MATLAB COM Builder

Creating The Visual Basic Form

The next step in the integration process develops a user interface for your add-in using the Visual Basic Editor. Follow the steps outlined here to create a new user form and populate it with the necessary controls:

1. Right-click on the VBAProject item in the project window and select Insert->UserForm from the pop-up menu.
2. A new form appears under Forms in the VBA Project. In the form's property page, set the name property to frmFourier and the Caption property to Spectral Analysis.

   

Figure 4-6: Creating the Visual Basic Form

3. Now add a series of controls to the blank form to complete the dialog, as summarized in the following table.
   
   

   Control Type	Control Name	Properties	Purpose
   Frame	Frame1	Caption = Input Data	Groups all input controls.
   Label	Label1	Caption = Input Data:	Labels the RefEdit for input data.
   RefEdit	refedtInput		Selects range for input data.
   Label	Label2	Caption = Sampling Interval	Labels the TextBox for sampling interval.
   CheckBox	chkPlot	Caption = Plot time domain Signal and Power Spectral Density	Plots input data and power spectral density.
   Frame	Frame2	Caption = Output Data	Groups all output controls.
   Label	Label3	Caption = Frequency:	Labels the RefEdit for frequency output.
   RefEdit	refedtFreq		Selects output range for frequency points.
   Label	Label4	Caption = FFT - Real Part:	Labels the RefEdit for real part of FFT.
   RefEdit	refedtReal		Selects output range for real part of FFT of input data.
   Label	Label5	Caption = FFT - Imaginary Part:	Labels the RefEdit for imaginary part of FFT.
   RefEdit	refedtImag		Selects output range for imaginary part of FFT of input data.
   Label	Label6	Caption = Power Spectral Density	Labels the RefEdit for power spectral density.
   RefEdit	refedtPowSpect		Selects output range for power spectral density of input data.
   CommandButton	btnOK	Caption = OK Default = True	Executes the function and dismisses the dialog
   CommandButton	btnCancel	Caption = Cancel Cancel = True	Dismisses the dialog without executing the function.

Figure 4-7, Layout of Controls on Main Form, shows the controls layout on the form.

Figure 4-7: Layout of Controls on Main Form

When the form and controls are complete, right-click on the form and select View Code from the pop-up menu. The following code listing shows the code to implement. Note that this code references the control and variable names listed above. If you have given different names for any of the controls or any global variable, change this code to reflect those differences.

• '
  'frmFourier Event handlers
  '
  Private Sub UserForm_Activate()
  'UserForm Activate event handler. This function gets called before
  'showing the form, and initializes all controls with values stored
  'in global variables.
      On Error GoTo Handle_Error
      If theFourier Is Nothing Or theFFTData Is Nothing Then Exit Sub
      'Initialize controls with current state
      If Not InputData Is Nothing Then
          refedtInput.Text = InputData.Address
      End If
      edtSample.Text = Format(Interval)
      If Not Frequency Is Nothing Then
          refedtFreq.Text = Frequency.Address
      End If
      If Not IsEmpty (theFFTData.Real) Then
      If IsObject(theFFTData.Real) And TypeOf theFFTData.Real Is Range Then
              refedtReal.Text = theFFTData.Real.Address
          End If
      End If
      If Not IsEmpty (theFFTData.Imag) Then
      If IsObject(theFFTData.Imag) And TypeOf theFFTData.Imag Is Range Then
              refedtImag.Text = theFFTData.Imag.Address
          End If
      End If
      If Not PowerSpect Is Nothing Then
          refedtPowSpect.Text = PowerSpect.Address
      End If
      chkPlot.Value = bPlot
      Exit Sub
  Handle_Error:
      MsgBox (Err.Description)
  End Sub
  
  Private Sub btnCancel_Click()
  'Cancel button click event handler. Exits form without computing fft
  'or updating variables.
      Unload Me
  End Sub
  Private Sub btnOK_Click()
  'OK button click event handler. Updates state of all variables from controls
  'and executes the computefft or plotfft method.
      Dim R As Range
      
      If theFourier Is Nothing Or theFFTData Is Nothing Then GoTo Exit_Form
      On Error Resume Next
      'Process inputs
      Set R = Range(refedtInput.Text)
      If Err <> 0 Then
          MsgBox ("Invalid range entered for Input Data")
          Exit Sub
      End If
      Set InputData = R
      Interval = CDbl(edtSample.Text)
      If Err <> 0 Or Interval <= 0 Then
          MsgBox ("Sampling interval must be greater than zero")
          Exit Sub
      End If
      'Process Outputs
      Set R = Range(refedtFreq.Text)
      If Err = 0 Then
          Set Frequency = R
      End If
      Set R = Range(refedtReal.Text)
      If Err = 0 Then
          theFFTData.Real = R
      End If
      Set R = Range(refedtImag.Text)
      If Err = 0 Then
          theFFTData.Imag = R
      End If
      Set R = Range(refedtPowSpect.Text)
      If Err = 0 Then
          Set PowerSpect = R
      End If
      bPlot = chkPlot.Value
      'Compute the fft and optionally plot power spectral density
      If bPlot Then
          Call theFourier.plotfft(3, theFFTData, Frequency, PowerSpect,_ 
  InputData, Interval)
      Else
          Call theFourier.computefft(3, theFFTData, Frequency, PowerSpect,_ 
  InputData, Interval)
      End If
      GoTo Exit_Form
  Handle_Error:
      MsgBox (Err.Description)
  Exit_Form:
      Unload Me
  End Sub
  

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