Glide绑定Activity生命周期
Glide.with()
下面都是它的重载方法，Context，Activity，FragmentActivity, Fragment, android.app.Fragment fragment,View都可以作为他的参数，内容大同小异，都是先getRetriever，然后再get
@NonNull
public static RequestManager with(@NonNull Context context) {
return getRetriever(context).get(context);
}
@NonNull
public static RequestManager with(@NonNull Activity activity) {
return getRetriever(activity).get(activity);
}
@NonNull
public static RequestManager with(@NonNull FragmentActivity activity) {
return getRetriever(activity).get(activity);
}
@NonNull
public static RequestManager with(@NonNull Fragment fragment) {
return getRetriever(fragment.getContext()).get(fragment);
}
@SuppressWarnings("deprecation")
@Deprecated
@NonNull
public static RequestManager with(@NonNull android.app.Fragment fragment) {
return getRetriever(fragment.getActivity()).get(fragment);
}
@NonNull
public static RequestManager with(@NonNull View view) {
return getRetriever(view.getContext()).get(view);
}
getRetriever()
原来获取的是Glide里面RequestManagerRetriever，Glide是个双重校验实现的单例
@NonNull
@NonNull
private static RequestManagerRetriever getRetriever(@Nullable Context context) {
...
return Glide.get(context).getRequestManagerRetriever();
}
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;
}
Glide的 getRequestManagerRetriever返回了requestManagerRetriever属性
返回到第一步with方法
return getRetriever(context).get(activity);
查看RequestManagerRetriver的get() 主要关注框出来的部分
获取到FragmentManeger 调用FragmentGet()
实例化了一个RequestManagerFragment， 然后给这个Fragment指定了一个RequestManager,最终返回这个fragment里面的requestManager；
@Deprecated
@NonNull
private RequestManager fragmentGet(
@NonNull Context context,
@NonNull android.app.FragmentManager fm,
@Nullable android.app.Fragment parentHint,
boolean isParentVisible) {
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);
//实例化requsetManager
requestManager =
factory.build(
glide, current.getGlideLifecycle(), current.getRequestManagerTreeNode(), context);
if (isParentVisible) {
requestManager.onStart();
}
current.setRequestManager(requestManager);
}
return requestManager;
}
@NonNull
private RequestManagerFragment getRequestManagerFragment(
@NonNull final android.app.FragmentManager fm, @Nullable android.app.Fragment parentHint) {
RequestManagerFragment current = (RequestManagerFragment) fm.findFragmentByTag(FRAGMENT_TAG);
if (current == null) {
current = pendingRequestManagerFragments.get(fm);
if (current == null) {
///创建Fragment
current = new RequestManagerFragment();
current.setParentFragmentHint(parentHint);
pendingRequestManagerFragments.put(fm, current);
// 将这个Frament添加到了Activity中
fm.beginTransaction().add(current, FRAGMENT_TAG).commitAllowingStateLoss();
handler.obtainMessage(ID_REMOVE_FRAGMENT_MANAGER, fm).sendToTarget();
}
}
return current;
}
有没有注意到实例化RequestManager时传入的参数，其中有一个是Fragment的LifeCycle
requestManager =
factory.build(
glide, current.getGlideLifecycle(), current.getRequestManagerTreeNode(), context);
看到RequestManagerFragment里面确实例化了一个LifeCycle对象
public RequestManagerFragment() {
this(new ActivityFragmentLifecycle());
}
@VisibleForTesting
@SuppressLint("ValidFragment")
RequestManagerFragment(@NonNull ActivityFragmentLifecycle lifecycle) {
this.lifecycle = lifecycle;
}
在RequestManager中给这个LifeCycle注册了一个观察者
这样在Fragment 生命周期发生变化时，RequestManager也能感受到了
小结
Gilde能感受Activity生命周期，在onStop的时候停止加载，在onStart的时候继续加载，在onDestory清除任务和进行缓存的回收
原因：
整个流程调用Glide.with时首先获取到Glide单例中的RequestManagerRetriever，再调用retriever的get()，再他的get方法中创建了一个无界面的Fragment并且注册给Activity，然后将这个Fragment里面的LifeCycle传递给要返回的RequestManager，在这个RequestManager中给LifeCycle注册了一个观察者，这样就完成了生命周期在Activity->Fragment->RequestManager之间的传递；
