Why am I getting this error when selecting files with uigetfile? - matlab

Question

I used uigetfile to select multiple images. When I select the images and push the open button or press the enter key everything is okay. But when I instead select the images and double click on the selected images, I get this error:
Cell contents reference from a non-cell array object.
Error in Picketfence>insertpb_Callback (line 141)
file = fullfile(PathName,FileNames{i});
Here's my code:
c={'*.*', 'All Files(*.*)';'*.jpeg','figure (*.jpg)';'*.tif',...
'figure (*.tif)'};
[FileNames,PathName] = uigetfile(c, 'Select Images','MultiSelect','on');
if char(FileNames)
nfiles = length(FileNames);
handles.profile = zeros(1024,1024);
for i = 1:nfiles
file = fullfile(PathName,FileNames{i});
handles.profile = handles.profile+im2double(imread(file));
end
end
Why am I getting this error and how can I fix it?

Answer 1

The problem is that you can't select multiple files by double-click. When you select your files, then double-click on one of them, what's actually happening is that you are selecting only the one you double-clicked on. In other words, the first click of the double-click selects just that one, clearing the others.
When the GUI closes and returns to your code, you only have a single file selected, so FileNames isn't a cell array, just a character string. This is why the cell content indexing with {} fails.
A few more points about your code...
Your conditional check if char(FileNames) is wrong. The char function doesn't return logical (i.e. boolean) values. It converts things to character arrays. As per the documentation for uigetfile, the outputs will be zero when the selection is cancelled or the GUI closed, so the appropriate check in your case would be:
if ~isequal(FileNames, 0)
% Do your processing here...
else
% Nothing was selected; take some other action
end
You may want to account for the possibility of only 1 file being selected, thus having FileNames be a character array. The simplest way to do this is to first check if FileNames is a character array using ischar, and if so encapsulate it in a 1 element cell array (since your code expects cell arrays):
if ischar(FileNames)
FileNames = {FileNames};
end
Then you can do all your processing as you have it written above.