Android中用onSaveInstanceState保存Fragment状态的方法

易采站长站为您分析Android中用onSaveInstanceState保存Fragment状态的方法,onSaveInstanceState可以将数据保存在Fragment或Activity中,需要的朋友可以参考下  

在Fragment里面，利用onSaveInstanceState保存数据，并可在onActivityCreated里面恢复数据。

public void onActivityCreated(Bundle savedInstanceState) {
  super.onActivityCreated(savedInstanceState);
  ...
  if (savedInstanceState != null) {
    // Restore the fragment's state here
  }
}

public void onSaveInstanceState(Bundle outState) {
  super.onSaveInstanceState(outState);
  // Save the fragment's state here
}

在Activity里面，利用onSaveInstanceState保存Fragment实例的数据，并可在onCreate里面恢复数据：

private Fragment myFragment;

public void onCreate(Bundle savedInstanceState) {
  ...
  if (savedInstanceState == null) {
    // Instantiate fragment
  } else {
    // Restore the fragment's instance
    myFragment = getSupportFragmentManager().getFragment(
          savedInstanceState, "fragment");
  }
  ...
}

@Override
protected void onSaveInstanceState(Bundle outState) {
  super.onSaveInstanceState(outState);
  //Save the fragment's instance
  // fragment instance may be null
  if (myFragment != null) {
    getSupportFragmentManager().putFragment(outState, "fragment", myFragment);
  }
}

实例
首先看一个步骤,如果是人为关闭Activity或者Fragment, 比如点击了后退键,主动关闭当前页面,就会走 onPause() --> onStop()  --> onDestroy()  而onSaveInstanceState() 并不会被调用. onSaveInstanceState() 只有在系统即将要自动清理销毁Activity或Fragment前才会调用, 比如

1, 由于重力感应 手机从竖屏变为横屏,

2, 手机点击Home键和长按Home键

3, 点击电源键锁屏时

4, 从当前Activity跳到另一个Activity