I have created a simple GUI to preview webcam stream and to get snapshot from it. For this I have created on axes to show video, one push button(pushbutton1) to start preview, one push button(pushbutton2) to get snapshot. Following is the code for these two push buttons.
function pushbutton1_Callback(hObject, eventdata, handles)
% hObject handle to pushbutton1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
axes(handles.axes1);
vidObj = videoinput('winvideo',1);
videoRes = get(vidObj, 'VideoResolution');
numberOfBands = get(vidObj, 'NumberOfBands');
handleToImage = image( zeros([videoRes(2), videoRes(1), numberOfBands], 'uint8') );
preview(vidObj, handleToImage);
% --- Executes on button press in pushbutton2.
function pushbutton2_Callback(hObject, eventdata, handles)
% hObject handle to pushbutton2 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
a=getsnapshot(get(axes,'Children'));
imshow(a);
In pushbutton2_Callback I am trying to get child of axes ie. vidObj. But this gives me error ??? Undefined function or method 'getsnapshot' for input arguments of type 'double'.. Why is it returing double type instead of child object vidObj?
How can I fix it and get snapshot?
Is there any other better way?
(I just started learning GUI.)
Thanks.
A better alternative to declaring your variables global, is to use the handles structure for sharing data. GUIDE already uses this structure to store handles to all GUI components. Simply add your data as a field to this structure that gets passed around to all callback functions.
So inside the first callback:
function pushbutton1_Callback(hObject, eventdata, handles)
%# ... your existing code ...
%# store video object in handles, and persist
handles.vidObj = vidObj;
guidata(hObject,handles)
end
Then in the second, you can retrieve the video object from the handles structure:
function pushbutton2_Callback(hObject, eventdata, handles)
frame = getsnapshot(handles.vidObj);
imshow(frame);
end
Related
I am starting with MatLab.
I created a guide UI. I went ahead and assumed I could just add new feild to the handles structure created.
Can I do this?
For example, when I refer to handle.s in my program, I get an error that I am reffering to a non existing feild.
handles.s was created to store a serial port object generated in a function that initialises serial communication between my PC and a microcontroller.
the serial port object has methods and feild of its own...could it be that I cannot pass an object as a feild to the handles object that contains the property of the guide UI?
Here is the code I am working with
function [ s, flag] = setupSerial(comPort)
%Initialize serial port communication between Arduino and Matlab
%Ensure that the arduino is also communicating with Matlab at this time.
%if setup is complete then the value of setup is returned as 1 else 0.
flag =1;
s = serial(comPort);
set(s,'DataBits',8);
set(s,'StopBits',1);
set(s,'BaudRate',9600);
set(s,'Parity','none');
fopen(s);
a='b';
while (a~='a')
a=fread(s,1,'uchar');
end
if (a=='a')
disp('serial read');
end
fprintf(s,'%c','a');
mbox = msgbox('Serial Communication setup.'); uiwait(mbox);
fscanf(s,'%u');
end
Within my UserInterface.m file, I pass over the object in a claaback function as follows
function SerialBtn_Callback(hObject, eventdata, handles)
% hObject handle to SerialBtn (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA
comPort = get(handles.COMportTxt,'String');
if(~exist('serialFlag','var'))
[handles.s, handles.serialFlag] = setupSerial(comPort);
end
end
I get the error when I press the 'Home' button. Here is the callback funciton
function HomeButton_Callback(hObject, eventdata, handles)
% hObject handle to HomeButton (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
disp('home button pressed');
fprintf(handles.s,'%s', 'G2');
set(handles.CurrentPositionTxt, 'String', '0');
end
There error I get is the following
Reference to non-existent field 's'.
Here the GUI for you information
The callback where handles.s is defined is not saving the handles object. You must save it using guidata in order to have it available later in another callback.
function SerialBtn_Callback(hObject, eventdata, handles)
% hObject handle to SerialBtn (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA
comPort = get(handles.COMportTxt,'String');
if(~exist('serialFlag','var'))
[handles.s, handles.serialFlag] = setupSerial(comPort);
end
guidata(hObject,handles)
Hope this helps.
I am developing a GUI in Matlab and I would like to know which is the workflow when you click a button. Being more specific, I would like to know 'what happens' when I click a button, because its callback is not triggered.
If you are using GUIDE for developing, every time you add a button to your GUI a chunk of code is generated:
% --- Executes on button press in pushbutton1.
function pushbutton1_Callback(hObject, eventdata, handles)
% hObject handle to pushbutton1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
This function is called every time you push the said button. So, if you need something to be executed when you click the button you just need to add the lines of code you want to execute below that generated chunk of code. For example, imagine you have an edit text variable called edit1 with value
edit1 = 'hello';
If you want to interact with it you need to call handles, but first you need to create a global variable:
%set the current figure handle to main application data
setappdata(0,'figureHandle',gcf);
%set the handles to figure's application data
setappdata(gcf,'EDIT1',handles.edit1);
Then, in the callback function of your button you need write the following:
% --- Executes on button press in pushbutton1.
function pushbutton1_Callback(hObject, eventdata, handles)
% hObject handle to pushbutton1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
figureHandle = getappdata(0,'figureHandle');
EDIT1 = getappdata(figureHandle,'EDIT1 ');
new_string = 'updated string';
set(EDIT1, 'String', new_string);
Hope this helps
I created a GUI layout using Matlabs GUID application, essentially my problem is simple, i have a text box where I want to enter data, and a push button which i want to display that value entered inside the text box, the text box is define as
function edit1_Callback(hObject, eventdata, handles)
% hObject handle to edit1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
myString = get(hObject, 'String')
set(hObject,'Value',str2num(myString));
at this point, i entered some numerical value into the text box, lets say 44, now 44 is stored inside the "Value" element of hObject for this function.
Now I want to output this value when a button is pushed
function pushbutton1_Callback(hObject, eventdata, handles)
% hObject handle to pushbutton1 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
fHandle = #edit1_Callback
get(fHandle,'Value')
^^^on this last line i should see some output(since i dont have a ";" which allows matlab to print out the data), the issue is....i get an error that says "Conversion to double from function_handle is not possible." , shouldnt I be able to call "get" using a function handle which points to my earlier function, thanks for any help!
I would go for
get(handles.edit1,'value')
All your uicontrols are stored in the handles. Knowing the tag of your uicontrol (for your edit box I guess this is edit1), you can get the handles of this object with handles.edit1.
You can even write
my_value = get(handles.edit1,'Value');
I'm kind of new to MATLAB and I'm doing some experiments for a school project.
What I want is a GUI with 3 buttons, when you press either of the first two, it adds up to one on a variable (one variable for each button), and when you press the third button, it does something with the variables from the first two buttons.
I used "guide" and dragged and dropped the buttons, and then I modified the functions.
But I realized that my variables only exist inside the function for the button, so if I initialize them they would restart everytime I press the button, and also there is no way for my third button to know the value of the first two.
Is there a way to make this variables always present? Or pass them from a function to another?
My code it's just the automatic code generated by "guide", with a v1 = v1+1; in the first button callback function and v2 = v2+1 in the second one, and disp(v1) disp(v2) in the third.
I hope you understand what I mean, I'm not a native english speaker so...
Anyway, thanks a lot, hope it's something easy to fix.
You have several options:
use global variables as nhowe suggested. But using global variables is not a good practice: see Top 10 MATLAB code practices that make me cry, or Wikipedia article
use setappdata / getappdata functions to store your variables (this is the simpler one)
learn how to use and properly update the handles structure that appears in each callback function for GUI controls created in GUIDE (this one is more complicated).
Here is an example of *.m file for case #3. Most of GUIDE-generated code was removed showing only things related to your variables. Basically, you have to update the handles structure in each callback function that does some changes to it with guidata(hObject, handles); line. After this all subsequent callbacks will see the updated handles structure.
function varargout = GUIProgramWithVariables(varargin)
% Here goes some comment from GUIDE
% Begin initialization code - DO NOT EDIT
% . . . actual code skipped
% End initialization code - DO NOT EDIT
% --- Executes just before GUIProgramWithVariables is made visible.
function GUIProgramWithVariables_OpeningFcn(hObject, eventdata, handles, varargin)
% This function has no output args, see OutputFcn.
% hObject handle to figure
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% varargin command line arguments to GUIProgramWithVariables (see VARARGIN)
% Choose default command line output for GUIProgramWithVariables
handles.output = hObject;
% Here your code starts. It should be at the end of OpeningFcn
% Add your fields to handles structure
handles.C1 = 1;
handles.C2 = 2;
handles.C3 = 3;
% this updates modified handles structure
% so all subsequent call-backs will see the changes
guidata(hObject, handles);
% --- Executes on button press in Button1
function Button1_Callback(hObject, eventdata, handles)
% hObject handle to BrowseButton (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Here we do the magic with Button1
handles.C1 = handles.C1 + 1;
% this updates modified handles structure
% so all subsequent call-backs will see the changes
guidata(hObject, handles);
% --- Executes on button press in Button2
function Button1_Callback(hObject, eventdata, handles)
% hObject handle to BrowseButton (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Here we do the magic with Button2
handles.C2 = handles.C2 + 1;
% this updates modified handles structure
% so all subsequent call-backs will see the changes
guidata(hObject, handles);
% --- Executes on button press in Button3
function Button3_Callback(hObject, eventdata, handles)
% hObject handle to BrowseButton (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
% Here we do the magic with Button3
handles.C3 = handles.C1 + handles.C2;
% this updates modified handles structure
% so all subsequent call-backs will see the changes
guidata(hObject, handles);
The following is not the best practice for large complicated programs, but for something simple like what you're trying to do it sounds like global variables would be perfect. Say that X, Y, and Z are the variables you want to share between functions. Add the following at the beginning of every function that uses them, and they will all have access to the same values.
global X Y Z
I want to view the number of the slice that I'm examining via a simple previous/next slice GUI. I store number of the slice that I'm viewing on handles.index and I'm able to update it via the previous, next pushbuttons.
I wrote the following on the edit text callback function:
function edit2_Callback(hObject, eventdata, handles)
handles.output=hObject
set (edit2.handles,'Tag', handles.index); %also tried with the 'String' property and failed
The Property is not updating when the code is running. It remains as 'Edit Text', what's wrong here?
Full Code, Dicom file
Duh, I made the update on the pushbutton callbacks, and it works fine :)
% --- Executes on button press in pushbutton2.
function pushbutton2_Callback(hObject, eventdata, handles)
% hObject handle to pushbutton2 (see GCBO)
% eventdata reserved - to be defined in a future version of MATLAB
% handles structure with handles and user data (see GUIDATA)
handles.output = hObject;
handles.index = handles.index+1;
Cek (hObject, eventdata, handles);
imshow(handles.image_data(:,:,handles.index),'DisplayRange',[]);
set (handles.edit2,'String', handles.index);