How To Create Button In Android

Button in Android

In Android applications, a Button is a user interface that is used to perform some action when clicked or tapped. It is a very common widget in Android and developers often use it. This article demonstrates how to create a button in Android Studio.

The Class Hierarchy of the Button Class in Kotlin

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XML Attributes of Button Widget

XML Attributes	Description
android:id	Used to specify the id of the view.
android:text	Used to the display text of the button.
android:textColor	Used to the display color of the text.
android:textSize	Used to the display size of the text.
android:textStyle	Used to the display style of the text like Bold, Italic, etc.
android:textAllCaps	Used to display text in Capital letters.
android:background	Used to set the background of the view.
android:padding	Used to set the padding of the view.
android:visibility	Used to set the visibility of the view.
android:gravity	Used to specify the gravity of the view like center, top, bottom, etc

Example

In this example step by step demonstration of creating a Button will be covered. The application will consist of a button that displays a toast message when the user taps on it.

Note: Following steps are performed on Android Studio version 4.0

Step 1: Create a new project

Click on File, then New => New Project.
Choose "Empty Activity" for the project template.
Select language as Kotlin.
Select the minimum SDK as per your need.

Step 2: Modify the strings.xml file

Navigate to the strings.xml file under the "values" directory of the resource folder. This file will contain all strings that are used in the Application. Below is the appropriate code.

XML

< resources >

< string name = "app_name" >GfG | Button In Kotlin</ string >

< string name = "btn" >Button</ string >

< string name = "message" >Hello Geeks!! This is a Button.</ string >

</ resources >

Step 3: Modify the activity_main.xml file

Add a button widget in the layout of the activity. Below is the code of the activity_main.xml file which does the same.

XML

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

< androidx.constraintlayout.widget.ConstraintLayout

android:layout_width = "match_parent"

android:layout_height = "match_parent"

android:background = "#168BC34A"

tools:context = ".MainActivity" >

< Button

android:id = "@+id/button"

android:layout_width = "wrap_content"

android:layout_height = "wrap_content"

android:background = "#4CAF50"

android:paddingStart = "10dp"

android:paddingEnd = "10dp"

android:text = "@string/btn"

android:textColor = "@android:color/background_light"

android:textSize = "24sp"

app:layout_constraintBottom_toBottomOf = "parent"

app:layout_constraintEnd_toEndOf = "parent"

app:layout_constraintStart_toStartOf = "parent"

app:layout_constraintTop_toTopOf = "parent" />

</ androidx.constraintlayout.widget.ConstraintLayout >

Step 4: Accessing the button in the MainActivity file

Add functionality of button in the MainActivity file. Here describe the operation to display a Toast message when the user taps on the button. Below is the code to carry out this task.

Java

import androidx.appcompat.app.AppCompatActivity;

import android.content.Context;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

@Override

protected void onCreate( Bundle savedInstanceState ) {

super .onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

Button button = (Button)findViewById(R.id.button);

if (button != null ) {

button.setOnClickListener((View.OnClickListener)( new View.OnClickListener() {

public final void onClick(View it) {

Toast.makeText((Context)MainActivity. this , R.string.message, Toast.LENGTH_LONG).show();

}

}));

}

Kotlin

import androidx.appcompat.app.AppCompatActivity

import android.os.Bundle

import android.widget.Button

import android.widget.Toast

class MainActivity : AppCompatActivity() {

override fun onCreate(savedInstanceState: Bundle?) {

super .onCreate(savedInstanceState)

setContentView(R.layout.activity_main)

val button = findViewById<Button>(R.id.button)

button?.setOnClickListener()

{

Toast.makeText( this @MainActivity , R.string.message, Toast.LENGTH_LONG).show() }

}

Output: