Qt load indicator by animated image (aka preloader) or alternative?

Question

I want to display an animated loader image on my table view while loading. The screenshot below shows an impression.

I have used an animated gif for that, displayed by setStyleSheet as centered background image.

I face two issues:

The gif is displayed, but not animated. Is it possible to display an animated gif as background image (via stylesheet)? Remark: In general an animated gif is possible as shown in Qt - How to show gif(animated) image in QGraphicsPixmapItem but there seems to be no animated gif with style sheets Animated Gif static in QStyleSheet
I have problems to clear the image once loading is done. If I clear the stylesheet with setStyleSheet("") then it is still displayed. The only trick working for me is to override it as 1 pixel transparent image

Is there a solution to those issues or even a better approach (overlay widget? / specialized Qt widget for that)?

(My code exampled with Qt 5.4 / Win7)

Edit: https://stackoverflow.com/a/26958738/356726 shows how such a gif can be animated, but I have no idea to use that in such a kind of overlay / background style.

You can draw radial gradient then mask with an alpha mask. When it's done just stop drawing. — user3528438, Sep 17 '15 at 17:59

score 1 · Accepted Answer · answered Sep 17 '15 at 20:36

1

Use QProgressIndicator insted of gif animation.

PS: it says that it Qt4, but it works with Qt5.

answered Sep 17 '15 at 20:36

RazrFalcon

Interesting hint, but it seems to be a normal widget. Does it work as overlay, as I want to display the indicator as part of the table view. Or is there an easy way to center a widget over an existing one (I am not aware of any). – Horst Walter Sep 17 '15 at 20:58
Widget is an example. Main idea is the paint function. You can basically reimplement paintEvent for your table. It would be much faster than gif. And because it's QPainter-based implementation - you can draw it everywhere. If you want to paint indicator on widget and then place it over another widget - you can use resizeEvent to update it's position. – RazrFalcon Sep 17 '15 at 22:49
Following that idea, but got some issues. Follow up created: http://stackoverflow.com/q/32653267/356726 – Horst Walter Sep 18 '15 at 13:30
With the paint issue solved, I use a modified version of `QProgressIndicator` painted itself into the `QTableView` viewport. – Horst Walter Sep 18 '15 at 16:54

Matheus Torquato · Answer 2 · 2020-08-19T16:55:04.590

1

QtWaitingSpinner is also an elegant solution.

edited Aug 19 '20 at 16:55

answered Aug 14 '20 at 14:47

Matheus Torquato

2 Answers2