How to print text message in UI App in Matlab - matlab

Question

I am working on a App in MATLAB and I use the app design to build it. I have added a text area element in which I display messages to the user (similar use as the command window). In the the app the user can press buttons, which trigger functions to be executed and within those functions, I would like to be able to display some messages in this text area element.
This is an example of the code I use to display the text in this text area. I use a counter to add text in the list and simulate display without overwriting the previous messages.
% display execution message
app.nb_Text_stock = app.nb_Text_stock + 1;
app.OutputStatusTextArea.Value(app.nb_Text_stock) = {'My test here'};
As you can see, I need the app element. I could then pass it to the function all the way to the level where I need to display the text but my real question is, can I access the app element from within the function without passing it as an argument? The reason I want to do that is I have also a non-GUI version of the script where I would not be able to pass app as argument. So to make things simpler, I would like to have a parameters GUI = 1 or 0, and then based on that display either in the command window if GUI = 0 or in the text area in the GUI if GUI = 1. But for that I need to access the app element from inside my function. Is there a proper way to do that? Or do you have any suggestion for another approach for this problem?

Answer 1

You can store app object using setappdata, and get the object using getappdata:
Store app in startupFcn function (Code that executes after component creation):
Add startupFcn by adding callback in "Code View".
% Code that executes after component creation
function startupFcn(app)
% Store app in the root object (setappdata(groot, 'my_app', app) also works).
setappdata(0, 'my_app', app)
end
Read app object from any function:
app = getappdata(0, 'my_app');
Note:
This is not a good coding practice.
What you supposed to do:
function NonGuiFun()
app = app1();
app.func();
What you are asking to do:
function NonGuiFun()
% Get app object (assuming `app` GUI is already open)
app = getappdata(0, 'my_app');
if ~isempty(app)
app.func();
end
Here is the entire code of app1 class, that I used for testing (most of it is automatically generated):
classdef app1 < matlab.apps.AppBase
% Properties that correspond to app components
properties (Access = public)
UIFigure matlab.ui.Figure
Button matlab.ui.control.StateButton
TextAreaLabel matlab.ui.control.Label
OutputStatusTextArea matlab.ui.control.TextArea
end
properties (Access = private)
nb_Text_stock = 0; % Description
end
methods (Access = public)
function results = func(app)
app.nb_Text_stock = app.nb_Text_stock + 1;
app.OutputStatusTextArea.Value(app.nb_Text_stock) = {num2str(app.nb_Text_stock)};
end
end
% Callbacks that handle component events
methods (Access = private)
% Code that executes after component creation
function startupFcn(app)
setappdata(0, 'my_app', app)
end
% Value changed function: Button
function ButtonValueChanged(app, event)
value = app.Button.Value;
func(app);
end
% Close request function: UIFigure
function UIFigureCloseRequest(app, event)
setappdata(0, 'my_app', [])
delete(app)
end
end
% Component initialization
methods (Access = private)
% Create UIFigure and components
function createComponents(app)
% Create UIFigure and hide until all components are created
app.UIFigure = uifigure('Visible', 'off');
app.UIFigure.Position = [100 100 640 480];
app.UIFigure.Name = 'UI Figure';
app.UIFigure.CloseRequestFcn = createCallbackFcn(app, #UIFigureCloseRequest, true);
% Create Button
app.Button = uibutton(app.UIFigure, 'state');
app.Button.ValueChangedFcn = createCallbackFcn(app, #ButtonValueChanged, true);
app.Button.Text = 'Button';
app.Button.Position = [214 295 214 85];
% Create TextAreaLabel
app.TextAreaLabel = uilabel(app.UIFigure);
app.TextAreaLabel.HorizontalAlignment = 'right';
app.TextAreaLabel.Position = [210 211 56 22];
app.TextAreaLabel.Text = 'Text Area';
% Create OutputStatusTextArea
app.OutputStatusTextArea = uitextarea(app.UIFigure);
app.OutputStatusTextArea.Position = [281 175 150 60];
% Show the figure after all components are created
app.UIFigure.Visible = 'on';
end
end
% App creation and deletion
methods (Access = public)
% Construct app
function app = app1
% Create UIFigure and components
createComponents(app)
% Register the app with App Designer
registerApp(app, app.UIFigure)
% Execute the startup function
runStartupFcn(app, #startupFcn)
if nargout == 0
clear app
end
end
% Code that executes before app deletion
function delete(app)
% Delete UIFigure when app is deleted
delete(app.UIFigure)
end
end
end
Note that UIFigureCloseRequest executes: setappdata(0, 'my_app', []).

Answer 2

If you have the handle of any graphical object, you can find pretty much any other object in the same figure using the .Parent and .Children fields (e.g. hObject.Parent.Parent.Children(3).String = 'foo'), optionally using ancestor. If you don't have any object handles, you can use findall, but this would require some means of identifying the correct figures/controls. This can be done using their Tag field, but it would require specifying it beforehand.