作为google主推的一款图片加载框架,从glide3.x 到glide4.x加入apt的注解编译;详细的使用可以详见官方文档
[Glide v4] https://muyangmin.github.io/glide-docs-cn/
首先来看Glide的基本使用:
(1)支持Memory和Disk图片缓存。
(2)支持gif和webp格式图片。
(3)根据Activity/Fragment生命周期自动管理请求。
(4)使用Bitmap Pool可以使Bitmap复用。*
(5)对于回收的Bitmap会主动调用recycle，减小系统回收压力。GlideApp.with(this) //.asBitmap() --- 转换为bitmap //.asDrawable() ---- 转换为drawable .asGif() --- 转换为gif .load(url) .placeholder(R.mipmap.ic_launcher_round) .error(R.mipmap.ele) .fitCenter() //.fallback()当请求图片为null的时候 .into(mIv);在Glide v4中通过注解会在build 下apt生成部分外部文件 来操作glide,大大提高glide的可定制性,可以去看文章开头的官网地址来看使用方式;下面的解析以v4为准
1.首先来看glide的初始化:
GlideApp.with(this)
GlideApp:
@NonNull
public static GlideRequests with(@NonNull FragmentActivity arg0) {
return (GlideRequests) Glide.with(arg0);
}
Glide:
@NonNull
public static RequestManager with(@NonNull FragmentActivity activity) {
return getRetriever(activity).get(activity);
}这里是对Glide的初始化,以及对生命周期的管理:
核心代码:
getRetriever(activity).get(activity);其中 getRetriever(activity)是glide的初始化
@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();
}这里主要来看Glide.get(context):
@NonNull
public static Glide get(@NonNull Context context) {
if (glide == null) {
synchronized (Glide.class) {
if (glide == null) {
checkAndInitializeGlide(context);
}
}
}
return glide;
}
private static void checkAndInitializeGlide(@NonNull Context context) {
// In the thread running initGlide(), one or more classes may call Glide.get(context).
// Without this check, those calls could trigger infinite recursion.
if (isInitializing) {
throw new IllegalStateException("You cannot call Glide.get() in registerComponents(),"
+ " use the provided Glide instance instead");
}
isInitializing = true;
initializeGlide(context);
isInitializing = false;
}
private static void initializeGlide(@NonNull Context context) {
initializeGlide(context, new GlideBuilder());
}
@SuppressWarnings("deprecation")
private static void initializeGlide(@NonNull Context context, @NonNull GlideBuilder builder) {
......省略部分代码
Glide glide = builder.build(applicationContext);
for (com.bumptech.glide.module.GlideModule module : manifestModules) {
module.registerComponents(applicationContext, glide, glide.registry);
}
if (annotationGeneratedModule != null) {
annotationGeneratedModule.registerComponents(applicationContext, glide, glide.registry);
}
applicationContext.registerComponentCallbacks(glide);
Glide.glide = glide;
}
在initializeGlide中有一个构建中模式的glide初始化,见怪不怪这是glide的真正初始化: Glide glide = builder.build(applicationContext);
继续深入:
@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
(requestManagerFactory);
return new Glide(
context,
engine,
memoryCache,
bitmapPool,
arrayPool,
requestManagerRetriever,
connectivityMonitorFactory,
logLevel,
defaultRequestOptions.lock(),
defaultTransitionOptions);
}在这里glide初始化就完全初始化完毕:
相关图片线程池—bitmapPool
图片加载器engin等的初始化 等就基本完成了
当然没有必要去细究其具体的参数,主要是理解其思想;
ok~到这里 glide的初始化完毕,下面通过glide的api
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getRetriever(activity).get(activity);看到其中的get方法没有,这里是glide的一个亮点;通过传入activity/fragment/或者view等来控制图片加载的周期来提高其性能:
下面看具体的代码:
@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) {
return get(((ContextWrapper) context).getBaseContext());
}
}
return getApplicationManager(context);
}
@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, null /*parentHint*/);
}
}
@NonNull
public RequestManager get(@NonNull Fragment fragment) {
Preconditions.checkNotNull(fragment.getActivity(),
"You cannot start a load on a fragment before it is attached or after it is destroyed");
if (Util.isOnBackgroundThread()) {
return get(fragment.getActivity().getApplicationContext());
} else {
FragmentManager fm = fragment.getChildFragmentManager();
return supportFragmentGet(fragment.getActivity(), fm, fragment);
}
}
@NonNull
public RequestManager get(@NonNull Activity activity) {
if (Util.isOnBackgroundThread()) {
return get(activity.getApplicationContext());
} else {
assertNotDestroyed(activity);
android.app.FragmentManager fm = activity.getFragmentManager();
return fragmentGet(activity, fm, null /*parentHint*/);
}
}
@NonNull
public RequestManager get(@NonNull View view) {
if (Util.isOnBackgroundThread()) {
return get(view.getContext().getApplicationContext());
}
Preconditions.checkNotNull(view);
Preconditions.checkNotNull(view.getContext(),
"Unable to obtain a request manager for a view without a Context");
Activity activity = findActivity(view.getContext());
// The view might be somewhere else, like a service.
if (activity == null) {
return get(view.getContext().getApplicationContext());
}
// Support Fragments.
// Although the user might have non-support Fragments attached to FragmentActivity, searching
// for non-support Fragments is so expensive pre O and that should be rare enough that we
// prefer to just fall back to the Activity directly.
if (activity instanceof FragmentActivity) {
Fragment fragment = findSupportFragment(view, (FragmentActivity) activity);
return fragment != null ? get(fragment) : get(activity);
}
// Standard Fragments.
android.app.Fragment fragment = findFragment(view, activity);
if (fragment == null) {
return get(activity);
}
return get(fragment);
}可以看到glide 支持的是fragmentActivity/activity/fragment/view/context;其中view是通过判断其所依托的碎片来进行周期管理;
殊途同归,下面以activity为例来简单剖析:
@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, null /*parentHint*/);
}
}大致可以猜出一二,这里是依托于activity之下碎片fragment来进行周期的回调;同理fragment也是这样fragment.getChildFragmentManager();
@NonNull
private RequestManager supportFragmentGet(@NonNull Context context, @NonNull FragmentManager fm,
@Nullable Fragment parentHint) {
SupportRequestManagerFragment current = getSupportRequestManagerFragment(fm, parentHint);
RequestManager requestManager = current.getRequestManager();
if (requestManager == null) {
// TODO(b/27524013): Factor out this Glide.get() call.
Glide glide = Glide.get(context);
requestManager =
factory.build(
glide, current.getGlideLifecycle(), current.getRequestManagerTreeNode(), context);
current.setRequestManager(requestManager);
}
return requestManager;
}上面代码第一行: SupportRequestManagerFragment current = getSupportRequestManagerFragment(fm, parentHint);
@NonNull
SupportRequestManagerFragment getSupportRequestManagerFragment(
@NonNull final FragmentManager fm, @Nullable Fragment parentHint) {
SupportRequestManagerFragment current =
(SupportRequestManagerFragment) fm.findFragmentByTag(FRAGMENT_TAG);
if (current == null) {
current = pendingSupportRequestManagerFragments.get(fm);
if (current == null) {
current = new SupportRequestManagerFragment();
current.setParentFragmentHint(parentHint);
pendingSupportRequestManagerFragments.put(fm, current);
fm.beginTransaction().add(current, FRAGMENT_TAG).commitAllowingStateLoss();
handler.obtainMessage(ID_REMOVE_SUPPORT_FRAGMENT_MANAGER, fm).sendToTarget();
}
}
return current;
}
@Override
public boolean handleMessage(Message message) {
boolean handled = true;
Object removed = null;
Object key = null;
switch (message.what) {
case ID_REMOVE_FRAGMENT_MANAGER:
android.app.FragmentManager fm = (android.app.FragmentManager) message.obj;
key = fm;
removed = pendingRequestManagerFragments.remove(fm);
break;
case ID_REMOVE_SUPPORT_FRAGMENT_MANAGER:
FragmentManager supportFm = (FragmentManager) message.obj;
key = supportFm;
removed = pendingSupportRequestManagerFragments.remove(supportFm);
break;
default:
handled = false;
break;
}
if (handled && removed == null && Log.isLoggable(TAG, Log.WARN)) {
Log.w(TAG, "Failed to remove expected request manager fragment, manager: " + key);
}
return handled;
}在getSupportRequestManagerFragment中通过创建SupportRequestManagerFragment并且添加到activity中,同时把SupportRequestManagerFragment从缓存队列pendingSupportRequestManagerFragments中移除,进行加载;
然后继续看supportFragmentGet:
获取到SupportRequestManagerFragment,然后通过SupportRequestManagerFragment获取requestManager: RequestManager requestManager = current.getRequestManager();如果为空则通过
factory.build(
glide, current.getGlideLifecycle(), current.getRequestManagerTreeNode(), context);进行创建最后set到SupportRequestManagerFragment中;注意其参数.current.getGlideLifecycle()其实就是这个接口来回调SupportRequestManagerFragment的周期方法进而进行周期的控制;
- 2.接着来看glide的相关配置:图形属性,
GlideApp.with(this)
.load(url)
首先来看url的加载:
#GlideApp
@Override
@NonNull
@CheckResult
public GlideRequest<TranscodeType> load(@Nullable String arg0) {
return (GlideRequest<TranscodeType>) super.load(arg0);
}
#Glide --- 多种实现类
@NonNull
@Override
@CheckResult
public RequestBuilder<TranscodeType> load(@Nullable String string) {
return loadGeneric(string);
}
@NonNull
@CheckResult
@Override
public RequestBuilder<TranscodeType> load(@Nullable Uri uri) {
return loadGeneric(uri);
}
....
@NonNull
private RequestBuilder<TranscodeType> loadGeneric(@Nullable Object model) {
this.model = model;
isModelSet = true;
return this;
}
由以上代码中可以看到load有很多实现类,最后都是在RequestBuilder中初始化参数model,在into的时候进行加载;
接着看Glide对图片属性的支持:
GlideApp.with(this)
//.asBitmap() — 对图片格式的编码转化
//.asDrawable()
.asGif()
.miniThumb(100)
.placeholder(R.mipmap.ic_launcher_round) — 占位图
.error(R.mipmap.ele) —- 错误之后的显示图
.fitCenter() — 图片显示样式
//.fallback()当请求图片为null的时候
一般Glide通过一系列链式来配置图片的属性,和加载的属性;当然也可以通过RequestOption来自定义(把相关配置apply进去),最后把RequestOption apply到RequstBuilder中;
举一例.asGif():
#GlideApp
@Override
@NonNull
@CheckResult
public GlideRequest<GifDrawable> asGif() {
return (GlideRequest<GifDrawable>) super.asGif();
}
#Glide
private static final RequestOptions DECODE_TYPE_GIF = decodeTypeOf(GifDrawable.class).lock();
@NonNull
@CheckResult
public RequestBuilder<GifDrawable> asGif() {
return as(GifDrawable.class).apply(DECODE_TYPE_GIF);
}
从以上代码可以看到decodeTypeOf(GifDrawable.class).lock();转化为一个GifDrawable之后apply到RequstBuilder中,看到这里是不是感觉RequstBuilder就是一个总指挥,主导Glide的大部分行为(如下 附decodeTypeOf的源码)
@NonNull
@CheckResult
public static RequestOptions decodeTypeOf(@NonNull Class<?> resourceClass) {
return new RequestOptions().decode(resourceClass);
}当这里我们对RequestOptions这个原型有了一定的了解;
当然你可以参阅文章开头的Glide v4官网来看其使用,慢慢体会这个思想;
- 3.最后看glide的加载与最终实现:
GlideApp.with(this)
.into(tartget);
同样由浅入深来看:
@NonNull
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);
}首先是对图片的现实样式进行设置,通过目标getScaleType来同步requstoption的相关设置,继续看:
glideContext.buildImageViewTarget(view, transcodeClass), null,requestOptions);
这里的三个参数分别是目标target,targetListener,requestOptions;继续看源码:
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();
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;
}其中:
options = options.autoClone();
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;
}以上代码中通过对比当前请求和之前的请求对比来去定是否复用(在图片网络框架中很常见);继续看核心代码:
requestManager.clear(target);
target.setRequest(request);
requestManager.track(target, request);接着看 requestManager.track(target, request);其他就是清楚和设置requst的代码,一目了然:
void track(@NonNull Target<?> target, @NonNull Request request) {
targetTracker.track(target);
requestTracker.runRequest(request);
}
public void track(@NonNull Target<?> target) {
targets.add(target);
}
注意在Glide中是可以设置优先级的,在 targetTracker.track(target);中把目标图片统一通过targets来管理,而targets是Set集合是具有排序功能的;
继续看 requestTracker.runRequest(request);源码:
public void runRequest(@NonNull Request request) {
requests.add(request);
if (!isPaused) {
request.begin();
} else {
pendingRequests.add(request);
}
}到这里可以看到当没有onPause时候requst会开始加载,onPause时候加入缓存队列等待;当然我们看到了Glide所谓的周期管理:追根溯源:
1.在glide.with中提到activity中创建了SupportRequestManagerFragment,并通过传入 current.getGlideLifecycle()来current.setRequestManager(requestManager);
2.在SupportRequestManagerFragment中通过会调lifecycle来监听其周期:
eg:
@Override
public void onStop() {
super.onStop();
lifecycle.onStop();
}注意这里的lifecycle不是一个接口,而是一个接口的包装类,我们可以看下ActivityFragmentLifecycle lifecyle的周期控制;
@Override
public void addListener(@NonNull LifecycleListener listener) {
lifecycleListeners.add(listener);
if (isDestroyed) {
listener.onDestroy();
} else if (isStarted) {
listener.onStart();
} else {
listener.onStop();
}
}
void onStart() {
isStarted = true;
for (LifecycleListener lifecycleListener : Util.getSnapshot(lifecycleListeners)) {
lifecycleListener.onStart();
}
}当然在SupportRequestManagerFragment的构造中会实例化lifecycle这里不做赘述;
3.这里比较绕,我们回到request初始化的位置RequestManagerRetriever中,fragmentGet中requstManager的初始化类:
@NonNull
private RequestManager fragmentGet(@NonNull Context context,
@NonNull android.app.FragmentManager fm,
@Nullable android.app.Fragment parentHint) {
RequestManagerFragment current = getRequestManagerFragment(fm, parentHint);
RequestManager requestManager = current.getRequestManager();
if (requestManager == null) {
// TODO(b/27524013): Factor out this Glide.get() call.
Glide glide = Glide.get(context);
requestManager =
factory.build(
glide, current.getGlideLifecycle(), current.getRequestManagerTreeNode(), context);
current.setRequestManager(requestManager);
}
return requestManager;
}继续看核心代码:
requestManager =
factory.build(
glide, current.getGlideLifecycle(), current.getRequestManagerTreeNode(), context);这里对requestManager进行实例化,然后这里的current.getGlideLifecycle()就是周期控制的lifecycle;他来自SupportRequestManagerFragment,就是SupportRequestManagerFragment初始化时候实例化的lifecycle;然后在RequstManger的构造中:lifecycle.addListener(this)对周期的回调接口进行注册;然后在周期的会调是实现方法中用targetTracker管理起来:
到这里基本清楚了,就是接口回调,那么按照源码继续看
# requstManger
@Override
public void onStop() {
pauseRequests();
targetTracker.onStop();
}
public void pauseRequests() {
Util.assertMainThread();
requestTracker.pauseRequests();
}
#RequstTracker
public void pauseRequests() {
isPaused = true;
for (Request request : Util.getSnapshot(requests)) {
if (request.isRunning()) {
request.pause();
pendingRequests.add(request);
}
}
}ok~ 到了这里就明白了
1.SupportRequestManagerFragment—->实例化ActivityFragmentLifecycle ,并在fragment周期中回调ActivityFragmentLifecycle的onstart onStop….进行glide周期控制
2.RequestManagerRetriever —–>实例化requstManager,并传入SupportRequestManagerFragment提供的ActivityFragmentLifecycle实例,然后在requstManager注册周期会调接口lifecycle.addListener(this)
3.requstManager中周期接口实现方法中匹配targetTracker;
4.到这里周期已经很好的得到控制,然后通过一系列的标志位来控制glide的加载开始 结束….etc
之前讲到
public void runRequest(@NonNull Request request) {
requests.add(request);
if (!isPaused) {
request.begin();
} else {
pendingRequests.add(request);
}
}这里的周期判断就已经明了了,在Glide中SingleRequst比较常用,那么来看他的begin源码:
@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;
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.
status = Status.WAITING_FOR_SIZE;
if (Util.isValidDimensions(overrideWidth, overrideHeight)) {
onSizeReady(overrideWidth, overrideHeight);
} else {
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));
}
}
以上代码中Glide对加载状态进行了判断,并且对其width和height进行重新处理,当然一些策略是不错的,比如:
if (status == Status.COMPLETE) {
onResourceReady(resource, DataSource.MEMORY_CACHE);
return;
}
@SuppressWarnings("unchecked")
@Override
public void onResourceReady(Resource<?> resource, DataSource dataSource) {
stateVerifier.throwIfRecycled();
loadStatus = null;
if (resource == null) {
GlideException exception = new GlideException("Expected to receive a Resource<R> with an "
+ "object of " + transcodeClass + " inside, but instead got null.");
onLoadFailed(exception);
return;
}
Object received = resource.get();
if (received == null || !transcodeClass.isAssignableFrom(received.getClass())) {
releaseResource(resource);
GlideException exception = new GlideException("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."));
onLoadFailed(exception);
return;
}
if (!canSetResource()) {
releaseResource(resource);
// We can't put the status to complete before asking canSetResource().
status = Status.COMPLETE;
return;
}
onResourceReady((Resource<R>) resource, (R) received, dataSource);
}完成之后进行资源释放,并修改资源状态等 ,这里不做详尽的解释(太多);ok 继续回来看请求逻辑
if (Util.isValidDimensions(overrideWidth, overrideHeight)) {
onSizeReady(overrideWidth, overrideHeight);
} else {
target.getSize(this);
}glide的请求在onSizeReady中:
@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));
}
}
主要的加载逻辑是engine.load并且传入一堆参数,主要是各种属性的线程池,内存状态,OPtion等;那么继续看加载的实质代码:
public <R> LoadStatus load(
.....参数省略) {
......
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;
}
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);
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);
}OMG 代码好长;首先Glide并不会直接加载他是有两次缓存的:LruCash和ActiveCash;在Glide中当加载完毕,首先会将图片短时间从LruCash中取出来放入ActiveCash,进行临时存储;所以首先从ActiveCash中获取图片
EngineResource<?> active = loadFromActiveResources(key, isMemoryCacheable);接着是从LruCash中获取图片:
EngineResource<?> cached = loadFromCache(key, isMemoryCacheable);最后才进行加载:url:
engineJob.addCallback(cb);
engineJob.start(decodeJob);注意Glide会有会调来监听加载图片的每一个阶段;比如我们在开发中会有这样的场景:
SimpleTarget<Drawable> into = GlideApp.with(this)
.load(url)
.placeholder(R.mipmap.ic_launcher_round)
//开始请求
.into(new SimpleTarget<Drawable>() {
@Override
public void onResourceReady(@NonNull Drawable resource, @Nullable Transition<? super Drawable> transition) {
Log.i("glide_life", "onResourceReady");
mIv.setImageDrawable(resource);
}
@Override
public void setRequest(@Nullable Request request) {
super.setRequest(request);
Log.i("glide_life", "setRequest");
}
.....省略一些方法
});ok 继续回归网络加载 engineJob.start(decodeJob);
public void start(DecodeJob<R> decodeJob) {
this.decodeJob = decodeJob;
GlideExecutor executor = decodeJob.willDecodeFromCache()
? diskCacheExecutor
: getActiveSourceExecutor();
executor.execute(decodeJob);
}由上面代码 继续看GlideExecutor下execute:
public void execute(Runnable command) {
if (command == null)
throw new NullPointerException();
int c = ctl.get();
if (workerCountOf(c) < corePoolSize) {
if (addWorker(command, true))
return;
c = ctl.get();
}
if (isRunning(c) && workQueue.offer(command)) {
int recheck = ctl.get();
if (! isRunning(recheck) && remove(command))
reject(command);
else if (workerCountOf(recheck) == 0)
addWorker(null, false);
}
else if (!addWorker(command, false))
reject(command);
}what? 为什么传的是DecodeJob回来的是Runable,而且execute明显是一些资源收尾的工作;好吧 DecodeJob 实现了Runable,并且在run方法中实现网络请求:
@Override
public void run() {
DataFetcher<?> localFetcher = currentFetcher;
try {
if (isCancelled) {
notifyFailed();
return;
}
runWrapped();
} catch (Throwable t) {
if (Log.isLoggable(TAG, Log.DEBUG)) {
Log.d(TAG, "DecodeJob threw unexpectedly"
+ ", isCancelled: " + isCancelled
+ ", stage: " + stage, t);
}
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();
}
}在这里同样通过状态进行请求;当上请求cancle已经cancel则 notifyFailed()(注意glide是可以取消网络加载的),否则通过请求runWrapped()来请求网络;这里使用了状态机:
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 Stage getNextStage(Stage current) {
switch (current) {
case INITIALIZE:
return diskCacheStrategy.decodeCachedResource()
? Stage.RESOURCE_CACHE : getNextStage(Stage.RESOURCE_CACHE);
case RESOURCE_CACHE:
return diskCacheStrategy.decodeCachedData()
? Stage.DATA_CACHE : getNextStage(Stage.DATA_CACHE);
case DATA_CACHE:
// Skip loading from source if the user opted to only retrieve the resource from cache.
return onlyRetrieveFromCache ? Stage.FINISHED : Stage.SOURCE;
case SOURCE:
case FINISHED:
return Stage.FINISHED;
default:
throw new IllegalArgumentException("Unrecognized stage: " + current);
}
}首先是获取加载状态,然后在getNextGenerator()获取图片加载器;
private DataFetcherGenerator getNextGenerator() {
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() {
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;
}
}
if ((stage == Stage.FINISHED || isCancelled) && !isStarted) {
notifyFailed();
}
}在Glide中有3种加载器(暂时这样定义)DataCacheGenerator,SourceGenerator,ResourceCacheGenerator
基于以上3钟然后在runGenerators()中进行真正的加载:currentGenerator.startNext()
下面以SourceGenerator为例
@Override
public boolean startNext() {
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()) {
loadData = helper.getLoadData().get(loadDataListIndex++);
if (loadData != null
&& (helper.getDiskCacheStrategy().isDataCacheable(loadData.fetcher.getDataSource())
|| helper.hasLoadPath(loadData.fetcher.getDataClass()))) {
started = true;
loadData.fetcher.loadData(helper.getPriority(), this);
}
}
return started;
}核心加载逻辑: loadData.fetcher.loadData(helper.getPriority(), this);
尽可能详尽的对glide 就行剖析.重点是思想.希望对大家有所助益