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progress bar does not change color (Load)

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Khalala Mamouri
Khalala Mamouri on 18 Sep 2020
Edited: Adam Danz on 20 Sep 2020
Hi all,
so i wanna make a load progress bar for my app, (see joined picture). I found a code on matlab :
Unfortunately, the blue color does not show. anyone can tell what i've done wrong please ? thank you
% Change button name to "Processing"
app.ProgressButton.Text = 'Processing...';
% Put text on top of icon
app.ProgressButton.IconAlignment = 'left';
% Create waitbar with same color as button
wbar = permute(repmat(app.ProgressButton.BackgroundColor,150,1,2),[1,3,2]);
% Black frame around waitbar
wbar([1,end],:,:) = 0;
wbar(:,[1,end],:) = 0;
% Load the empty waitbar to the button
app.ProgressButton.Icon = wbar;
% Loop through something and update waitbar
n = 10;
for i = 1:n
% Update image data (royalblue)
currentProg = min(round((size(wbar,2)-2)*(i/n)),size(wbar,2)-2);
app.ProgressButton.Icon(2:end-1, 2:currentProg+1, 1) = 0.25391;
app.ProgressButton.Icon(2:end-1, 2:currentProg+1, 2) = 0.41016;
app.ProgressButton.Icon(2:end-1, 2:currentProg+1, 3) = 0.87891;
% Pause to slow down animation
% remove waitbar
app.ProgressButton.Icon = '';
% Change button name
app.ProgressButton.Text = 'Done !';
Adam Danz
Adam Danz on 20 Sep 2020
"... it is necessary to add a small delay..."
Yes, that's why the original demo you pointed to contains "pause(.3)" within the loop that updates the pseudo-progressbar. Sometimes the processes the user is waiting for much slower than 300ms so there's no need for a pause. However, you'll still likely need a drawnow so the image updates on each iteration.
You can probably replace those pause commands in your code with drawnow.

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Accepted Answer

Adam Danz
Adam Danz on 20 Sep 2020
Edited: Adam Danz on 20 Sep 2020
To summarize the discussion in the comment section under the question, to use the pseudo-colorbar shown in this community highlight,
  1. You must use Matlab r2020a or later
  2. Be sure to execute drawnow or drawnow limitrate within the loop when the progress bar should update. pause is used in the demo only because there is no other process that consumes time in that demo. Otherwise, you could use pause(n) to slow down the progress bar if your process is very fast.

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