Android中通过Fragment进行简单的页面切换

首先是activity中的布局

　　创建两个Fragment子类

这里以一个为例

package com.example.fragment;


import android.os.Bundle;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

public class f1 extends Fragment {



    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container,
                             @Nullable Bundle savedInstanceState) {
        return inflater.inflate(R.layout.f1_fragment2, container, false);
    }



}

　　其布局：

　　最后也是最重要的，Mainactivity内容：

package com.example.fragment;

import androidx.appcompat.app.AppCompatActivity;

import androidx.fragment.app.FragmentManager;



import androidx.fragment.app.FragmentTransaction;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;


public class MainActivity extends AppCompatActivity {
    private Button b1=null;
    private Button b2=null;
   private  FragmentManager fm=null ;
    private  FragmentTransaction transaction =null ;

    private f1 f1;
    private f2 f2;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        b1=(Button)findViewById(R.id.b1);
        b2=(Button)findViewById(R.id.b2);
       fm = getSupportFragmentManager();


    setDefaultFragment();
    b1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            transaction = fm.beginTransaction();
            f1=new f1();
            transaction.replace(R.id.fragment,f1);
            transaction.commit();
        }
    });
    b2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            transaction = fm.beginTransaction();
            f2=new f2();
            transaction.replace(R.id.fragment,f2);
            transaction.commit();
        }
    });
    }

    private void setDefaultFragment()
    {
        transaction = fm.beginTransaction();
        f1=new f1();
        transaction.replace(R.id.fragment,f1);
        transaction.commit();
    }



}

　　注意：每个FragmentTransaction只能提交一次，因此在每次提交前都要重新为transaction赋予一个新对象；

还有关于“fm = getSupportFragmentManager();”处使用“getSupportFragmentManager();”，而不使用“fm = getFragmentManager();”的原因请参照这篇帖子https://blog.csdn.net/qq_28484355/article/details/67824228

效果：

 

 点击“2”后：