Glide源码解析
2020-08-18 本文已影响0人
A邱凌
问题
- glide是如何进行缓存的?
- glide是如何多线程加载图片?
- glide如何进行内存管理?
- 为何要选择glide?
- 如何防止内存泄漏?
- OOM机制?
glide流程分析
先来一张glide整体流程图
整体流程.png
glide时序图.png
glide请求过程中thumbRequest作用
缩略图请求
glide是如何进行缓存的?
-
加载图片
glide在加载图片时 会先从弱引用列表查找 再从LRU缓存中查找 再从网络加载
弱引用列表是以空间换时间的一种方式 更加的高效 -
缓存图片
- 内部缓存存储的入口，等同于调用Engine.onEngineJobComplete()
EngineJob.notifyCallbacksOfResult()
-> engineJobListener.onEngineJobComplete(this, localKey, localResource); - 如果开启内存缓存的话，将解析后的图片添加到弱引用缓存,添加前先封装成 ResourceWeakReference对象，如果key有重复的则将之前的弱引用列表的中对应的数据制空。
Engine.onEngineJobComplete()
-> activeResources.activate(key, resource); - 磁盘缓存的入口
DecodeJob.notifyEncodeAndRelease()
->deferredEncodeManager.encode(diskCacheProvider, options);
- 内部缓存存储的入口，等同于调用Engine.onEngineJobComplete()
查找缓存.png
加入缓存.png
glide如何进行内存管理?
- 弱引用+LRU算法
- 监听TrimMemory和LowMemory
如何防止内存泄漏?
初始化glide的时候 根据传入的context生成一个一个无UI的fragment 将fragment的lifecycle传入requestManager中
OOM机制?
- 引入largeHeap属性，让系统为App分配更多的独立内存。
- 禁止Glide内存缓存。设置skipMemoryCache(true)。
- 自定义GlideModule。设置MemoryCache和BitmapPool大小。
- 升级到Glide4.0，使用asDrawable代替asBitmap，drawable更省内存。
- ImageView的scaleType为fitXY时，改为fitCenter/centerCrop/fitStart/fitEnd显示。
- 不使用application作为context。当context为application时，会把imageView是生命周期延长到整个运行过程中，imageView不能被回收，从而造成OOM异常。
- 使用application作为context。但是对ImageView使用弱引用或软引用，尽量使用SoftReference，当内存不足时，将及时回收无用的ImageView。
- 当列表在滑动的时候，调用Glide的pauseRequests()取消请求，滑动停止时，调用resumeRequests()恢复请求。
- Try catch某些大内存分配的操作。考虑在catch里面尝试一次降级的内存分配操作。例如decode bitmap的时候，catch到OOM，可以尝试把采样比例再增加一倍之后，再次尝试decode。
- BitmapFactory.Options和BitmapFactory.decodeStream获取原始图片的宽、高，绕过Java层加载Bitmap，再调用Glide的override(width,height)控制显示。
- 图片局部加载。参考：SubsamplingScaleImageView，先将图片下载到本地，然后去加载，只加载当前可视区域，在手指拖动的时候再去加载另外的区域。
为何要选择glide?
- 链式调用。
- 默认使用RGB_565格式（1像素占2byte），Picasso使用RGB_8888格式（1像素4byte）。
- 入侵性低，使用标准的ImageView，无需使用自定义的View。
- 支持的格式多（png，jpg，gif，webp，video等...）。
- 缓存处理好（正在使用的通过弱引用缓存，已使用过的通过Lru缓存，并且可缓存不同格式）。
- 可感知页面生命周期，动态控制图片加载。防止出现内存泄露。
- 性能好，能防止频繁主线程I/O导致的页面闪烁卡顿。
glide 源码解析
with()方法
看一下代码
@NonNull
public static RequestManager with(@NonNull Context context) {
/*
* 上面的注释的意思就是说 如果你的资源用在这个fragment上 就用这个fragment的context 别瞎用别的
* 总结 初始化glide 创建透明fragment 将生命周期绑定到RequestManager上
* */
return getRetriever(context).get(context);
}
@NonNull
private static RequestManagerRetriever getRetriever(@Nullable Context context) {
// Context could be null for other reasons (ie the user passes in null), but in practice it will
// only occur due to errors with the Fragment lifecycle.
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 Glide.get(context).getRequestManagerRetriever();
}
/**
* Get the singleton.
*
* @return the singleton
*/
@NonNull
public static Glide get(@NonNull Context context) {
if (glide == null) {
GeneratedAppGlideModule annotationGeneratedModule =
getAnnotationGeneratedGlideModules(context.getApplicationContext());
synchronized (Glide.class) {
if (glide == null) {
checkAndInitializeGlide(context, annotationGeneratedModule);
}
}
}
return glide;
}
//初始化glide
@GuardedBy("Glide.class")
@SuppressWarnings("deprecation")
private static void initializeGlide(
@NonNull Context context,
@NonNull GlideBuilder builder,
@Nullable GeneratedAppGlideModule annotationGeneratedModule) {
.......
//初始化glide
Glide glide = builder.build(applicationContext);
Glide.glide = glide;
.......
}
@NonNull
public RequestManager get(@NonNull Context context) {
if (context == null) {
throw new IllegalArgumentException("You cannot start a load on a null Context");
} else if (Util.isOnMainThread() && !(context instanceof Application)) {
if (context instanceof FragmentActivity) {
return get((FragmentActivity) context);
} else if (context instanceof Activity) {
return get((Activity) context);
} else if (context instanceof ContextWrapper
// Only unwrap a ContextWrapper if the baseContext has a non-null application context.
// Context#createPackageContext may return a Context without an Application instance,
// in which case a ContextWrapper may be used to attach one.
&& ((ContextWrapper) context).getBaseContext().getApplicationContext() != null) {
return get(((ContextWrapper) context).getBaseContext());
}
}
return getApplicationManager(context);
}
//创建一个透明的fragment 并绑定到requestmanager上 避免内存泄漏
@NonNull
public RequestManager get(@NonNull FragmentActivity activity) {
if (Util.isOnBackgroundThread()) {
return get(activity.getApplicationContext());
} else {
assertNotDestroyed(activity);
FragmentManager fm = activity.getSupportFragmentManager();
return supportFragmentGet(activity, fm, /*parentHint=*/ null, isActivityVisible(activity));
}
}
@NonNull
private RequestManager supportFragmentGet(
@NonNull Context context,
@NonNull FragmentManager fm,
@Nullable Fragment parentHint,
boolean isParentVisible) {
SupportRequestManagerFragment current =
getSupportRequestManagerFragment(fm, parentHint, isParentVisible);
RequestManager requestManager = current.getRequestManager();
if (requestManager == null) {
// TODO(b/27524013): factor out this glide.get() call.
Glide glide = Glide.get(context);
//新建一个透明的fragment 绑定fragment的lifecycle到requestManager上
requestManager =
factory.build(
glide, current.getGlideLifecycle(), current.getRequestManagerTreeNode(), context);
current.setRequestManager(requestManager);
}
return requestManager;
}
load()方法
/**
* Equivalent to calling {@link #asDrawable()} and then {@link RequestBuilder#load(Bitmap)}.
*
* @return A new request builder for loading a {@link Drawable} using the given model.
*/
@NonNull
@CheckResult
@Override
public RequestBuilder<Drawable> load(@Nullable Bitmap bitmap) {
/*
* asDrawable() 构建RequestBuilder对象
* load() 覆盖一下配置
* */
return asDrawable().load(bitmap);
}
into() 重点就在into方法上
@NonNull
public ViewTarget<ImageView, TranscodeType> into(@NonNull ImageView view) {
/*
* 注释的意思 就是取消正在加载的请求 释放已经加载到ImageView的资源 加载需要的资源到ImageView中
* */
Util.assertMainThread();
Preconditions.checkNotNull(view);
//设置scaletype
BaseRequestOptions<?> requestOptions = this;
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,
Executors.mainThreadExecutor());
}
然后我们跟着看into()方法 into方法主要是做一些检查 下面三个方法也很重要 我们一会会回来看这个方法 先留着
private <Y extends Target<TranscodeType>> Y into(
@NonNull Y target,
@Nullable RequestListener<TranscodeType> targetListener,
BaseRequestOptions<?> options,
Executor callbackExecutor) {
Preconditions.checkNotNull(target);
if (!isModelSet) {
throw new IllegalArgumentException("You must call #load() before calling #into()");
}
//构建request
Request request = buildRequest(target, targetListener, options, callbackExecutor);
//如果request和前面一样 或者正在运行 就继续
Request previous = target.getRequest();
if (request.isEquivalentTo(previous)
&& !isSkipMemoryCacheWithCompletePreviousRequest(options, previous)) {
// 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;
}
//下面三个方法很重要 我们一会再回来看
requestManager.clear(target);
target.setRequest(request);
requestManager.track(target, request);
return target;
}
我们看一下buildRequest方法 长长的一大段啊 不过我们看下去发现最后构造了SingleRequest对象
private Request buildRequest(
Target<TranscodeType> target,
@Nullable RequestListener<TranscodeType> targetListener,
BaseRequestOptions<?> requestOptions,
Executor callbackExecutor) {
return buildRequestRecursive(
/*requestLock=*/ new Object(),
target,
targetListener,
/*parentCoordinator=*/ null,
transitionOptions,
requestOptions.getPriority(),
requestOptions.getOverrideWidth(),
requestOptions.getOverrideHeight(),
requestOptions,
callbackExecutor);
}
private Request buildRequestRecursive(
Object requestLock,
Target<TranscodeType> target,
@Nullable RequestListener<TranscodeType> targetListener,
@Nullable RequestCoordinator parentCoordinator,
TransitionOptions<?, ? super TranscodeType> transitionOptions,
Priority priority,
int overrideWidth,
int overrideHeight,
BaseRequestOptions<?> requestOptions,
Executor callbackExecutor) {
// Build the ErrorRequestCoordinator first if necessary so we can update parentCoordinator.
//先新建错误请求协调
ErrorRequestCoordinator errorRequestCoordinator = null;
if (errorBuilder != null) {
errorRequestCoordinator = new ErrorRequestCoordinator(requestLock, parentCoordinator);
parentCoordinator = errorRequestCoordinator;
}
//创建Request
Request mainRequest =
buildThumbnailRequestRecursive(
requestLock,
target,
targetListener,
parentCoordinator,
transitionOptions,
priority,
overrideWidth,
overrideHeight,
requestOptions,
callbackExecutor);
if (errorRequestCoordinator == null) {
return mainRequest;
}
int errorOverrideWidth = errorBuilder.getOverrideWidth();
int errorOverrideHeight = errorBuilder.getOverrideHeight();
if (Util.isValidDimensions(overrideWidth, overrideHeight) && !errorBuilder.isValidOverride()) {
errorOverrideWidth = requestOptions.getOverrideWidth();
errorOverrideHeight = requestOptions.getOverrideHeight();
}
Request errorRequest =
errorBuilder.buildRequestRecursive(
requestLock,
target,
targetListener,
errorRequestCoordinator,
errorBuilder.transitionOptions,
errorBuilder.getPriority(),
errorOverrideWidth,
errorOverrideHeight,
errorBuilder,
callbackExecutor);
errorRequestCoordinator.setRequests(mainRequest, errorRequest);
return errorRequestCoordinator;
}
private Request buildThumbnailRequestRecursive(
Object requestLock,
Target<TranscodeType> target,
RequestListener<TranscodeType> targetListener,
@Nullable RequestCoordinator parentCoordinator,
TransitionOptions<?, ? super TranscodeType> transitionOptions,
Priority priority,
int overrideWidth,
int overrideHeight,
BaseRequestOptions<?> requestOptions,
Executor callbackExecutor) {
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.isPrioritySet()
? thumbnailBuilder.getPriority()
: getThumbnailPriority(priority);
int thumbOverrideWidth = thumbnailBuilder.getOverrideWidth();
int thumbOverrideHeight = thumbnailBuilder.getOverrideHeight();
if (Util.isValidDimensions(overrideWidth, overrideHeight)
&& !thumbnailBuilder.isValidOverride()) {
thumbOverrideWidth = requestOptions.getOverrideWidth();
thumbOverrideHeight = requestOptions.getOverrideHeight();
}
ThumbnailRequestCoordinator coordinator =
new ThumbnailRequestCoordinator(requestLock, parentCoordinator);
Request fullRequest =
obtainRequest(
requestLock,
target,
targetListener,
requestOptions,
coordinator,
transitionOptions,
priority,
overrideWidth,
overrideHeight,
callbackExecutor);
isThumbnailBuilt = true;
// Recursively generate thumbnail requests.
Request thumbRequest =
thumbnailBuilder.buildRequestRecursive(
requestLock,
target,
targetListener,
coordinator,
thumbTransitionOptions,
thumbPriority,
thumbOverrideWidth,
thumbOverrideHeight,
thumbnailBuilder,
callbackExecutor);
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(requestLock, parentCoordinator);
Request fullRequest =
obtainRequest(
requestLock,
target,
targetListener,
requestOptions,
coordinator,
transitionOptions,
priority,
overrideWidth,
overrideHeight,
callbackExecutor);
BaseRequestOptions<?> thumbnailOptions =
requestOptions.clone().sizeMultiplier(thumbSizeMultiplier);
Request thumbnailRequest =
obtainRequest(
requestLock,
target,
targetListener,
thumbnailOptions,
coordinator,
transitionOptions,
getThumbnailPriority(priority),
overrideWidth,
overrideHeight,
callbackExecutor);
coordinator.setRequests(fullRequest, thumbnailRequest);
return coordinator;
} else {
// Base case: no thumbnail.
return obtainRequest(
requestLock,
target,
targetListener,
requestOptions,
parentCoordinator,
transitionOptions,
priority,
overrideWidth,
overrideHeight,
callbackExecutor);
}
}
private Request obtainRequest(
Object requestLock,
Target<TranscodeType> target,
RequestListener<TranscodeType> targetListener,
BaseRequestOptions<?> requestOptions,
RequestCoordinator requestCoordinator,
TransitionOptions<?, ? super TranscodeType> transitionOptions,
Priority priority,
int overrideWidth,
int overrideHeight,
Executor callbackExecutor) {
return SingleRequest.obtain(
context,
glideContext,
requestLock,
model,
transcodeClass,
requestOptions,
overrideWidth,
overrideHeight,
priority,
target,
targetListener,
requestListeners,
requestCoordinator,
glideContext.getEngine(),
transitionOptions.getTransitionFactory(),
callbackExecutor);
}
我们已经构造了request对象 接着看上面的三行方法 这边省的往上翻 直接又拷贝了一份过来
//下面三个方法很重要 我们一会再回来看
requestManager.clear(target);
target.setRequest(request);
requestManager.track(target, request);
我们看track方法
synchronized void track(@NonNull Target<?> target, @NonNull Request request) {
targetTracker.track(target);
requestTracker.runRequest(request);
}
/** Starts tracking the given request. */
public void runRequest(@NonNull Request request) {
requests.add(request);
if (!isPaused) {
request.begin();
} else {
request.clear();
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "Paused, delaying request");
}
pendingRequests.add(request);
}
}
我们刚上面分析了 request对象其实是SingleRequest
@Override
public void begin() {
synchronized (requestLock) {
assertNotCallingCallbacks();
//确定对象没有被回收
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;
onLoadFailed(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.
//初始化状态
status = Status.WAITING_FOR_SIZE;
//如果已经设置好width
if (Util.isValidDimensions(overrideWidth, overrideHeight)) {
onSizeReady(overrideWidth, overrideHeight);
} else {
//异步 还是会调用onSizeReady
target.getSize(this);
}
if ((status == Status.RUNNING || status == Status.WAITING_FOR_SIZE)
&& canNotifyStatusChanged()) {
target.onLoadStarted(getPlaceholderDrawable());
}
if (IS_VERBOSE_LOGGABLE) {
logV("finished run method in " + LogTime.getElapsedMillis(startTime));
}
}
}
核心方法就在onSizeReady()中了
/** A callback method that should never be invoked directly. */
@Override
public void onSizeReady(int width, int height) {
........
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,
callbackExecutor);
.......
}
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,
Executor callbackExecutor) {
long startTime = VERBOSE_IS_LOGGABLE ? LogTime.getLogTime() : 0;
//构建key 我们可以确定 存储在内存中的key 和width height 原图有关
EngineKey key =
keyFactory.buildKey(
model,
signature,
width,
height,
transformations,
resourceClass,
transcodeClass,
options);
EngineResource<?> memoryResource;
synchronized (this) {
//1.先从内存中获取
memoryResource = loadFromMemory(key, isMemoryCacheable, startTime);
if (memoryResource == null) {
return waitForExistingOrStartNewJob(
glideContext,
model,
signature,
width,
height,
resourceClass,
transcodeClass,
priority,
diskCacheStrategy,
transformations,
isTransformationRequired,
isScaleOnlyOrNoTransform,
options,
isMemoryCacheable,
useUnlimitedSourceExecutorPool,
useAnimationPool,
onlyRetrieveFromCache,
cb,
callbackExecutor,
key,
startTime);
}
}
// Avoid calling back while holding the engine lock, doing so makes it easier for callers to
// deadlock.
cb.onResourceReady(memoryResource, DataSource.MEMORY_CACHE);
return null;
}
从缓存中尝试获取
@Nullable
private EngineResource<?> loadFromMemory(
EngineKey key, boolean isMemoryCacheable, long startTime) {
//1.1是否调过缓存 对应skipMemoryCacheOf
if (!isMemoryCacheable) {
return null;
}
//1.2
EngineResource<?> active = loadFromActiveResources(key);
if (active != null) {
if (VERBOSE_IS_LOGGABLE) {
logWithTimeAndKey("Loaded resource from active resources", startTime, key);
}
return active;
}
//1.3
EngineResource<?> cached = loadFromCache(key);
if (cached != null) {
if (VERBOSE_IS_LOGGABLE) {
logWithTimeAndKey("Loaded resource from cache", startTime, key);
}
return cached;
}
return null;
}
private static void logWithTimeAndKey(String log, long startTime, Key key) {
Log.v(TAG, log + " in " + LogTime.getElapsedMillis(startTime) + "ms, key: " + key);
}
@Nullable
private EngineResource<?> loadFromActiveResources(Key key) {
//1.2.1 从弱引用缓存列表中取 如果能获取到 则从弱引用列表中获取 并删除key
EngineResource<?> active = activeResources.get(key);
if (active != null) {
active.acquire();
}
return active;
}
private EngineResource<?> loadFromCache(Key key) {
//1.3.1
EngineResource<?> cached = getEngineResourceFromCache(key);
if (cached != null) {
cached.acquire();
activeResources.activate(key, cached);
}
return cached;
}
private EngineResource<?> getEngineResourceFromCache(Key key) {
//1.3.2 获取cache
Resource<?> cached = cache.remove(key);
final EngineResource<?> result;
if (cached == null) {
result = null;
} else if (cached instanceof EngineResource) {
// Save an object allocation if we've cached an EngineResource (the typical case).
result = (EngineResource<?>) cached;
} else {
result =
new EngineResource<>(
cached, /*isMemoryCacheable=*/ true, /*isRecyclable=*/ true, key, /*listener=*/ this);
}
return result;
}
没获取到的话就调用waitForExistingOrStartNewJob()方法
private <R> LoadStatus waitForExistingOrStartNewJob(
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,
Executor callbackExecutor,
EngineKey key,
long startTime) {
EngineJob<?> current = jobs.get(key, onlyRetrieveFromCache);
if (current != null) {
current.addCallback(cb, callbackExecutor);
if (VERBOSE_IS_LOGGABLE) {
logWithTimeAndKey("Added to existing load", startTime, key);
}
return new LoadStatus(cb, current);
}
EngineJob<R> engineJob =
engineJobFactory.build(
key,
isMemoryCacheable,
useUnlimitedSourceExecutorPool,
useAnimationPool,
onlyRetrieveFromCache);
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, callbackExecutor);
//decodeJob 是个runnable 调用start方法其实就是调用decodeJob的run方法
engineJob.start(decodeJob);
if (VERBOSE_IS_LOGGABLE) {
logWithTimeAndKey("Started new load", startTime, key);
}
return new LoadStatus(cb, engineJob);
}
查看DecodeJob的run方法
// We need to rethrow only CallbackException, but not other types of Throwables.
@SuppressWarnings("PMD.AvoidRethrowingException")
@Override
public void run() {
.......
//核心方法
runWrapped();
} catch (CallbackException e) {
// If a callback not controlled by Glide throws an exception, we should avoid the Glide
// specific debug logic below.
throw e;
} 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;
}
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();
}
GlideTrace.endSection();
}
}
查看runwrapped方法
private void runWrapped() {
switch (runReason) {
case INITIALIZE:
// 1.1
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() {
// 1.2
switch (stage) {
case RESOURCE_CACHE:
return new ResourceCacheGenerator(decodeHelper, this);
case DATA_CACHE:
return new DataCacheGenerator(decodeHelper, this);
case SOURCE:
return new SourceGenerator(decodeHelper, this);
case FINISHED:
return null;
default:
throw new IllegalStateException("Unrecognized stage: " + stage);
}
}
private void runGenerators() {
// 1.3
currentThread = Thread.currentThread();
startFetchTime = LogTime.getLogTime();
boolean isStarted = false;
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.
}
这里会调用currentGenerator.startNext()方法
先后调用ResourceCacheGenerator, DataCacheGenerator
最终会调用SourceGenerator.startNext()方法
@Override
public boolean startNext() {
//缓存数据
if (dataToCache != null) {
Object data = dataToCache;
dataToCache = null;
cacheData(data);
}
if (sourceCacheGenerator != null && sourceCacheGenerator.startNext()) {
return true;
}
sourceCacheGenerator = null;
loadData = null;
boolean started = false;
while (!started && hasNextModelLoader()) {
//获取LoadData
loadData = helper.getLoadData().get(loadDataListIndex++);
if (loadData != null
&& (helper.getDiskCacheStrategy().isDataCacheable(loadData.fetcher.getDataSource())
|| helper.hasLoadPath(loadData.fetcher.getDataClass()))) {
started = true;
//开始加载
startNextLoad(loadData);
}
}
return started;
}
private void startNextLoad(final LoadData<?> toStart) {
//这里的fetcher 其实是HttpUrlFetch
loadData.fetcher.loadData(
helper.getPriority(),
new DataCallback<Object>() {
@Override
public void onDataReady(@Nullable Object data) {
if (isCurrentRequest(toStart)) {
//数据回调
onDataReadyInternal(toStart, data);
}
}
@Override
public void onLoadFailed(@NonNull Exception e) {
if (isCurrentRequest(toStart)) {
onLoadFailedInternal(toStart, e);
}
}
});
}
接下来就是通过HTTP请求获取数据
@Override
public void loadData(
@NonNull Priority priority, @NonNull DataCallback<? super InputStream> callback) {
long startTime = LogTime.getLogTime();
try {
//通过http获取数据
InputStream result = loadDataWithRedirects(glideUrl.toURL(), 0, null, glideUrl.getHeaders());
callback.onDataReady(result);
} catch (IOException e) {
if (Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(TAG, "Failed to load data for url", e);
}
callback.onLoadFailed(e);
} finally {
if (Log.isLoggable(TAG, Log.VERBOSE)) {
Log.v(TAG, "Finished http url fetcher fetch in " + LogTime.getElapsedMillis(startTime));
}
}
}
private InputStream loadDataWithRedirects(
URL url, int redirects, URL lastUrl, Map<String, String> headers) throws IOException {
if (redirects >= MAXIMUM_REDIRECTS) {
throw new HttpException("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 HttpException("In re-direct loop");
}
} catch (URISyntaxException e) {
// Do nothing, this is best effort.
}
}
//获取HttpurlConnection
urlConnection = connectionFactory.build(url);
for (Map.Entry<String, String> headerEntry : headers.entrySet()) {
urlConnection.addRequestProperty(headerEntry.getKey(), headerEntry.getValue());
}
urlConnection.setConnectTimeout(timeout);
urlConnection.setReadTimeout(timeout);
urlConnection.setUseCaches(false);
urlConnection.setDoInput(true);
// Stop the urlConnection instance of HttpUrlConnection from following redirects so that
// redirects will be handled by recursive calls to this method, loadDataWithRedirects.
urlConnection.setInstanceFollowRedirects(false);
// Connect explicitly to avoid errors in decoders if connection fails.
urlConnection.connect();
// Set the stream so that it's closed in cleanup to avoid resource leaks. See #2352.
stream = urlConnection.getInputStream();
if (isCancelled) {
return null;
}
final int statusCode = urlConnection.getResponseCode();
//判断响应码
if (isHttpOk(statusCode)) {
//把响应流返回
return getStreamForSuccessfulRequest(urlConnection);
} else if (isHttpRedirect(statusCode)) {
String redirectUrlString = urlConnection.getHeaderField("Location");
if (TextUtils.isEmpty(redirectUrlString)) {
throw new HttpException("Received empty or null redirect url");
}
URL redirectUrl = new URL(url, redirectUrlString);
// Closing the stream specifically is required to avoid leaking ResponseBodys in addition
// to disconnecting the url connection below. See #2352.
cleanup();
return loadDataWithRedirects(redirectUrl, redirects + 1, url, headers);
} else if (statusCode == INVALID_STATUS_CODE) {
throw new HttpException(statusCode);
} else {
throw new HttpException(urlConnection.getResponseMessage(), statusCode);
}
}
接下来数据其实已经获取到了 我们接下来要做的就是缓存 解码 显示
编码的代码真的是又臭又长 我不想复制了 直接看源码吧 我把最后一步复制上来
private static Bitmap decodeStream(
ImageReader imageReader,
BitmapFactory.Options options,
DecodeCallbacks callbacks,
BitmapPool bitmapPool)
throws IOException {
if (!options.inJustDecodeBounds) {
// Once we've read the image header, we no longer need to allow the buffer to expand in
// size. To avoid unnecessary allocations reading image data, we fix the mark limit so that it
// is no larger than our current buffer size here. We need to do so immediately before
// decoding the full image to avoid having our mark limit overridden by other calls to
// mark and reset. See issue #225.
callbacks.onObtainBounds();
imageReader.stopGrowingBuffers();
}
// BitmapFactory.Options out* variables are reset by most calls to decodeStream, successful or
// otherwise, so capture here in case we log below.
int sourceWidth = options.outWidth;
int sourceHeight = options.outHeight;
String outMimeType = options.outMimeType;
final Bitmap result;
TransformationUtils.getBitmapDrawableLock().lock();
try {
result = imageReader.decodeBitmap(options);
} catch (IllegalArgumentException e) {
IOException bitmapAssertionException =
newIoExceptionForInBitmapAssertion(e, sourceWidth, sourceHeight, outMimeType, options);
if (Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(
TAG,
"Failed to decode with inBitmap, trying again without Bitmap re-use",
bitmapAssertionException);
}
if (options.inBitmap != null) {
try {
//加入bitmap池
bitmapPool.put(options.inBitmap);
options.inBitmap = null;
return decodeStream(imageReader, options, callbacks, bitmapPool);
} catch (IOException resetException) {
throw bitmapAssertionException;
}
}
throw bitmapAssertionException;
} finally {
TransformationUtils.getBitmapDrawableLock().unlock();
}
return result;
}
这时候我们已经拿到了bitmap对象 接下来还要做数据转换
//BitmapDrawableTranscoder.transcode()
public Resource<BitmapDrawable> transcode(@NonNull Resource<Bitmap> toTranscode, @NonNull Options options) {
return LazyBitmapDrawableResource.obtain(resources, toTranscode);
}
//BitmapDrawableTranscoder.transcode()
@Nullable
public static Resource<BitmapDrawable> obtain(Resources resources, Resource<Bitmap> bitmapResource) {
if (bitmapResource == null) {
return null;
}
return new LazyBitmapDrawableResource(resources, bitmapResource);
}
