ListBox

From Real Software Documentation

For web applications, see WebListBox.

The scrollable ListBox control, used to display one or more columns of information. You can add a checkbox and/or a picture to a row and make a cell or column editable. You can control font style on a cell-by-cell basis and set the column alignment. With some programming, you can create hierarchical lists that use disclosure triangles to show nested items.

Events

CellAction ContextualMenuAction KeyUp CellBackgroundPaint DoubleClick LostFocus CellClick DragEnter MouseDown CellGotFocus DragExit MouseDrag CellKeyDown DragOver MouseEnter CellLostFocus DragReorderRows MouseExit CellTextChange DragRow MouseMove CellTextPaint DropObject MouseUp Change EnableMenuItems MouseWheel Close ExpandRow Open CollapseRow GotFocus SortColumn CompareRows HeaderPressed ConstructContextualMenu KeyDown

Properties

Active EnableDragReorder Name ActiveCell Enabled PanelIndex AutoDeactivate Expanded Parent AutoHideScrollBars GridLinesHorizontal RequiresSelection Bold GridLinesVertical RowHeight Border Handle Scope CellAlignment HasHeading ScrollBarHorizontal CellAlignmentOffset HeaderHeight ScrollBarVertical CellBorderBottom Heading ScrollPosition CellBorderLeft HeadingIndex ScrollPositionX CellBorderRight Height SelCount CellBorderTop HelpTag Selected CellCheck Hierarchical SelectionType CellTag Index SortedColumn CellType InitialValue TabIndex Column Italic TabStop ColumnAlignment LastIndex Text ColumnAlignmentOffset Left TextFont ColumnCount List TextSize ColumnSortDirection ListCount Top ColumnTag ListIndex TrueWindow ColumnType LockBottom Underline ColumnWidths LockLeft UseFocusRing ColumnsResizable LockRight Visible DataField LockTop Width DataSource MouseCursor Window DefaultRowHeight MouseX EnableDrag MouseY

Methods

AcceptFileDrop CellUnderline PressHeader AcceptPictureDrop Close Refresh AcceptRawDataDrop ColumnFromXY RefreshRect AcceptTextDrop DeleteAllRows RemoveRow AddFolder DrawInto RowFromXY AddRow EditCell RowPicture Cell HeaderType RowTag CellBold InsertFolder SetFocus CellHelpTag InsertRow Sort CellItalic Invalidate CellState InvalidateCell

Class Constants

CellType

The following class constants can be used to specify the values of the CellType and ColumnType properties.

Class Constant	Description
TypeDefault	Default, the same as the column type.
TypeNormal	Normal, read only.
TypeCheckBox	A check box is added to the cell.
TypeEditable	The cell is inline editable.

Cell Alignment

The following class constants can be used to specify the value of the CellAlignment and ColumnAlignment properties.

Class Constant	Description
AlignDefault	Default alignment, the same as the column type.
AlignLeft	Left alignment.
AlignCenter	Center alignment.
AlignRight	Right alignment.
AlignDecimal	Decimal alignment. Aligns the decimal separator to the right edge of the cell.

Sort Direction

The following class constants can be used to specify the value of the ColumnSortDirection property.

Class Constant	Description
SortDescending	Sort in descending order.
SortAscending	Sort in ascending order.
SortNone	No sort.

Grid Lines

The following class constants can be used to specify the values of the GridLinesHorizontal and GridLinesVertical properties.

Class Constant	Description
BorderDefault	Default border.
BorderNone	No border.
BorderThinDotted	Thin dotted border.
BorderThinSolid	Thin solid border.
BorderThickSolid	Thick solid border.
BorderDoubleThinSolid	Double thin solid border.

SelectionType

The following class constants can be used to specify the value of the SelectionType property.

Class Constant	Description
SelectionSingle	Single row selection (default).
SelectionMultiple	Multiple row selection.

HeaderTypes

The ListBox.HeaderTypes enum contains the following values:

Enum	Description
Sortable	The column is sortable. This is the default.
NotSortable	The column is not sortable. It will not display mouse over events and does not respond to mouse clicks.

The following code in the Open event of a ListBox sets the second column to not sortable.

Passing -1 instead of a valid column number causes the statement to affect all columns.

Notes

Items in single-column ListBoxes can be accessed using the List property. The List property is an array. Arrays are zero-based. This means that the first row of the List property of a ListBox is row number 0 (zero).

Multi-Column ListBoxes

You can create multi-column ListBoxes by changing the ColumnCount property. The first column in a multi-column ListBox is column 0 (zero). This means that the ColumnCount property will always be one more than the number of the last column. The maximum number of visible columns is 64 (columns 0 through 63). You should set ColumnCount to the number of columns that you want to display. If you want to put data in an invisible column, set the column width to zero.

You can use the InitialValue property to set up the inital values of multi-column ListBoxes by separating the column values with tabs and row values with carriage returns.

The widths of columns in multi-column ListBoxes can be set by passing the widths as a list of values separated by commas to the ColumnWidths property. The widths can be passed in pixels or as percentages of the total width of the ListBox. If you don't pass widths for all the columns, the remaining columns will be evenly spaced over the remaining space. If too many widths are passed, the additional values are ignored. If the total of the widths passed is greater than the width of the ListBox, then the remaining columns will be truncated.

Specific cells in a multi-column ListBox can be accessed using the Cell method. To populate a multi-column ListBox, first use the AddRow method to create the new row and populate the first column. Then use the Cell method to add values to the other columns in the row. Use the LastIndex property to get the index of the current row.

For example, the following code populates a two-column ListBox with the names of the controls in the window and their indexes.

Determining which cell was double-clicked

The DoubleClick event fires when the user double-clicks anywhere inside a ListBox, but the indexes of the cell that was double-clicked are not passed. You can determine which cell was double-clicked with the RowFromXY and ColumnFromXY methods. They use the x,y mouse coordinates where the double-click took place and translate them into the row and column indexes of the cell that was clicked. You need to adjust for the location of the ListBox on the screen relative to the top-left corner of the display.

This code in the DoubleClick event obtains the indexes of the cell that was double-clicked.

Making a Cell Editable

Use the CellType or ColumnType properties to change a cell or column to "inline editable" when you want the user to be able to edit the contents of the ListBox. Then call the EditCell method for each cell. This gives the focus to the editable cell and selects the current text of the cell, if any. Typing replaces the cell's contents. When the user presses Tab or Return or clicks in another cell, the cell loses the focus and the contents of the cell are saved.

The following code in the CellClick event makes the cell the user clicked on editable. The parameters row, and column are passed to the function.

When a cell is editable, the ActiveCell property is the TextField that contains the contents of that cell. You can use this property to set or get the text of the Listbox cell, set the selection, or change other properties of the ListBox's TextField.

Decimal Alignment

When you use decimal alignment in a cell or column, you must take into account the fact that Real Studio aligns the decimal separator with the right edge of the column or cell. You must pass a negative number to CellAlignmentOffset or ColumnAlignmentOffset to make room for the numbers to the right of the decimal place. The correct value to pass depends on the number of digits to the right of the decimal place in the column or cell.

The following illustrates the problem and the solution.

Hierarchical ListBoxes

Creating a simple hierarchical ListBox is more involved than a two-column ListBox because you must manage hiding and displaying the sublist data. A simple way to do this is to assign the sublists to a "hidden" column in the ListBox and toggle the display of that data when the user double-clicks on a "parent" element.

You create a row with a disclosure triangle using the AddFolder method (rather than the AddRow method) and then set the Hierarchical property to True. See the Example for a simple hierarchical ListBox with one level.

Resizing Columns

There are two "modes" for column resizing. There is no formal mode property. Rather, the "mode" is implicitly set according to whether every column width is specified as an absolute amount. If you specify all columns either in pixels or as a percentage, you will be using the second mode. If you use an asterisk or leave a column width blank, you will be using the first mode.

• A change to one column width affects the width of another column.

If column i gets bigger, column i+1 gets smaller by the same amount. This mode is great when using a ListBox without a horizontal scrollbar. You turn this mode on when you have at least one column width that is blank, or specified using an asterisk (e.g. "", " ", "*", or "4*").

NOTE: By design you can't resize the right edge of the last column in this mode. To resize the last column you need to resize the previous column.

• Each column width is independent and can grow or shrink on its own.

You are responsible when the user does this, and you need to provide a horizontal scrollbar so that the user can get to the any headers that have been pushed out of view to the right. You enable this mode by making sure every column width is specified in terms of an absolute pixel width, or a percentage width (e.g. "20", or "35%"). If you use an asterisk or leave a column width blank, you will automatically be using the first mode.

You can switch between mode 1 and 2 at runtime using the same criteria as above.

The ColumnWidths property (which can only be specified at design time), is equivalent to the concatenation of all of the ColumnWidthExpressions.

ColumnWidthExpressions are strings and they can represent several different types of column width calculations: absolute pixels (e.g., "45"), percentages (e.g. "22.3%"), and asterisk widths (or blanks), e.g. " ", "4*". The value "*" is equivalent to "1*" and can be used to mean "fill the remaining space."

ColumnWidthExpressions retain their type even when a column is resized. This means that if you:

• Resize a window to which a ListBox is locked, it will grow or shrink. The columns grow or shrink as well if their expressions were *-based (unless you use "0*"), or percentage based (0%). If you want them to stay fixed, you need to express the ColumnWidthExpression as an absolute pixel value.

• Resize a column by dragging it internally, it will recompute its percentage or asterisk value. This is so that you can, say, start with a two-column ListBox with no column widths specified (each column will take up half the space). Then drag one column to take up 3/4 of the space, then enlarge the ListBox, and now both column widths will enlarge so that their widths remain in a 3/4 to 1/4 ratio.

Changing the pixel value of a column will not change its fundamental type, but will change the value of that type.

Finally, if you want to create columns that won't get resized, change the UserResizable property for each of the columns in question. If you are using mode 1, you will need to change the UserResizable property for both the column and the one to its left.

Databases

A ListBox is often used to display the results of database queries. A ListBox can be populated with the results of a query programmatically. See the example "Database Example" in the Examples folder.

CellState

The CellState method enables you to get or set the value of a tri-state Checkbox cell. Any cell of type TypeCheckbox box can store one of three values: Checked, Unchecked, and Indeterminate.

To set up a cell as TypeCheckbox, use code such as this in the Open event:

To change the state of the cell, use the CheckedStates enum of the CheckBox control:

The Indeterminate state places a minus sign in the checkbox (Macintosh) or fills in checkbox (Windows and Linux).

Customized Scroll Controls

Suppose you want a horizontal scroll bar that leaves room for a pop-up menu. In this example, a Scrollbar control has been added to the bottom area of the ListBox and a BevelButton control has been added to its right. The two controls take up the area that would be used by the built-in horizontal scrollbar.

The Scrollbar control has the following code in its Open event handler:

The values for maximum and linestep were chosen to match the total width of the ListBox's columns. Adjust these values to suit your ListBox. Its ValueChanged event handler has the following line of code:

In this way, the user can scroll the ListBox horizontally, bringing all columns into view.

The BevelButton enables the user to switch the ListBox between single-line selection and multiple-line selection. The BevelButton is set to have a normal menu and its Open event handler populates the menu with two items:

The BevelButton's Action event sets the value of the ListBox's SelectionType property:

Horizontal and Vertical Rules

The following screenshots illustrate four types of horizontal and vertical rules that can be drawn with the GridLinesHorizontal and GridLinesVertical properties and the CellBorderTop, CellBorderLeft, CellBorderRight, and CellBorderBottom properties.

The default style is "Normal."

With the CellBorderTop, ...Left, ...Bottom, and ...Right methods, you can apply these ruling styles to selected cells or even selected cell borders.

For example, in this ListBox a cell containing a phone number is highlighted using Thick Solid borders while the remainder of the ListBox uses Thin Dotted rules.

Examples

Adding a row to ListBox1:

Inserting a row at row 1 in ListBox1:

Creating a three-column ListBox and adding the headings and the first row of information:

Changing all items in the ListBox to bold, underline:

Copying the fifth element of ListBox1 to another variable:

Adding a column to ListBox1 and setting the widths of the columns to 50 and 65 pixels, respectively:

Setting the number of columns of ListBox1 to three and setting the widths of the columns to 60%, 20% and 20% respectively:

If ListBox1 is 100 pixels wide and has three columns, the following code will set the columns widths as indicated but the last column will only be 10 pixels wide instead of 20:

If ListBox1 is 100 pixels wide and has three columns, the following code will set the columns widths but the last column will not be displayed:

Copying the fifth row of the third column of ListBox1 to another variable:

Assigning a value to the fifth row of the third column of ListBox1:

Setting the fifth row of the third column of ListBox1 to bold, italic:

Adding a row with the text "Users" in the first cell and placing an image of a folder to the left of the text. The picture "usersFolder" has been added to the Project Editor.

Setting up the DragRow event handler to allow the user to drag a value from a ListBox:

Summing the numeric values of the selected rows:

This example expands the first row of ListBox1 (if it is collapsed) or collapses it (if it was expanded). The row must have been added with the AddFolder method:

This example populates a three-column ListBox with headings:

This example sets up a ListBox with four visible columns plus one hidden column. Column zero is hidden:

The following line of code displays the value of the hidden column in the selected row:

Hierarchical ListBoxes

The following example creates a single-level hierarchical ListBox.

Windows uses plus and minus signs to indicate disclosure; Macintosh and Linux use disclosure triangles. To display these widgets, set the set the Hierarchical property of the ListBox to True in the Properties pane.

The following code, which is in the ListBox's Open event handler, populates the hierarchy: The s1 string contains the parent level and sub1 contains the elements that are nested within each of s1's elements. It is a list of comma-delimited lists, with each list delimited by semicolons.The elements of sub1 are initially hidden because they are stored in a hidden column.

Note that the AddFolder method, rather than AddRow, is used to add the State names.

The following line of code in the DoubleClick event handler toggles the expanded state of the row that was double-clicked:

The following code in the ExpandRow event handler runs when the user double-clicks a collapsed element:

It creates the sublist rows each time the user double-clicks a collapsed state name.

If the ListBox has the Hierarchical property selected, then Real Studio handles the collapsing automatically when the user collapses an item. If Hierarchical is not set, then you need code such as this in the CollapseRow event handler:

It removes the rows that were created by the ExpandRow event handler.

Drag and Drop Between ListBoxes

The following example allows the user to drag one row from ListBox1 to ListBox2. ListBox1 has its EnableDrag property set to True and its SelectionType property set to zero (Single). Its DragRow event handler is as follows:

ListBox2's Open event handler has the line:

Its DropObject event handler is this:

Drag and Drop Multiple Rows Between ListBoxes

The following example allows the user to drag more than one row from ListBox1 to ListBox2. The dragged rows are added to the end of the list.

ListBox1 has its EnableDrag property set to True, enabling items in its list to be dragged, and its SelectionType property set to 1 (Multiple row selection). Its DragRow event handler is as follows:

It uses the AddItem method of the DragItem to add an additional item to the DragItem each selected row. The DropObject event handler then cycles through all items to retrieve all dragged rows.

ListBox2 has the following line of code in its Open event handler. It permits it to receive dragged text.

Its DropObject event handler checks to see if the dragged object is text; if it is, it adds a row to the end of the list and assigns the text property of the dragged object to the new row: It loops through all items in the DragItem until NextItem returns False.

You can also drag from ListBox1 to the desktop to get a text clipping or to another application that supports text drag and drop.

Colors

This example, which is placed in the CellBackgroundPaint event, assigns alternating colors to the rows in a ListBox:

Notes: The CellBackgroundPaint event passes the parameters g (Graphics), and the row and column numbers (as Integer). You can assign a color to the ForeColor property by creating it as a constant in the App class or a module and assign the color constant to the ForeColor property.

The following line in the CellTextPaint event tells Real Studio to draw the text in the preceding example in red:

The CellTextPaint event is passed the coordinates of the suggested starting position to draw text in the parameters x and y. You can use them in a call to the DrawString property to specify the string to draw in a particular cell:

Sorts

To sort a ListBox, set the column on which the ListBox will be sorted with the SortedColumn property. Specify the sort direction on that column with the ColumnSortDirection property, and then do the sort by calling the Sort method.

The following example sorts a Listbox in descending order on the first column.

You can also sort a column based on the current value of ColumnSortDirection by calling the PressHeader method. This method programmatically clicks the header for the column passed to it.

Custom Sorts

The following example uses the CompareRows event to sort columns of numbers. If you rely on default sorting, numbers are not sorted in numerical order, i.e., 2 is greater than 100 and less than 200.

With this code in place, the correct (numerical) sorting is done whenever the user clicks the header area. Test to be sure that the custom sort affects only the numerical columns.

To sort dates, store the TotalSeconds property of the Date in a column of width zero and sort the rows based on that column.

See Also

DatabaseQuery, TextField controls; DatabaseField, ListColumn, RecordSet classes.