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
    }
});

Use the following snippet to add a Switch to your layout via XML:

<Switch
     android:id="@+id/on_off_switch"
     android:layout_width="wrap_content"
     android:layout_height="wrap_content"
     android:textOff="OFF"
     android:textOn="ON"/>

Then in your Activity's onCreate method, get a reference to your Switch and set its OnCheckedChangeListener:

Switch onOffSwitch = (Switch)  findViewById(R.id.on_off_switch); 
onOffSwitch.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {

@Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
    Log.v("Switch State=", ""+isChecked);
}       

});

Define your XML layout:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.neoecosystem.samplex.SwitchActivity">

    <Switch
        android:id="@+id/myswitch"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content" />

</RelativeLayout> 

Then create an Activity

public class SwitchActivity extends ActionBarActivity implements CompoundButton.OnCheckedChangeListener {

    Switch mySwitch = null;


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


        mySwitch = (Switch) findViewById(R.id.myswitch);
        mySwitch.setOnCheckedChangeListener(this);
    }

    @Override
    public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
        if (isChecked) {
            // do something when check is selected
        } else {
            //do something when unchecked
        }
    }

    ****
}

======== For below API 14 use SwitchCompat =========

XML

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.neoecosystem.samplex.SwitchActivity">

    <android.support.v7.widget.SwitchCompat
        android:id="@+id/myswitch"
        android:layout_height="wrap_content"
        android:layout_width="wrap_content" />

</RelativeLayout>

Activity

public class SwitchActivity extends ActionBarActivity implements CompoundButton.OnCheckedChangeListener {

    SwitchCompat mySwitch = null;


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


        mySwitch = (SwitchCompat) findViewById(R.id.myswitch);
        mySwitch.setOnCheckedChangeListener(this);
    }

    @Override
    public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
        if (isChecked) {
            // do something when checked is selected
        } else {
            //do something when unchecked
        }
    }
   *****
}

For those using Kotlin, you can set a listener for a switch (in this case having the ID mySwitch) as follows:

    mySwitch.setOnCheckedChangeListener { _, isChecked ->
         // do whatever you need to do when the switch is toggled here
    }

isChecked is true if the switch is currently checked (ON), and false otherwise.