How to find value of modifier with keypressfcn?

Question

Lyn 2015-1-7

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/169199-how-to-find-value-of-modifier-with-keypressfcn

评论： Geoff Hayes 2015-1-9

采纳的回答： Geoff Hayes

在 MATLAB Online 中打开

Hi, I'm trying to make a simple gui where 'tab' increases variable 'a' and 'shift+tab' decreases it.

Unfortunately, my code can't seem to pick up the shift modifier being pressed?

function varargout = modt(varargin)
% Begin initialization code - DO NOT EDIT
gui_Singleton = 1;
gui_State = struct('gui_Name',       mfilename, ...
                   'gui_Singleton',  gui_Singleton, ...
                   'gui_OpeningFcn', @modt_OpeningFcn, ...
                   'gui_OutputFcn',  @modt_OutputFcn, ...
                   'gui_LayoutFcn',  [] , ...
                   'gui_Callback',   []);
if nargin && ischar(varargin{1})
    gui_State.gui_Callback = str2func(varargin{1});
end
if nargout
    [varargout{1:nargout}] = gui_mainfcn(gui_State, varargin{:});
else
    gui_mainfcn(gui_State, varargin{:});
end
% End initialization code - DO NOT EDIT
function modt_OpeningFcn(hObject, eventdata, handles, varargin)
handles.a = 0;
guidata(hObject, handles);
function varargout = modt_OutputFcn(hObject, eventdata, handles) 
function figure1_KeyPressFcn(hObject, eventdata, handles)
handles = guidata(hObject);
if strcmp(eventdata.Key,'tab')
    handles.a = handles.a + 1
elseif strcmp(eventdata.Modifier{:},'shift') && strcmp(eventdata.Key,'tab')
    handles.a = handles.a - 1
end
guidata(hObject,handles)

Thanks for the help!

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Answer 1

Geoff Hayes 2015-1-8

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/169199-how-to-find-value-of-modifier-with-keypressfcn#answer_164281

在 MATLAB Online 中打开

Lyn - look closely at your if/elseif

 if strcmp(eventdata.Key,'tab')
    handles.a = handles.a + 1
 elseif strcmp(eventdata.Modifier{:},'shift') && strcmp(eventdata.Key,'tab')
    handles.a = handles.a - 1
 end

For your elseif there are two conditions:

strcmp(eventdata.Modifier{:},'shift') && strcmp(eventdata.Key,'tab')

So the code will decrement a by one if both conditions are true. BUT, the second condition is the (only) condition for the if statement! So your elseif will never evaluate because the if will always take precedence.

Try the following instead

 if strcmp(eventdata.Key,'tab')
    if isempty(eventdata.Modifier)
        handles.a = handles.a + 1
    elseif strcmp(eventdata.Modifier{:},'shift') 
        handles.a = handles.a - 1
    end
 end