Question

When working with Matlab GUIs, is there a way to place a “hint” in an Edit Text box? That is, text that will disappear once the user starts typing? I’ve used similar functionalities in Android, but I’m not as familiar with other GUIs, so I’m not sure how widespread this functionality is.

Answer 1

This is possible in Matlab, but you have to define a custom MouseClickCallback, which is only accessible using findjobj by Yair Altman (download it from the Matlab File Exchange using the link and save it somewhere on your Matlab path).

Since I like the idea, I have written a function that conveniently takes care of all this. It creates a grayed-out, italic help text that disappears once you click the edit box.

function setInitialHelp(hEditbox,helpText)
%SETINITIALHELP adds a help text to edit boxes that disappears when the box is clicked
%
% SYNOPSIS: setInitialHelp(hEditbox,helpText)
%
% INPUT hEditbox: handle to edit box. The parent figure cannot be docked, the edit box cannot be part of a panel.
%       helpText: string that should initially appear as help. Optional. If empty, current string is considered the help.
%
% SEE ALSO uicontrol, findjobj
%
% EXAMPLE   
%           fh = figure;
%           % define uicontrol. Set foregroundColor, fontAngle, before 
%           % calling setInitialHelp
%           hEditbox = uicontrol('style','edit','parent',fh,...
%             'units','normalized','position',[0.3 0.45 0.4 0.15],...
%             'foregroundColor','r');
%           setInitialHelp(hEditbox,'click here to edit')
%

% check input
if nargin < 1 || ~ishandle(hEditbox) || ~strcmp(get(hEditbox,'style'),'edit')
    error('please supply a valid edit box handle to setInitialHelp')
end

if nargin < 2 || isempty(helpText)
    helpText = get(hEditbox,'string');
end

% try to get java handle
jEditbox = findjobj(hEditbox,'nomenu');
if isempty(jEditbox)
    error('unable to find java handle. Figure may be docked or edit box may part of panel')
end

% get current settings for everything we'll change
color = get(hEditbox,'foregroundColor');
fontAngle = get(hEditbox,'fontangle');

% define new settings (can be made optional input in the future)
newColor = [0.5 0.5 0.5];
newAngle = 'italic';

% set the help text in the new style
set(hEditbox,'string',helpText,'foregroundColor',newColor,'fontAngle',newAngle)

% add the mouse-click callback
set(jEditbox,'MouseClickedCallback',@(u,v)clearBox());

% define the callback "clearBox" as nested function for convenience
    function clearBox
        %CLEARBOX clears the current edit box if it contains help text

        currentText = get(hEditbox,'string');
        currentColor = get(hEditbox,'foregroundColor');

        if strcmp(currentText,helpText) && all(currentColor == newColor)
            % delete text, reset color/angle
            set(hEditbox,'string','','foregroundColor',color,'fontAngle',fontAngle)
        else
            % this is not help text anymore - don't do anything
        end

    end % nested function

end % main fcn