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GridEx Class

  + Object
    + Display
      + UIComponent
        + Control
          + GridEx

Description

The GridEx class implements the behaviours specific to grid controls. Like all classes derived from UIComponent, this class is not instantiable, cloneable or derivable. The only instances available to the programmer are those automatically generated by HB++ when you place the corresponding control on a form.

The GridEx control allows you display and edit data in a tabular form. It is very similar to the previously existing Grid control, but provides both vertical and horizontal scrolling, extended selection modes (free, by rows, or by cells), resizeable columns, and compatibility with the new Dynamic Input Area feature. On the other hand, this new control does not provide in-place editing of text yet. When possible, it is advised you use this control instead of the old Grid control.

Unlike other controls, GridEx controls do not store the data to be displayed directly, but only a single, Long value for each row, called ItemData. When the control needs to display a given row, the data to be displayed in each column are claimed on-the-fly by raising a LoadItem event; it is then up to your code to provide the requested data. The following example schematically shows how to fill and display a grid control with data from a table:

Private db As New tblMyDatabase ' Replace this by the name of your table

Private Sub Form_Load()
  db.OpenTable hbModeOpenExisting+hbModeReadOnly
  Grid1.Populate db
End Sub

Private Sub Form_Unload()
  db.Close
End Sub

Private Sub Grid1_LoadItem(ByVal iRow As Integer, ByVal lItemData As Long, ByVal vValue() As Variant)
  db.LookupUniqueID lItemData
  
  vValue(0) = db.SomeTextField     ' Replace this by the name of field to display in the first column
  vValue(1) = db.AnotherTextField  ' Replace this by the name of field to display in the second column
End Sub

An internal caching mechanism avoids your code receive to many LoadItem events, which would impact performances.

The type of each column in a grid is determined at design time by the Columns property. The following table summarizes the various types of columns the grid control supports; please refer to this property for detailed information:

There are two ways to specify the number of rows in the Grid object; either by using the Rows property or by adding rows one by one with the AddItem method which also allows to specify for each line added an associated value in the ItemData property and an initial value for the Masked property. When you use the GridEx class to display the contents of a database, it is convenient to store in the ItemData property the unique identifier associated with each record in a database.

Whichever method is used to set the number of rows in the Grid object, the Rows property returns the number of items in the Grid object.

The Click event is raised when the user clicks on the GridEx control. If the clicked cell is editable, it enters in edit mode; as soon as the user is done, the control reverts to standard mode, and a Change event is raised. The various parameters passed along with this event allows to determine which cell was edited and the new value the user entered.

The SelectionMode property lets you choose the selection mode: free, by rows, or by column. This mode can be changed at any time. Note however that cells cannot be edited if the SelectionMode is not set to hbSelectCell. You can also programmatically select and highlight a given cell using the SelectItem method.

Members

System requirements