Android Button click 事件监听

[code]public class MainActivity extends Activity implements
        android.view.View.OnClickListener {

    private Button button1, button2, button3;

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

        button1 = (Button) findViewById(R.id.button1);
        button2 = (Button) findViewById(R.id.button2);
        button3 = (Button) findViewById(R.id.button3);

        button1.setOnClickListener(this);
        button2.setOnClickListener(this);
        button3.setOnClickListener(this);
    }

    public void onClick(View v) {

        switch (v.getId()) {

        case R.id.button1:
            System.out.println("button1");
            break;

        case R.id.button2:
            System.out.println("button2");
            break;

        case R.id.button3:
            System.out.println("button3");
            break;
        }
    }

}