In this example we create a stopwatch native-module which we use to create a cool stopwatch app.

The Stopwatch module

The Stopwatch class is used for the actual time measurement. It derives from NativeModule and defines four functions which we can call from JavaScript:

public class Stopwatch : NativeModule
	public Stopwatch()
		AddMember(new NativeFunction("Start", (NativeCallback)Start));
		AddMember(new NativeFunction("Stop", (NativeCallback)Stop));
		AddMember(new NativeFunction("Pause", (NativeCallback)Pause));
		AddMember(new NativeFunction("GetSeconds", (NativeCallback)GetSeconds));

	... implementation ...

By adding a Stopwatch instance to our UX and giving it a ux:Global name, we can control it from JavaScript using require('Stopwatch'):

<Stopwatch ux:Global="Stopwatch"/>
var Stopwatch = require("Stopwatch");

A trigger to go along

We also create a few triggers to go along with our Stopwatch component, so that we can animate our UX in response to time passing:

We define an abstract class in Uno code called StopwatchTrigger. It inherits from Trigger and implements the general functionality we need for each of the more specific triggers.

public abstract class StopwatchTrigger : Trigger
	Stopwatch _stopwatch;
	public Stopwatch Stopwatch
		get { return _stopwatch; }
			if (_stopwatch != null)
				_stopwatch.Ticked -= Tick;
			_stopwatch = value;
			_stopwatch.Ticked += Tick;

	void Tick()
		var time = Math.Mod(Time(), 1.0) * _factor;
		if (IsRooted)

	double _factor = 1.0;
	public double Factor { get { return _factor; } set { _factor = value; } }

	protected abstract double Time();

We can inherit from this class to make triggers which responds more specifically. In our case, we want a trigger which triggers on seconds passing:

public class Seconds : StopwatchTrigger
	protected override double Time()
		return Stopwatch.EllapsedSeconds;

We can then use this trigger in our UX to animate the watch face.

The watch face

The watch face is composed of four circles. The background is a circle with a SolidColor inside its Stroke. The foreground has an ImageFill with a gradient image for its Stroke. It also has a copy which is used for the tick animation. Lastly there is a small Circle which represents the clock hand.

<Circle Width="10" Height="10" Color="#fff">
    <Rotation ux:Name="trackerBall" Degrees="0" />
    <Translation Y="-0.487" RelativeTo="ParentSize" />
<Circle ux:Name="clock" StartAngleDegrees="0" EndAngleDegrees="0">
    <Rotation Degrees="-90" />
    <Stroke Width="6" Alignment="Inside" Offset="-1" LineCap="Round">
        <ImageFill File="gradient.png" WrapMode="ClampToEdge"/>
    <Stroke Width="6" Alignment="Inside" Offset="-1" Brush="#455493" />
<Circle ux:Name="tickCircle" Visibility="Hidden">
    <Stroke Width="6" Alignment="Inside" Offset="-1">
        <ImageFill File="gradient.png" WrapMode="ClampToEdge"/>
    <Scaling ux:Name="circleScale" />

We animate the EndAngleDegrees property of our “clock” Circle inside the Seconds trigger. The tick animation is triggered by using a Pulse animator.

<Timeline ux:Name="tickCircleAnimation">
    <Change Target="tickCircle.Visibility" Value="Visible" />
    <Change Target="tickCircle.Opacity" Value="0" Duration="0.5" Easing="QuadraticOut" DurationBack="0" />
    <Change Target="circleScale.Factor" Value="1.3" Duration="0.5" Easing="QuadraticOut" DurationBack="0" />

<Seconds Stopwatch="Stopwatch">
    <Change Target="clock.EndAngleDegrees" Value="360" Duration="1" />
    <Change Target="trackerBall.Degrees" Value="360" Duration="1" />
    <Pulse Target="tickCircleAnimation" />
  • Notice that we can access the global Stopwatch object we made in MainView.ux even though our Seconds trigger is inside the WatchFace.ux file.

Recording laps

We add laps to a an Observable whenever the user clicks the lap button while the stopwatch is running.

var laps = Observable();
var running = Observable(false);
var timeString = Observable("");
function addLapOrReset(){
    if (running.value){
        if (Stopwatch.GetSeconds() > 0)
            laps.insertAt(0, {
                title:("Lap " + (laps.length + 1)),
                time: timeString.value
    } else {

We use Adding-, Removing- and LayoutAnimation to move all the list elements as we add new items. Since we use laps.insertAt(0, item), we make sure new laps are always on the top of the list.

<StackPanel Margin="20,40">
    <Each Items="{laps}">
        <Panel Height="50" Clicked="{removeLap}" HitTestMode="LocalBoundsAndChildren">
                <FadeText Alignment="Center" FontSize="24" Color="#fff" Dock="Left" Value="{title}"/>
                <FadeText Alignment="Center" FontSize="24" Color="#fff" Dock="Right" Value="{time}"/>
            <Rectangle Color="#8FBFE8" Height="1" Alignment="Bottom"/>
                <Move Y="-1" RelativeTo="Size" Duration="0.3"/>
                <Move X="1.4" RelativeTo="ParentSize" Duration="0.3"/>
                <Move Y="1" RelativeTo="LayoutChange" Duration="0.3" Easing="CircularInOut"/>

That’s it!