Change "Items" in a Discrete Knob with another knob

Question

Douglas Anderson 2019-9-11

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/479945-change-items-in-a-discrete-knob-with-another-knob

评论： Adam Danz 2020-4-23

Hi,

I have a test App in App Designer, with 2 Discrete knobs, Knob and Knob2. I want to change the settings ("Items") on "Knob" by moving "Knob2". This was just set up in App Designer, and the following Callback for "Knob2" added with the switch. Why doesn't this work?

methods (Access = private)
        % Value changed function: Knob2
        function Knob2ValueChanged(app, event)
            value = app.Knob2.Value;
            switch value
                case '1-10'
                    set(app.Knob,'Items',{1,2,3,4,5,6,7,8,9,10},'Value',{5});
                case '11-20'
                    set(app.Knob,'Items',{11,12,13,14,15,16,17,18,19,20},'value',{15});
                case '21-30'
                    set(app.Knob,'Items',{21,22,23,24,25,26,27,28,29,30},'value',{25});
                    
            end
        end
        enda

Thanks!

Doug Anderson

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Adam 2019-9-11

What is 'value' if you put a breakpoint in? What does happen given you say it doesn't work?

I've never worked with knobs in app designer, but it would surprise me if the 'value' field evaluated to '1-10' as a char.

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Answer 1

Adam Danz 2019-9-11

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/479945-change-items-in-a-discrete-knob-with-another-knob#answer_391427

编辑：Adam Danz 2019-9-11

For Knobs (continuous)

There are a few things wrong with your callback function. I've listed them in order of importance.

The "Value" of your switch-case is numeric but your cases are character vectors so none of the cases will ever be chosen. Use a series of if-elseif conditionals. You could also use a switch-case with logical comparisons as in this answer.
"Items" is not a property of a knob. Instead, use the "MajorTicks" property which expects a vector (not a cell array).
In addition to MajorTicks, set the "Limits" propery to maximize the full range of your knob
The "value" property expects a scalar, not a cell.

Here's how the callback should appear (showing 1 line, you can adapt the rests)>

if value >=1 && value <= 10
    set(app.Knob,'MajorTicks',[1,2,3,4,5,6,7,8,9,10],'Limits',[1,10],'Value',5);
elseif
    % set()
else
    % set()
end

For "Discrete Knobs"

The 'Items" property is expected to be a cell array of strings or chars. You can use num2str with strsplit to convert your numeric vector to a cell array of chars.
The "value" property is expected to be a char array that belongs to the updated Items list.

Here's how the callback should appear (showing 1 line, again)

switch value
    case '1-10'
        set(app.Knob3,'Items',strsplit(num2str([1,2,3,4,5,6,7,8,9,10])),'Value','5');

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Douglas Anderson 2020-4-23

Adam, I am having a different problem now, may be just stupid!

I am making a new discrete knob in Design View, and trying to change the Items by clicking on the ... on the right. I change the "Selected", and it works fine, but if I change the text in the table, it changes what is in the Items box, but has no effect on what is on the screen. I click elswhere -- nada! Back to Off Low Medium High. Matlab 2019b now, haven't installed 2020a.

Thanks!

Adam Danz 2020-4-23

I suggest making a new question. You can copy the URL to the new question here so I know where to look when I get the time to look at it (tomorrow, likely).

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