/**
 * Called to retrieve per-instance state from an activity before being killed
 * so that the state can be restored in {@link #onCreate} or
 * {@link #onRestoreInstanceState} (the {@link Bundle} populated by this method
 * will be passed to both).
 *
 * <p>This method is called before an activity may be killed so that when it
 * comes back some time in the future it can restore its state.  For example,
 * if activity B is launched in front of activity A, and at some point activity
 * A is killed to reclaim resources, activity A will have a chance to save the
 * current state of its user interface via this method so that when the user
 * returns to activity A, the state of the user interface can be restored
 * via {@link #onCreate} or {@link #onRestoreInstanceState}.
 *
 * <p>Do not confuse this method with activity lifecycle callbacks such as
 * {@link #onPause}, which is always called when an activity is being placed
 * in the background or on its way to destruction, or {@link #onStop} which
 * is called before destruction.  One example of when {@link #onPause} and
 * {@link #onStop} is called and not this method is when a user navigates back
 * from activity B to activity A: there is no need to call {@link #onSaveInstanceState}
 * on B because that particular instance will never be restored, so the
 * system avoids calling it.  An example when {@link #onPause} is called and
 * not {@link #onSaveInstanceState} is when activity B is launched in front of activity A:
 * the system may avoid calling {@link #onSaveInstanceState} on activity A if it isn't
 * killed during the lifetime of B since the state of the user interface of
 * A will stay intact.
 *
 * <p>The default implementation takes care of most of the UI per-instance
 * state for you by calling {@link android.view.View#onSaveInstanceState()} on each
 * view in the hierarchy that has an id, and by saving the id of the currently
 * focused view (all of which is restored by the default implementation of
 * {@link #onRestoreInstanceState}).  If you override this method to save additional
 * information not captured by each individual view, you will likely want to
 * call through to the default implementation, otherwise be prepared to save
 * all of the state of each view yourself.
 *
 * <p>If called, this method will occur before {@link #onStop}.  There are
 * no guarantees about whether it will occur before or after {@link #onPause}.
 *
 * @param outState Bundle in which to place your saved state.
 *
 * @see #onCreate
 * @see #onRestoreInstanceState
 * @see #onPause
 */
protected void onSaveInstanceState(Bundle outState) {
    outState.putBundle(WINDOW_HIERARCHY_TAG, mWindow.saveHierarchyState());
    Parcelable p = mFragments.saveAllState();
    if (p != null) {
        outState.putParcelable(FRAGMENTS_TAG, p);
    }
    getApplication().dispatchActivitySaveInstanceState(this, outState);
}

/**
    * This is the same as {@link #onSaveInstanceState} but is called for activities
    * created with the attribute {@link android.R.attr#persistableMode} set to
    * <code>persistAcrossReboots</code>. The {@link android.os.PersistableBundle} passed
    * in will be saved and presented in {@link #onCreate(Bundle, PersistableBundle)}
    * the first time that this activity is restarted following the next device reboot.
    *
    * @param outState Bundle in which to place your saved state.
    * @param outPersistentState State which will be saved across reboots.
    *
    * @see #onSaveInstanceState(Bundle)
    * @see #onCreate
    * @see #onRestoreInstanceState(Bundle, PersistableBundle)
    * @see #onPause
    */
   public void onSaveInstanceState(Bundle outState, PersistableBundle outPersistentState) {
       onSaveInstanceState(outState);
   }

也就是重载两个参数的方法

Paste_Image.png

只有这么设置的时候才会调用，

在开发中由于代码提示直接复写两个参数的方法，状态未保存，跟踪进去发现原来是重写方法的不正确，坑爹

1、PersistableBundle outPersistentState 保存的数据，关机开机还是有的，当然需要设置android:persistableMode="persistAcrossReboots"
2、Bundle outState 应用关闭就没了