Android Studio Changing TextView using a Button

Issue

I want to change the text in message when the button is clicked to "Hello World!".The idea would be that it would use a method inorder to change the text from a blank TextView into one that has writing on.

activity_main.xml

<?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">

    <TextView
        android:id="@+id/message"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello World!"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="sendMessage"
        android:text="Button"
        tools:layout_editor_absoluteX="158dp"
        tools:layout_editor_absoluteY="282dp" />

</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity.java

package com.example.clickmeapp;

import androidx.appcompat.app.AppCompatActivity;

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

import java.util.Set;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    public void sendMessage(View message){
        message.text="Hello World!";
    }
}

Any help in solving this issue would be amazing.

Solution

In my code, when you click the button, you will see the "Hello World!" text.

xml

<TextView
        android:id="@+id/message"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

Java

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

        //Button Click
        findViewById(R.id.button).setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View view) {

               //Set TextView
               setMessage("Hello World!");

           }
         });

   }

   public void setMessage(String message){
       findViewById(R.id.message).setText(message);
   }

Answered By - SiamSaleh