一、基本用法：
Glide.with(context).load(url).into(imageview);
with()方法：给glide添加生命周期的监听；返回的是一个RequestManager对象所以load()方法也是RequestManager的
RequestManager-->RequestManagerRetriver-->RequestTracker(负责跟踪、取消、重启)
RequestTracker可知其实就是在Glide内部维护了一个Request请求的list，不管你context传入的是Activity还是 FragmentActivitiy，都会在Activity的基础上创建一个Fragment，这是为什么呢？因为Glide无法监听到Activity的生命周期，所以往Activity中添加一个Fragment来监听Fragment的生命周期，因为如果Activity消亡了，Fragment当然也就消亡了，具体代码看下面，不过传入的参数跟之前Application的不同，这里的SupportRequestManagerFragment的current.getLifecycle()方法我们进去会发现这其实是一个继承了Fragment的类，也就是往Activity里添加的Fragment。
load()方法：其实就是做一个状态的保存
public DrawableTypeRequest<String> load(String string) {
return (DrawableTypeRequest<String>) fromString().load(string);
}
private <T> DrawableTypeRequest<T> loadGeneric(Class<T> modelClass) {
//根据不同的class来创建不同的ModelLoader
ModelLoader<T, InputStream> streamModelLoader = Glide.buildStreamModelLoader(modelClass, context);
ModelLoader<T, ParcelFileDescriptor> fileDescriptorModelLoader =
Glide.buildFileDescriptorModelLoader(modelClass, context);
if (modelClass != null && streamModelLoader == null && fileDescriptorModelLoader == null) {
throw new IllegalArgumentException("Unknown type " + modelClass + ". You must provide a Model of a type for"
+ " which there is a registered ModelLoader, if you are using a custom model, you must first call"
+ " Glide#register with a ModelLoaderFactory for your custom model class");
}
return optionsApplier.apply(
//通过获取到的ModelLoadder来创建DrawableTypeRequest对象返回给上一级
new DrawableTypeRequest<T>(modelClass, streamModelLoader, fileDescriptorModelLoader, context,
glide, requestTracker, lifecycle, optionsApplier));
}
提供一个InputStream输入流
public static <T> ModelLoader<T, InputStream> buildStreamModelLoader(Class<T> modelClass, Context context) {
return buildModelLoader(modelClass, InputStream.class, context);
}
public static <T, Y> ModelLoader<T, Y> buildModelLoader(Class<T> modelClass, Class<Y> resourceClass,
Context context) {
if (modelClass == null) {
if (Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(TAG, "Unable to load null model, setting placeholder only");
}
return null;
}
return Glide.get(context).getLoaderFactory().buildModelLoader(modelClass, resourceClass);
}
public synchronized <T, Y> ModelLoader<T, Y> buildModelLoader(Class<T> modelClass, Class<Y> resourceClass) { ModelLoader<T, Y> result = getCachedLoader(modelClass, resourceClass); if (result != null) { // We've already tried to create a model loader and can't with the currently registered set of factories, // but we can't use null to demonstrate that failure because model loaders that haven't been requested // yet will be null in the cache. To avoid this, we use a special signal model loader. if (NULL_MODEL_LOADER.equals(result)) { return null; } else { return result; } } final ModelLoaderFactory<T, Y> factory = getFactory(modelClass, resourceClass); if (factory != null) { result = factory.build(context, this); cacheModelLoader(modelClass, resourceClass, result); } else { // We can't generate a model loader for the given arguments with the currently registered set of factories. cacheNullLoader(modelClass, resourceClass); } return result; } private <T, Y> ModelLoaderFactory<T, Y> getFactory(Class<T> modelClass, Class<Y> resourceClass) { Map<Class/*Y*/, ModelLoaderFactory/*T, Y*/> resourceToFactories = modelClassToResourceFactories.get(modelClass); ModelLoaderFactory/*T, Y*/ result = null; if (resourceToFactories != null) { result = resourceToFactories.get(resourceClass); } // 关于注册的 这块在Glide类的构造函数统一注册了 if (result == null) { for (Class<? super T> registeredModelClass : modelClassToResourceFactories.keySet()) { // This accounts for model subclasses, our map only works for exact matches. We should however still // match a subclass of a model with a factory for a super class of that model if if there isn't a // factory for that particular subclass. Uris are a great example of when this happens, most uris // are actually subclasses for Uri, but we'd generally rather load them all with the same factory rather // than trying to register for each subclass individually. if (registeredModelClass.isAssignableFrom(modelClass)) { Map<Class/*Y*/, ModelLoaderFactory/*T, Y*/> currentResourceToFactories = modelClassToResourceFactories.get(registeredModelClass); if (currentResourceToFactories != null) { result = currentResourceToFactories.get(resourceClass); if (result != null) { break; } } } } } return result; }以上就是生成streamModelLoader和fileDescriptorModelLoader。
fromString()方法之后返回一个DrawableTypeRequest对象，然后就是调用这个对象的load(string)方法，其实是调用了父类DrawableRequestBuilder里load()
into():此方法也是在父类DrawableRequestBuilder里
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.
}
}
return into(glide.buildImageViewTarget(view, transcodeClass));
}
<R> Target<R> buildImageViewTarget(ImageView imageView, Class<R> transcodedClass) {
return imageViewTargetFactory.buildTarget(imageView, transcodedClass);
}
//返回一个Target
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)");
}
}
}
将返回的Target传入进来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())");
}
Request previous = target.getRequest();
if (previous != null) {
previous.clear();
requestTracker.removeRequest(previous);
previous.recycle();
}
//调用buildRequest()方法构建出了一个Request对象
Request request = buildRequest(target);
target.setRequest(request);
lifecycle.addListener(target);
//执行这个Request。
requestTracker.runRequest(request);
return target;
}
private Request buildRequest(Target<TranscodeType> target) {
if (priority == null) {
priority = Priority.NORMAL;
}
return buildRequestRecursive(target, null);
}
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()");
}
// Recursive case: contains a potentially recursive thumbnail request builder.
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 {
// Base case: no thumbnail.上面的代码处理略缩图的
return obtainRequest(target, sizeMultiplier, priority, parentCoordinator);
}
}
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);
}
public static <A, T, Z, R> GenericRequest<A, T, Z, R> obtain(
LoadProvider<A, T, Z, R> loadProvider,
A model,
Key signature,
Context context,
Priority priority,
Target<R> target,
float sizeMultiplier,
Drawable placeholderDrawable,
int placeholderResourceId,
Drawable errorDrawable,
int errorResourceId,
Drawable fallbackDrawable,
int fallbackResourceId,
RequestListener<? super A, R> requestListener,
RequestCoordinator requestCoordinator,
Engine engine,
Transformation<Z> transformation,
Class<R> transcodeClass,
boolean isMemoryCacheable,
GlideAnimationFactory<R> animationFactory,
int overrideWidth,
int overrideHeight,
DiskCacheStrategy diskCacheStrategy) {
@SuppressWarnings("unchecked")
GenericRequest<A, T, Z, R> request = (GenericRequest<A, T, Z, R>) REQUEST_POOL.poll();
if (request == null) {
、新建一个通用的请求对象
request = new GenericRequest<A, T, Z, R>();
}
主要看这个init方法主要就是给一些常量赋值
request.init(loadProvider,
model,
signature,
context,
priority,
target,
sizeMultiplier,
placeholderDrawable,
placeholderResourceId,
errorDrawable,
errorResourceId,
fallbackDrawable,
fallbackResourceId,
requestListener,
requestCoordinator,
engine,
transformation,
transcodeClass,
isMemoryCacheable,
animationFactory,
overrideWidth,
overrideHeight,
diskCacheStrategy);
return request;
}
回到into()方法执行request
public void runRequest(Request request) {
requests.add(request);
// 判断是否暂停状态
if (!isPaused) {
// begin方法是request接口中的方法，调用的就是GenericRequest中的begin()
request.begin();
} else {
pendingRequests.add(request);
}
}
@Override
public void begin() {
startTime = LogTime.getLogTime();
if (model == null) {
// 执行错误占位图
onException(null);
return;
}
status = Status.WAITING_FOR_SIZE;
if (Util.isValidDimensions(overrideWidth, overrideHeight)) {
onSizeReady(overrideWidth, overrideHeight);
} else {
target.getSize(this);
}
if (!isComplete() && !isFailed() && canNotifyStatusChanged()) {
target.onLoadStarted(getPlaceholderDrawable());
}
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logV("finished run method in " + LogTime.getElapsedMillis(startTime));
}
}
@Override
public void onException(Exception e) {
if (Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(TAG, "load failed", e);
}
status = Status.FAILED;
//TODO: what if this is a thumbnail request?
if (requestListener == null || !requestListener.onException(e, model, target, isFirstReadyResource())) {
setErrorPlaceholder(e);
}
}
private void setErrorPlaceholder(Exception e) {
if (!canNotifyStatusChanged()) {
return;
}
Drawable error = model == null ? getFallbackDrawable() : null;
if (error == null) {
error = getErrorDrawable();
}
if (error == null) {
error = getPlaceholderDrawable();
}
// 此处的target就是GenericRequestBuilder中into()
return into(glide.buildImageViewTarget(view, transcodeClass));中的target所以onLoadFailed方法也就是ImageViewTarget中的onLoadFailed
target.onLoadFailed(e, error);
}
设置错误图片
@Override
public void onLoadFailed(Exception e, Drawable errorDrawable) {
view.setImageDrawable(errorDrawable);
}
设置loading占位图
@Override
public void onLoadStarted(Drawable placeholder) {
view.setImageDrawable(placeholder);
}
再次回到GenericRequest的begin方法中。。。判断是否设置override（手动设置宽高）属性的
if (Util.isValidDimensions(overrideWidth, overrideHeight)) {
onSizeReady(overrideWidth, overrideHeight);
} else {
// 同理getsize也是ImageViewTarget中的，但是ImageViewTarget中的并没有所以在他的父类ViewTarget中
target.getSize(this);
}
@Override
public void getSize(SizeReadyCallback cb) {
sizeDeterminer.getSize(cb);
}
public void getSize(SizeReadyCallback cb) {
int currentWidth = getViewWidthOrParam();
int currentHeight = getViewHeightOrParam();
if (isSizeValid(currentWidth) && isSizeValid(currentHeight)) {
// 最终还是调用了GenericRequest中的onSizeReady方法
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 observer = view.getViewTreeObserver();
layoutListener = new SizeDeterminerLayoutListener(this);
observer.addOnPreDrawListener(layoutListener);
}
}
}
@Override
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);
// load()方法里的loadGeneric()在buildModelLoader()的时候通过getFactory()创建了一个ModelLoaderFactory，在那里生
// 成返回了一个DrawableTypeRequest对象，在创建DrawableTypeRequest的时候new出了一个FixedLoadProvider类
// 这个loadProvider其实就是FixedLoadProvider类的一个封装类ChildLoadProvider的一个实体对象
ModelLoader<A, T> modelLoader = loadProvider.getModelLoader();
// 调用的是ImageVideoModelLoader的getResourceFetcher
final DataFetcher<T> dataFetcher = modelLoader.getResourceFetcher(model, width, height);
if (dataFetcher == null) {
onException(new Exception("Failed to load model: \'" + model + "\'"));
return;
}
// 得到的是GIfBitmapWrapperDrawableTranscoder
ResourceTranscoder<Z, R> transcoder = loadProvider.getTranscoder();
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logV("finished setup for calling load in " + LogTime.getElapsedMillis(startTime));
}
loadedFromMemoryCache = true;
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));
}
}
DrawableTypeRequest(Class<ModelType> modelClass, ModelLoader<ModelType, InputStream> streamModelLoader,
ModelLoader<ModelType, ParcelFileDescriptor> fileDescriptorModelLoader, Context context, Glide glide,
RequestTracker requestTracker, Lifecycle lifecycle, RequestManager.OptionsApplier optionsApplier) {
super(context, modelClass,
// 构建Provider
buildProvider(glide, streamModelLoader, fileDescriptorModelLoader, GifBitmapWrapper.class,
GlideDrawable.class, null),
glide, requestTracker, lifecycle);
this.streamModelLoader = streamModelLoader;
this.fileDescriptorModelLoader = fileDescriptorModelLoader;
this.optionsApplier = optionsApplier;
}
private static <A, Z, R> FixedLoadProvider<A, ImageVideoWrapper, Z, R> buildProvider(Glide glide,
ModelLoader<A, InputStream> streamModelLoader,
ModelLoader<A, ParcelFileDescriptor> fileDescriptorModelLoader, Class<Z> resourceClass,
Class<R> transcodedClass,
ResourceTranscoder<Z, R> transcoder) {
if (streamModelLoader == null && fileDescriptorModelLoader == null) {
return null;
}
if (transcoder == null) {
// 构建一个代码转换器ResourceTranscoder（这是一个接口）实际上构建出的是GIfBitmapWrapperDrawableTranscoder对象
transcoder = glide.buildTranscoder(resourceClass, transcodedClass);
}
// 构建一个编解码器DataLoadProvider（这是一个接口）实际上构建出的是ImageVideoGifDrwableLoadProvider对象
DataLoadProvider<ImageVideoWrapper, Z> dataLoadProvider = glide.buildDataProvider(ImageVideoWrapper.class,
resourceClass);
// 把之前loadGeneric中生成的两个ModelLoader对象封装到ImageVideoModelLoader中
ImageVideoModelLoader<A> modelLoader = new ImageVideoModelLoader<A>(streamModelLoader,
fileDescriptorModelLoader);
// 把前面生成的对象封装进去就生成了前面onSizeReady()方法中的loadProvider了
return new FixedLoadProvider<A, ImageVideoWrapper, Z, R>(modelLoader, transcoder, dataLoadProvider);
}
回到GenericRequest中begin调用的onSizeReady()中的这句代码
ModelLoader<A, T> modelLoader = loadProvider.getModelLoader();
final DataFetcher<T> dataFetcher = modelLoader.getResourceFetcher(model, width, height);
// 调用的是ImageVideoModelLoader的getResourceFetcher
public class ImageVideoModelLoader<A> implements ModelLoader<A, ImageVideoWrapper> {
...
@Override
public DataFetcher<ImageVideoWrapper> getResourceFetcher(A model, int width, int height) {
DataFetcher<InputStream> streamFetcher = null;
if (streamLoader != null) {
// 先调用我们在loadGeneric中构建出的StreamStringLoader的父类StringLoader中的getResourceFetcher()，
// 最后返回的是uilLoder.getResourceFetcher(uri, width, height);,所以得到的是一个HttpUrlFetcher对象
streamFetcher = streamLoader.getResourceFetcher(model, width, height);
}
DataFetcher<ParcelFileDescriptor> fileDescriptorFetcher = null;
if (fileDescriptorLoader != null) {
fileDescriptorFetcher = fileDescriptorLoader.getResourceFetcher(model, width, height);
}
if (streamFetcher != null || fileDescriptorFetcher != null) {
// 最后还是得到一个ImageVideoFetcher
return new ImageVideoFetcher(streamFetcher, fileDescriptorFetcher);
} else {
return null;
}
}
...
}
回到前面的onSizeReady()中的这句代码
loadStatus = engine.load(signature, width, height, dataFetcher, loadProvider, transformation, transcoder,
priority, isMemoryCacheable, diskCacheStrategy, this);
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());
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);
}
// 开启一个线程为后期的异步加载图片做准备
EngineJob engineJob = engineJobFactory.build(key, isMemoryCacheable);
// 创建DecodeJob对图片进行解码等操作
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);
}
EngineRunnable的run方法:@Override
public void run() {
if (isCancelled) {
return;
}
Exception exception = null;
Resource<?> resource = null;
try {
// 所有的逻辑在此方法执行
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);
}
}
private Resource<?> decode() throws Exception {
// 一个是从资源一个是从缓存
if (isDecodingFromCache()) {
return decodeFromCache();
} else {
return decodeFromSource();
}
}
private Resource<?> decodeFromSource() throws Exception {
return decodeJob.decodeFromSource();
}
public Resource<Z> decodeFromSource() throws Exception {
Resource<T> decoded = decodeSource();
return transformEncodeAndTranscode(decoded);
}
// 跟进decodeSource()
private Resource<T> decodeSource() throws Exception {
Resource<T> decoded = null;
try {
long startTime = LogTime.getLogTime();
// 就是ImageVideoFetcher的loadData()
final A data = fetcher.loadData(priority);
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logWithTimeAndKey("Fetched data", startTime);
}
if (isCancelled) {
return null;
}
// 这个方法其实就是起到一个解码的作用
decoded = decodeFromSourceData(data);
} finally {
fetcher.cleanup();
}
return decoded;
}
@Override
public ImageVideoWrapper loadData(Priority priority) throws Exception {
InputStream is = null;
if (streamFetcher != null) {
try {
// 此处的streamFetcher就是前面构建ImageVideoFetcher时传入的HttpUrlFetcher，所以此处是调用的
HttpUrlFetcher的loadData
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);
}
调用的HttpUrlFetcher的loadData@Override
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());
}
}
private InputStream getStreamForSuccessfulRequest(HttpURLConnection urlConnection)
throws IOException {
if (TextUtils.isEmpty(urlConnection.getContentEncoding())) {
int contentLength = urlConnection.getContentLength();
stream = ContentLengthInputStream.obtain(urlConnection.getInputStream(), contentLength);
} else {
if (Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(TAG, "Got non empty content encoding: " + urlConnection.getContentEncoding());
}
stream = urlConnection.getInputStream();
}
return stream;
}
上面就是请求网络的代码，但只是得到了一个inputStream的输入流，再回到DecodeJob的decodeSource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();
loadProvider就是刚刚的FixedLoadProvider，所以getSourceDecoudr()就是GifBitmapWrapperResourceDecoder的一个对象
decoded = loadProvider.getSourceDecoder().decode(data, width, height);
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logWithTimeAndKey("Decoded from source", startTime);
}
}
return decoded;
}
来到GifBitmapWrapperResourceDecoder的decode()@SuppressWarnings("resource")
// @see ResourceDecoder.decode
@Override
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 {
result = decodeBitmapWrapper(source, width, height);
}
return result;
}
private GifBitmapWrapper decodeStream(ImageVideoWrapper source, int width, int height, byte[] bytes)
throws IOException {
InputStream bis = streamFactory.build(source.getStream(), bytes);
// 先取出2个字节来判断是否是GIF
bis.mark(MARK_LIMIT_BYTES);
ImageHeaderParser.ImageType type = parser.parse(bis);
bis.reset();
GifBitmapWrapper result = null;
if (type == ImageHeaderParser.ImageType.GIF) {
result = decodeGifWrapper(bis, width, height);
}
// Decoding the gif may fail even if the type matches.
if (result == null) {
// We can only reset the buffered InputStream, so to start from the beginning of the stream, we need to
// pass in a new source containing the buffered stream rather than the original stream.
ImageVideoWrapper forBitmapDecoder = new ImageVideoWrapper(bis, source.getFileDescriptor());
result = decodeBitmapWrapper(forBitmapDecoder, width, height);
}
return result;
}
private GifBitmapWrapper decodeBitmapWrapper(ImageVideoWrapper toDecode, int width, int height) throws IOException {
GifBitmapWrapper result = null;
// 这个bitmapDecoder实际上就是ImageVideoBitmapDecode
Resource<Bitmap> bitmapResource = bitmapDecoder.decode(toDecode, width, height);
if (bitmapResource != null) {
result = new GifBitmapWrapper(bitmapResource, null);
}
return result;
}
ImageVideoBitmapDecode的decode()@SuppressWarnings("resource")
// @see ResourceDecoder.decode
@Override
public Resource<Bitmap> decode(ImageVideoWrapper source, int width, int height) throws IOException {
Resource<Bitmap> result = null;
InputStream is = source.getStream();
if (is != null) {
try {
// 其实是StreamBitmapDecoder的decode方法
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;
}
StreamBitmapDecoder的decode方法
@Override
public Resource<Bitmap> decode(InputStream source, int width, int height) {
Bitmap bitmap = downsampler.decode(source, bitmapPool, width, height, decodeFormat);
return BitmapResource.obtain(bitmap, bitmapPool);
}
这里就是对服务器返回的InputStream进行读取，图片的加载和逻辑（旋转、圆角等）的处理也全都在这个方法内@Override
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();
// Use to fix the mark limit to avoid allocating buffers that fit entire images.
RecyclableBufferedInputStream bufferedStream = new RecyclableBufferedInputStream(
is, bytesForStream);
// Use to retrieve exceptions thrown while reading.
// TODO(#126): when the framework no longer returns partially decoded Bitmaps or provides a way to determine
// if a Bitmap is partially decoded, consider removing.
ExceptionCatchingInputStream exceptionStream =
ExceptionCatchingInputStream.obtain(bufferedStream);
// Use to read data.
// Ensures that we can always reset after reading an image header so that we can still attempt to decode the
// full image even when the header decode fails and/or overflows our read buffer. See #283.
// 这里读取数据
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);
// BitmapFactory swallows exceptions during decodes and in some cases when inBitmap is non null, may catch
// and log a stack trace but still return a non null bitmap. To avoid displaying partially decoded bitmaps,
// we catch exceptions reading from the stream in our ExceptionCatchingInputStream and throw them here.
final Exception streamException = exceptionStream.getException();
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);
}
}
带着上面返回的bitmap对象-->StreamBitmapDecoder(转化成Resource对象)-->ImageVideoBitmapDecoder-->GIfBitmapWrapperResourceDecoder
private GifBitmapWrapper decodeBitmapWrapper(ImageVideoWrapper toDecode, int width, int height) throws IOException {
GifBitmapWrapper result = null;
// 经过层层返回的Resource对象
Resource<Bitmap> bitmapResource = bitmapDecoder.decode(toDecode, width, height);
if (bitmapResource != null) {
// 将经过层层返回的Resource对象封装到GifBitmapWrapper中：意思就是既能加载gif也能加载静态图
result = new GifBitmapWrapper(bitmapResource, null);
}
return result;
}
返回到最外层的decode()发现:
return wrapper != null ? new GifBitmapWrapperResource(wrapper) : null;
public class GifBitmapWrapperResource implements Resource<GifBitmapWrapper> {
private final GifBitmapWrapper data;
public GifBitmapWrapperResource(GifBitmapWrapper data) {
if (data == null) {
throw new NullPointerException("Data must not be null");
}
this.data = data;
}
@Override
public GifBitmapWrapper get() {
return data;
}
@Override
public int getSize() {
return data.getSize();
}
@Override
public void recycle() {
Resource<Bitmap> bitmapResource = data.getBitmapResource();
if (bitmapResource != null) {
bitmapResource.recycle();
}
Resource<GifDrawable> gifDataResource = data.getGifResource();
if (gifDataResource != null) {
gifDataResource.recycle();
}
}
}
经过这一层是图片可以通过Resource接口形式返回，所以在DecodeJob的decodeFromSourceData中返回的其实也就是Resource<GifBitmapWrapper>类型的对象，把这个对象带入到最上面的public Resource<Z> decodeFromSource() throws Exception {
Resource<T> decoded = decodeSource();
return transformEncodeAndTranscode(decoded);
}
转化成Resource<Z>类型的对象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();
// T类型转成Z类型
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;
}
// 这里的transcoder其实就是很早以前传过来的GifBitmapWrapperDrawableTranscoder
（load()-->loadGeneric()-->DrawableTYpeRequest-->FixedLoadProvider）
return transcoder.transcode(transformed);
}
@SuppressWarnings("unchecked")
@Override
public Resource<GlideDrawable> transcode(Resource<GifBitmapWrapper> toTranscode) {
// 1、从Resource<GifBitmapWrapper>取出GifBitmapWrapper对象
GifBitmapWrapper gifBitmap = toTranscode.get();
// 2、从GifBitmapWrapper中取出Resource<Bitmap>对象
Resource<Bitmap> bitmapResource = gifBitmap.getBitmapResource();
final Resource<? extends GlideDrawable> result;
// 3、判断如果为空就是gif反之则是静态图
if (bitmapResource != null) {
// 需要转化成为Bitmap或者Drawable对象才能显示到ImageView上，所以在调用GlideBItmapDrawableTranscoder进行转码
result = bitmapDrawableResourceTranscoder.transcode(bitmapResource);
} else {
// gif的加载是使用GifDrawable这个类本身就是一个Drawable对象
result = gifBitmap.getGifResource();
}
// This is unchecked but always safe, anything that extends a Drawable can be safely cast to a Drawable.
return (Resource<GlideDrawable>) result;
}
GlideBitmapDrawableTranscoder的transcode()
@Override
public Resource<GlideBitmapDrawable> transcode(Resource<Bitmap> toTranscode) {
GlideBitmapDrawable drawable = new GlideBitmapDrawable(resources, toTranscode.get());
return new GlideBitmapDrawableResource(drawable, bitmapPool);
}
不过是静态图（Resource<GlideBitmapDrawable>）还是gif（Resource<GifDrawable>）都是Resource<GlideDrawable>的子类GifBitmapWrapperDrawableTranscoder的transcode返回的是一个Resource<GlideDrawable>类型的对象带着返回的Resource<GlideDrawable>回到DecodeJob的transformEncodeAndTranscode()-->decodeFromSource()-->EngineRunnable的run()@Override
public void run() {
if (isCancelled) {
return;
}
Exception exception = null;
Resource<?> resource = null;
try {
// 这个是转码以后的Resource<GlideDrawable>
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 {
// 加载图片的方法
onLoadComplete(resource);
}
}
private void onLoadComplete(Resource resource) {
// 此处的manager就是EngineJob的对象
manager.onResourceReady(resource);
}
EngineJob的onResourceReady()
@Override
public void onResourceReady(final Resource<?> resource) {
this.resource = resource;
// 通过Handle发送了一条MSG_COMPLETE的消息，在MainThreadCallBack中接收消息
MAIN_THREAD_HANDLER.obtainMessage(MSG_COMPLETE, this).sendToTarget();
}
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;
}
}
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;
// Hold on to resource for duration of request so we don't recycle it in the middle of notifying if it
// synchronously released by one of the callbacks.
engineResource.acquire();
listener.onEngineJobComplete(key, engineResource);
// 通过循环调用所有的ResourceCallback的onResourceReady()方法，而ResourceCallback则是从addCallback得到的
for (ResourceCallback cb : cbs) {
if (!isInIgnoredCallbacks(cb)) {
engineResource.acquire();
cb.onResourceReady(engineResource);
}
}
// Our request is complete, so we can release the resource.
engineResource.release();
}
addCallback则是在Engine的load方法中调用的
public void addCallback(ResourceCallback cb) {
Util.assertMainThread();
if (hasResource) {
cb.onResourceReady(engineResource);
} else if (hasException) {
cb.onException(exception);
} else {
cbs.add(cb);
}
}
Engine的load方法
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) {
...
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);
// 此处调用了addCallback，里面所传的cb又是什么？？？跟上去到GennericRequest中传的是个this
engineJob.addCallback(cb);
engineJob.start(runnable);
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logWithTimeAndKey("Started new load", startTime, key);
}
return new LoadStatus(cb, engineJob);
}
EngineJob中addCallback中所调用的onResourceReady()其实就是GenericRequest中的onResourceReady()
@SuppressWarnings("unchecked")
@Override
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;
}
// 获取到一个GlideDrawable对象
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) {
// We must call isFirstReadyResource before setting status.
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);
// 这个target实际上就是GenericRequestBuilderinto的into()中glide.buildImageViewTarget()构建出来的target，就是GlideDrawableImageViewTarget
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);
}
}
@Override
public void onResourceReady(GlideDrawable resource, GlideAnimation<? super GlideDrawable> animation) {
if (!resource.isAnimated()) {
//TODO: Try to generalize this to other sizes/shapes.
// This is a dirty hack that tries to make loading square thumbnails and then square full images less costly
// by forcing both the smaller thumb and the larger version to have exactly the same intrinsic dimensions.
// If a drawable is replaced in an ImageView by another drawable with different intrinsic dimensions,
// the ImageView requests a layout. Scrolling rapidly while replacing thumbs with larger images triggers
// lots of these calls and causes significant amounts of jank.
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();
}
@Override
public void onResourceReady(Z resource, GlideAnimation<? super Z> glideAnimation) {
if (glideAnimation == null || !glideAnimation.animate(resource, this)) {
// 这是一个抽象方法，所以具体实现在子类
setResource(resource);
}
}
@Override
protected void setResource(GlideDrawable resource) {
view.setImageDrawable(resource);
}
至此图片也就终于显示出来了