触发UIApplicationDidBecomeActiveNotification后会调用什么？

Question

In my app I'm trying to make my navigation bar not shrink from 44px to 32px when the phone is rotated to horizontal orientation. I've been able to accomplish this by setting the navigationBars frame when the view is rotated and also in viewDidAppear. However, when I push the home button to exit the app and then I reenter the app, the navigation bar still shrinks. So I implemented a notification to detect UIApplicationDidBecomeActiveNotification, and in that method I reset the navigationBar frame height to 44px. However, it doesn't work because something is getting called which is resetting my views frame. Does anyone know what gets called after a UIApplicationDidBecomeActiveNotification gets triggered that resets the viewcontrollers frame?

Answer 1

我遇到了同样的问题，如果你通过Key Value Observers附加一个观察者，你可以看到在UIApplicationDidBecomeActiveNotification之后调用了一些东西。

Answer 2

In Your application any class can be an "observer" for different notifications. When you create view controller, you can register it as an observer for the UIApplicationDidBecomeActiveNotification and specify which method that you want call when that notification gets sent your your application.

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(myMethod:) name: UIApplicationDidBecomeActiveNotification object:nil];

remove observer in ViewWillDisappear/viewDidDisAppear/Dealloc as per your need:

[[NSNotificationCenter defaultCenter] removeObserver:self];