WORKING WITH BUTTON

activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/LinearLayout1"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">


    <Button
        android:id="@+id/clickButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_marginTop="50dp"
        android:text="Click Me"
        android:textSize="20dp" />

</LinearLayout>

MainActivity.java

package com.blogspot.kantapp.workingwithbutton;

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

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends Activity implements OnClickListener {

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


        Button clickBtn = (Button)findViewById(R.id.clickButton);

        clickBtn.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        Toast.makeText(getApplicationContext(), "button is working", Toast.LENGTH_LONG).show();
    }



}