5. Multiple document Interface:

The MDI was designed to simplify the exchange of information among documents, all under the same roof.   With a MDI application, you can maintain multiple windows, but not multiple copies of the application.  Data exchange is easier when you can view and compare many documents simultaneously.   The main form or MDI form is not duplicated, but it acts as a container for all the windows, and it is called the parent window. 

  A MDI application must have at least two forms, the parent form and one or more child forms.   There can be many child forms, but only one parent form.  He parent form may not contain controls.   While the parent form is open in the design mode, though the icons in the toolbox are not disabled, but you cannot place any control on the form.   But you can place controls in child forms.

To create a MDI application follow these steps:

1.      Start a new project, and choose Project>Add MDI form to add the form

2.      Set the form’s caption to MDIwindow.

3.      Choose Project>Add form to add a regular form.

4.      Make this form child by setting its MDIChild property true.   To denote that this is a child form set its caption to MDIChild.

5.      Double-click your picture control in the tool box.   It will appear as toolbar to your MDI form.

6.      Place three command buttons on this toolbar and change their names and captions to newchild, cascade and tile respectively.

7.      The MDI window will look as in the figure 9.  

8.      Enter the codes as shown in the figure 9a.

9.      Save and run the project.

10.  See how you can arrange the child windows in tiles or cascades.  You cannadd any number of child windows by clicking the newchild button.   A typical tile arrangement of child windows is shown in the figure 10 and cascade arrangement of the child windows in the figure 11.

Dim i

Private Sub cascade_Click()

MDIForm1.Arrange 0

End Sub

Private Sub newchild_Click()

Dim obj As Form1

Set obj = New Form1

obj.Caption = obj.Caption & i

obj.Show

i = i + 1

End Sub

Private Sub MDIForm_Load()

i = 2

End Sub

Private Sub tile_Click()

MDIForm1.Arrange 1

End Sub

     Figure 9a

 
                                                 Figure 9

                                Figure 10

                                 Figure 11