GEOG 490/590: GIS Programming

 

Lab3. Sorting & File I/O

 

Due Feb 11 before class.

 

Introduction:

 

Lab 3 has two parts. In the first part you will continue taking Modules 5 and 6 of the “Learning Visual Basic for Applications for New ArcGIS Developers” course on ESRI Virtual Campus. The second part of the exercise involve using the GxDialog ArcObjects coclass and the QuickSort subroutine to create a tool that sorts a list of numbers in an input file and write the result to an output file.

 

Make sure you put your lab data in a folder in the C:\Users folder and regularly back up your data to your H drive or portable device. Click here to down the files needed for the second part of the exercise. You will need to unzip the files after download.

 

The Lab3.zip file contains for files:

Notepad.gif

Openfile.gif

QSort.txt

Lab3_input.txt

 

 Now you can start your online course (http://training.esri.com). Make sure you experiment with the programming instructions in ArcMap while reading the online document.

 

Sorting Tool:

 

After finishing the online modules, you will design and develop a simple AP that allows a user to select an input file containing a list of random integer numbers and sort the list of numbers to an output ASCII file specified by the user. A sample layout of the UserForm of the AP is shown in Figure 1. The form should have:

l           two textboxes for showing the specified file paths and names,

l           two command buttons for selecting input and output files,

l           two command buttons for viewing the input and output files (Figure 2),

l           two radio buttons (aka, option buttons) for specifying sorting order (i.e., descending or ascending),

l           one command button to execute the sorting, and

l           one command button to end the AP.

 

Picture Command Buttons:

The command buttons for selecting and viewing the input and output files will use pictures on the button face. You need to prepare an image file (e.g., gif or jpg) and put the image file to the “Picture” property. Use the openfile.gif file as the picture for the file selection buttons. Use the notepad.gif file as the picture for the file viewing command buttons (Figure_2). You will need to set the “Caption” property of those command buttons to “” (i.e., empty strings) to remove the captions. All these steps can be done in VBA IDE, without writing any code.

 

Enabled and Visible Properties of Controls:

 It’s clear that a user cannot view the contents of a file before the file name has being selected. Also, only when both input and output files have being selected can the sorting tool does the sorting. We should use the Visible and Enabled properties of command button controls to guide the sequence of using the sorting tool. If you set the Visible (or Enabled) properties to “FALSE” in VBA IDE, then these controls are invisible (or disabled) when the program is executed. You can change the values of these properties during run-time as well. This can only be done through VB code, for example,

 

IF Len(Trim(txtInput.text)) > 0 THEN cmbViewInput.Visible = True

 

GxDialog coclass:

            Please refer to Week4’s lecture notes for sample code.

 

Option (Radio) Buttons:

You will provide the options of sorting ascendingly or descendingly in the sorting tool. This can be done through a set of option button. When the “Value” property of an option button is True, then the option button is checked (or, if you check an option button, then its Value property is set to True.) Only one option button can be checked in a group of option buttons. VB controls such a mechanism for you, so you don’t have to worry about setting the values of other option buttons when one is checked. If you have more than one option categories, then you should use a “Frame” control to group the option buttons into categories.

 

Shell Function:

You can use the Shell function to run an executable program. Please use the online help to see what the function’s return values are. You will write a VB procedure to view the input (or output) file using the notepad.exe program. Here is an example of how this is done:

 

Dim commandstr As String, ReturnCode

commandstr = “Notepad.exe ” & txtInput.text ‘note that there is a space after .exe

ReturnCode = Shell( commandstr, vbNormalFocus)

 

            vbNormalFocus is a constant that controls the behavior of window style so that, in this case, notepad window becomes the active window with a normal size.

 

Input, Outpur File Format and File I/O:

            The input (i.e., Lab3_input.txt) and output (whatever name you specify) are both in ASCII format. That means you can use notepad to see their contents. The input file has a list of random integer number, each separated by a newline character. The output should include a list of sorted numbers and their original line numbers in the input file, delimited by commas.

            If you plan to use dynamic arrays, which is preferred, be sure to count the number of lines in the input first. This can be done by using the EOF() function and a simple Do While loop. Here is an example:

           

            LineNo = 0

            Do While Not EOF(infile)

                        Input #infile, LineString

                        If Len(Trim(LineString)) > 0 Then LineNo = LineNo + 1

            Loop

           

            Close #infile

 

            ReDim inputArr( 1 to LineNo)

            ReDim LineNumberArr(1 to LineNo)

 

Please refer to the lecture notes on the functions to open, read, write, and close the files.

 

QuickSort Subroutine:

We will use the QuickSort algorithm that we talked about in the lecture to do the sorting. The Qsort.txt file contains the source code of the algorithm.

 

Public Sub QuickSort(keyarr() As Long, dataarr() As Long, _

Optional ByVal numEls As Variant, Optional ByVal descending As Variant)

 

            Keyarr() stores the numbers you want to sort. Dataarr() stores the numbers that are associated with the numbers in Keyarr. In this exercise, you will put the original line numbers in it, so when sorted, you still know the original line numbers of each input integer number. numEls indicates how many elements in the input arrays are sorted. In this exercise, we don’t provide any value for this argument so the subroutine sorts every element in the input arrays. Descending determines the sorting order. The default value is False, that is, the output numbers are sorted ascendingly. If you want to do descending sorting, then provide a True value to this argument. Here is an example of calling this subroutine:

 

            QuickSort InputArr, LineNumberArr, , optDescend.Value

 

Lab Deliverables:

 

Submit the documents listed below in a zipped file.

1.          In ESRI online module 5 – Using custom classes, you created a class called Airport. Please explain what its class diagram (Figure 3) means and describe how these properties and methods were implemented in the Airport class module.

2.          The pseudo-code of the sorting AP. (Note: You don’t need to write the pseudo-code for the quicksort subroutine.)

3.          Your mxd file that contains the following features:

1)      A UserForm of the Sorting Tool (see the instructions above for the spec of the tool).

2)      An ArcMap ToolBar called “Sorting Tools” containing a button that when clicked brings up the Sorting Tool UserForm.

3)      Make sure your code is properly commented.

4.          The output of your sorting tool. Please use the Lab3_input.txt as the input file. The output file should include the sorted integer numbers and their associated line numbers in the input file.

 

Location of your lab file(s):

Computer Name:                              File Path & Name:                                                      .