java keydown事件_keydown 事件响应处理

java.lang.IllegalStateException: Can not perform this action after onSaveInstanceStateat android.app.Activity.onBackPressed(Activity.java:2066)

at android.app.Activity.onKeyDown(Activity.java:1962)

at android.view.KeyEvent.dispatch(KeyEvent.java:2482)

at android.app.Activity.dispatchKeyEvent(Activity.java:2274)

at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1668)

at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1112)

at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1112)

at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1112)

at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1112)

at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1112)

at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1112)

at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchKeyEvent(PhoneWindow.java:1720)

at com.android.internal.policy.impl.PhoneWindow.superDispatchKeyEvent(PhoneWindow.java:1258)

at android.app.Activity.dispatchKeyEvent(Activity.java:2269)

at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1668)

at android.view.ViewRoot.deliverKeyEventPostIme(ViewRoot.java:2851)

at android.view.ViewRoot.handleFinishedEvent(ViewRoot.java:2824)

at android.view.ViewRoot.handleMessage(ViewRoot.java:2011)

at android.os.Handler.dispatchMessage(Handler.java:99)

其说明keydown 事件不能在onSaveInstanceState之后执行。

1. 为什么按键消息会在onSaveInstanceState之后执行

2. 为什么按钮响应消息不能在onSaveInstanceState之后执行，那其应该在哪个方法之后才能执行

１.　A –>Ｂ

２.　b  pres back key

3.   b 响应了 onkeydown 而之前 A是响应onKeyUp

–> 导致 b 在响应onkeydown之后，就没有响应onKeyUp了，系统就从下就keyup发送到其他activity, 而A就响应了keyup消息，但A应该是在onresum之后才响应onKeyup消息才是合理了。

改法：

A响应keydown消息

说明：