1, Method and steps of static registration of fragment

1. Create a static fragment.java file to inherit fragment class and a static_fragment.xml file to complete fragment layout. Overloading oncreateview in StaticFragment.java ( )Method by calling inflate. Inflate ( )Method and pass in the layout resource ID to generate the view resource of fragment, bind the relevant components in static_fragment.xml and implement its functions. The implementation code is as follows:
static_fragment.xml

<?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"
    tools:context=".StaticFragment"
    android:orientation="vertical">
    <Button
        android:id="@+id/btn_fm"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="This is fragment Static registration"
        android:textAllCaps="false">
        
    </Button>
    <EditText
        android:id="@+id/et_fm"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:hint="Please enter what you want to change:">
        
    </EditText>
</LinearLayout>

StaticFragment.java:

package com.example.myapplication;


import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;

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


public class StaticFragment extends Fragment {
    private Button mBtnFm;
    private EditText mEtFm;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater,
                             @Nullable ViewGroup container,
                             @Nullable Bundle savedInstanceState) {

        //The view resource of fragment is directly through the call to inflate. Inflate ( )Method and passed in the generated by the layout resource ID.
        View v = inflater.inflate(R.layout.static_fragment,
                                  container,false);

        mEtFm = v.findViewById(R.id.et_fm);
        mBtnFm = v.findViewById(R.id.btn_fm);

        mBtnFm.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mBtnFm.setText(mEtFm.getText().toString());
            }
        });

        return v;
    }
}

2. Bind the fragment layout file in the main layout activity main.xml file. The implementation code is as follows:
activity_main.xml

<?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"
    tools:context=".MainActivity"
    android:orientation="vertical">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="This is the main layout"
        android:textColor="@color/colorAccent"
        android:textSize="30sp">

    </TextView>
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Below is fragment Layout"
        android:textColor="@color/colorPrimaryDark"
        android:textSize="30sp">

    </TextView>
    <fragment
        android:id="@+id/static_fm"
        android:name="com.example.myapplication.StaticFragment"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

    </fragment>
</LinearLayout>

Note: add the fragment node to the layout file, and the name attribute must fill in the complete path
MainActivity.java

package com.example.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;

public class MainActivity extends AppCompatActivity {

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

Demonstration:

2, Methods and steps of dynamic registration and creation of fragment

1. Create a new project, create two Fragment inheritance classes MyFragment1.java and MyFragment2.java, and then create two layout files fragment1.xml and fragment2.xml. The detailed code is as follows:
fragment1.xml:

<?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"
    tools:context=".MyFragment1"
    android:gravity="center"
    android:background="@color/colorPrimaryDark">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:gravity="center"
        android:text="@string/hello_blank_fragment"
        android:textSize="30sp"
        android:textAllCaps="false"
        android:textColor="#F70505">

    </TextView>

</LinearLayout>

MyFragment1.java:

package com.example.myapplication;

import android.content.Context;
import android.net.Uri;
import android.os.Bundle;

import androidx.fragment.app.Fragment;

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

public class MyFragment1 extends Fragment {


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment1, container, false);
    }
}

fragment2.xml:

<?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"
    tools:context=".MyFragment2"
    android:gravity="center"
    android:background="@color/colorAccent">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:gravity="center"
        android:text="@string/hello_blank_fragment"
        android:textSize="30sp"
        android:textAllCaps="false"
        android:textColor="#03FAE3">

    </TextView>

</LinearLayout>

MyFragment2.java:

package com.example.myapplication;


import android.os.Bundle;

import androidx.fragment.app.Fragment;

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

public class MyFragment2 extends Fragment {



    @Override
    public View onCreateView(LayoutInflater inflater,
                             ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment2, container, false);
    }

}

The above code is not much different from static creation.
2. Adding fragment to activity in the form of code requires calling fragment manager directly in activity.

FragmentManager fm = getSupportFragmentManager();

Then through the code block:

FragmentTransaction ts = fm.beginTransaction();
Fragment mfg1 = new MyFragment1();
ts.add(R.id.fragment_container,mfg1);
ts.commit();

Commit a fragment transaction. Its core is ts.add( Method.
The detailed code is as follows:
activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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=".MainActivity">
    <LinearLayout
        android:id="@+id/linear"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center"
        android:layout_alignParentBottom="true">
        <Button
            android:id="@+id/btn_dy1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="fragment1"
            android:textColor="@color/colorAccent"
            android:textSize="30sp">

        </Button>
        <Button
            android:id="@+id/btn_dy2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="fragment2"
            android:textColor="@color/colorPrimaryDark"
            android:textSize="30sp">

        </Button>
    </LinearLayout>
    <FrameLayout
        android:id="@+id/fragment_container"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

    </FrameLayout>

</RelativeLayout>

Note: generally, the FrameLayout layout is used to carry the fragment module
MainActivity.java

package com.example.myapplication;

import androidx.appcompat.app.AppCompatActivity;
import androidx.fragment.app.Fragment;
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 implements View.OnClickListener {
    private Button mBtnDy1;
    private Button mBtnDy2;
    FragmentManager fm;
    Fragment mfg1;
    Fragment mfg2;

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

        fm = getSupportFragmentManager();

        mBtnDy1 = findViewById(R.id.btn_dy1);
        mBtnDy2 = findViewById(R.id.btn_dy2);

        mBtnDy1.setOnClickListener(this);
        mBtnDy2.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        clearSelection();//Clear button status
        FragmentTransaction ts = fm.beginTransaction();
        hideFragments(ts);

        switch (v.getId()){
            case R.id.btn_dy1:
                mBtnDy1.setBackgroundColor(0xff0000ff);
                if(mfg1 == null){
                    mfg1 = new MyFragment1();
                    ts.add(R.id.fragment_container,mfg1);
                }else {
                    ts.show(mfg1);
                }
                break;

            case R.id.btn_dy2:
                mBtnDy2.setBackgroundColor(0xff0000ff);
                if(mfg2 == null){
                    mfg2 = new MyFragment2();
                    ts.add(R.id.fragment_container,mfg2);
                }else {
                    ts.show(mfg2);
                }
                break;

                default:
                    break;
        }

        ts.commit();
    }

//    Hide all fragments.
    private void hideFragments(FragmentTransaction transaction) {
        if (mfg1 != null) {
            transaction.hide(mfg1);
        }
        if (mfg2 != null) {
            transaction.hide(mfg2);
        }

    }

//     Clear all selected states.
    private void clearSelection() {
        mBtnDy1.setBackgroundColor(0xffffffff);
        mBtnDy2.setBackgroundColor(0xffffffff);
    }

}

Demonstration: