How to display an error message with Try/catch?

Hi

I am a complete newbie. I have created a GUI, and in this GUI at the first the user should choose a video to load, after that he should enter a number(of frame) for visualising the photo of this frame. I want to use a try/catch who doesn't let the user to enter a number which is superior than the existing number of frames and display an error message. But I don't know how to do that...( The user can choose any video at the first, so I won't know the number of frames. How should I specify the range of the numbers that he can enter? I know that it could be with the size() but I don't know how...)

[Image Analyst]

You already asked this twice before, and accepted my answer in this post - what's different now?

Answer 1

[Sean de Wolski]

Instead of using a try/catch, inside of the callback for the edit box where they enter the number figure out if the value they have entered is accurate. If it's not, write back the previous value and use errordlg to display the error message.

More

function exampleVerifyString

uicontrol('Style','edit',...
    'Units','normalized',...
    'Position',[0.1 0.1 0.3 0.5],...
    'String','5',...
    'Callback',@verifyString);

end

function verifyString(src,~)
    %Get the string
    val = str2double(get(src,'String'));

      %If it's not a number, or integerbetween 0 and 100
      if isnan(val) || val<0 || val>100 || val ~= round(val)
          set(src,'String','5');
          errordlg('Please enter an integer between 0 and 100','Invalid Input');        
      end
  end

Save the above as exampleVerifyString.m

[anahita]

Thank you soooooooo much for the answer.

[Sean de Wolski]

See more

Answer 2

[Chandrasekhar]

    try
  % code in try part
  catch
  errordlg('error')
  end