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TAMING THE MICROSOFT LISTVIEW CONTROL

A free class that will take the hard work out of list views
If you've experimented with the ActiveX controls that come with Visual FoxPro, you've probably come across the Microsoft ListView. This versatile control provides an attractive way of displaying data in a list, and offers a worthwhile alternative to VFP's native listbox and grid controls.

But while the ListView has some useful features, it can be frustratingly difficult to program. Unlike with a VFP grid, you cannot bind it to a table simply by setting a property, and even such mundane tasks as specifying the column headers require several lines of code.


If you like the idea of having a ListView in your applications but have been put off by its complexity, take a look at my SimpleList control. As its name suggests, SimpleList takes the hard work out of using a ListView. It is essentially a wrapper for the ListView control, its aim being to provide a simple cursor-based method of populating a list. In fact, once you have a cursor in place, you only need three lines of code to make your list appear. (Note that SimpleList requires Visual FoxPro 7.0 or later.)

What exactly is a ListView?
To see a ListView in action, you need look no further than the right-hand pane in Windows Explorer. It is the ListView that provides the list of files and folders, with its familiar large icon, small icon, list and detail views. The ListView ActiveX control can provide that same kind of functionality in your own applications.

With typical databased applications, you'll probably only be interested in displaying your list in detail view (also knows as report view), as this provides the most intuitive way of viewing tabular data. However, the ListView does support the other three views as well. Figure 1 shows an example of detail view, while Figure 2 shows large icon view.


Figure 1: A ListView in detail view


Figure 2: The same list in large icon view

As well as providing four different views, the ListView control offers several other benefits:
- In detail view, the user can easily move and resize the columns.
- Also in detail view, the user can sort the data by clicking on a column header. Click once to sort to ascending sequence; click again to sort to descending sequence.
- Each item in the list can have an associated icon or graphic. This is pretty well essential in large icon and small icon views, but perhaps less useful in list and detail views (although icons are completely optional in all four views).
- You can add a checkbox to each item. This provides an easy way of letting the user make multiple selections from a list.
- In detail view, you can give each item its own tooltip. This is useful for displaying additional information that would otherwise be too wide for the list.
- You can let the user edit an item's text simply by clicking on it (in the way that you would rename a file in Windows Explorer).
- Various cosmetic settings can be applied. For example, you can choose to show grid lines in detail view, and you can opt to switch on 'hot tracking'.
- Drag-and-drop is supported. Users can drag an item from the list and drop it in another control or application.

Limitations
Although SimpleList supports most of the ListView's features, it does have some limitations:

- If you choose to use icons, you must use the same icon for a given item in all four views.
- In detail view, the user can resize the columns but cannot rearrange them.
- There are some event-trapping limitations. SimpleList lets you trap clicks, double-clicks and changes in the position of the highlight, but it cannot distinguish between left- and right-clicks.

Getting started
So now you know what SimpleList can and cannot do, your next step is to download a copy - see How to download SimpleList below.

SimpleList is completely free, and you are welcome to give copies to friends and colleagues. I ask only that you do not remove my copyright notices or disclaimers. I have tested SimpleList in many applications, but I make no guarantees that it will work in yours, so be sure to test it thoroughly before relying on the results.

In the rest of this article, I will give you an overview of SimpleList's features. My aim here is to give you a flavour of what the control can do. When you have download your copy, you will get a longer version of this article which gives full details of all these features.

In the rest of this article, I will give you an overview of SimpleList's features. My aim here is to give you a flavour of what the control can do. When you have download your copy, you will get a longer version of this article which gives full details of all these features.

The least you need to know
To put SimpleList to work, follow these steps:


- Create a cursor to hold the data that you want to display in the list (although I will use the term cursor throughout this article, it could just as well be a table or a view). As a minimum, the cursor must contain a single character field; it is the data from this field that will be used to populate the list.
- Drop the SimpleList on a form.
- To populate the list, write code similar to the following (this would typically go in the control's Init event):

WITH THIS 
	.cAlias = "Customer" 
	.cData = "Company" 
	.PopulateList 
ENDWITH 

That's all there is to it. Let's just recap the above properties and methods.

cAlias
The alias of the cursor (or table or view) that contains the data for the list. When you call PopulateList, the cursor must be open in the current data session.

cData
A comma-delimited list of the cursor fields that are to be used to populate the list. You need to specify at least one field, and this must be a character field. The contents of this field will show up in all four views.

You can optionally list more fields in the cData property. If you do, their contents will show up as separate columns in detail view, but they will be ignored in the other three views. These additional fields can be of any data type.

PopulateList
Call this method to populate the list with data from the cursor. Each time you call it, the list will revert to its default view, column widths, sort order, etc. If you want to retain these settings, call instead:

RefreshList
This will re-populate the list, but will retain the current view, column widths, sort order, etc. You should call this method if the underlying data changes after you have initially populated the list.

As another example, consider this cursor:


Company City Country Amount
------- ---- ------- ------
Alfreds Futterkiste Berlin Germany 6300
Ana Trujillo Emparedado.. México D.F.Mexico 3500
Antonio Moreno Taquería México D.F.Mexico 8500
Around the Horn London UK 17100
Blauer See Delikatessen Mannheim Germany 5000
Blondel père et fils Strasbourg France 22205
Bon app' Marseille France 27100
Bottom-Dollar Markets Tsawassen Canada 27800
B's Beverages London UK 11000
Centro comercial Moctez.. México D.F.Mexico 1000
Chop-suey Chinese Bern Switzer.. 17696
Ernst Handel Graz Austria 122900


The following code will produce the list shown in Figure 1 (but without the icons):

WITH THIS 
	.cAlias = "Customer" 
	.cData = "Company,City,Country,Amount" 
	.PopulateList 
ENDWITH

Full details of the features described in the remainder of this article can be found in the documentation accompanying SimpleList.

Choosing the view
By default, PopulateList displays the list in detail view. Use the nDefaultView property to specify a different initial view (0 = large icons, 1 = small icons, 2 = list, 3 = detail). Call ChangeView to subsequently switch to a different view (pass the required view number as a parameter).

Columns
By default, the columns headers in detail view will show the field names from the cursor. The columns will be left-aligned and will start out with equal widths. You can vary that behaviour in several way. You can provide different text to appear in the column headers; you can vary the initial widths of the columns and the alignment of the text within the columns; and you can choose to hide the column headers completely.

Icons
If you plan to display your list in large icon or small icon view, you will probably want to assign icons to the list items - after all, that is the whole point of those views. If you do assign icons, they will also show up in list and detail views. But it's your choice. If you are not interested in icons, you can ignore the issue.

SimpleList lets you specify a single icon to appear against each item in the list. Alternatively, you can specify a different icon for each item. To do that, you store the icon's filename in a field in the underlying cursor.

Tooltips
Each item in the list can have an optional tooltip containing the contents of any specified field in the underlying cursor. This is useful if you want to let the user see subsidiary information that would not otherwise fit in the list.

Sorting
In detail view, you can optionally allow the user to sort the list by clicking on a column header. You can also specify an initial sort order and direction for the list, where this is different from the order of the underlying cursor.

Checkboxes
If you have ever wanted to give your users a scrolling list of checkboxes, you will find this feature indispensable. Essentially, it lets you display a checkbox against each item in the list. This provides an intuitive way of making multiple selections, for example, to let the user choose the customers who are to appear in a report, or the reports that you want to send to a batch-printing process.
Going further, you can map the checkboxes to a logical field in the underlying cursor. The field will then be updated to reflect the current state of the checkbox.

Editing an item's text
By default, your list will be read-only. However, you can optionally give the user the ability to edit an item's text (in detail view, only the left-most column can be edited). You can further choose whether to write your own code to process the edits or to have SimpleList automatically update the corresponding field in the underlying cursor.

Drag and drop
SimpleList supports drag-and-drop. When enabled, this lets the user drag an item out of the list and drop it in any control or application that knows how to receive it. For example, you can drop the text of an item into a native Visual FoxPro textbox or a Word document.

SimpleList cannot itself act as a drop target. In other words, you can drag items from the list, but you cannot drag anything to it.

Cosmetic settings
You can modify the appearance and behaviour of your list in various ways. For example, you can decide whether grid lines should appear in detail view, and whether to enable 'hot tracking'.

Retrieving information
SimpleList provides a variety of ways of getting information about what's in the list and which item the user has selected. You can retrieve the text, index number or record number of the selected item; you can retrieve the text, record number or checkbox status of any item; and you can programmatically select an item. You can also opt to keep the underlying cursor in sync with the list (so that, when the user moves the highlight, the record pointer in the cursor will automatically move to the corresponding record).

Event Trapping
SimpleList lets you trap clicks, double-clicks and changes to the position of the highlight. However, it cannot distinguish between left- and right-clicks or between left- and right-double-clicks.

New features in Version 1.1
Here is a summary of the new features in SimpleList Version 1.1,, which I published in March 2003. These are all described in the SimpleList documentation.

- Ability to synchronise the cursor with the list.
- Ability to ensure that an item is visible without scrolling when it is programmatically selected.
- Option to raise a VFP error when SimpleList detects an invalid property setting.
- Mapping of checkboxes to a logical field in the cursor (this was previously documented but not implemented).
- Better support for editing an item's text.
- Updating of logical fields mapped to checkboxes.
- Drag-and-drop support.
- The Redraw method is no longer required when certain cosmetic properties are changed.
- Fixes to several minor problems and documentation errors.

How to download SimpleList
Click here to download SIMPLELIST.ZIP. This zip file contains a class library, which in turn contains the SimpleList control. It also contains a longer version of this article (in both HTML and text format); this constitutes the full documentation for the control. The total download size is 66 KB.

I hope you find SimpleList as useful in your applications as I do in mine. As always, I greatly welcome your feedback.

ABOUT THE AUTHOR: MIKE LEWIS

Mike Lewis Mike Lewis is a Visual FoxPro developer and trainer. His company, Mike Lewis Consultants Ltd., runs training courses at clients' sites throughout Europe and North America. Please visit his company's web site at www.ml-consult.co.uk for company and contact information.
© Copyright Mike Lewis Consultants Ltd.

FEEDBACK

jay @ 8/13/2013 2:15:55 PM
v good

Rumil Mendoza @ 2/13/2014 4:44:38 PM
Thanks

Mapasac @ 8/28/2015 11:45:55 PM
Hola

Luis Suescun @ 12/14/2015 8:36:01 PM
Excelent..



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