C ++检查是否按下了键，没有按下

Question

I have the following code:

for (int i = 0; i < 1;) {
        if (GetKeyState(VK_SHIFT) & 0x8000)
        {
            cout << "op";
        }
}

This prints out op if the Shift key is held down, actually it spams the output if you hold down the key.

This is what I want instead:

The program prints out something ONCE when you press/hold down a key instead of spamming it, and the only way to print it again is to let go of the key and press it again. No matter how long you hold down the key, the program will only execute the following code ONCE, unless you press it again.

How do I make my code do this?

Answer 1

You could simply set a bool to true when you've detected a "key down" event and then only set it back to false once you detect a "key up" event. That way you can know if the key was already down and only report that it was pressed if it was not already in that state.

Answer 2

Have you used Windows APIs? If not, try GetKeyState(key) < 0

If Windows messages are used with a window callback function, you can use bools array and check the WM_KEYDOWN WM_KEYUP events.