程序起来之后，按下home键，发现程序并不会进入onSaveInstanceState函数

package com.example.duany.state;

import android.os.PersistableBundle;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;

import java.text.SimpleDateFormat;
import java.util.Date;

public class MainActivity extends AppCompatActivity {

   private long createTime;
   private static final String TAG = "MainActivity-vv";
   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);
       createTime=System.currentTimeMillis();
       String formatTime=new SimpleDateFormat("yyyy-MM-dd hh:mm:ss").format(new Date(createTime));
       TextView tvCreateTime=(TextView)findViewById(R.id.tvCreateTime);
       tvCreateTime.setText(formatTime);

       Log.d(TAG, "onCreate: "+this);
   }

   @Override
   protected void onDestroy() {
       super.onDestroy();
       Log.d(TAG, "onDestroy: "+this);
   }

   @Override
   public void onSaveInstanceState(Bundle outState, PersistableBundle outPersistentState) {
       super.onSaveInstanceState(outState, outPersistentState);
       Log.d(TAG, "onSaveInstanceState() called with: "+"outState=["+outState+"]");
   }

   @Override
   protected void onRestoreInstanceState(Bundle savedInstanceState) {
       super.onRestoreInstanceState(savedInstanceState);
       Log.d(TAG, "onRestoreInstanceState() called with: "+"savedInstanceState=["+savedInstanceState+"]");

   }
}