Table scroll position - Update problem

Question

Peter Borda 2014-12-17

1
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/166939-table-scroll-position-update-problem

评论： Walter Roberson 2019-12-13

Hello, I have the following problem. I am appending new empty rows to a table in my GUI with this code:

function AddNRows(handles,newRow)
% appends N empty rows to the end of table
%
% handles  --> handles structure of GUI
% newRows  --> number of new rows
% handles.DataTable is the name of the table 
oldData = get(handles.DataTable,'Data'); % get old data from table
nRows = size(oldData,1);                 % get actual row number
data = cell(nRows+newRow,3);             % create new cell with additional rows
data(1:nRows,:) = oldData;               % store old data in new cell 
set(handles.DataTable,'Data',data)       % modify Data field of table
guidata(handles.DataTable,handles)

My original problem was that every time this function is evaluated, the scroll jumps up to the original position, which is really bothering since the new rows are added to the end of the table. The solution I found ( http://undocumentedmatlab.com/blog/customizing-listbox-editbox-scrollbars ) is to use this code:

jScrollpane = findjobj(handles.DataTable);                % get the handle of the table
scrollMax = jScrollpane.getVerticalScrollBar.getMaximum;  % get the end position of the scroll
AddNRows(handles,1);                                     % appending 1 new row
jScrollpane.getVerticalScrollBar.setValue(scrollMax);     % set scroll position to the end

And here is the funny thing! If I run this code in debug mode, step-by-step, my problems are solved, new rows are added and the scroll stays where it should (or actually jumps to the end after the GUI element is updated). But when I run the code normally, without debugging, the scroll jumps back to the zero position, as if setValue(scrollMax) wouldn't be there.

Any idea what is happening?

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Answer 1

matt dash 2014-12-17

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https://ww2.mathworks.cn/matlabcentral/answers/166939-table-scroll-position-update-problem#answer_162622

Usually when something works in debug mode but not in normal operation, it means you need to add a "drawnow" to your code. In debug mode, there is an implicit "drawnow" that occurs each time you step through the code. Try adding one before the "scrollMax=..." line and see if that fixes it.