Button and Button.OnClickListener

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:orientation="vertical"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  >
<TextView
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:text="@string/hello"
  />
<Button
  android:id="@+id/button"
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:text="- I'm a Button -"
  />
</LinearLayout>

package com.android.coding.HelloWorld;

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

public class HelloWorld extends Activity {
  /** Called when the activity is first created. */
  @Override
  public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.main);
    
      Button button = (Button)findViewById(R.id.button);
      button.setOnClickListener(new Button.OnClickListener(){

   @Override
   public void onClick(View v) {
    // TODO Auto-generated method stub
    Toast.makeText(HelloWorld.this, "I'm a Toast!", Toast.LENGTH_LONG).show();
   }});
  }
}