android.widget.Switch – on/off event listener?

Switch inherits CompoundButton‘s attributes, so I would recommend the OnCheckedChangeListener

mySwitch.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
    public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
        // do something, the isChecked will be
        // true if the switch is in the On position
    }
});