Two-Fragments in Android Studio (Java) in one Activity

This Project has:

1- One activity (MainActivity) with two buttons (button , button2) and a fragment container (fragmentContainerView).

2- Two fragments (ChannelsFragment, PlayerFragment), both has nothing inside just they have a different background colors.

 MainActivity: Layout:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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=".MainActivity">


    <Button
        android:id="@+id/button"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:onClick="load_channels"
        android:text="Load Channels"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="@+id/fragmentContainerView" />

    <Button
        android:id="@+id/button2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="load_player"
        android:text="Load Player"
        app:layout_constraintBottom_toBottomOf="@+id/fragmentContainerView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent" />

    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/fragmentContainerView"
        android:name="mr.safwan.iptv.PlayerFragment"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

 MainActivity: Java:

package mr.safwan.iptv;

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;

public class MainActivity extends AppCompatActivity {
Fragment fragment_channels,fragment_player;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void load_channels(View view) {
        fragment_channels =new ChannelsFragment();
        FragmentManager pfm=getSupportFragmentManager();
        FragmentTransaction pft=pfm.beginTransaction();
        pft.replace(R.id.fragmentContainerView,fragment_channels);
        pft.commit();
    }

    public void load_player(View view) {
        fragment_player =new PlayerFragment();
        FragmentManager pfm=getSupportFragmentManager();
        FragmentTransaction pft=pfm.beginTransaction();
        pft.replace(R.id.fragmentContainerView,fragment_player);
        pft.commit();
    }
}

 PlayerFragment: Layout:

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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:background="@color/purple_700"
    tools:context=".PlayerFragment" />

 ChannelsFragment: Layout:

<FrameLayout 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:background="@color/teal_200"
    tools:context=".ChannelsFragment">


</FrameLayout>

Note: for the fragments activities: we leave them as they will be created without any changes.