Update slider Limits after loading data?

I am using app designer and I created a slider called "FrameSelect".

The function called just before returns numFrames which I store to the app's properties. The line only works if I hard code the limits. How do I update the limits of this slider?

        function OpenMenuSelected(app, event)
            [file, path] = uigetfile('*.jpg;*.seq',"Select `.seq` file for analysis");
            [app.imageSequence, app.minTemp, app.maxTemp, app.numFrames, app.frameRate] = load_image_sequence(app, strcat(path,file));
            app.numFrames
            app.FrameSelect.Value = 1;
            limits = [1 app.numFrames]
            app.FrameSelect.Limits = limits;
            app.FrameSelect.MajorTicks = 1:15:app.numFrames;
            notify(app.FrameSelect, 'ValueChanged');
        end

Error using thermal_image_viewer/OpenMenuSelected

'Limits' must be a 1-by-2 array of real finite numbers that are increasing.

limits =

  1×2 int32 row vector

     1   317

And yes, numFrames is an int32 value between [200, 1500] after the load_image call.

When I hard code in a value, there is no error.

Answer 1

[Voss]

MATLAB doesn't appear to allow the Limits property of a uislider to take on int32 values, at least in R2016b.

So it's worth a shot to try casting the value to double before using it in Limits:

app.FrameSelect.Limits = [1 double(app.numFrames)];

Answer 2

[Ian]

I created a min reproducable example (min_example.mlapp) that has no issues updating the sliders limits, so there must a problem with how the dll I am using is interfaced with Matlab.

In my code doing the following worked.

        function OpenMenuSelected(app, event)
            [file, path] = uigetfile('*.jpg;*.seq',"Select `.seq` file for analysis");
            [app.imageSequence, app.minTemp, app.maxTemp, app.numFrames, app.frameRate] = load_image_sequence(app, strcat(path,file));
            x = int2str(app.numFrames);
            y = str2num(x);
            UpdateSlider(app, y);
        end
        
        function UpdateSlider(app, maxFrame)
            app.FrameSelect.Limits = [1 maxFrame];
            app.FrameSelect.MajorTicks = 1:15:app.numFrames;
            app.FrameSelect.Value = 1;
            UpdateImage(app, 1);
        end

I am going to change my load function to calculate the number of frames instead of using the dll's functions.