How to change background color of edit box while entering data by user?

I have some edit boxes and user must enter only positive numbers. I want the background color of edit boxes turns to red if user enters non-numeric or negative numbers. How can I do this? This must be done while entering data in edit box, not after clicking on a push button.

[Rik]

If you want to check the number while the user is typing: that is not possible with a normal edit field. If you insist, you will have to create an edit field that the user cannot interact with. Then you need to capture clicks and key presses (don't forget clicking on the middle of the string, or backspace, or pasting).

In short, it is much easier to have a callback to check the value. Callbacks respond to the enter key (and tab key).

Alternatively, you could create a timer that checks the value of the field every few seconds. If you store the previously checked string in a persistent, you can avoid rechecking the same over and over again. That way you can minimize the performance loss.

Answer 1

[Ronit]

Hi,

Use the following function to create a box that turns red for non-negative integers.

function positiveNumberCheck()
    fig = figure('Position', [200, 200, 300, 100]);
    editBox = uicontrol('Style', 'edit', 'Position', [10, 40, 280, 30]);
    set(editBox, 'Callback', @checkInput);

    function checkInput(src, ~)
        enteredValue = str2double(get(src, 'String'));
        if isnan(enteredValue) || enteredValue <= 0
            set(src, 'BackgroundColor', 'red');
        else
            set(src, 'BackgroundColor', 'white');
        end
    end
end

You can run the "positiveNumberCheck" function to create a figure window with an edit box.

[rmpirooz]

This works when user is done with entering the data and when the users presses the "Tab" or "Enter" on keyboard, the edit box turns red.

Now, if instead pressing the Tab, user uses the mouse to move over the next text field, the callback function will not be called and no red color as a result.

[Rik]

Which is why I suggested using a function activated by a timer. Live checking is not possible (as far as I'm aware) with Matlab natively, unless you implement everything from scratch.

Answer 2

[N A POORNA CHANDRA]

hi rmpirooz, here is the code to change the background color of edit boxes for your requirement

function positiveNumbersGUI()

fig = figure('Position', [300, 300, 250, 100]);

editBox = uicontrol('Style', 'edit', ...

'Position', [20, 40, 100, 20], ...

'Callback', @validateInput);

function validateInput(~, ~)

userInput = str2double(get(editBox, 'String'));

if ~isnumeric(userInput) || isnan(userInput) || userInput < 0

set(editBox, 'BackgroundColor', 'red');

else

set(editBox, 'BackgroundColor', 'white');

end

end

end

also refer to this documentation for further understanding

Create text or numeric edit field component - MATLAB uieditfield - MathWorks India

[rmpirooz]

This works when user is done with entering the data and when the users presses the "Tab" or "Enter" on keyboard, the edit box turns red.

Now, if instead pressing the Tab, user uses the mouse to move over the next text field, the callback function will not be called and no red color as a result.