浅析回退栈

一、Fragment回退栈

Activity切换时，相信大家都知道是通过栈的形式，不断压栈出栈，在Fragment的时候，如果你不是手动开启回退栈，它是直接销毁再重建，但如果将Fragment任务添加到回退栈，情况就会不一样了，它就有了类似Activity的栈管理方式。

二、代码：

主类代码：

package com.example.day13_new;

import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.FrameLayout;
import android.widget.RelativeLayout;

public class Activity_newday13 extends AppCompatActivity {
    Button jump;
    Button dia;
    FragmentManager manager;
    FrameLayout r1;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_newday13);

        jump = findViewById(R.id.jump);
        r1 = findViewById(R.id.r1);
        dia = findViewById(R.id.dialog);
        jump.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                jumpTo();
            }
        });
        dia.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                dialogShow();
            }
        });
    }



    public void jumpTo(){
        manager = getSupportFragmentManager();
        FragmentTransaction transaction = manager.beginTransaction();
        transaction.add(R.id.r1,new SecondFragment());
        transaction.addToBackStack("fragment1");//添加到栈中
        transaction.commit();//事件提交

    }

    public void dialogShow(){
        SecondFragment_2 fragment2 = new SecondFragment_2();
        fragment2.show(getSupportFragmentManager(),"sss");

    }

}

定义的Fragment的代码：

package com.example.day13_new;

import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v4.app.ListFragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ListView;

public class SecondFragment extends ListFragment {


    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        return inflater.inflate(R.layout.jump_one,container,false);
    }

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setListAdapter(new ArrayAdapter<String>(getActivity(),R.layout.support_simple_spinner_dropdown_item,new String[]{"北京","天津","上海"}));
    }

    @Override
    public void onListItemClick(ListView l, View v, int position, long id) {
        super.onListItemClick(l, v, position, id);

    }
}