如何正确暂停/延迟Windows Forms应用程序

Question

I am a beginner to the OOP and the C#.

I am working on a quiz game using the Windows Forms. My problem is related to two classes, the form and the game logic . I have a basic UI with classic Froms controls. Take a look.

The thing I want to achieve is, when a player presses any answer button, it will higlight that pressed button by red or green color, depending on if it is right or wrong answer. After changing the color I want the program to wait for a while and then go to the next question.

Probelm is, that I don´t know how to achieve this correctly. I don´t know how to work with threads and how exactly the Form app works related to threads. Should I use a thread sleep or a timer or a async?

I will show you the method in game logic class which should handle this.

public static void Play(char answer) //Method gets a char representing a palyer answer
    {
        if (_rightAnswer == answer) //If the answer is true, the button should become green
        {
            Program.MainWindow.ChangeBtnColor(answer, System.Drawing.Color.LightGreen);
            _score++;
        }
        else //Otherwise the button becomes Red
        {
            Program.MainWindow.ChangeBtnColor(answer, System.Drawing.Color.Red);
        }

        //SLEEP HERE

        if (!(_currentIndex < _maxIndex)) //If it is the last question, show game over
        {
            Program.MainWindow.DisplayGameOver(_score);
        }
        else //If it is not the last question, load next question and dispaly it and finally change the button color to default
        {
            _currentIndex++;
            _currentQuestion = Database.ListOfQuestions.ElementAt(_currentIndex);
            _rightAnswer = _currentQuestion.RightAnswer;
            Program.MainWindow.DisplayStats(_score, _currentIndex + 1, _maxIndex + 1);
            Program.MainWindow.DisplayQuestion(_currentQuestion.Text);
            Program.MainWindow.DisplayChoices(_currentQuestion.Choices);
        }
        Program.MainWindow.ChangeBtnColor(answer, System.Drawing.SystemColors.ControlLight);
    }

I don´t want to completely block the UI but also I don´t want users to make other events by pressing other buttons during the pause. Because it will result in improper run of app.

Answer 1

If the program is really simple and you do not want to implement Threads I would suggest using Timer. Just start your Timer when clicking answer button. Your timer should contain function which would stop itself after some time and do other actions needed (eg pick another question).

Answer 2

Once the user has selected an answer you can disable all the buttons so they can't press anything else.

Then start a timer so you don't block the UI. The timer is basically a thread but handles all the threading for you so you don't have to worry about that aspect.

When the timer reaches the desired delay stop it and fire an event to select the next question.

Answer 3

At //SLEEP HERE add this line of code

Timer timer = new Timer(new TimerCallback(timerCb), null, 2000, 0);

The 2000 is milliseconds and is the wait time, timerCb is a call back method.

Also under that disable all your buttons so new events wont be generated.

private void timerCb(object state)
    {
        Dispatcher.Invoke(() =>
        {
            label1.Content = "Foo!";              
        });
    }

You can do whatever you want in the callback, however if you do something that would change anything in the UI, you need to use the Dispatcher like I have changing the label content.

Answer 4

Suspending execution in a GUI scenario is very easy thanks to await :

await Task.Delay(2000);

This does not block the UI.

You should research what await does and how to use it. If you have never heard about it and are programming WinForms you are doing something wrong.

No timers or threads are needed. No callbacks, no Invoke .