[MATLAB] Basic use of APP Designer timer (Timer)

The timer is powerful, and this article records a simple use case.

Function description

Click to start timing, and call the callback function when the set time is reached.
In the callback function, the value of "numerical display" is incremented by one.
The period of the timer can be modified manually.

UI layout

Among them: The character boxes are all numeric boxes, not text boxes.
component name

Implementation steps

1. Add properties

Here I choose the handle of the private attribute
timer

   properties (Access = private)
        Timer_id;        % 定时器id
   end

2. Add timer control function

Here I choose private function

methods (Access = private)
        
       % 定时器初始化，重复模式
        function timer_init(app)
            app.Timer_id = timer;
            app.Timer_id.StartDelay = 0.01; % 开启的延时生效时间
            app.Timer_id.Period = 1.0;% 周期
            app.Timer_id.ExecutionMode = 'fixedSpacing';
            app.Timer_id.TimerFcn = @(~, ~) timer_handler(app);
        end
    
        % 定时器启动
        function timer_start(app)
            start(app.Timer_id);
        end
    
        % 定时停止
        function timer_stop(app)
            stop(app.Timer_id);
        end
    
        % 删除定时器
        function timer_delete(app)
            delete(app.Timer_id);
        end
    
        %定时器回调
        function timer_handler(app)
            %执行定时器任务
            app.EditField.Value = app.EditField.Value +1;
        end
    end

Explanation of some concepts:

• The period timed by the Period
  timer.
• The interval between when StartDelay
  starts the timer and when the countdown starts.
  For example: StartDelay = 4, Period = 2
  start(app.Timer_id); will wait for 4s of StartDelay first, then count down 2s of Period, and then call the callback function of TimerFcn for processing.
• ExecutionMode
  specifies the triggering method of the timer (trigger once, or cyclically...) There are four methods in total, which can be selected according to actual needs.

sigleShot; only executed once, the timer will be automatically closed after execution. In other modes, fixedDelay can be executed cyclically; fixedRate
is the interval between the time when the last TimerFcn is executed and the time when the next TimerFcn is added to the queue; the interval between the last execution and the next addition to the queue is fixedSpacing: two times before and after are added to the execution Interval between statement queue moments

• delete and modify period
  To delete a timer, you can delete or modify the period only after the timer is stopped.

3. Initialize the timer

Right-click app.UIFigure to add a callback function

        % Code that executes after component creation
        function startupFcn(app)
            timer_init(app);
          
        end

After the software is opened, the initialization of the timer will be performed.

4. Start or stop the timer

Add keypress callback for stop button. (This button uses the status button)

       % Value changed function: Button_Contrl
        function Button_ContrlValueChanged(app, event)
            value = app.Button_Contrl.Value;
            if value == 1
                app.Button_Contrl.Text = '停止';
                timer_start(app);
            else
                app.Button_Contrl.Text = '开始';
                timer_stop(app);
            end
        end

5. Set the timer period

You can add the callback function of the corresponding button.
Note that you must stop it before you can modify it.

        % Button pushed function: Button_SetPeriod
        function Button_SetPeriodPushed(app, event)
            timer_stop(app);
            app.Timer_id.Period = app.EditField_PeriodValue.Value;
            timer_start(app);
        end

Add a callback function for clearing the value to zero.

      % Button pushed function: Button_Clear
        function Button_ClearPushed(app, event)
            app.EditField_Show.Value = 0;
        end

6. Set the software to close the callback

When the software is closed, release the timer

        function UIFigureCloseRequest(app, event)
            
            % 停止定时器，然后删除
            timer_stop(app);
            timer_delete(app);
            
            
            delete(app);
            
        end

Experimental results

Click the start button

and click clear to clear the data to 0.

Set the timing period to 0.2, and the speed of the value increase is significantly faster.

Click stop, the timer stops, and the value does not increase.