learn how to set a clicklistener on a button in android

As we want to perform an event of click listener on a button so first of all you should declare a widget of button in your xml file such as
name as ist_activity

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

<RelativeLayout

 xmlns:android="http://schemas.android.com/apk/res/android"

 xmlns:tools="http://schemas.android.com/tools"

 android:id="@+id/ist_activity"

 android:layout_width="match_parent"

 android:layout_height="match_parent"

 android:paddingBottom="@dimen/activity_vertical_margin"

 android:paddingLeft="@dimen/activity_horizontal_margin"

android:paddingRight="@dimen/activity_horizontal_margin"

android:paddingTop="@dimen/activity_vertical_margin"

tools:context="com.stck.fun.contactsofvipsIstActivity">
    <Button 

  android:layout_width="wrap_content"

  android:layout_height="wrap_content"

  android:id="@+id/btn1"
 android:text="Hello World!" 

/>
</RelativeLayout>

then you should go to your java file.and your java file should be like this

named as IstJava

package com.stck.fun.contactsofvips;

import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;

public class IstActivityextends AppCompatActivity  {

    Button btn1;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.ist_activity);
        btn1=(Button) findViewById(R.id.btn1);

    btn1.setOnClickListener(new View.onClickListener){

   pulic void onClick(View v)

{

////perform your desired work

});

}

}

Should Mention tour activity name in android studio's xml file

mine is following

<?xml version="1.0" encoding="utf-8"?><manifest 
xmlns:android="http://schemas.android.com/apk/res/android"
package="contctsofvips.fun.stack.com.myapp">
    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".IstActivity">
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
   </intent-filter>
        </activity>
    </application>

</manifest>

How To Place A button Inside a Android Studio Project

My XML File is following
named as activity_asad_xml

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

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:id="@+id/activity_asad__class"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:paddingBottom="@dimen/activity_vertical_margin"

    android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    tools:context="com.example.asad.se.Asad_Class">
    <Button

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:text="Hello World!"

        android:id="@+id/btn"
        />
</RelativeLayout>

My Java File is following

named as Asad_Class

package com.example.asad.se;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.Button;

public class Asad_Class extends AppCompatActivity {
    Button btn1;

    @Override    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_asad__class);
        btn1=(Button) findViewById(R.id.btn);
        
    }
}


My Manifest File Is Following





<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.asad.se">
    <application   
     android:allowBackup="true"  
      android:icon="@mipmap/ic_launcher" 
       android:label="@string/app_name"
        android:supportsRtl="true"   
        android:theme="@style/AppTheme">
        <activity android:name=".Asad_Class">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

This is the simple android application for the declaration of a button.

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How To Make My First Android Project

Open Your Android Studio .You have Following View  
                                                             

                                                     

After This Click On Start A new Android Studio Project Then You Have Follwing View

After This Write Your Application Name such As mt application And then Click Go to Next

 

Press Next

Then Write Your Activities Names Which shoud be customized according to you will

Then Creating project ang gradle build remain cool and calm hust wait

And Here Is YOUR jAVA file name MainActivity

Your Xml FILE IS like THAT

After THIS rUN YOU PROJECT .hELLO WORLD WILL be the FIRST OUTPUT