CODEWITHSUNDEEP
delphilistboxfiremonkeydelphi-xe6
user3841244
user3841244

Reputation: 1

Listbox highlight only when pressed

I am creating a Delphi XE6 Firemonkey mobile application and want to highlight a listbox item but only while it is being pressed. For an example of the effect I am after, create a new Firemonkey desktop application, add a TListBox and add the following event handlers and code:-

procedure TForm1.FormCreate(Sender: TObject);
var
i: Integer;
begin  
//populate the listbox
for i := 0 to 19 do
ListBox1.Items.Add(IntToStr(i));
end;

procedure TForm1.ListBox1ItemClick(const Sender: TCustomListBox;
const Item: TListBoxItem);
begin
ListBox1.ItemIndex:=-1;
end;

Now click an item in the listbox and the highlight should disappear on release of the mouse button. Repeating the exercise for mobile sees only a long press producing the desired result and a short press causes the highlight to remain. So I dropped a timer on the form, setting enabled to FALSE, an interval of 200 and creating an OnTimer event:-

procedure TForm1.FormCreate(Sender: TObject);
var
i: Integer;
begin  
//populate the listbox
for i := 0 to 19 do
ListBox1.Items.Add(IntToStr(i));
end;

procedure TForm1.ListBox1ItemClick(const Sender: TCustomListBox;
const Item: TListBoxItem);
begin
Timer1.Enabled:=TRUE;
end;

procedure TForm1.Timer1Timer(Sender: TObject);
begin
ListBox1.ItemIndex:=-1;
Timer1.Enabled:=FALSE;
end;

Progress is made but by rapid pressing of the listbox it is easily possible for the listbox to remain highlighted. I tried the timer option on a TListView and it appears to work as hoped but I'm eager to find a solution for TListBox.

Next brainwave was to add a button to the listboxitem:-

procedure TForm1.FormCreate(Sender: TObject);
var i:integer;
BoxItem: TListBoxItem;
ListBoxSpeedButton: TSpeedButton;

begin
for i := 0 to 99 do
 begin
 ListBox1.Items.Add(IntToStr(i));
 BoxItem := ListBox1.ListItems[ListBox1.Items.Count-1];
 ListBoxSpeedButton:=TSpeedButton.Create(nil);
 ListBoxSpeedButton.Parent:=BoxItem;
 ListBoxSpeedButton.CanFocus:=FALSE;
 ListBoxSpeedButton.Align:=TAlignLayout.Client;
 end;
end;

However, when scrolling the listbox, the button gets activated and when using a custom Speedbutton, the scrolling is jerky and unresponsive and I can't help feeling I'm using controls when there is no need.

Is there a simple solution here?

Upvotes: 0

Views: 2528

Answers (1)

ThisGuy
ThisGuy

Reputation: 1415

Uhm... I will start off by saying DONT USE listboxes when scrolling.... FMX Listboxes are meant to be stagnant and performance when scrolling is horrendous. Use a TListView and TListViewItems. There are tons of examples on SO and in the packaged Delphi XE6 examples on how to implement a list via TListView. That being said, there is no need for timers.. Make use of events already available to use for such things, such as OnMouseDown and onMouseUp which are events assigned to basically every FMX control ( ListBox ListBoxItem or ListView, etc.).... Tons of ways to go about implementing this...

Try this - setting onMouseDown and MouseUp events for every listboxItem to what you see below:

procedure TForm1.ListBoxItem5MouseDown(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Single);
begin
  if sender is TListboxItem then
    ListBox.ItemIndex:=TListBoxItem(sender).index
end;

procedure TForm1.ListBoxItem5MouseUp(Sender: TObject; Button: TMouseButton;
  Shift: TShiftState; X, Y: Single);
begin
  ListBox.ItemIndex:=-1;
end;

Upvotes: 1

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