Background

Here we go with our first small CSC 101 application in Xamarin.

Outline

1. addControls
   • instantiate Button Object
   • If in manual mode
     • Add event handler for Button Click
   • Instantiate StackLayout
     • Add Button
2. OnButtonClick
   • handle buttonclick event
     • call triggerNextState
3. triggerNextState
   • Call Device.BeginInvokeOnMainThread
     • Have next method be processed on main thread
4. reflectState
   • Update Button Text
   • Base next procession based on whether manual or automated
     • Enable Button
     • Update Button Background Color
5. initializeData
   • Instantiate each trafficLightState
   • Add trafficLightState object to collection list
6. initializeTimer
   • Instantiate timer
   • instantiate Time Event Handler
7. Process Timer Event
   • call triggerNextState

Code

Add Controls

 void addControls()
{

	btnTL = new Button
	{

		  Text = btnLTText + " " + strMode
		, HorizontalOptions = LayoutOptions.StartAndExpand

	};

	if (bManualOrAutomated == false)
	{
		btnTL.Clicked += OnButtonClicked_btnTL;

	}

	// Assemble the page.
	this.Content = new StackLayout
	{

		Children =
		{
			new StackLayout
			{

				  // Stack Orientation
				  Orientation = StackOrientation.Horizontal

				  // Add Children
				, Children =
				{
					btnTL
				}

			 } // Stack Layout
		} // Children

	}; // Assemble the page.

} // addControls() 

OnButtonClicked_btnTL

void OnButtonClicked_btnTL(object sender, EventArgs args)
{

	Button button = (Button)sender;

	if (button == btnTL)
	{

		triggerNextState();

	}

}

triggerNextState

void triggerNextState()
{

	//prepare for next transition
	iTrafficLightStateCurrent = iTrafficLightStateCurrent + 1;

	try
	{
		Device.BeginInvokeOnMainThread
			(
				() =>
				{
					reflectState();
				}
			);
	}
	catch (Exception)
	{

	}

}

reflectState

void reflectState()
{

	try
	{

		//reset display
		//btnTL.Text = btnLTText;
		btnTL.Text = btnLTText + " " + strMode;

		if (dtSignalTime != null)
		{
			btnTL.Text += " ("
							+ dtSignalTime.ToLongTimeString().TrimStart()
							+ " )"
							;
		}

		btnTL.IsEnabled = (bManualOrAutomated == false);

		//reset marker if at end of line
		if (
				(iTrafficLightStateCurrent > iTrafficLightStatesCountZeroBased)
		   )
		{
			iTrafficLightStateCurrent = 0;
		}

		// get object at current node
		objTLSCurrent = objTLS[iTrafficLightStateCurrent];

		// if valid object
		if (objTLSCurrent != null)
		{

			//set background color
			btnTL.BackgroundColor = objTLSCurrent.color;

		}

	}
	catch (Exception ex)
	{

		//show exception
		btnTL.Text = ex.Message;

		//reset counter
		iTrafficLightStateCurrent = 0;

	}
}

initializeData

void initializeData()
{

	tlStateRed = new trafficLightState();
	tlStateRed.color = Color.Red;
	objTLS.Add(tlStateRed);

	tlStateGreen = new trafficLightState();
	tlStateGreen.color = Color.Green;
	objTLS.Add(tlStateGreen);

	tlStateYellow = new trafficLightState();
	tlStateYellow.color = Color.Yellow;
	objTLS.Add(tlStateYellow);

	// Get Number of Elements
	iTrafficLightStatesCount = objTLS.Count;

	// Get Number of Elements ( 0 Based )
	iTrafficLightStatesCountZeroBased = objTLS.Count - 1;

	// Set Current at 0
	iTrafficLightStateCurrent = 0;

}

initializeTimer

void initializeTimer(Boolean bTimer)
{

	if (bTimer)
	{

		// Create a timer with a two second interval.
		objTimer = new System.Timers.Timer(lSecondsInThousands);

		// Hook up the Elapsed event for the timer.
		objTimer.Elapsed += OnTimedEvent;

	}
	else
	{

		if (objTimer != null)
		{

			//unsubscribe
			objTimer.Elapsed -= OnTimedEvent;

			objTimer = null;

		}

	}

	if (objTimer != null)
	{

		objTimer.AutoReset = bTimer;

		objTimer.Enabled = bTimer;

	}

}

OnTimedEvent

private void OnTimedEvent(Object source, ElapsedEventArgs e)
{

    dtSignalTime = e.SignalTime;

    triggerNextState();

}

Source Code Control

GitHub

VS Studio Xamarin Traffic Light
Link

References

1. Microsoft
   • Microsoft | Docs
     • Docs / .NET / .NET API Browser / Xamarin.Forms / Device / Methods / BeginInvokeOnMainThread
       Link