Why slider not working?

Question

Stelios Fanourakis 2018-6-1

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/403498-why-slider-not-working

评论： Stelios Fanourakis 2018-6-5

I got this function

function slider1_Callback(hObject,eventdata, handles,im2,S,sno)
% test it out - get the handles object and display the current value
handles.sliderImages = handles.im2;
im2 = handles.sliderImages
SIZE_Z = handles.SIZE_Z;
set(handles.slider1,'Value',1);
set(hObject,'Min',1,'Max',SIZE_Z);
set(hObject,'SliderStep',[1/(SIZE_Z-1),1/(SIZE_Z-1)]);
slider2Val=floor(get(hObject,'Value'));
currentSlice=slider2Val;
imshow(im2(:,:,currentSlice),[752 1512],'Parent',handles.axes1); 
handles.currentSlice=currentSlice;
guidata(hObject,handles);
edit12_Callback(hObject, eventdata, handles);

And I get the error "Struct contents reference from a non-struct array object." at line

handles.sliderImages = handles.im2;

What can this mean?

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Stelios Fanourakis 2018-6-3

在 MATLAB Online 中打开

I have this code:

    function SliderDemo
    clc
    filelist=dir(fullfile('D:\stelios phd files\DesMoines\karadokei\New\*.dcm'));
    handles.filelist = filelist;
    handles.frameindex = 1;
    NumFrames = 15; %// Check below for dummy 4D matrix/image sequence
    hFig = figure('Position',[100 100 500 500],'Units','normalized');
    handles.axes1 = axes('Units','normalized','Position',[.2 .2 .6 .6]);
    %// Create slider and listener object for smooth visualization
    handles.SliderFrame = uicontrol('Style','slider','Position',[60 20 400 50],'Min',1,'Max',NumFrames,'Value',1,'SliderStep',[1/NumFrames 2/NumFrames],'Callback',@XSliderCallback);
    handles.SliderxListener = addlistener(handles.SliderFrame,'Value','PostSet',@XListenerCallBack);
    handles.Text1 = uicontrol('Style','Text','Position',[180 420 60 30],'String','Current frame');
    handles.Edit1 = uicontrol('Style','Edit','Position',[250 420 100 30],'String','1');
    %// Create dummy image sequence, here 4D sequence of grayscale images.
    Img = DicomReader('S0000009.dcm')
    isoImage = makeImIsoRGB(Img, [1,1,15], 1.5, 'cubic')
    MyImage = isoImage;
    MyMatrix = MyImage;
    %// Use setappdata to store the image stack and in callbacks, use getappdata to retrieve it and use it. Check the docs for the calling syntax.
    setappdata(hFig,'MyMatrix',MyMatrix); %// You could use %//setappdata(0,'MyMatrix',MyMatrix) to store in the base workspace. 
    %// Display 1st frame
    imshow(MyMatrix(:,:,1),[])
    %// IMPORTANT. Update handles structure.
    guidata(hFig,handles);
    %// Listener callback, executed when you drag the slider.
    %// Slider callback; executed when the slider is release or you press
    %// the arrows.
        function XSliderCallback(~,~)
            handles = guidata(gcf);
    %// Here retrieve MyMatrix using getappdata.
        MyMatrix = getappdata(hFig,'MyMatrix');
            CurrentFrame = round((get(handles.SliderFrame,'Value')));
            set(handles.Edit1,'String',num2str(CurrentFrame));
            imshow(MyMatrix(:,:,CurrentFrame),'parent',handles.axes1);
            filelist = handles.filelist;
            frameindex  = handles.frameindex;
            myfolder='D:\stelios phd files\DesMoines\karadokei\New';
            currentframefile = filelist(frameindex).name;
            handles.frameindex = frameindex+1;
            ff=fullfile(myfolder,currentframefile);
            I=dicomread(ff);
            imshow(I);
            guidata(hFig,handles);
        end
    end

It perfectly works, only once. Untill the left slider bar reaches the right end. When I try to reslide it again backwards, from right to left, it becomes a mess and get errors like

Warning: Error executing listener callback for PostSet event on Value dynamic property in object of
matlab.ui.control.UIControl class:
Undefined function 'XListenerCallBack' for input arguments of type 'matlab.graphics.internal.GraphicsMetaProperty'. 
Index exceeds matrix dimensions.
Error in SliderDemo/XSliderCallback (line 60)
        currentframefile = filelist(frameindex).name;
Error while evaluating UIControl Callback.

Please, help.

Walter Roberson 2018-6-3

Type that at the command line and then run the code.

Stelios Fanourakis 2018-6-3

Well. When the slider finishes at the end right and start to drag it back to left. I get the error at the first left click and the values are, CurrentFrame: 14 frameindex: 16.

Should they be equal? What to do to change it/?

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Answer 1

Walter Roberson 2018-6-2

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/403498-why-slider-not-working#answer_322947

You cannot bring a variable defined in another function into the current function just by mentioning its name in the function() definition.

If you are defining those variables in the load image callback, then you need to store those values somewhere that the slider callback can get at, such as in the handles structure (though storing an entire image in a handles structure is not the best idea for performance reasons.)

http://matlab.wikia.com/wiki/FAQ#How_can_I_share_data_between_callback_functions_in_my_GUI.28s.29.3F

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Walter Roberson 2018-6-4

SliderDemo.m

Unfortunately, you did not describe your intention for having the two different imshow, so I cannot give you finished code. I have attached modified code that works as best practical considering my lack of knowledge about your intentions.

You will notice that the right hand image only changes once. There are two reasons combined for that:

The slider Callback is being invoked only once, so you are setting frameindex only once. After that, the Listener callback is being invoked
Your first imshow displays from CurrentFrame, but your second imshow reads according to frameindex and displays that. Because two different sources of data are being used, I have to assume that it was deliberate that you did that, that you want to be accessing two different relative indices, and that your only mistake for the Listener Callback is in displaying them both to the same axes (because the target axes had not been specified for the second imshow())

If I were writing code that had to slide through a single data source, I would use only the Callback and not the listener at all. But I have to assume you had good reason for using both with different functionality.

Walter Roberson 2018-6-4

As I explained, that is because you are asking to display according to frameindex, but frameindex is only changed by the slider Callback; your Listener callback changes CurrentFrame not frameindex. It happens to be the case that when you have both a slider Callback and a Listener for that slider, that the slider Callback will be called the first time but after that as long as the slider is what has focus, the listener callback will be called instead.

The one on your left is displaying information from your Matrix variable. The right one is displaying information read in from files. Your code was displaying both, one on top of the other, which resulted in the second one erasing the first.

I do not know why you are maintaining Matrix separate from reading from a file, and I do not know why you programmed a Slider callback separate from a Listener callback. If you can explain why you programmed Callback and Listener as well, and if you can explain the difference for your purposes between CurrentFrame and frameindex, and if you can explain the difference between the Matrix variable and reading from the file, then I might be able to get further.

I cannot repair your code until you explain what your intentions were in creating the code that way.

You must have had a reason for having frameindex separate from CurrentFrame ??

Stelios Fanourakis 2018-6-5

I know what I want. I explained to my previous comment. If you can give me a code that actually changes images forward and backwards, I'll accept your answer

Stelios Fanourakis 2018-6-5

在 MATLAB Online 中打开

Can you please let me know how can I make this line

CurrentFrame = round((get(handles.SliderFrame,'Value')));

To actually work and change between frames and not just dim the first image.

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Why slider not working?

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Why slider not working?

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