matlab - Matlab 编辑文本框 - 显示提示？

Question

使用 Matlab GUI 时，有没有办法在编辑文本框中放置“提示”？也就是说，一旦用户开始输入，文本就会消失？我在 Android 中使用过类似的功能，但我对其他 GUI 不太熟悉，所以我不确定这个功能的普及程度。

Answer 1

这在 Matlab 中是可能的，但您必须定义一个 custom MouseClickCallback，它只能使用Yair Altman 的findjobj访问（使用链接从 Matlab File Exchange 下载它并将其保存在您的 Matlab 路径中的某个位置）。

因为我喜欢这个想法，所以我编写了一个函数来方便地处理所有这些。它会创建一个灰显的斜体帮助文本，一旦单击编辑框就会消失。

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