Android learning part 5 - Button click many ways

 JAVA Part : 

package first.learn.buttonclick;

import androidx.appcompat.app.AppCompatActivity;

import android.graphics.Color;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity implements View.OnClickListener  {

    Button btnOne, btnThree ;
    TextView tvOne ;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        btnOne = (Button) findViewById(R.id.btnOne);
        btnThree = (Button)findViewById(R.id.btnThree);

        btnOne.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                setTextOnTextView("This is Button One");
            }
        });

        tvOne = (TextView) findViewById(R.id.tvOne);

        Button btnTwo = (Button) findViewById(R.id.btnTwo);
        btnTwo.setOnClickListener(this);
        btnThree.setOnClickListener(this);



        Button btnFour = (Button) findViewById(R.id.btnFour);
        btnFour.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                setTextOnTextView("This is Button Four");
                changeColorOfButtonOne();
            }
        });


    }


    void  changeColorOfButtonOne (){
        btnOne.setTextColor(Color.RED);
    }

    void setTextOnTextView ( String text ){

        tvOne.setText(text);

        btnOne.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                btnOne.setTextColor(Color.WHITE);
                setTextOnTextView("This is Button One");
            }
        });

    }


    @Override
    public void onClick(View v) {

        int id = v.getId();

               if(id == R.id.btnTwo){
                   setTextOnTextView( "this is Clicked Button Two ");
               }

               if (id == R.id.btnThree){
                   setTextOnTextView("This is Button Three");
               }



    }

    public void btnFiveClick(View view) {
        setTextOnTextView ("Button Five Click");
    }
}

XML part : 

<?xml version="1.0" encoding="utf-8"?>
<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=".MainActivity"
    android:orientation="vertical">

    <TextView
        android:id="@+id/tvOne"
        android:layout_margin="20dp"
        android:textSize="25dp"
        android:textColor="@color/purple_700"
        android:gravity="center"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        />

    <Button
        android:id="@+id/btnOne"
        android:layout_margin="20dp"
        android:text="Button One"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>


    <Button
        android:id="@+id/btnTwo"
        android:layout_margin="20dp"
        android:text="Button Two"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>


    <Button
        android:id="@+id/btnThree"
        android:layout_margin="20dp"
        android:text="Button Three"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>



    <Button
        android:id="@+id/btnFour"
        android:layout_margin="20dp"
        android:text="Button Four"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>



    <Button
        android:id="@+id/btnFive"
        android:layout_margin="20dp"
        android:text="Button Five"
        android:onClick="btnFiveClick"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

</LinearLayout>