问题描述

我需要在我的 Android 应用程序中处理方向更改.为此，我决定使用 OrientationEventListener 便利类.但是他的回调方法被赋予了一些奇怪的行为.

我的应用程序以纵向模式启动，然后最终切换到横向模式.我在回调 onOrientationChanged 方法中执行了一些自定义代码，该方法提供了一些额外的 UI 处理逻辑 - 它有一些对 findViewById 的调用.奇怪的是，当从横向模式切换回纵向模式时，onOrientationChanged 回调被调用了两次，更糟糕的是 - 第二次调用处理的是 bad Context - findViewById 方法开始返回 null.这些调用直接从 MainThread

 @Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);监听器 = 新的方向监听器()；}@覆盖受保护的无效 onResume() {超级.onResume();//启用监听listener.enable();}@覆盖受保护的无效 onPause() {超级.onPause();//禁用监听listener.disable();}

我已经用一个虚拟的 Activity 复制了相同的行为，除了处理方向处理的逻辑之外没有任何逻辑.我通过按 Ctrl+F11 从 Android 2.2 模拟器启动方向切换有什么问题?

更新:实现 OrientationEventListener

私有类 OrientationListener 扩展 OrientationEventListener {公共方向L(){超级(getBaseContext())；}@覆盖公共无效onOrientationChanged(int方向){toString();}}

}

这只是模拟器中记录的错误.真实设备不会表现出这种双生命周期事件行为.不久前我遇到了同样的问题，但它在真实设备上消失了.

如果可以的话，我建议忽略这个问题，只测试一个方向的方向变化，直到你拿到一部实体手机.否则，您可以通过保持一个静态布尔值来跳过"第二组生命周期调用，以指示您已经完成了第一组.

有关详细信息，请参阅此问题报告.p>

I need to handle orientation changes in my Android application. For this purpose I decided to use OrientationEventListener convenience class. But his callback method is given somewhat strange behavior.

My application starts in the portrait mode and then eventually switches to the lanscape one. I have some custom code executing in the callback onOrientationChanged method that provides some additional UI handling logic - it has a few calls to findViewById. What is strange is that when switching back from landscape to portrait mode onOrientationChanged callback is called twice, and what's even worse - the second call is dealing with bad Context - findViewById method starts returning null. These calls are made right from the MainThread

    @Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    listener = new OrientationListener();
}

    @Override
protected void onResume() {     
    super.onResume();
    // enabling listening
    listener.enable();
}
    @Override
protected void onPause() {
    super.onPause();
    // disabling listening
    listener.disable();
}

I've replicated the same behavior with a dummy Activity without any logic except for one that deals with orientation hadling. I initiate orientation switch from the Android 2.2 emulator by pressing Ctrl+F11 What could be wrong?

Upd: Inner class that implements OrientationEventListener

private class OrientationListener extends OrientationEventListener {
    public OrientationL() {
        super(getBaseContext());
    }

    @Override
    public void onOrientationChanged(int orientation) {

        toString();

    }
}

}

This is a documented bug in the emulator ONLY. A real device will not exhibit this double-lifecycle-events behavior. I had the same issue a while ago and it disappears on a real device.

I would suggest ignoring the problem if you can by only testing orientation changes in one direction until you get your hands on a physical phone. Otherwise you might be able to "skip" the second set of lifecycle calls by keeping a static boolean around indicating you've already gone through the first set.

See this issue report for more info.

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