
}
}
在這個Downsampler類的decode()方法中j進行InputStream的讀取，以及對圖片的加載全都在這里了，最后會返回一個Bitmap對象。
回到StreamBitmapDecoder類的decode()方法方法中，這個方法會將Downsampler類的decode()方法返回的Bitmap對象包裝成BitmapResource對象。
回到ImageVideoBitmapDecoder類中的decode()方法中，這個方法繼續(xù)返回BitmapResource對象給GifBitmapWrapperResourceDecoder類中的decodeBitmapWrapper()方法。
回到GifBitmapWrapperResourceDecoder類中的decodeBitmapWrapper(方法，在這個方法中會將返回的BitmapResource對象包裝成GifBitmapWrapper對象，最后回到GifBitmapWrapperResourceDecoder類中的decode()方法，該方法將decodeBitmapWrapper()方法中返回的GifBitmapWrapper對象包裝成GifBitmapWrapperResource對象。
loadProvider.getSourceDecoder().decode(data, width, height);這句代碼的過程分析結(jié)束了，最后得到了GifBitmapWrapperResource()對象，這個對象對象里面包含要加載的Bitmap對象。(BitmapResource對象里面包裝的是Bitmap對象，GifBitmapWrapper對象里面包裝的是BitmapResource對象，GifBitmapWrapperResource對象里面包裝的是GifBitmapWrapper對象)。
回到DecodeJob的decodeFromSourceData()方法中，執(zhí)行完loadProvider.getSourceDecoder().decode();后返回GifBitmapWrapperResource對象到decodeSource()方法，最后回到decodeFromSource()方法中，執(zhí)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;
}
//這個transcoder指向了在Engine中創(chuàng)建DecodeJob對象時傳入的GifBitmapWrapperDrawableTranscoder類
return transcoder.transcode(transformed);
}
進入GifBitmapWrapperDrawableTranscoder對象的transcode(transformed)方法。
GifBitmapWrapperDrawableTranscoder對象的transcode(transformed)方法
public Resource<GlideDrawable> transcode(Resource<GifBitmapWrapper> toTranscode) {
private final ResourceTranscoder<Bitmap, GlideBitmapDrawable> bitmapDrawableResourceTranscoder;
//得到GifBitmapWrapper對象
GifBitmapWrapper gifBitmap = toTranscode.get();
//從GifBitmapWrapper中取出Bitmap對象
Resource<Bitmap> bitmapResource = gifBitmap.getBitmapResource();
final Resource<? extends GlideDrawable> result;
//bitmapResource為null說明為Gif類型
if (bitmapResource != null) {
//新建GlideBitmapDrawableTranscoder對象，將Bitmap進行
result =
bitmapDrawableResourceTranscoder.transcode(bitmapResource);
} else {
result = gifBitmap.getGifResource();
}
return (Resource<GlideDrawable>) result;
}
進入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()方法中將Bitemap對象保存在GlideBitmapDrawableResource中。
一路返回到EngineRunnable的run()方法中，EngineRunnable的run()方法
中的1過程分析結(jié)束了，最后的到了GlideBitmapDrawableResource對象，里面保存了要展示的Bitmp。再貼一下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，調(diào)用了EngineRunnable的onLoadComplete(resource)方法。
EngineRunnable的onLoadComplete(resource)方法
private void onLoadComplete(Resource resource) {
manager.onResourceReady(resource);
}
這個manager指向的是EngineRunnable的構(gòu)造器中傳來的EngineRunnableManager參數(shù)，這個EngineRunnableManager被EngineJob實現(xiàn)。
進入EngineJob類中。
EngineJob類中的方法
private static final Handler MAIN_THREAD_HANDLER = new Handler(Looper.getMainLooper(), new MainThreadCallback());
public void onResourceReady(final Resource<?> resource) {
this.resource = resource;
//通過Handler發(fā)送了一條消息，切換到主線程，準備進行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);
//這個ResourceCallback前面已經(jīng)分析過了，GenericRequest類實現(xiàn)了，在for()循環(huán)中處理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;
}
}
處理ResourceCallback接口時，會調(diào)用GenericRequest中的實現(xiàn)了ResourceCallback接口的方法。
進入GenericRequest類中。
GenericRequest類中
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);
//調(diào)用Target來展示圖片
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類中
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) {
//這個view就是我們之前into()中傳進來的ImageView
view.setImageDrawable(resource);
}
最后圖片就顯示出來了。
