Features of an ObjectListView
Why should I learn to love the ListView?
Features of an ObjectListView¶
Why take the time to learn how to use an ObjectListView? What’s the benefit? The return on investment? This page tries to document the useful features of an ObjectListView. Not all features are equally useful, but it’s better to be aware of what’s available so that you can use it when the need arises.
- Alternate rows background colors
- Automatic grouping
- Automatic sorting
- Automatically create the ListView from model objects
- Buttons in cells
- Checkboxes in any column
- Cell events
- Collapsible groups
- Copy selected rows to clipboard
- Custom row and cell formatting
- Custom selection colours
- Data binding
- Different flavours of ObjectListView for different purposes
- Displays a “list is empty” message
- Drag and drop
- Ease of use
- Editing cell values
- Groups on virtual lists
- Header check boxes
- Header formatting
- Header images
- Header drawn vertically
- Header visible in all views
- Hierarchical checkboxes
- Hot item tracking
- In-place modifications of the list
- INotifyPropertyChanged support
- Model object level operations
- More control over column width
- Owner drawing
- Overlays and decorations
- Row height can be changed
- Save and restore state
- Searching on the sort column
- SelectionChanged event
- Selected Column
- Supports all ListView views
- Tool Tips
- User-selection of visible columns
Ease of use¶
The major goal of an ObjectListView is to make your life easier. All common ListView tasks should be easier – or at least no more difficult – with an ObjectListView. For the investment of configuration the Columns, you receive a great deal of convenience and value added functions.
See Getting Started for an introduction to the basics.
Automatically create the ListView from model objects¶
The major way in which the ObjectListView makes your life easier is by being able to automatically build the ListView from a collection of model objects. Once the columns are defined, an ObjectListView is able to build the rows of the ListView without any other help. It only takes a single method call: SetObjects().
If ShowGroups is true, the control will automatically create groups and partition the rows into those groups.
This grouping can be customised in several ways:
- the way a row is assigned to a group can be changed by installing a GroupKeyGetter on the column.
- the name for a groups can be changed by installing a GroupKeyToTitleConverter on the oolumn
For values that form a continous range (like salaries, height, grades), the MakeGroupies utility method can easily create more meaningful groupings.
Groups normally change according to the sort column. You can “lock” the groups to be on a particular column via the AlwaysGroupByColumn property.
See Grouping for more details.
This is the most requested feature ever. Under Vista, groups are now collapsible. This is enabled by default. If you don’t want your groups to be collapsible, set HasCollapsibleGroups to false.
Under XP, groups cannot be collapsed.
Each flavour of control (ObjectListView, FastObjectListView, TreeListView) has a data bindable version: DataListView, FastDataListView, DataTreeListView.
Each data bindable version has two additional properties: DataSource and DataMember. These let you control which data set is bound to the control.
Groups on virtual lists¶
Grouping on virtual lists is normally impossible. The SDK says so. But with a little exploring of undocumented features, it can be made to work. Thanks to Geoff Chapell for all his hard work in finding out what is possible.
So, as of v2.3, virtual lists can show groups. FastObjectListViews support grouping without any further effort – simple set ShowGroups to true. If you have a VirtualObjectListView and have done the work of implementing a virtual data source, you will need to implement the IVirtualGroups interface, and then set GroupingStrategy property to an object that implements that interface.
Under Vista and later, groups can now have icons, sub titles, footers and tasks.
ObjectListView will automatically sort the rows when the user clicks on a column header. This sorting understands the data type of the column, so sorting is always correct according to the data type. Sorting does not use the string representation.
Sorting can be customised either by listening for the BeforeSorting event or by installing a CustomSorter.
Different flavours of ObjectListView for different purposes¶
An ObjectListView is the plain vanilla version of the control. It accepts a list of model objects, and builds the control from those model objects.
A DataListView is a data bindable version of an ObjectListView. Give it a data source, and it automatically keep itself in sync with the data source, propagating changes to and fro. It will even create the columns of the list view for you, if you don’t want to do it yourself.
A FastObjectListView is a faster version of an ObjectListView. Typically, it can build a list of 10,000 objects in less than 0.1 seconds.
A VirtualObjectListView does not require a list of model objects. Instead, it asks for model objects as it requires them. In this way, it can support an unlimited number of rows. Most simply, a VirtualObjectListView can be given a RowGetter delegate, which is called when the list needs to display a particular model object. This gives a functional, but limited ListView. It’s better to implement the IVirtualListDataSource interface to give a fully functional virtual ListView.
A TreeListView combines the tree structure of a TreeView with the multi-column display of a ListView.
Editing cell values¶
ListViews normally allow only the primary cell (column 0) to be edited. An ObjectListView allows all cells to be edited. This editing knows to use different editors for different data types. It also allows auto-completion based on existing values for that column.
See ObjectListView Cell Editing for more details.
Sometimes, you want to show more than just text and an icon in your ListView. ObjectListView has extensive support for owner drawing, providing a collection of useful renderers, and making it easy to develop your own renderers.
There is even a renderer provided that draws animations within a cell (if anyone ever actually uses this feature in a real application please let me know).
See Owner drawing a ListView for more information.
Drag and drop¶
ObjectListView supports dragging rows to other places, including other application. It also supports accepting drops from other sources including cross-application drops. Special support is provide for drops from other ObjectListViews in the same application.
In many cases, an ObjectListView becomes a full drag source by setting IsSimpleDragSource to true.
Similarly, to accept drops, it is usually enough to set IsSimpleDropSink to true, and then handle the CanDrop and Dropped events (or the ModelCanDrop and ModelDropped events, if you only want to handle drops from other ObjectListViews in your application).
See ObjectListView and Drag & Drop for more information.
Supports all ListView views¶
An ObjectListView supports all views: report, tile, list, large and small icons. All functions should work equally in all views: drag and drop, editing, check state, icons, selection.
You can even owner draw the non-details views (through the ItemRenderer property).
More control over column width¶
An ObjectListView allows the programmer to have control over the width of columns after the ListView is created.
When a column is created, it is normally given a width in pixels. This is the width of the column when the ListView is first shown. After creation, the user can resize that column to be something else.
By using the MinimumWidth and MaximumWidth properties, the programmer can control the lower and upper limits of a column. Combining these two properties can give a fixed width column.
Finally, the programmer can specify that a column should resize automatically to be wider when the ListView is made wider and narrower when the ListView is made narrower. This type of column is a space filling column, and is created by setting IsSpaceFilling to true.
See these recipes:
Displays a “list is empty” message¶
An empty ListView can be confusing to the user: did something go wrong? Do I need to wait longer and then something will appear?
An ObjectListView can show a “this list is empty” message when there is nothing to show in the list, so that the user knows the control is supposed to be empty. You can even apply some fairly customizations to the appearance of the message.
Checkboxes in any column¶
An ObjectListView supports checkboxes on rows. In fact, it supports checkboxes in subitems, if you are really keen. These work even in virtual mode (which a normal ListView cannot do).
See this recipe for more details: 10. How do I use checkboxes in my ObjectListView?.
Alternate rows background colors¶
Having subtly different row colours for even and odd rows can make a ListView easier for users to read. ObjectListView supports this alternating of background colours. It is enabled by setting UseAlternatingBackColors to true (the default). The background of odd numbered rows will be AlternateRowBackColor.
Custom row and cell formatting¶
An ObjectListView allows rows and even cells to be formatted with custom colours and fonts. For example, you could draw clients with debts in red, or big spending customers could be given a gold background. See here: 8. How can I change the colours of a row or just a cell?
Model object level operations¶
The ObjectListView allows operations at the level that makes most sense to the application: at the level of model objects. Properties like SelectedObjects and CheckedObjects and operations like RefreshObjects() provide a high-level interface to the ListView.
Searching on the sort column¶
When a user types into a normal ListView, the control tries to find the first row where the value in cell 0 begins with the character that the user typed.
ObjectListView extends this idea so that the searching can be done on the column by which the control is sorted (the “sort column”). If your music collection is sorted by “Album” and the user presses “z”, ObjectListView will move the selection to the first track of the “Zooropa” album, rather than find the next track whose title starts with “z”.
In many cases, this is behaviour is quite intuitive. iTunes works in this fashion on its string value columns (e.g. Name, Artist, Album, Genre).
Hot item tracking¶
It sometimes useful to emphasis the row that the mouse is currently over. This is called “hot tracking.” The normal ListView can underline the text of the hot item. In an ObjectListView, the font, font style, text color, and background color can all be set for the hot item.
See this recipe for details: 18. How can I emphasise the row under the mouse?
Copy selected rows to clipboard¶
When one or more rows are selected and the user pressed Ctrl-C, a text representation and a HTML representation of the selected rows is pasted into the clipboard. This allows users to easily copy information from your application into their word processing documents.
Save and restore state¶
If the user makes adjustments to the size, order and selection of columns in one of your ListViews, it would be good manners to make sure those changes are still there when the user runs your application tomorrow. The methods SaveState() and RestoreState() let you do this effortlessly.
User-selection of visible columns¶
it is sometimes nice to let the user choose which columns they wish to see in a ListView. ObjectListView allows you to define many columns for a particular ListView but only have some of them initially visible. The user can right click on the column headers and be presented with a menu of all defined columns from which they can choose which columns they wish to see.
The programmer can also control which columns are visible via the IsVisible property. To hide a column, set IsVisible to false and then call RebuildColumns() to make the change take effect.
With a normal ListView, the SelectedIndexChanged event is the normal way of detecting when the selection has changed. This event is triggered whenever a row is selected or deselected. Although this sounds obvious, it can be quite annoying. If the user selects 100 rows and then clicks on another row, you will received 101 SelectedIndexChanged events: 1 for each row deselected and 1 for the new row selected.
ObjectListView has a SelectionChanged event which is triggered once, no matter how many rows are selected or deselected. This is normally far more convenient.
If you set the SelectedColumn property, that column will be lightly tinted to show that it is selected.
If you set the TintSortColumn property, the sort column will automatically be selected.
Row height can be changed¶
With a normal ListView, the row height is calculated from a combination of the control font and the SmallImageList height. It cannot be changed. But, an ObjectListView has a RowHeight property which allows the height of all rows to be specified.
N.B. Every row has the same height. No variable height rows are allowed. See Can an ObjectListView have rows of different heights? to understand why.
Custom selection colours¶
The colours used to indicate a selected row are governed by the operating system and cannot be changed. However, if you set UseCustomSelectionColors to true, the ObjectListView will use HighlightBackgroundColor and HighlightForegroundColor as the colours for the selected rows.
A standard ListView cannot display tooltips on individual cells (apart from showing truncated cell values when FullRowSelect is true).
But an ObjectListView can show arbitrary tool tips for both cells and headers. See 17. How can I show more information in the tooltip when the mouse hovers over a cell? for details.
In-place modifications of the list¶
ObjectListView supports AddObjects() and RemoveObjects() method which modify the contents of the list in place. Use the Objects property to fetch the current contents of the list.
Not all flavours of ObjectListView support this capacity equally. Plain ObjectListViews support it fully, as do FastObjectListViews. VirtualObjectListViews simply hand off these methods to their data source, so whether these methods work depends on the implementor of the data source.
DataListViews do not support these methods since they are controlled by their DataSource.
TreeListViews interpret these operations as modifying the top level item (“roots”) of their list.
Overlays and decorations¶
ObjectListViews can draw images and text over the top of the control. This drawing is normally done transluscently, so that the drawn images/text do not completely obscure the underlying information.
Overlays are drawing over the control itself. Decorations are added to rows and subitems.
See: * 19. How can I put an image (or some text) over the top of the ListView? for how to use them; * Overlays and Decorations for some gotchas * Technical Blog - Overlays for the history of their development.
A normal ListView triggers mouse events for the list as a whole. ObjectListView can trigger events for cells: CellClick, CellOver and CellRightClick. These events allow you to easily know what the user clicked (or what the mouse is over), and then react appropriately.
Header check boxes¶
Each column header can show a checkbox. Checking or uncheckeding this checkbox can change the checkedness of all checkboxes in the column.
Each column header can be given its own font, text color, background color and border. These can be set per column or on all headers at once using HeaderFormatStyle on the ObjectListView itself.
The text of column header can also be word wrapped, rather than truncated.
Each column can have an image drawn to the left of the text by setting the HeaderImageKey property.
Header drawn vertically¶
To save horizonal space, a header can be drawn vertically.
Header visible in all views¶
In Details view, the user can click on a column heading to sort the items according to that column. But in other views, there is no way to specify how to sort the items. To help with this, ObjectListView has a ShowHeaderInAllView property, which if set to true, shows the header in all views, not just Details, so that the items can be sorted however the user wants.
ObjectListView integrates with the Sparkle library to allow animations on cells, rows, or whole lists.
See Sparkle Animations.
ObjectListViews (in all flavours) support filtering of their contents. This filtering is done by installing ModelFilters (or less often ListFilters) which select which rows will be shown in the list. See 32. Can I filter the contents of the ObjectListView?.
ObjectListView comes with some standard filters, most usefully a text match filter which includes only rows that contains a certain string in any cell. This can be combined with a special renderer to highlight the text matches. See 33. Is there an easy way to only show rows that contain some text?.
These filters are of course extensible.
Yet more slothful!
If you set UseNotifyPropertyChanged to true, then ObjectListView will listen for changes on your model classes, and automatically update the rows when properties on the model classes changed.
Obviously, your model objects have to implement INotifyPropertyChanged.
TreeListView has hierarchical check boxes, which is where the checkedness of the parent summaries the checkedness of the all the subitems. Checking the parent checks all the descendent items. Similarly, unchecking the parent unchecks all the descendent items.
See 48. Can a TreeListView calculate checkboxes based on subitems? and this blog entry: Hierarchy-aware checkboxes