In this tutorial we will learn about how to implement a button, how to set onClick listener for button,show a toast when button is clicked and their example .

Android provides another supporting widget , i.e. android.widget.Button which is used to click to perform an action or event . Button is an user interface i.e. the user can tap to perform an event/action .

Button provides the onClick() method which is used if button get clicked it will listen and call the method or perform an action.

1. Create a New Project :

Lets we start with a new project in Android Studio from File New Project ⇒
select Empty Activity and go through it.

2. Implement button in android xml layout :

Add Button to your XML Layout file i.e. activity_main.xml to implement clickListener to display it for better user experience or just add the following code to activity_main.xml file .

    <Button
        android:background="@android:color/holo_red_light"
        android:id="@+id/btn"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:layout_centerInParent="true"
        android:text="Button" />

activity_main.xml :

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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">

    <Button
        android:background="@android:color/holo_red_light"
        android:id="@+id/btn"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:layout_centerInParent="true"
        android:text="Button" />


</RelativeLayout>

3. Implement onClickListener of Button :

Now set onClickListener of Button to perform an action or event, like toast message in MainActivity.java file .

btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
            Toast.makeText(MainActivity.this,"Hello world",Toast.LENGTH_SHORT).show();

            }
        });

MainActivity.java :

package net.technxt;

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    Button btn;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        btn = findViewById(R.id.btn);

        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
            Toast.makeText(MainActivity.this,"Hello world",Toast.LENGTH_SHORT).show();

            }
        });

    }   
}

Now run the project/app in android device or any Emulator to add button in android app.

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