Drag and Drop in GUI

Question

Is it possible to create an object in a GUI whose position I can define by the cursor position (drag when clicked) by setting its 'Position' property to whatever the cursor position is? What function should I be using?

Answer 1

You can use the SELECTMOVERESIZE function to turn on moving and resizing for your GUI object. Then you can just click and drag the object with the mouse. It's as simple as this:

set(hObject,'ButtonDownFcn','selectmoveresize');

What's not so simple is if your GUI object is a uicontrol object, in which case you will have to disable the object by setting the 'Enable' property to 'off' or 'inactive' in order to have the 'ButtonDownFcn' function execute instead of the 'Callback' function. This is true even if you haven't defined a callback for the object.

You will also probably need to add a means to your GUI to turn the moving and resizing of the object on and off, perhaps an extra button or a menu item you can select. To show how you could do this with a push button, here's a simple example that creates a figure with an editable text box and a push button that turns on and off the ability to move and resize the editable text box:

function GUI_example

  hFigure = figure('Position',[100 100 200 200],...  %# Create a figure
                   'MenuBar','none',...
                   'ToolBar','none');
  hEdit = uicontrol('Style','edit',...               %# Create a multi-line
                    'Parent',hFigure,...             %#   editable text box
                    'Position',[10 30 180 160],...
                    'Max',2,...
                    'String',{'(type here)'});
  hButton = uicontrol('Style','pushbutton',...       %# Create a push button
                      'Parent',hFigure,...
                      'Position',[50 5 100 20],...
                      'String','Turn moving on',...
                      'Callback',@button_callback);

  function button_callback(hSource,eventData)        %# Nested button callback

    if strcmp(get(hSource,'String'),'Turn moving on')
      set(hSource,'String','Turn moving off');          %# Change button text
      set(hEdit,'Enable','inactive',...                 %# Disable the callback
                'ButtonDownFcn','selectmoveresize',...  %# Turn on moving, etc.
                'Selected','on');                       %# Display as selected
    else
      set(hSource,'String','Turn moving on');           %# Change button text
      set(hEdit,'Enable','on',...                       %# Re-enable the callback
                'ButtonDownFcn','',...                  %# Turn off moving, etc.
                'Selected','off');                      %# Display as unselected
    end

  end

end

Note: although the documentation lists the 'Selected' property as read-only, I was able to modify it without a problem. It must be a typo in the documentation.