Code checking error in App Designer, it thinks xxxx.BackgroundColor is a scalar

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Alessandro Livi
Alessandro Livi 2024-7-6
评论： Voss 2024-7-10
I'm changing the background color to alert the user about various (async) conditions and button pressed.
if app.STOPTRIALSButton.BackgroundColor == [0.95 0.33 0.10]
app.STOPTRIALSButton.BackgroundColor = [0 1 0];
end
and I get the warning:
Unexpected use of '[' in a scalar context.
but of course colors are RGB three values, so the code runs fine.
Also while the Component browser shows (another) color as 0.65, 0.65, 0.65 that's the wrong syntax (no commas please for easier cut and paste) and in the startup code the values are actually [0.651 0.651 0.651] so my compare failed without significant research as to why.
Finally, App Designer isn't listed as a product below, so I can't flag that. Just saying MATLAB is the product.

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回答（2 个）

Voss
Voss 2024-7-6
To avoid the warning, use:
if isequal(app.STOPTRIALSButton.BackgroundColor,[0.95 0.33 0.10])
app.STOPTRIALSButton.BackgroundColor = [0 1 0];
end
  3 个评论
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Walter Roberson
Walter Roberson 2024-7-7
Do not compare floating point numbers for exact equality.
if isnumeric(app.STOPTRIALSButton.BackgroundColor) && all(abs(app.STOPTRIALSButton.BackgroundColor - [0.95 0.33 0.10]) <= 0.01)
Voss
Voss 2024-7-7
If App Designer puts a line of code that says
app.STOPTRIALSButton.BackgroundColor = [0.949 0.3294 0.102]
and you want to check that that BackgroundColor is still in effect, use
if isequal(app.STOPTRIALSButton.BackgroundColor,[0.949 0.3294 0.102])

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Alessandro Livi
Alessandro Livi 2024-7-10
This is crazy that you can't simply compare colors, consder options I mention above meanwhie
if isnumeric(app.STOPTRIALSButton.BackgroundColor) && all(abs(app.STOPTRIALSButton.BackgroundColor - [0.95 0.33 0.10]) <= 0.01
should work,
(make this a documented (or included) function SameColor( Color1 Color2) as above?
Also I was directed to a colors names list (not in MatLab) and most of the names don't work.
'color name' must match a rather short list, none of the off white names work (like a name for [0.94 0.94 0.94] or [0.90 0.90 0.90] which seem to be common default background colors
  1 个评论
Voss
Voss 2024-7-10
Here's the list of named colors in MATLAB
https://www.mathworks.com/help/matlab/creating_plots/specify-plot-colors.html
They are the eight colors all of whose RGB components are 0 or 1 (i.e. [0,0,0], [0,0,1], [0,1,0], [0,1,1], [1,0,0], [1,0,1], [1,1,0], [1,1,1]).

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