Create Continuous Knob

fig = uifigure;
kb = uiknob(fig);

Create Discrete Knob

Specify a Figure object as the parent container.

fig = uifigure('Position',[100 100 300 250]);
kb = uiknob(fig,'discrete');

Set and Access Continuous Knob Property Values

fig = uifigure;
kb = uiknob(fig);

limits = kb.Limits

limits =

     0   100

kb.Limits = [-10 10];
kb.Value = 5;

Set and Access Property Values

fig = uifigure;
kb = uiknob(fig,'discrete');

kb.Items = {'Cold', 'Warm', 'Hot'};
kb.ItemsData = {32, 80, 212};

degrees = kb.Value

degrees =

    32

Code Response to Changed Discrete Knob Setting

Create a discrete knob that performs an action after the app user turns it. Turning the knob updates the value of a text field to reflect the app user's choice.

function displayKnobValue
% Create figure window

fig = uifigure('Position',[100 100 283 275]);

% Create the text field
txt = uieditfield(fig,'text',...
    'Position', [69 82 100 22]);

% Create the knob
kb = uiknob(fig,'discrete',...
    'Position',[89 142 60 60],...
    'ValueChangedFcn',@(kb,event) knobTurned(kb,txt));
end

% Code the knob callback function
function knobTurned(knob,txt)
txt.Value = knob.Value;
end

Code Response to Changed Continuous Knob Setting

Create a continuous knob that performs an action after the user turns it. Turning the knob updates the value of a label to reflect the user's choice.

function showKnobValue
% Create figure window and components
fig = uifigure('Position',[100 100 283 275]);

% Create label
lbl = uilabel(fig,...
    'Position',[218 177 50 15],...
    'Text','0');

% Create knob
kb = uiknob(fig,...
    'Position',[89 142 60 60],...
    'ValueChangedFcn', @(kb,event) knobTurned(kb,lbl));
end

% Create ValueChangedFcn callback
function knobTurned(kb,lbl)
num = kb.Value;
lbl.Text = num2str(num);
end

Code Response to Changing Continuous Knob Setting

Create a continuous knob that repeatedly performs an action as the user is turning it. Instead of updating a label once when the user releases the mouse button, this knob updates the label as the knob is being turned.

function showChangingValue
% Create figure window
fig = uifigure('Position',[100 100 283 275]);

% Create numeric edit field
num = uieditfield(fig,'numeric',...
    'Position',[69 82 100 20]);

% Create knob
kb = uiknob(fig,...
    'Position',[89 142 60 60],...
    'ValueChangingFcn',@(kb,event) knobTurned(kb,event,num));
end

% Create ValueChangingFcn callback
function knobTurned(kb,event,num)
num.Value = event.Value;
end

Code Response to Invalid Knob Setting

Create a continuous knob that performs an action after the user turns it. each turn of the knob causes MATLAB to perform a calculation using the current and previous knob values.

Copy and paste the following code into a file named increaseOnly.m on your MATLAB path. This code creates a window containing a continuous knob. It specifies a ValueChangedFcn callback for the knob to display an Invalid Value dialog box when the app user attempts to decrease the knob value.

function increaseOnly
% Create figure window
fig = uifigure('Position',[100 100 400 275]);

% Create knob
kb = uiknob(fig,...
    'Position',[150 125 60 60],...
    'ValueChangedFcn',@(kb,event) nValChanged(kb,event,fig));
end

% Create ValueChangedFcn callback
function nValChanged(kb,event,fig)
newvalue = event.Value;
previousvalue = event.PreviousValue;
if previousvalue >  newvalue
   uialert(fig, 'Increase value only. Value set to previous value.',...
        'Invalid Value');
   kb.Value = previousvalue;
end
end

Run increaseOnly, increase the knob value, and then try to decrease it. When you try to decrease the value, an error dialog box displays and the value is reverted to the previous valid value. You can only increase the knob value.