前言
本篇基于4.8.0版本
- 【源码阅读】Glide源码阅读之with方法（一）
大多数情况下，我们使用glide 就一句代码
Glide.with(context).load(url).into(imageView);
但是这一句代码里面蕴含着成吨的代码！
with方法有以下几个重载方法
public static RequestManager with(@NonNull Context context) { return getRetriever(context).get(context); } public static RequestManager with(@NonNull Activity activity) { return getRetriever(activity).get(activity); } public static RequestManager with(@NonNull FragmentActivity activity) { return getRetriever(activity).get(activity); } public static RequestManager with(@NonNull Fragment fragment) { return getRetriever(fragment.getActivity()).get(fragment); } public static RequestManager with(@NonNull android.app.Fragment fragment) { return getRetriever(fragment.getActivity()).get(fragment); } public static RequestManager with(@NonNull View view) { return getRetriever(view.getContext()).get(view); }复制代码 其中，getRetriever返回的是个RequestManagerRetriever对象
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(); }复制代码 接着是RequestManagerRetriever.get方法，在传入Context、Activity、FragmentActivity、Fragment、 android.app.Fragment、View几种情况略有不同，大致可以分为Application和非Application
Application它生命周期即应用程序的生命周期，如果应用程序关闭的话，Glide的加载也会同时终止。
@NonNull private RequestManager getApplicationManager(@NonNull Context context) { // Either an application context or we're on a background thread. if (applicationManager == null) { synchronized (this) { if (applicationManager == null) { // Normally pause/resume is taken care of by the fragment we add to the fragment or // activity. However, in this case since the manager attached to the application will not // receive lifecycle events, we must force the manager to start resumed using // ApplicationLifecycle. // TODO(b/27524013): Factor out this Glide.get() call. Glide glide = Glide.get(context.getApplicationContext()); applicationManager = factory.build( glide, new ApplicationLifecycle(), new EmptyRequestManagerTreeNode(), context.getApplicationContext()); } } } return applicationManager; }复制代码 非Application都是向当前Activity添加一个隐藏的Fragment，当Activity销毁时，该Fragment也会销毁，销毁时，Glide就会取消本次加载。
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); }复制代码 唯一有区别的是，FragmentActivity和Fragment使用的是SupportRequestManagerFragment，Activity使用的是RequestManagerFragment；SupportRequestManagerFragment继承的是v4包的，而RequestManagerFragment是继承android.app.Fragment。
@NonNull private SupportRequestManagerFragment getSupportRequestManagerFragment( @NonNull final FragmentManager fm, @Nullable Fragment parentHint, boolean isParentVisible) { SupportRequestManagerFragment current = (SupportRequestManagerFragment) fm.findFragmentByTag(FRAGMENT_TAG); if (current == null) { current = pendingSupportRequestManagerFragments.get(fm); if (current == null) { current = new SupportRequestManagerFragment(); current.setParentFragmentHint(parentHint); if (isParentVisible) { current.getGlideLifecycle().onStart(); } pendingSupportRequestManagerFragments.put(fm, current); fm.beginTransaction().add(current, FRAGMENT_TAG).commitAllowingStateLoss(); handler.obtainMessage(ID_REMOVE_SUPPORT_FRAGMENT_MANAGER, fm).sendToTarget(); } } return current; }复制代码 @NonNull private RequestManagerFragment getRequestManagerFragment( @NonNull final android.app.FragmentManager fm, @Nullable android.app.Fragment parentHint, boolean isParentVisible) { RequestManagerFragment current = (RequestManagerFragment) fm.findFragmentByTag(FRAGMENT_TAG); if (current == null) { current = pendingRequestManagerFragments.get(fm); if (current == null) { current = new RequestManagerFragment(); current.setParentFragmentHint(parentHint); if (isParentVisible) { current.getGlideLifecycle().onStart(); } pendingRequestManagerFragments.put(fm, current); fm.beginTransaction().add(current, FRAGMENT_TAG).commitAllowingStateLoss(); handler.obtainMessage(ID_REMOVE_FRAGMENT_MANAGER, fm).sendToTarget(); } } return current; }复制代码 SupportRequestManagerFragment中部分代码
@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); } } } @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(); }复制代码 ActivityFragmentLifecycle相关代码
@Override public void addListener(@NonNull LifecycleListener listener) { lifecycleListeners.add(listener); if (isDestroyed) { listener.onDestroy(); } else if (isStarted) { listener.onStart(); } else { listener.onStop(); } } @Override public void removeListener(@NonNull LifecycleListener listener) { lifecycleListeners.remove(listener); } void onStart() { isStarted = true; for (LifecycleListener lifecycleListener : Util.getSnapshot(lifecycleListeners)) { lifecycleListener.onStart(); } } void onStop() { isStarted = false; for (LifecycleListener lifecycleListener : Util.getSnapshot(lifecycleListeners)) { lifecycleListener.onStop(); } } void onDestroy() { isDestroyed = true; for (LifecycleListener lifecycleListener : Util.getSnapshot(lifecycleListeners)) { lifecycleListener.onDestroy(); } }复制代码