image callback in app designer

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Gordon Edwards
Gordon Edwards 2019-6-25
评论： Guillaume 2019-6-25
I have an app with a UIAxes which contains an image with the returned image object im i.e.im=image(UIAxesObject, array). I create a buttondownfcn callback using
im.ButtonDownFcn = @FCN. However, if I create the function FCN(app, event) inside the private or public function area of the app designer I get an error. The only way I seem to be able to get the callback to work is to put function FCN in a separate m. file. Is there another way of creating callback functions in app designer?
  2 个评论
Guillaume
Guillaume 2019-6-25
I get an error
What is the full text of the error message?
Gordon Edwards
Gordon Edwards 2019-6-25
The error message is when the callback function is a private method is ---
Undefined function 'ImageButtonDownCallBack' for input
arguments of type 'matlab.graphics.primitive.Image'.
Error while evaluating Image ButtonDownFcn.

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回答（1 个）

Guillaume
Guillaume 2019-6-25
You may want to consider using a uiimage instead of an Image inside a uiaxes.
I suspect you've defined the callback incorrectly. Typically the code would be something likle
classdef myapp < matlab.apps.AppBase
% Properties that correspond to app components
properties (Access = public)
UIFigure matlab.ui.Figure
UIAxes matlab.ui.control.UIAxes
%... other controls. You can't edit this directly
end
%your own properties
properties (Access = private)
myimage; %property to hold the image
end
%...
methods (Access = private)
function ImageButtonDownCallback(app, source, eventargs)
%... the callback code
end
%The function that creates the image and enable the callback
function something(app)
app.myimage = imshow(someimage, 'Parent', app.UIAxes); %image creation
app.myimage.ButtonDownFcn = @app.ImageButtonDownCallback; %create callback. IMPORTANT: You must use app.****
end
end
end
  2 个评论
Gordon Edwards
Gordon Edwards 2019-6-25
Thankyou - that works fine. I hadn't realised that the syntax @app.ImageButtonDownCallback is required.
I use the image function as I am creating one in UIAxes from an array. I find MatLab's nomenclature confusing at times - for example, use of the word 'image' as a function displaying an image from an array and also, in app designer, for an icon.
Guillaume
Guillaume 2019-6-25
Indeed, you have:
  • the image function
  • the image type, returned by image, imshow, imagesc and probably other functions. The full name of that type is actually matlab.graphics.primitive.Image. It's not really well documented. The only doc page is its property page.
  • the app designer image control whose full name is matlab.ui.control.Image. Again, not very well documented. It has a different set of properties and callbacks from the previous image type.

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