想要写一个fragment，但是为什么写不出来啊？请问这里为什么显示不出来啊？详解必采纳

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
<FrameLayout
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:id="@+id/list"
    android:name="com.example.studytest06.ListFragment1"
    android:layout_weight="1"/>
    <FrameLayout
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:name="com.example.studytest06.DetailFragment"
        android:id="@+id/detail"
        android:layout_weight="1"/>
LinearLayout>

package com.example.studytest06;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

public class DetailFragment extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_detail_fragment);
    }
}

package com.example.studytest06;

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

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

public class ListFragment1 extends AppCompatActivity {
//    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
//        View view = inflater.inflate(R.layout.fragment_list, container, false);
//        return view;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_list_fragment1);
    }
    }

package com.example.studytest06;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageView;

public class MainActivity extends Activity {

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if(requestCode==0x11&&requestCode==0x11){
            Bundle bundle=data.getExtras();
            int imageId=bundle.getInt("imageId");
            ImageView imageView=findViewById(R.id.touxiang);
            imageView.setImageResource(imageId);
        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main1);
}
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".DetailFragment">
   <TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Detail Fragment"
    android:textSize="30sp"/>
LinearLayout>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".ListFragment1">
<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="ListView Fragment"
    android:textSize="30sp"/>
LinearLayout>

请问这里为什么显示不出来啊？详解必采纳。我想要的效果图：

1：首先你要写一个fragment，你想在一个MainActivity 的布局里显示由ListFragment1和DetailFragment两个模块组成的界面，那首先这两个得是Fragment类,继承Fragment或者他的子类
2：其次在MainActivity 的布局里得用<fragment来加载这个些Fragment
具体代码如下，记得运行就可看到效果了

public class DetailFragment extends Fragment {
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        //加载布局
        return inflater.inflate(R.layout.activity_detail_fragment, container, false);
    }
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".DetailFragment">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Detail Fragment"
        android:textSize="30sp" />
</LinearLayout>

public class ListFragment1  extends Fragment {
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        //加载布局
        return inflater.inflate(R.layout.activity_list_fragment1, container, false);
    }
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".ListFragment1">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="ListView Fragment"
        android:textSize="30sp"/>
</LinearLayout>

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal">

    <fragment
        android:id="@+id/list"
        android:name="com.snxun.gzgynm.myapplication.ListFragment1"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1"
        tools:ignore="Instantiatable" />

    <fragment
        android:id="@+id/detail"
        android:name="com.snxun.gzgynm.myapplication.DetailFragment"
        android:layout_width="0dp"
        android:layout_height="match_parent"
        android:layout_weight="1" />

</LinearLayout>