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90public static RequestManager with(FragmentActivity activity) {
//单例拿到一个RequestManagerRetriever
RequestManagerRetriever retriever = RequestManagerRetriever.get();
return retriever.get(activity);
}
public RequestManager get(FragmentActivity activity) {
if (Util.isOnBackgroundThread()) {
return get(activity.getApplicationContext());
} else {
assertNotDestroyed(activity);
FragmentManager fm = activity.getSupportFragmentManager();
return supportFragmentGet(activity, fm);
}
}
RequestManager supportFragmentGet(Context context, FragmentManager fm) {
//根据TAG拿到SupportRequestManagerFragment 防止第二次重复创建
SupportRequestManagerFragment current = getSupportRequestManagerFragment(fm);
//拿到RequestManager
RequestManager requestManager = current.getRequestManager();
if (requestManager == null) {
requestManager = new RequestManager(context, current.getLifecycle(), current.getRequestManagerTreeNode());
current.setRequestManager(requestManager);
}
return requestManager;
}
SupportRequestManagerFragment getSupportRequestManagerFragment(final FragmentManager fm) {
SupportRequestManagerFragment current = (SupportRequestManagerFragment) fm.findFragmentByTag(FRAGMENT_TAG);
if (current == null) {
current = pendingSupportRequestManagerFragments.get(fm);
if (current == null) {
current = new SupportRequestManagerFragment();
pendingSupportRequestManagerFragments.put(fm, current);
fm.beginTransaction().add(current, FRAGMENT_TAG).commitAllowingStateLoss();
handler.obtainMessage(ID_REMOVE_SUPPORT_FRAGMENT_MANAGER, fm).sendToTarget();
}
}
return current;
}
public class RequestManager implements LifecycleListener {
private final Context context;
private final Lifecycle lifecycle;
private final RequestManagerTreeNode treeNode;
private final RequestTracker requestTracker;
private final Glide glide;
private final OptionsApplier optionsApplier;
private DefaultOptions options;
//RequestManager初始化
public RequestManager(Context context, Lifecycle lifecycle, RequestManagerTreeNode treeNode) {
this(context, lifecycle, treeNode, new RequestTracker(), new ConnectivityMonitorFactory());
}
RequestManager(Context context, final Lifecycle lifecycle, RequestManagerTreeNode treeNode,
RequestTracker requestTracker, ConnectivityMonitorFactory factory) {
this.context = context.getApplicationContext();
this.lifecycle = lifecycle;
this.treeNode = treeNode;
this.requestTracker = requestTracker;
this.glide = Glide.get(context);
this.optionsApplier = new OptionsApplier();
ConnectivityMonitor connectivityMonitor = factory.build(context,
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.
if (Util.isOnBackgroundThread()) {
new Handler(Looper.getMainLooper()).post(new Runnable() {
public void run() {
lifecycle.addListener(RequestManager.this);
}
});
} else {
lifecycle.addListener(this);
}
lifecycle.addListener(connectivityMonitor);
}
//...
}
总结：
- 创建一个
Fragment绑定到Activity上面，Fragment调用setRequestManager()进行RequestManager赋值。Fragment的作用是用于生命周期管理,当我们new Fragment的时候我们一同会new一个ActivityFragmentLifecycle- 当
Frament onLowMemory的时候RequestManager会回调onLowMemory回调。ActivityFragmentLifecycle是使用观察者模式来管理LifecycleListener，当fragment触发生命周期的时候（onStart onStop onDestroy），ActivityFragmentLifecycle将会进行遍历回调。RequestManager是一个LifecycleListener,当初始化的时候，RequestManager将会被注册到Fragent里面的ActivityFragmentLifecycle进行生命管理。