C# .NET 控制台应用程序获取键盘输入

Question

I am trying to make a console application and it (don't ask me why) requires keyboard input (DownArrow and UpArrow). So far so good. The keyboard input needs to be in a While(true) loop and run forever, it is checked with an if statement. I tried using Console.ReadKey() == ConsoleKey.UpArrow; but that seems to pause the loop from running. Anyway I can run an if(Keyboard.input == Key.UpArrow){} statement without pausing the loop (basically skipping over it if it isn't the case)?

Here is an example of what I mean:

while (true){

if (Console.ReadKey() == ConsoleKey.UpArrow){ // this pauses the loop until input, which is not what I want / need.
 // Do stuff
}
Frame.Update();
}

Answer 1

The trick is that you first need to check if there is a KeyAvailable in the cache, and then use ReadKey() to read it. After that, your code should work as you expect. The line of code that does this would look something like:

// Check if there's a key available. If not, just continue to wait.
if (Console.KeyAvailable) { var key = Console.ReadKey(); }

Here's a sample to demonstrate:

public static void Main(string[] args)
{
    Console.SetCursorPosition(Console.WindowWidth / 2, Console.WindowHeight / 2);
    Console.CursorVisible = false;
    Console.Write('*');

    var random = new Random();

    while (true)
    {
        if (Console.KeyAvailable)
        {
            var key = Console.ReadKey(true);

            switch (key.Key)
            {
                case ConsoleKey.UpArrow:
                    if (Console.CursorTop > 0)
                    {
                        Console.SetCursorPosition(Console.CursorLeft - 1, 
                            Console.CursorTop - 1);
                        Console.Write('*');
                    }
                    break;
                case ConsoleKey.DownArrow:
                    if (Console.CursorTop < Console.BufferHeight)
                    {
                        Console.SetCursorPosition(Console.CursorLeft - 1, 
                            Console.CursorTop + 1);
                        Console.Write('*');
                    }
                    break;
                case ConsoleKey.LeftArrow:
                    if (Console.CursorLeft > 1)
                    {
                        Console.SetCursorPosition(Console.CursorLeft - 2, 
                            Console.CursorTop);
                        Console.Write('*');
                    }
                    break;
                case ConsoleKey.RightArrow:
                    if (Console.CursorLeft < Console.WindowWidth - 1)
                    {
                        Console.Write('*');
                    }
                    break;
            }
        }

        // This method should be called on every iteration, 
        // and the iterations should not wait for a key to be pressed
        // Instead of Frame.Update(), change the foreground color every three seconds  
        if (DateTime.Now.Second % 3 == 0) 
            Console.ForegroundColor = (ConsoleColor) random.Next(0, 16);
    }
}

Answer 2

Console.ReadKey locks thread. You should create another thread and read key there. Example Here:

Task.Factory.StartNew(() =>
            {
                if (Console.ReadKey().Key == ConsoleKey.UpArrow)
                {
                    Console.WriteLine("Pressed");
                }
            });