Android的onSaveInstanceState和onRestoreInstanceState用法
很多不明白Activity类中包含的onSaveInstanceState和onRestoreInstanceState有什么用，首先声明下使用这两方法时一定要注意情况和了解Activity的生命周期，否则有的时候 onSaveInstanceState和onRestoreInstanceState
可能不会被触发，虽然他们都是Activity的重写方法。
他们比较常用到的地方是 Sensor、Land和Port布局的自动切换，过去Android开发网曾经说过解决横屏和竖屏切换带来的数据被置空或者说onCreate被重复调用问题，其实Android提供的onSaveInstanceState方法可以保存当前的窗口状态在即将布局切换前或当前Activity被推入历史栈，其实布局切换也调用过onPause所以被推入Activity的history stack，如果我们的Activity在后台没有因为运行内存吃紧被清理，则切换回时会触发onRestoreInstanceState方法。这两个方法中参数均为Bundle，可以存放类似 SharedPreferences 的数据，所以使用它们作为当前窗口的状态保存是比较合适的。实际使用代码
- @Override
- protectedvoidonSaveInstanceState(BundleoutState){
- outState.putString("lastPath","/sdcard/android123/cwj/test");
- }
- @Override
- publicvoidonRestoreInstanceState(BundlesavedInstanceState){
- super.onRestoreInstanceState(savedInstanceState);
- StringcwjString=savedInstanceState.getString("lastPath");
- }
publicvoidonSaveInstanceState(BundlesavedInstanceState){
savedInstanceState.putBoolean("MyBoolean",true);
savedInstanceState.putDouble("myDouble",1.9);
savedInstanceState.putInt("MyInt",1);
savedInstanceState.putString("MyString","WelcomebacktoAndroid");
//etc.
super.onSaveInstanceState(savedInstanceState);
}
@Override
publicvoidonRestoreInstanceState(BundlesavedInstanceState){
super.onRestoreInstanceState(savedInstanceState);
booleanmyBoolean=savedInstanceState.getBoolean("MyBoolean");
doublemyDouble=savedInstanceState.getDouble("myDouble");
intmyInt=savedInstanceState.getInt("MyInt");
StringmyString=savedInstanceState.getString("MyString");
}