将多个侦听器附加到 android 中的视图？

Question

Is it possible to attach multiple onClick listeners to buttons in android? Example:

btn1.setOnClickListener(listener1);
btn1.setOnCliclListener(listener2);

And when the button is clicked onClick event of both listener1 and listener2 are triggered?

In normal GUI applications I know that we can attach more than one event handler for an event. Is it possible for android too or is there any restrictions?

Regards, Lalith

Answer 1

Android only supports one registered listener in general. However, you can easily create a listener that simply forwards the events to other listeners using the composite pattern.

Answer 2

Should someone bump into a similar problem, try this out:

private void setClickListeners(View view, List<View.OnClickListener> clickListeners){
    view.setOnClickListener(v -> {
        for(View.OnClickListener listener: clickListeners){
            listener.onClick(v);
        }
    });
}

Answer 3

An easy way to achieve this would be simply do:

btn1.setOnClickListener(new View.OnClickListener(){
 @Override
 public void onClick(View v) {  
   listener1.onClick(v);
   listener2.onClick(v);
}})

Or call listener2.onClick(v) inside the definition of your listener1

Answer 4

This is what I'll do in Kotlin:

arrayListOf(
        view1,
        view2,
        view3
    ).forEach { it.setOnClickListener { /*do stuff here*/ } }

very readable, and copy-paste error safe.

Answer 5

public void onClick(View v) {
    if(v.getId() == R.id.button1) {
        // do this
    }else if(v.getId() == R.id.button2) {
        // do that
    }
}

Answer 6

Nope, for example just do this :

Set Listener:

btn.setOnClickListener(this);

Implement Method:

public void Onclick(View arg0){

   // check your id and do what you want
}