How do I determine whether a UI callback was triggered by a keypress or a mouse click?

I have a UI table in my app (using App Designer) and when editing data in the table cells, the user can exit the cell (and hence trigger the CellEdit callback) either by hitting the Enter key or by clicking elsewhere with the mouse. In the case where the keypress is used, I would like the focus to move to the cell beneath (in the next row), similar to the typical behavior in a spreadsheet application. In the case where the mouse click is used, I want it to just use the default behavior (focus goes to wherever the user clicked). So I’m assuming I need to know whether the callback was triggered with the keyboard or the mouse, so that I can act accordingly. But I’ve searched the properties of the CellEditData event and can’t find this information anywhere. Does anybody know if it’s possible to get this information? Or is there a better way to achieve the desired behavior?

Answer 1

[Samay Sagar]

Since the “CellEditEvent” data doesn't provide direct information about the input method used to trigger the callback, we can use a workaround by introducing a flag to track the last input method. This flag will be set within a “KeyPressFcn” that listens for the Enter key. When the “CellEditCallback” is invoked, it will check this flag to determine the next action allowing for different behaviours based on the input method.

Here's how you can implement this solution:

Firstly, add a private property to your app class to store the last input method:

properties (Access = private)
    LastInputMethod = 'mouse'; % Default to mouse
end

Next, define a “KeyPressFcn” for the table to update this property when the Enter key is pressed

function UITableKeyPress(app, event)
    if strcmp(event.Key, 'return')
        app.LastInputMethod = 'keyboard';
    else
        app.LastInputMethod = 'mouse';
    end
end

In the “CellEditCallback”, you can then check the LastInputMethod property:

function UITableCellEdit(app, event)
    indices = event.Indices;
    if strcmp(app.LastInputMethod, 'keyboard')
        % Move focus to the cell below if the Enter key was used
        nextRow = indices(1) + 1;
        if nextRow <= size(app.UITable.Data, 1)
            app.UITable.Selection = [nextRow, indices(2)]; % Move focus to the cell below
        end
    end
    % Reset the input method to mouse after processing
    app.LastInputMethod = 'mouse';
end

Make sure to assign both the “KeyPressFcn” and the “CellEditCallback” to your table. You can do this in the “startupFcn” of the app

function startupFcn(app)
    app.UITable.KeyPressFcn = @app.UITableKeyPress;
    app.UITable.CellEditCallback = @app.UITableCellEdit;
end

[David Sempsrott]

Perfect! Clean and elegant solution. Many thanks.