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Introduction
In this day and age, it is critical to know on which platform your application is run. Today, I will show you how to check if your application is running on a touchable device.
Detecting Touch
There are a few ways to detect touch events in your non-UWP applications. Non-UWP applications are not Universal apps. UWP has its own ways and means of identifying which devices your applications are run on. I am talking about ordinary Windows applications here. I will demonstrate two methods of detecting a touchscreen in your program.
With both methods that I will show you today, one Windows API is involved. This API is named GetSystemMetrics. The GetSystemMetrics API function retrieves various system metrics (widths and heights of Windows display elements) and system configuration settings. System metrics are the dimensions (widths and heights) of Windows display elements. All dimensions retrieved by GetSystemMetrics are in pixels.
Our Project
Design your project as per Figure 1.
Figure 1: Our Design
Add the GetSystemMetrics API with its associated Constants:
Public Declare Auto Function GetSystemMetrics Lib _
"user32.dll" (ByVal smIndex As Integer) As Integer
Const SM_MAXIMUMTOUCHES As Integer = 95
Const SM_DIGITIZER As Integer = 94
Const NID_READY As Integer = 128
SM_MAXIMUMTOUCHES returns the maximum number of contacts supported by each digitizer in the system. If the system has only single-touch digitizers, the return value will be 1. If the system has multi-touch digitizers, the return value is the number of simultaneous contacts the hardware can provide.
The SM_DIGITIZER setting specifies the type of digitizers that are installed on a device. NID_READY identifies if the device is ready to receive digitizer input.
Add the two functions that check if you have a touch-enabled screen:
Public Function TouchScreen1() As Boolean
Dim intTouch As Integer
intTouch = GetSystemMetrics(SM_MAXIMUMTOUCHES)
Return intTouch > 0
End Function
Private Function TouchScreen2() As Boolean
Return GetSystemMetrics(SM_DIGITIZER) And NID_READY
End Function
The TouchScreen1 Function returns the number of touch-enabled devices. The TouchScreen2 function returns true or false, depending on whether or not your device is touch-enabled.
The following code creates an onscreen keyboard. I decided to include it in this project because touchscreens are quite common in kiosks. Add the CreateKeyboard sub:
Private Sub CreateKeyBoard()
Dim btnAlpha As Button
Dim intLeft As Integer = 10
Dim intTop As Integer = 60
For i As Integer = Asc("A") To Asc("Z")
' The following code creates the alphabetic '
' keypad, as shown in Figure 2 '
btnAlpha = New Button
With btnAlpha
.Name = "btnAlpha_" & Chr(i)
.Text = "&" & Chr(i)
.Size = New Size(25, 25)
.Location = New Point(intLeft, intTop)
.Tag = Chr(i)
intLeft = intLeft + 20
If Chr(i) = "M" Then
intTop = intTop + 30
intLeft = 10
End If
.Visible = True
End With
Me.Controls.Add(btnAlpha)
Next
Dim btnNum As Button
intLeft = 10
intTop = 60
For j As Integer = 0 To 9
' The following code creates the numeric '
' keypad, as shown in Figure 3 '
btnNum = New Button
With btnNum
.Name = "btnNum_" & j
.Text = "&" & j
.Size = New Size(25, 25)
.Location = New Point(intLeft, intTop)
.Tag = j
intLeft = intLeft + 20
.Visible = True
End With
Me.Controls.Add(btnNum)
Next
End Sub
Figure 2: Letters
Figure 3: Numbers
First, I created a new button object named btnAlpha. This button or buttons will be placed on the form and will hold all the letters of the alphabet. Next, I created two objects to hold the first button’s location (in pixels), and later on I will manipulate the left and top objects to put the buttons next to each other. I then made use of a with structure to set the dynamic button’s Name, Text, Size, Location, and Tag properties inside the For loop.
When the character M is reached, the characters must continue under the previous 13 buttons. I then set the Visible property to true, added the dynamic button to the form, and created an event handler for when the particular button is clicked. Lastly, I added the number buttons. I won’t go into too many details here because I have written a more complete and more advanced Onscreen keyboard, which you are welcome to look at.
Add the last event:
Private Sub Form1_Load(sender As Object, _
e As EventArgs) Handles Me.Load
If TouchScreen1() Then
CreateKeyBoard()
End If
If TouchScreen2() Then
CreateKeyBoard()
End If
End Sub
You do not have to run both tests. The preceding code in the Form_Load event is just an example of the implementation of both methods.
Download the Code
Below this article, you’ll find a link to download the code that accompanies this article. Please feel free to use it.
Conclusion
Detecting touchscreens is an important trick to know, especially today, when there are so many different Windows Operating Systems and devices.
