[android] android.widget.Switch - on/off event listener?

I would like to implement a switch button, android.widget.Switch (available from API v.14).

<Switch
    android:id="@+id/switch1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Switch" />

But I'm not sure how to add an event listener for the button. Should it be an "onClick" listener? And how would I know if it is toggled "on" or not?

My solution, using a SwitchCompat and Kotlin. In my situation, i needed to react to a change only if the user triggered it through the UI. In fact, my switch reacts to a LiveData, and this made both setOnClickListener and setOnCheckedChangeListener unusable. setOnClickListener in fact reacts correctly to user interaction, but it's not triggered if the user drags the thumb across the switch. setOnCheckedChangeListener on the other end is triggered also if the switch is toggled programmatically (for example by an observer). Now in my case the switch was present on two fragments, and so onRestoreInstanceState would trigger in some cases the switch with an old value overwriting the correct value.

So, i looked at the code of SwitchCompat, and was able to mimic it's behaviour successfully in distinguishing click and drag and used that to build a custom touchlistener that works as it should. Here we go:

/**
 * This function calls the lambda function passed with the right value of isChecked
 * when the switch is tapped with single click isChecked is relative to the current position so we pass !isChecked
 * when the switch is dragged instead, the position of the thumb centre where the user leaves the
 * thumb is compared to the middle of the switch, and we assume that left means false, right means true
 * (there is no rtl or vertical switch management)
 * The behaviour is extrapolated from the SwitchCompat source code
 */
class SwitchCompatTouchListener(private val v: SwitchCompat, private val lambda: (Boolean)->Unit) :  View.OnTouchListener {
    companion object {
        private const val TOUCH_MODE_IDLE = 0
        private const val TOUCH_MODE_DOWN = 1
        private const val TOUCH_MODE_DRAGGING = 2
    }

    private val vc = ViewConfiguration.get(v.context)
    private val mScaledTouchSlop = vc.scaledTouchSlop
    private var mTouchMode = 0
    private var mTouchX = 0f
    private var mTouchY = 0f

    /**
     * @return true if (x, y) is within the target area of the switch thumb
     * x,y and rect are in view coordinates, 0,0 is top left of the view
     */
    private fun hitThumb(x: Float, y: Float): Boolean {
        val rect = v.thumbDrawable.bounds
        return x >= rect.left && x <= rect.right && y >= rect.top && y <= rect.bottom
    }

    override fun onTouch(view: View, event: MotionEvent): Boolean {
        if (view == v) {
            when (MotionEventCompat.getActionMasked(event)) {
                MotionEvent.ACTION_DOWN -> {
                    val x = event.x
                    val y = event.y
                    if (v.isEnabled && hitThumb(x, y)) {
                        mTouchMode = TOUCH_MODE_DOWN;
                        mTouchX = x;
                        mTouchY = y;
                    }
                }
                MotionEvent.ACTION_MOVE -> {
                    val x = event.x
                    val y = event.y
                    if (mTouchMode == TOUCH_MODE_DOWN &&
                        (abs(x - mTouchX) > mScaledTouchSlop || abs(y - mTouchY) > mScaledTouchSlop)
                    )
                        mTouchMode = TOUCH_MODE_DRAGGING;
                }
                MotionEvent.ACTION_UP,
                MotionEvent.ACTION_CANCEL -> {
                    if (mTouchMode == TOUCH_MODE_DRAGGING) {
                        val r = v.thumbDrawable.bounds
                        if (r.left + r.right < v.width) lambda(false)
                        else lambda(true)
                    } else lambda(!v.isChecked)
                    mTouchMode = TOUCH_MODE_IDLE;
                }
            }
        }
        return v.onTouchEvent(event)
    }
}

How to use it:

the actual touch listener that accepts a lambda with the code to execute:

myswitch.setOnTouchListener(
    SwitchCompatTouchListener(myswitch) {
        // here goes all the code for your callback, in my case
        // i called a service which, when successful, in turn would 
        // update my liveData 
        viewModel.sendCommandToMyService(it) 
    }
)

For the sake of completeness, this is how the observer for the state switchstate (if you have it) looked like:

switchstate.observe(this, Observer {
    myswitch.isChecked = it
})

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.

In Kotlin:

        switch_button.setOnCheckedChangeListener { buttonView, isChecked ->
        if (isChecked) {
            // The switch enabled
            text_view.text = "Switch on"

        } else {
            // The switch disabled
            text_view.text = "Switch off"

        }
    }

there are two ways,

1. using xml onclick view Add Switch in XML as below:

   <Switch
   android:id="@+id/switch1"
   android:onClick="toggle"/>
   

In YourActivity Class (For E.g MainActivity.java)

    Switch toggle; //outside oncreate
    toggle =(Switch) findViewById(R.id.switch1); // inside oncreate

    public void toggle(View view) //outside oncreate
    {
        if( toggle.isChecked() ){
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                start.setBackgroundColor(getColor(R.color.gold));
                stop.setBackgroundColor(getColor(R.color.white));
            }
        }
        else
        {
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                stop.setBackgroundColor(getColor(R.color.gold));
                start.setBackgroundColor(getColor(R.color.white));
            }
        }
    }

2. using on click listener

Add Switch in XML as below:

In YourActivity Class (For E.g MainActivity.java)

    Switch toggle; // outside oncreate
    toggle =(Switch) findViewById(R.id.switch1);  // inside oncreate


    toggle.setOnClickListener(new View.OnClickListener() {   // inside oncreate
        @Override
        public void onClick(View view) {

            if( toggle.isChecked() ){
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                    start.setBackgroundColor(getColor(R.color.gold));
                }
            }
            else
            {
                if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
                    stop.setBackgroundColor(getColor(R.color.gold));
                }
            }

        }

    });

You can use DataBinding and ViewModel for Switch Checked Change event

<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools">

    <data>

        <variable
                name="viewModel"
                type="com.example.ui.ViewModel" />
    </data>
    <Switch
            android:id="@+id/on_off_switch"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:onCheckedChanged="@{(button, on) -> viewModel.onCheckedChange(on)}"
     />

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
        }
    }
   *****
}

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);
}       

});

The layout for Switch widget is something like this.

<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical">
    <Switch
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginRight="20dp"
        android:gravity="right"
        android:text="All"
        android:textStyle="bold"
        android:textColor="@color/black"
        android:textSize="20dp"
        android:id="@+id/list_toggle" />
</LinearLayout>

In the Activity class, you can code by two ways. Depends on the use you can code.

First Way

public class ActivityClass extends Activity implements CompoundButton.OnCheckedChangeListener {
Switch list_toggle;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.return_vehicle);

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

public void onCheckedChanged(CompoundButton buttonView,boolean isChecked) {
    if(isChecked) {
        list_toggle.setText("Only Today's");  //To change the text near to switch
        Log.d("You are :", "Checked");
    }
    else {
        list_toggle.setText("All List");   //To change the text near to switch
        Log.d("You are :", " Not Checked");
    }
}

Second way

public class ActivityClass extends Activity {
Switch list_toggle;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.return_vehicle);

    list_toggle=(Switch)findViewById(R.id.list_toggle);
    list_toggle.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
       @Override
       public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
          if(isChecked) {
             list_toggle.setText("Only Today's");  //To change the text near to switch
             Log.d("You are :", "Checked");
          }
          else {
             list_toggle.setText("All List");  //To change the text near to switch
             Log.d("You are :", " Not Checked");
          }
       }       
     });
   }
}

September 2020 - Programmatically Answer

You can do it with programmatically for Switch Widget and Material Design:

Switch yourSwitchButton = findViewById(R.id.switch_id);

yourSwitchButton.setChecked(true); // true is open, false is close.

yourSwitchButton.setOnCheckedChangeListener((compoundButton, b) -> {
        if (b){
          //open job.
        }  
        else  {
          //close job.
        }
    });

@canerkaseler