学习目标：
Glide源码解析学习内容：
1.首先我们先看一下三个问题？
- Glide的生命周期怎么实现的？
- 缓存，内存，硬盘缓存？
- 这里面会有网络访问请求队列？
我们肯定依旧是从使用的角度入手，我们平时都是按照以下的方式使用Glide的。
//一般情况下都是这么使用
Glide.with(this).load(url).into(image);
我们从with开始
public class Glide implements ComponentCallbacks2 {
......
@NonNull
public static RequestManager with(@NonNull FragmentActivity activity) {
return getRetriever(activity).get(activity);
}
......
}
我们首先看getRetriever(activity)
public class Glide implements ComponentCallbacks2 {
private static volatile Glide glide;
.......
@NonNull
private static RequestManagerRetriever getRetriever(@Nullable Context context) {
Preconditions.checkNotNull(context, "You cannot start a load on a not yet attached View or a Fragment where getActivity() returns null (which usually occurs when getActivity() is called before the Fragment is attached or after the Fragment is destroyed).");
return get(context).getRequestManagerRetriever();
}
.........
//很明显这是个单例
@NonNull
public static Glide get(@NonNull Context context) {
if (glide == null) {
Class var1 = Glide.class;
synchronized(Glide.class) {
if (glide == null) {
checkAndInitializeGlide(context);
}
}
}
return glide;
}
private static void checkAndInitializeGlide(@NonNull Context context) {
if (isInitializing) {
throw new IllegalStateException("You cannot call Glide.get() in registerComponents(), use the provided Glide instance instead");
} else {
isInitializing = true;
initializeGlide(context);
isInitializing = false;
}
}
...........
private static void initializeGlide(@NonNull Context context) {
//我们这里 new了一个GlideBuilder
initializeGlide(context, new GlideBuilder());
}
//这里就开始初始化Glide
private static void initializeGlide(@NonNull Context context, @NonNull GlideBuilder builder) {
Context applicationContext = context.getApplicationContext();
GeneratedAppGlideModule annotationGeneratedModule = getAnnotationGeneratedGlideModules();
List<GlideModule> manifestModules = Collections.emptyList();
if (annotationGeneratedModule == null || annotationGeneratedModule.isManifestParsingEnabled()) {
manifestModules = (new ManifestParser(applicationContext)).parse();
}
Iterator iterator;
GlideModule current;
if (annotationGeneratedModule != null && !annotationGeneratedModule.getExcludedModuleClasses().isEmpty()) {
Set<Class<?>> excludedModuleClasses = annotationGeneratedModule.getExcludedModuleClasses();
iterator = manifestModules.iterator();
while(iterator.hasNext()) {
current = (GlideModule)iterator.next();
if (excludedModuleClasses.contains(current.getClass())) {
if (Log.isLoggable("Glide", 3)) {
Log.d("Glide", "AppGlideModule excludes manifest GlideModule: " + current);
}
iterator.remove();
}
}
}
if (Log.isLoggable("Glide", 3)) {
Iterator var9 = manifestModules.iterator();
while(var9.hasNext()) {
GlideModule glideModule = (GlideModule)var9.next();
Log.d("Glide", "Discovered GlideModule from manifest: " + glideModule.getClass());
}
}
RequestManagerFactory factory = annotationGeneratedModule != null ? annotationGeneratedModule.getRequestManagerFactory() : null;
builder.setRequestManagerFactory(factory);
iterator = manifestModules.iterator();
while(iterator.hasNext()) {
current = (GlideModule)iterator.next();
current.applyOptions(applicationContext, builder);
}
if (annotationGeneratedModule != null) {
annotationGeneratedModule.applyOptions(applicationContext, builder);
}
//构建一个glide
Glide glide = builder.build(applicationContext);
Iterator var13 = manifestModules.iterator();
while(var13.hasNext()) {
GlideModule module = (GlideModule)var13.next();
module.registerComponents(applicationContext, glide, glide.registry);
}
if (annotationGeneratedModule != null) {
annotationGeneratedModule.registerComponents(applicationContext, glide, glide.registry);
}
applicationContext.registerComponentCallbacks(glide);
Glide.glide = glide;
}
.........
}
首先我们需要来看一下GlideBuilder
/**
* A builder class for setting default structural classes for Glide to use.
*/
public final class GlideBuilder {
.........
@NonNull
public Glide build(@NonNull Context context) {
if (sourceExecutor == null) {
sourceExecutor = GlideExecutor.newSourceExecutor();
}
if (diskCacheExecutor == null) {
diskCacheExecutor = GlideExecutor.newDiskCacheExecutor();
}
if (animationExecutor == null) {
animationExecutor = GlideExecutor.newAnimationExecutor();
}
if (memorySizeCalculator == null) {
memorySizeCalculator = new MemorySizeCalculator.Builder(context).build();
}
if (connectivityMonitorFactory == null) {
connectivityMonitorFactory = new DefaultConnectivityMonitorFactory();
}
if (bitmapPool == null) {
int size = memorySizeCalculator.getBitmapPoolSize();
if (size > 0) {
bitmapPool = new LruBitmapPool(size);
} else {
bitmapPool = new BitmapPoolAdapter();
}
}
if (arrayPool == null) {
arrayPool = new LruArrayPool(memorySizeCalculator.getArrayPoolSizeInBytes());
}
if (memoryCache == null) {
memoryCache = new LruResourceCache(memorySizeCalculator.getMemoryCacheSize());
}
if (diskCacheFactory == null) {
diskCacheFactory = new InternalCacheDiskCacheFactory(context);
}
if (engine == null) {
engine =
new Engine(
memoryCache,
diskCacheFactory,
diskCacheExecutor,
sourceExecutor,
GlideExecutor.newUnlimitedSourceExecutor(),
GlideExecutor.newAnimationExecutor(),
isActiveResourceRetentionAllowed);
}
RequestManagerRetriever requestManagerRetriever =
new RequestManagerRetriever(requestManagerFactory);
return new Glide(
context,
engine,
memoryCache,
bitmapPool,
arrayPool,
requestManagerRetriever,
connectivityMonitorFactory,
logLevel,
defaultRequestOptions.lock(),
defaultTransitionOptions);
}
........
}
好到这里getRetriever(activity)就是返回了一个Glide对象。我们再看getRetriever(activity).get(activity);中的get(activity)方法.
public class RequestManagerRetriever implements Callback {
.......
//获取一个无UI的fragment
//Glide的生命周期就与这个fragment了
SupportRequestManagerFragment getSupportRequestManagerFragment(@NonNull androidx.fragment.app.FragmentManager fm, @Nullable Fragment parentHint) {
SupportRequestManagerFragment current = (SupportRequestManagerFragment)fm.findFragmentByTag("com.bumptech.glide.manager");
if (current == null) {
current = (SupportRequestManagerFragment)this.pendingSupportRequestManagerFragments.get(fm);
if (current == null) {
//这个就是我们得到的无UIfragment。
current = new SupportRequestManagerFragment();
current.setParentFragmentHint(parentHint);
this.pendingSupportRequestManagerFragments.put(fm, current);
//添加一个无UI的fragment
fm.beginTransaction().add(current, "com.bumptech.glide.manager").commitAllowingStateLoss();
this.handler.obtainMessage(2, fm).sendToTarget();
}
}
return current;
}
@NonNull
private RequestManager supportFragmentGet(@NonNull Context context, @NonNull androidx.fragment.app.FragmentManager fm, @Nullable Fragment parentHint) {
//获取fragment(生命周期就靠它了)
SupportRequestManagerFragment current = this.getSupportRequestManagerFragment(fm, parentHint);
RequestManager requestManager = current.getRequestManager();
if (requestManager == null) {
Glide glide = Glide.get(context);
//看下面这行代码,我们在这里调用了current.getGlideLifecycle(),记住它。
requestManager = this.factory.build(glide, current.getGlideLifecycle(), current.getRequestManagerTreeNode(), context);
current.setRequestManager(requestManager);
}
return requestManager;
}
.......
@NonNull
public RequestManager get(@NonNull FragmentActivity activity) {
if (Util.isOnBackgroundThread()) {
return this.get(activity.getApplicationContext());
} else {
assertNotDestroyed(activity);
androidx.fragment.app.FragmentManager fm = activity.getSupportFragmentManager();
return this.supportFragmentGet(activity, fm, (Fragment)null);
}
}
......
}
我们看到我们获取无UI的时候，new 了一个fragment,这个fragment与我们的生命周期绑定有着重要作用(lifecycle与fragment的生命周期绑定)。
public class SupportRequestManagerFragment extends Fragment {
......
private final ActivityFragmentLifecycle lifecycle;
......
public SupportRequestManagerFragment() {
this(new ActivityFragmentLifecycle());
}
.......
//向外部暴露接口
ActivityFragmentLifecycle getGlideLifecycle() {
return lifecycle;
}
........
@Override
public void onAttach(Context context) {
super.onAttach(context);
try {
registerFragmentWithRoot(getActivity());
} catch (IllegalStateException e) {
// OnAttach can be called after the activity is destroyed, see #497.
if (Log.isLoggable(TAG, Log.WARN)) {
Log.w(TAG, "Unable to register fragment with root", e);
}
}
}
//下面的fragmet生命周期代码,大家必然很熟悉,
//可以看到我们这里的生命周期都回调了lifecycle里的方法，
//而lifecycle还有一个get()方法，说明，这个lifecycle
//必然会在别的地方调用或者赋值。
//很明显lifecycle再fragment的生命周期里都会调用
//记住这里
@Override
public void onDetach() {
super.onDetach();
parentFragmentHint = null;
unregisterFragmentWithRoot();
}
@Override
public void onStart() {
super.onStart();
lifecycle.onStart();
}
@Override
public void onStop() {
super.onStop();
lifecycle.onStop();
}
@Override
public void onDestroy() {
super.onDestroy();
lifecycle.onDestroy();
unregisterFragmentWithRoot();
}
}
到这with就结束了，接下来我们看load(url)干了啥。
public class RequestManager
....
@Override
public RequestBuilder<Drawable> load(@Nullable String string) {
return asDrawable().load(string);
}
.....
@NonNull
@CheckResult
public RequestBuilder<Drawable> asDrawable() {
return as(Drawable.class);
}
......
@NonNull
@CheckResult
public <ResourceType> RequestBuilder<ResourceType> as(
@NonNull Class<ResourceType> resourceClass) {
//最后返回一个RequestBuilder对象
return new RequestBuilder<>(glide, this, resourceClass, context);
}
}
所以asDrawable().load(string); = RequestBuilder.load(string);
/**
* A generic class that can handle setting options and staring loads for generic resource types.
*
* @param <TranscodeType> The type of resource that will be delivered to the
* {@link com.bumptech.glide.request.target.Target}.
*/
// Public API.
@SuppressWarnings({"unused", "WeakerAccess"})
public class RequestBuilder<TranscodeType> implements Cloneable,
ModelTypes<RequestBuilder<TranscodeType>> {
.......
/**
* Returns a request builder to load the given {@link java.lang.String}.
*
* <p> Note - this method caches data using only the given String as the cache key. If the data is
* a Uri outside of your control, or you otherwise expect the data represented by the given String
* to change without the String identifier changing, Consider using
* {@link com.bumptech.glide.request.RequestOptions#signature(com.bumptech.glide.load.Key)} to
* mixin a signature you create that identifies the data currently at the given String that will
* invalidate the cache if that data changes. Alternatively, using
* {@link com.bumptech.glide.load.engine.DiskCacheStrategy#NONE} and/or
* {@link com.bumptech.glide.request.RequestOptions#skipMemoryCache(boolean)} may be
* appropriate.
* </p>
*
* @see #load(Object)
*
* @param string A file path, or a uri or url handled by
* {@link com.bumptech.glide.load.model.UriLoader}.
*/
@NonNull
@Override
@CheckResult
public RequestBuilder<TranscodeType> load(@Nullable String string) {
return loadGeneric(string);
}
.......
@NonNull
private RequestBuilder<TranscodeType> loadGeneric(@Nullable Object model) {
this.model = model;
isModelSet = true;
return this;
}
}
看到这而load(url)这一块也就看完了，接下来该into(iv)这个方法了。
/**
* Sets the {@link ImageView} the resource will be loaded into, cancels any existing loads into
* the view, and frees any resources Glide may have previously loaded into the view so they may be
* reused.
*
* @see RequestManager#clear(Target)
*
* @param view The view to cancel previous loads for and load the new resource into.
* @return The
* {@link com.bumptech.glide.request.target.Target} used to wrap the given {@link ImageView}.
*/
@NonNull
public ViewTarget<ImageView, TranscodeType> into(@NonNull ImageView view) {
Util.assertMainThread();
Preconditions.checkNotNull(view);
//设置了一些对图片的操作
RequestOptions requestOptions = this.requestOptions;
if (!requestOptions.isTransformationSet()
&& requestOptions.isTransformationAllowed()
&& view.getScaleType() != null) {
// Clone in this method so that if we use this RequestBuilder to load into a View and then
// into a different target, we don't retain the transformation applied based on the previous
// View's scale type.
switch (view.getScaleType()) {
case CENTER_CROP:
requestOptions = requestOptions.clone().optionalCenterCrop();
break;
case CENTER_INSIDE:
requestOptions = requestOptions.clone().optionalCenterInside();
break;
case FIT_CENTER:
case FIT_START:
case FIT_END:
requestOptions = requestOptions.clone().optionalFitCenter();
break;
case FIT_XY:
requestOptions = requestOptions.clone().optionalCenterInside();
break;
case CENTER:
case MATRIX:
default:
// Do nothing.
}
}
return into(
glideContext.buildImageViewTarget(view, transcodeClass),
/*targetListener=*/ null,
requestOptions);
}
private <Y extends Target<TranscodeType>> Y into(
@NonNull Y target,
@Nullable RequestListener<TranscodeType> targetListener,
@NonNull RequestOptions options) {
Util.assertMainThread();
Preconditions.checkNotNull(target);
if (!isModelSet) {
throw new IllegalArgumentException("You must call #load() before calling #into()");
}
options = options.autoClone();
//构建请求了
Request request = buildRequest(target, targetListener, options);
Request previous = target.getRequest();
if (request.isEquivalentTo(previous)
&& !isSkipMemoryCacheWithCompletePreviousRequest(options, previous)) {
request.recycle();
// If the request is completed, beginning again will ensure the result is re-delivered,
// triggering RequestListeners and Targets. If the request is failed, beginning again will
// restart the request, giving it another chance to complete. If the request is already
// running, we can let it continue running without interruption.
if (!Preconditions.checkNotNull(previous).isRunning()) {
// Use the previous request rather than the new one to allow for optimizations like skipping
// setting placeholders, tracking and un-tracking Targets, and obtaining View dimensions
// that are done in the individual Request.
previous.begin();
}
return target;
}
requestManager.clear(target);
target.setRequest(request);
//添加请求
requestManager.track(target, request);
return target;
}
我们点击这行代码requestManager.track(target, request);
public class RequestManager implements LifecycleListener,
ModelTypes<RequestBuilder<Drawable>> {
.......
void track(Target<?> target, Request request) {
targetTracker.track(target);
requestTracker.runRequest(request);
}
......
}
再点击requestTracker.runRequest(request);
//管理运行时队列和带运行队列
public class RequestTracker {
// Most requests will be for views and will therefore be held strongly (and safely) by the view
// via the tag. However, a user can always pass in a different type of target which may end up not
// being strongly referenced even though the user still would like the request to finish. Weak
// references are therefore only really functional in this context for view targets. Despite the
// side affects, WeakReferences are still essentially required. A user can always make repeated
// requests into targets other than views, or use an activity manager in a fragment pager where
// holding strong references would steadily leak bitmaps and/or views.
//运行队列
private final Set<Request> requests =
Collections.newSetFromMap(new WeakHashMap<Request, Boolean>());
// A set of requests that have not completed and are queued to be run again. We use this list to
// maintain hard references to these requests to ensure that they are not garbage collected
// before they start running or while they are paused. See #346.
@SuppressWarnings("MismatchedQueryAndUpdateOfCollection")
//等待队列
private final List<Request> pendingRequests = new ArrayList<>();
private boolean isPaused;
.........
/**
* Starts tracking the given request.
*/
public void runRequest(Request request) {
requests.add(request);
if (!isPaused) {
request.begin();
} else {
pendingRequests.add(request);
}
}
......
/**
* Stops any in progress requests.
*/
public void pauseRequests() {
isPaused = true;
for (Request request : Util.getSnapshot(requests)) {
if (request.isRunning()) {
request.pause();
pendingRequests.add(request);
}
}
}
}
可以发现这里面有很多方法维护了队列，但这些方法是谁调用的呢？所以反推pauseRequests()；看这个方法被谁调用，谁就维护了这个队列。
public class RequestManager implements LifecycleListener,
ModelTypes<RequestBuilder<Drawable>> {
.......
private final Runnable addSelfToLifecycle = new Runnable() {
@Override
public void run() {
lifecycle.addListener(RequestManager.this);
}
};
.......
RequestManager(
Glide glide,
Lifecycle lifecycle,
RequestManagerTreeNode treeNode,
RequestTracker requestTracker,
ConnectivityMonitorFactory factory,
Context context) {
this.glide = glide;
this.lifecycle = lifecycle;
this.treeNode = treeNode;
this.requestTracker = requestTracker;
this.context = context;
connectivityMonitor =
factory.build(
context.getApplicationContext(),
new RequestManagerConnectivityListener(requestTracker));
// If we're the application level request manager, we may be created on a background thread.
// In that case we cannot risk synchronously pausing or resuming requests, so we hack around the
// issue by delaying adding ourselves as a lifecycle listener by posting to the main thread.
// This should be entirely safe.
//注意这if-else
//其实都是为了执行 lifecycle.addListener(this);
if (Util.isOnBackgroundThread()) {
mainHandler.post(addSelfToLifecycle);
} else {
lifecycle.addListener(this);
}
lifecycle.addListener(connectivityMonitor);
setRequestOptions(glide.getGlideContext().getDefaultRequestOptions());
glide.registerRequestManager(this);
}
........
public void pauseRequests() {
Util.assertMainThread();
requestTracker.pauseRequests();
}
}
可见ReqestManager是管理请求队列的工具
lifecycle.addListener(RequestManager.this);
glide实现生命周期问题小结：
上面的代码中注意这句代码把RequestManager绑定到lifecycle上，而在上面我们说过lifecycle又跟fragment绑定在一起了，所以RequestManager被绑定到了fragment了，每次前后台切换或者关闭activity，fragment必然会走生命周期(fragment依附于activity存在)，这样就会调用RequestManager里的方法进行暂停请求和重启请求。
到这我们就知道请求在哪里被维护，为什么具有生命周期。我们接着看这些请求在哪里执行的。还是从Glide.with(this).load(url).into(image);中的into(image);方法看起。
public ViewTarget<ImageView, TranscodeType> into(@NonNull ImageView view) {
Util.assertMainThread();
Preconditions.checkNotNull(view);
RequestOptions requestOptions = this.requestOptions;
if (!requestOptions.isTransformationSet()
&& requestOptions.isTransformationAllowed()
&& view.getScaleType() != null) {
// Clone in this method so that if we use this RequestBuilder to load into a View and then
// into a different target, we don't retain the transformation applied based on the previous
// View's scale type.
switch (view.getScaleType()) {
case CENTER_CROP:
requestOptions = requestOptions.clone().optionalCenterCrop();
break;
case CENTER_INSIDE:
requestOptions = requestOptions.clone().optionalCenterInside();
break;
case FIT_CENTER:
case FIT_START:
case FIT_END:
requestOptions = requestOptions.clone().optionalFitCenter();
break;
case FIT_XY:
requestOptions = requestOptions.clone().optionalCenterInside();
break;
case CENTER:
case MATRIX:
default:
// Do nothing.
}
}
return into(
glideContext.buildImageViewTarget(view, transcodeClass),
/*targetListener=*/ null,
requestOptions);
}
点into方法
private <Y extends Target<TranscodeType>> Y into(
@NonNull Y target,
@Nullable RequestListener<TranscodeType> targetListener,
@NonNull RequestOptions options) {
Util.assertMainThread();
Preconditions.checkNotNull(target);
if (!isModelSet) {
throw new IllegalArgumentException("You must call #load() before calling #into()");
}
options = options.autoClone();
//这里就是构建请求了
Request request = buildRequest(target, targetListener, options);
Request previous = target.getRequest();
if (request.isEquivalentTo(previous)
&& !isSkipMemoryCacheWithCompletePreviousRequest(options, previous)) {
request.recycle();
// If the request is completed, beginning again will ensure the result is re-delivered,
// triggering RequestListeners and Targets. If the request is failed, beginning again will
// restart the request, giving it another chance to complete. If the request is already
// running, we can let it continue running without interruption.
if (!Preconditions.checkNotNull(previous).isRunning()) {
// Use the previous request rather than the new one to allow for optimizations like skipping
// setting placeholders, tracking and un-tracking Targets, and obtaining View dimensions
// that are done in the individual Request.
previous.begin();
}
return target;
}
requestManager.clear(target);
target.setRequest(request);
requestManager.track(target, request);
return target;
}
点击buildRequest
private Request buildRequest(
Target<TranscodeType> target,
@Nullable RequestListener<TranscodeType> targetListener,
RequestOptions requestOptions) {
return buildRequestRecursive(
target,
targetListener,
/*parentCoordinator=*/ null,
transitionOptions,
requestOptions.getPriority(),
requestOptions.getOverrideWidth(),
requestOptions.getOverrideHeight(),
requestOptions);
}
private Request buildRequestRecursive(
Target<TranscodeType> target,
@Nullable RequestListener<TranscodeType> targetListener,
@Nullable RequestCoordinator parentCoordinator,
TransitionOptions<?, ? super TranscodeType> transitionOptions,
Priority priority,
int overrideWidth,
int overrideHeight,
RequestOptions requestOptions) {
// Build the ErrorRequestCoordinator first if necessary so we can update parentCoordinator.
ErrorRequestCoordinator errorRequestCoordinator = null;
if (errorBuilder != null) {
errorRequestCoordinator = new ErrorRequestCoordinator(parentCoordinator);
parentCoordinator = errorRequestCoordinator;
}
Request mainRequest =
buildThumbnailRequestRecursive(
target,
targetListener,
parentCoordinator,
transitionOptions,
priority,
overrideWidth,
overrideHeight,
requestOptions);
if (errorRequestCoordinator == null) {
return mainRequest;
}
int errorOverrideWidth = errorBuilder.requestOptions.getOverrideWidth();
int errorOverrideHeight = errorBuilder.requestOptions.getOverrideHeight();
if (Util.isValidDimensions(overrideWidth, overrideHeight)
&& !errorBuilder.requestOptions.isValidOverride()) {
errorOverrideWidth = requestOptions.getOverrideWidth();
errorOverrideHeight = requestOptions.getOverrideHeight();
}
Request errorRequest = errorBuilder.buildRequestRecursive(
target,
targetListener,
errorRequestCoordinator,
errorBuilder.transitionOptions,
errorBuilder.requestOptions.getPriority(),
errorOverrideWidth,
errorOverrideHeight,
errorBuilder.requestOptions);
errorRequestCoordinator.setRequests(mainRequest, errorRequest);
return errorRequestCoordinator;
}
private Request buildThumbnailRequestRecursive(
Target<TranscodeType> target,
RequestListener<TranscodeType> targetListener,
@Nullable RequestCoordinator parentCoordinator,
TransitionOptions<?, ? super TranscodeType> transitionOptions,
Priority priority,
int overrideWidth,
int overrideHeight,
RequestOptions requestOptions) {
if (thumbnailBuilder != null) {
// Recursive case: contains a potentially recursive thumbnail request builder.
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()");
}
TransitionOptions<?, ? super TranscodeType> thumbTransitionOptions =
thumbnailBuilder.transitionOptions;
// Apply our transition by default to thumbnail requests but avoid overriding custom options
// that may have been applied on the thumbnail request explicitly.
if (thumbnailBuilder.isDefaultTransitionOptionsSet) {
thumbTransitionOptions = transitionOptions;
}
Priority thumbPriority = thumbnailBuilder.requestOptions.isPrioritySet()
? thumbnailBuilder.requestOptions.getPriority() : getThumbnailPriority(priority);
int thumbOverrideWidth = thumbnailBuilder.requestOptions.getOverrideWidth();
int thumbOverrideHeight = thumbnailBuilder.requestOptions.getOverrideHeight();
if (Util.isValidDimensions(overrideWidth, overrideHeight)
&& !thumbnailBuilder.requestOptions.isValidOverride()) {
thumbOverrideWidth = requestOptions.getOverrideWidth();
thumbOverrideHeight = requestOptions.getOverrideHeight();
}
ThumbnailRequestCoordinator coordinator = new ThumbnailRequestCoordinator(parentCoordinator);
Request fullRequest =
obtainRequest(
target,
targetListener,
requestOptions,
coordinator,
transitionOptions,
priority,
overrideWidth,
overrideHeight);
isThumbnailBuilt = true;
// Recursively generate thumbnail requests.
Request thumbRequest =
thumbnailBuilder.buildRequestRecursive(
target,
targetListener,
coordinator,
thumbTransitionOptions,
thumbPriority,
thumbOverrideWidth,
thumbOverrideHeight,
thumbnailBuilder.requestOptions);
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,
targetListener,
requestOptions,
coordinator,
transitionOptions,
priority,
overrideWidth,
overrideHeight);
RequestOptions thumbnailOptions = requestOptions.clone()
.sizeMultiplier(thumbSizeMultiplier);
Request thumbnailRequest =
obtainRequest(
target,
targetListener,
thumbnailOptions,
coordinator,
transitionOptions,
getThumbnailPriority(priority),
overrideWidth,
overrideHeight);
coordinator.setRequests(fullRequest, thumbnailRequest);
return coordinator;
} else {
// Base case: no thumbnail.
//调到最后就会执行这个方法
//为什么？
//因为我们没有设置缩略图
return obtainRequest(
target,
targetListener,
requestOptions,
parentCoordinator,
transitionOptions,
priority,
overrideWidth,
overrideHeight);
}
}
//初始化一个request
private Request obtainRequest(
Target<TranscodeType> target,
RequestListener<TranscodeType> targetListener,
RequestOptions requestOptions,
RequestCoordinator requestCoordinator,
TransitionOptions<?, ? super TranscodeType> transitionOptions,
Priority priority,
int overrideWidth,
int overrideHeight) {
return SingleRequest.obtain(
context,
glideContext,
model,
transcodeClass,
requestOptions,
overrideWidth,
overrideHeight,
priority,
target,
targetListener,
requestListener,
requestCoordinator,
glideContext.getEngine(),
transitionOptions.getTransitionFactory());
}
这里就可以看到返回的是SingleRequest然后我们看这个类
public final class SingleRequest<R> implements Request,
SizeReadyCallback,
ResourceCallback,
FactoryPools.Poolable {
public static <R> SingleRequest<R> obtain(
Context context,
GlideContext glideContext,
Object model,
Class<R> transcodeClass,
RequestOptions requestOptions,
int overrideWidth,
int overrideHeight,
Priority priority,
Target<R> target,
RequestListener<R> targetListener,
RequestListener<R> requestListener,
RequestCoordinator requestCoordinator,
Engine engine,
TransitionFactory<? super R> animationFactory) {
@SuppressWarnings("unchecked") SingleRequest<R> request =
(SingleRequest<R>) POOL.acquire();
if (request == null) {
request = new SingleRequest<>();
}
request.init(
context,
glideContext,
model,
transcodeClass,
requestOptions,
overrideWidth,
overrideHeight,
priority,
target,
targetListener,
requestListener,
requestCoordinator,
engine,
animationFactory);
return request;
}
private void init(
Context context,
GlideContext glideContext,
Object model,
Class<R> transcodeClass,
RequestOptions requestOptions,
int overrideWidth,
int overrideHeight,
Priority priority,
Target<R> target,
RequestListener<R> targetListener,
RequestListener<R> requestListener,
RequestCoordinator requestCoordinator,
Engine engine,
TransitionFactory<? super R> animationFactory) {
this.context = context;
this.glideContext = glideContext;
this.model = model;
this.transcodeClass = transcodeClass;
this.requestOptions = requestOptions;
this.overrideWidth = overrideWidth;
this.overrideHeight = overrideHeight;
this.priority = priority;
this.target = target;
this.targetListener = targetListener;
this.requestListener = requestListener;
this.requestCoordinator = requestCoordinator;
this.engine = engine;
this.animationFactory = animationFactory;
status = Status.PENDING;
}
}
//这里就是请求开始的地方
@Override
public void begin() {
assertNotCallingCallbacks();
stateVerifier.throwIfRecycled();
startTime = LogTime.getLogTime();
if (model == null) {
if (Util.isValidDimensions(overrideWidth, overrideHeight)) {
width = overrideWidth;
height = overrideHeight;
}
// Only log at more verbose log levels if the user has set a fallback drawable, because
// fallback Drawables indicate the user expects null models occasionally.
int logLevel = getFallbackDrawable() == null ? Log.WARN : Log.DEBUG;
onl oadFailed(new GlideException("Received null model"), logLevel);
return;
}
if (status == Status.RUNNING) {
throw new IllegalArgumentException("Cannot restart a running request");
}
// If we're restarted after we're complete (usually via something like a notifyDataSetChanged
// that starts an identical request into the same Target or View), we can simply use the
// resource and size we retrieved the last time around and skip obtaining a new size, starting a
// new load etc. This does mean that users who want to restart a load because they expect that
// the view size has changed will need to explicitly clear the View or Target before starting
// the new load.
if (status == Status.COMPLETE) {
onResourceReady(resource, DataSource.MEMORY_CACHE);
return;
}
// Restarts for requests that are neither complete nor running can be treated as new requests
// and can run again from the beginning.
status = Status.WAITING_FOR_SIZE;
if (Util.isValidDimensions(overrideWidth, overrideHeight)) {
//加载图片
onSizeReady(overrideWidth, overrideHeight);
} else {
target.getSize(this);
}
if ((status == Status.RUNNING || status == Status.WAITING_FOR_SIZE)
&& canNotifyStatusChanged()) {
//为view提前设置一些状态，比如placeholder信息等等，然后等待Engine后续的加载完成。
target.onLoadStarted(getPlaceholderDrawable());
}
if (IS_VERBOSE_LOGGABLE) {
logV("finished run method in " + LogTime.getElapsedMillis(startTime));
}
}
可以看到上面最后返回了SingleRequest,而我们之前分析过，当我们添加一个新请求时，会执行该请求的begin方法，所以begin时请求开始执行的地方。
点击onSizeReady(overrideWidth, overrideHeight);
@Override
public void onSizeReady(int width, int height) {
stateVerifier.throwIfRecycled();
if (IS_VERBOSE_LOGGABLE) {
logV("Got onSizeReady in " + LogTime.getElapsedMillis(startTime));
}
if (status != Status.WAITING_FOR_SIZE) {
return;
}
status = Status.RUNNING;
float sizeMultiplier = requestOptions.getSizeMultiplier();
this.width = maybeApplySizeMultiplier(width, sizeMultiplier);
this.height = maybeApplySizeMultiplier(height, sizeMultiplier);
if (IS_VERBOSE_LOGGABLE) {
logV("finished setup for calling load in " + LogTime.getElapsedMillis(startTime));
}
loadStatus = engine.load(
glideContext,
model,
requestOptions.getSignature(),
this.width,
this.height,
requestOptions.getResourceClass(),
transcodeClass,
priority,
requestOptions.getDiskCacheStrategy(),
requestOptions.getTransformations(),
requestOptions.isTransformationRequired(),
requestOptions.isScaleOnlyOrNoTransform(),
requestOptions.getOptions(),
requestOptions.isMemoryCacheable(),
requestOptions.getUseUnlimitedSourceGeneratorsPool(),
requestOptions.getUseAnimationPool(),
requestOptions.getOnlyRetrieveFromCache(),
this);
// This is a hack that's only useful for testing right now where loads complete synchronously
// even though under any executor running on any thread but the main thread, the load would
// have completed asynchronously.
if (status != Status.RUNNING) {
loadStatus = null;
}
if (IS_VERBOSE_LOGGABLE) {
logV("finished onSizeReady in " + LogTime.getElapsedMillis(startTime));
}
}
好，我们这里肯定点击engine.load()方法
public <R> LoadStatus load(
GlideContext glideContext,
Object model,
Key signature,
int width,
int height,
Class<?> resourceClass,
Class<R> transcodeClass,
Priority priority,
DiskCacheStrategy diskCacheStrategy,
Map<Class<?>, Transformation<?>> transformations,
boolean isTransformationRequired,
boolean isScaleOnlyOrNoTransform,
Options options,
boolean isMemoryCacheable,
boolean useUnlimitedSourceExecutorPool,
boolean useAnimationPool,
boolean onlyRetrieveFromCache,
ResourceCallback cb) {
Util.assertMainThread();
long startTime = LogTime.getLogTime();
EngineKey key = keyFactory.buildKey(model, signature, width, height, transformations,
resourceClass, transcodeClass, options);
//活动缓存
EngineResource<?> active = loadFromActiveResources(key, isMemoryCacheable);
if (active != null) {
cb.onResourceReady(active, DataSource.MEMORY_CACHE);
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logWithTimeAndKey("Loaded resource from active resources", startTime, key);
}
return null;
}
//内存缓存
EngineResource<?> cached = loadFromCache(key, isMemoryCacheable);
if (cached != null) {
cb.onResourceReady(cached, DataSource.MEMORY_CACHE);
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logWithTimeAndKey("Loaded resource from cache", startTime, key);
}
return null;
}
EngineJob<?> current = jobs.get(key, onlyRetrieveFromCache);
if (current != null) {
current.addCallback(cb);
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logWithTimeAndKey("Added to existing load", startTime, key);
}
return new LoadStatus(cb, current);
}
EngineJob<R> engineJob =
engineJobFactory.build(
key,
isMemoryCacheable,
useUnlimitedSourceExecutorPool,
useAnimationPool,
onlyRetrieveFromCache);
//开始网络请求
DecodeJob<R> decodeJob =
decodeJobFactory.build(
glideContext,
model,
key,
signature,
width,
height,
resourceClass,
transcodeClass,
priority,
diskCacheStrategy,
transformations,
isTransformationRequired,
isScaleOnlyOrNoTransform,
onlyRetrieveFromCache,
options,
engineJob);
jobs.put(key, engineJob);
engineJob.addCallback(cb);
engineJob.start(decodeJob);
if (Log.isLoggable(TAG, Log.VERBOSE)) {
logWithTimeAndKey("Started new load", startTime, key);
}
return new LoadStatus(cb, engineJob);
}
点击DecodeJob<R> decodeJob = decodeJobFactory.build()
class DecodeJob<R> implements DataFetcherGenerator.FetcherReadyCallback,
Runnable,
Comparable<DecodeJob<?>>,
Poolable {
@Override
public void run() {
// This should be much more fine grained, but since Java's thread pool implementation silently
// swallows all otherwise fatal exceptions, this will at least make it obvious to developers
// that something is failing.
TraceCompat.beginSection("DecodeJob#run");
// Methods in the try statement can invalidate currentFetcher, so set a local variable here to
// ensure that the fetcher is cleaned up either way.
DataFetcher<?> localFetcher = currentFetcher;
try {
if (isCancelled) {
notifyFailed();
return;
}
runWrapped();
} catch (Throwable t) {
// Catch Throwable and not Exception to handle OOMs. Throwables are swallowed by our
// usage of .submit() in GlideExecutor so we're not silently hiding crashes by doing this. We
// are however ensuring that our callbacks are always notified when a load fails. Without this
// notification, uncaught throwables never notify the corresponding callbacks, which can cause
// loads to silently hang forever, a case that's especially bad for users using Futures on
// background threads.
if (Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(TAG, "DecodeJob threw unexpectedly"
+ ", isCancelled: " + isCancelled
+ ", stage: " + stage, t);
}
// When we're encoding we've already notified our callback and it isn't safe to do so again.
if (stage != Stage.ENCODE) {
throwables.add(t);
notifyFailed();
}
if (!isCancelled) {
throw t;
}
} finally {
// Keeping track of the fetcher here and calling cleanup is excessively paranoid, we call
// close in all cases anyway.
if (localFetcher != null) {
localFetcher.cleanup();
}
TraceCompat.endSection();
}
}
private void runWrapped() {
switch (runReason) {
case INITIALIZE:
stage = getNextStage(Stage.INITIALIZE);
currentGenerator = getNextGenerator();
runGenerators();
break;
case SWITCH_TO_SOURCE_SERVICE:
runGenerators();
break;
case DECODE_DATA:
decodeFromRetrievedData();
break;
default:
throw new IllegalStateException("Unrecognized run reason: " + runReason);
}
}
private DataFetcherGenerator getNextGenerator() {
switch (stage) {
case RESOURCE_CACHE:
return new ResourceCacheGenerator(decodeHelper, this);
case DATA_CACHE:
//磁盘缓存
return new DataCacheGenerator(decodeHelper, this);
case SOURCE:
//从网络中加载到后直接进行磁盘缓存。
return new SourceGenerator(decodeHelper, this);
case FINISHED:
return null;
default:
throw new IllegalStateException("Unrecognized stage: " + stage);
}
}
private void runGenerators() {
currentThread = Thread.currentThread();
startFetchTime = LogTime.getLogTime();
boolean isStarted = false;
//currentGenerator.startNext()出发了每个加载器的startNext方法，
//加载器中的startNext()一定是我们读取图片的逻辑
while (!isCancelled && currentGenerator != null
&& !(isStarted = currentGenerator.startNext())) {
stage = getNextStage(stage);
currentGenerator = getNextGenerator();
if (stage == Stage.SOURCE) {
reschedule();
return;
}
}
// We've run out of stages and generators, give up.
if ((stage == Stage.FINISHED || isCancelled) && !isStarted) {
notifyFailed();
}
// Otherwise a generator started a new load and we expect to be called back in
// onDataFetcherReady.
}
}
可以看到这个类实现了Runnable说明在run方法里一定有东西。runWrapped()这个方法在这个run方法里尤其显眼。
在getNextGenerator()方法中我们看到有几个类，可以理解为三种不同的加载器把,加载过程是ResourceCacheGenerator -> DataCacheGenerator -> SourceGenerator顺序，不管哪种方式取到了数据，最终都会回调至DecodeJob中处理(SourceGenerator会更新磁盘缓存).
这里这三个加载器，就不细看了。
将到这儿，终于结束了，收工！
总结：
所有的请求都会添加到一个叫RequestTracker的队列里，里面有一个运行队列，一个是等待队列。如果当前页面停止，无UI的Fragment的onStop()会调用，ReqestManager就会把请求停止，并且都会添加到等待队列中，当又开始运行，所有的等待队列的请求又会放到运行队列中。
当RequestManager调用requestTracker.runRequest的时候，
所有的请求都会构建成一个SingleRequest，并且开始调用begin方法运行；
begin方法最终会调用engine.load方法
根据request构建EngineKey
根据EngineKey去活动缓存中获取数据
如果获取不到，去内存缓存中获取数据
如果获取不到，通过硬盘缓存的线程池去获取本地硬盘的数据
如果获取不到本地的，通过网络的线程池去获取网络的数据
Glide跟其他框架相比优势在哪里？
1：生命周期得管理
2：支持gif picasso支持gif
3：三级缓存，内存缓存中还分为活动缓存和内存缓存；活动缓存指得是讲正在使用得图片用弱引用缓存，使用完成后到内存缓存；再到磁盘缓存；
4：占用内存小，它默认得编码格式是rgb565； picasso用得argb8888 ImageLoader不支持gif图片加载 而且也很老了
个人总结，欢迎留言讨论！