Delphi-XE5 Android Development. What is the best way to free non-modal forms?

2
votes

In Delphi for windows there is no problem to Free (Form.free) closed secondary dynamicaly-created form because where is "ShowModal" method. But Delphi for Android does not support Form.ShowModal, and we have to use Show method. But I figured out what when I close (Form.close) secondary form it is still in memory and even run code Onresize event (???). What is the best way to Free forms in non-Modal call?

In another words: How do I close a form from an OnClick event handler on that form, and ensure that the form's destructor runs?

2
androiddelphimemory-leaksdelphi-xe5

2 Answers

3
votes

Update

See important note below.

In XE5 for Android there is a possibility to show a form with modal results, an overloaded ShowModal procedure using an anonymous method:

procedure ShowModal(const ResultProc: TProc); overload;

You can find it described in this article by Marco Cantu, Delphi XE5 Anonymous ShowModal and Android.

Here is the example how to use this procedure:

var
  dlg: TForm1;
begin
  dlg := TForm1.Create(nil);
  // select current value, if avaialble in the list
  dlg.ListBox1.ItemIndex := dlg.ListBox1.Items.IndexOf(Edit1.Text);
  dlg.ShowModal(
    procedure(ModalResult: TModalResult)
    begin
      if ModalResult = mrOK then
      // if OK was pressed and an item is selected, pick it
        if dlg.ListBox1.ItemIndex >= 0 then
          edit1.Text := dlg.ListBox1.Items [dlg.ListBox1.ItemIndex];
      dlg.DisposeOf;  // Wrong !!!, see note below
    end);

Note that the dlg.DisposeOf; will force the form to be destroyed, overriding the ARC automatic handling.

You can also find a description in the documentation, Using Modal Dialog Boxes in Mobile Apps and here, ShowModal Dialogs in FireMonkey Mobile Apps.

As found by others, http://www.malcolmgroves.com/blog/?p=1585, calling DisposeOf inside the anonymous method is wrong because the anonymous frame must be able to handle ModalResult from a valid object. Use this pattern instead to free the modal dialog, Freeing Your Modal Dialog Box.

procedure TModalForm.FormClose(Sender: TObject; var Action: TCloseAction);
begin
  Action := TCloseAction.caFree;
end;
0
votes

Don't forget to set in the ObjectInspector

ModalResult = mrOK

or in your 

procedure TForm1.ExitButtonClick(Sender: TObject);
begin
   ModalResult := mrOK;
end;

for the example dlg.ShowModal above!