Question

I don’t understand why I have to implement the OnClickListener to use the OnClick-method. Assuming this code:

public class KlickitestActivity extends Activity implements OnClickListener {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
}

@Override
public void onClick(View v) {
    // code what happens when a click is made
}

From the class OnClickListener I only use the method onClick(View v) – and this one is overwritten. Why can’t I just define the onClick-method without implementing the OnClickListener?

Answer 1

You can. You can do that by using an Anonymous Inner Class :

Button1.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View view) {
           //Do stuff
        }});
Button2.setOnClickListener(new OnClickListener() {
        @Override
        public void onClick(View view) {
           //Do stuff
        }});

However implementing an OnClickListener makes it easier to handle events, and improves code readability. i.e You can use one Listener method, and passing a View to handle multiple buttons/listeners with a switch statement, something similar to :

public void onClick(View view){
    switch(view.getId()){

    case R.id.Button1:
        //Stuff for button 1
        break;

    case R.id.Button2:
        //Stuff for button 2
        break;
        break;

   case R.id.Button3:
        //Stuff for button 3
        break;
    }