Step 4: Add Code
The Main() subroutine is called when the application is started, so we'll look at that first. As you can see from the following listing, this is standard Visual Basic code. AppForge supplies its own set of database access routines, all of which begin with PDB...().
Sub Main()
Dim txtCustomer As String
Load frmCustomer
If (OpenCustomerDatabase = True) Then
'Database was successfully opened.
'
'Populate the list box and show the form.
PDBMoveFirst dbCustomer
While Not (PDBEOF(dbCustomer) = True)
PDBGetField dbCustomer, tCustomerDatabaseFields.Name_Field, txtCustomer
frmCustomer.lbCustomers.AddItem txtCustomer
PDBMoveNext dbCustomer
Wend
frmCustomer.lbCustomers.ListIndex = 0
frmCustomer.Show
Else
'Unable To Open Database
frmCustomer.Hide
frmError.Show
End If
End Sub
The OpenCustomerDatabase() call was prebuilt by the conversion utility and is included in modCustomerDB.bas. The PDBMoveFirst() function jumps to the first record in the database; the PDBMoveNext() steps through the database one record at a time. We use the PDBGetField method to retrieve a specific field from a retrieved record. This field, tCustomerDatabaseFields.Name_Field, represents the customer's name and is added to the lbCustomers list box on the frmCustomer form (see Figure 3).
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The frmCustomer form at runtime.
Selecting OK from frmCustomer causes the customer selected in the lbCustomers list box to be loaded into the frmCustomerDetail form text boxes (see Figure 4).
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The frmCustomerDetail form at runtime.
The code that handles this button-click event is as follows:
Private Sub btnSelect_Click()
Dim Selection As String
Dim custRec As tCustomerRecord
Selection = lbCustomers.List(lbCustomers.ListIndex)
PDBMoveFirst dbCustomer
While Not (PDBEOF(dbCustomer) = True)
ReadCustomerRecord custRec
If (custRec.Name = Selection) Then
frmCustomerDetail.txtCustomerName.Text = custRec.Name
frmCustomerDetail.txtCustomerCompany.Text = custRec.Company
frmCustomerDetail.txtCustomerEMail.Text = custRec.EMail
frmCustomerDetail.txtCustomerAddress.Text = custRec.Address
frmCustomerDetail.txtCustomerCity.Text = custRec.City
frmCustomerDetail.txtCustomerState.Text = custRec.State
frmCustomerDetail.txtCustomerSalesRep.Text = custRec.SalesRep
Me.Hide
frmCustomerDetail.Show
Exit Sub
Else
PDBMoveNext dbCustomer
End If
Wend
'If we make it to this point, the record wasn't found!
Me.Hide
frmError.Show
End Sub
Selecting the Back button in frmCustomerDetail executes the following standard VB code:
Private Sub btnDetailBack_Click()
Me.Hide
frmCustomer.Show
End Sub
The AppForge Booster is the runtime "virtual machine" that's installed on the PalmOS, allowing our VB app to run unmodified. The Booster is freely distributable and can be downloaded from http://www.appforge.com.