Fragment内存回收后重叠及恢复数据问题

从源码角度分析，为什么会发生Fragment重叠？

package com.mine.fragmentdemo;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.TextView;

import static com.mine.fragmentdemo.FragmentFactory.F1;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
   

    private TextView tv1;
    private TextView tv2;
    private TextView tv3;
    private FragmentManager mFragmentManager;
    private Fragment mFragment1;
    private Fragment mFragment2;
    private Fragment mFragment3;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv1 = (TextView) findViewById(R.id.tv1);
        tv2 = (TextView) findViewById(R.id.tv2);
        tv3 = (TextView) findViewById(R.id.tv3);
        tv1.setOnClickListener(this);
        tv2.setOnClickListener(this);
        tv3.setOnClickListener(this);
        /*
        * Fragment重叠原因一
        * 1.Activity横竖屏切换(或者后台的Activity由于内存不足,被回收),导致Activity重走生命周期
        * 2.但是FragmentManager会保存之前的Fragment,当页面恢复时,会把这些Fragment都显示出来
        * 3.此时,在Activity的onCreate里面你再次new Fragment时并且add了一次,会导致Fragment的重叠
        * 4.解决方法是第一次时直接new，第二次页面恢复后&#x