C# 检测按下 Shift 键而不使用 Windows 窗体中的事件？
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Detect Shift key is pressed without using events in Windows Forms?
提问by
I need to be able to detect that the shift key is being held, but I don't want to use events or global variables to determine that. Is there an API in C# that lets you ask what keys are currently pressed instead of using the event?
我需要能够检测到正在按住 shift 键，但我不想使用事件或全局变量来确定。C# 中是否有 API 可以让您询问当前按下了哪些键而不是使用事件？
回答by JoshBerke
Not sure if this available in C# but you can call GetAsyncKeyState. This method returns the state of a key at the time the method is called.
不确定这在 C# 中是否可用，但您可以调用GetAsyncKeyState。此方法返回调用该方法时键的状态。
To call it from C# you'll need to use interop like any other Win32 API.
要从 C# 调用它，您需要像任何其他 Win32 API 一样使用互操作。
回答by Dan Bystr?m
Form.ModifierKeys(static property)
Form.ModifierKeys（静态属性）
回答by ConsultUtah
You can install a low-level keyboard hook.
您可以安装一个低级键盘钩子。
using System;
using System.Diagnostics;
using System.Windows.Forms;
using System.Runtime.InteropServices;
class InterceptKeys
{
private const int WH_KEYBOARD_LL = 13;
private const int WM_KEYDOWN = 0x0100;
private static LowLevelKeyboardProc _proc = HookCallback;
private static IntPtr _hookID = IntPtr.Zero;
public static void Main()
{
_hookID = SetHook(_proc);
Application.Run();
UnhookWindowsHookEx(_hookID);
}
private static IntPtr SetHook(LowLevelKeyboardProc proc)
{
using (Process curProcess = Process.GetCurrentProcess())
using (ProcessModule curModule = curProcess.MainModule)
{
return SetWindowsHookEx(WH_KEYBOARD_LL, proc,
GetModuleHandle(curModule.ModuleName), 0);
}
}
private delegate IntPtr LowLevelKeyboardProc(
int nCode, IntPtr wParam, IntPtr lParam);
private static IntPtr HookCallback(
int nCode, IntPtr wParam, IntPtr lParam)
{
if (nCode >= 0 && wParam == (IntPtr)WM_KEYDOWN)
{
int vkCode = Marshal.ReadInt32(lParam);
Console.WriteLine((Keys)vkCode);
}
return CallNextHookEx(_hookID, nCode, wParam, lParam);
}
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern IntPtr SetWindowsHookEx(int idHook,
LowLevelKeyboardProc lpfn, IntPtr hMod, uint dwThreadId);
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool UnhookWindowsHookEx(IntPtr hhk);
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode,
IntPtr wParam, IntPtr lParam);
[DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern IntPtr GetModuleHandle(string lpModuleName);
}
回答by SLaks
if ((Control.ModifierKeys & Keys.Shift) != 0)
This will also be trueif another modifier key is also down (eg, Ctrl+Shift). If you want to check whether Shift alone is pressed without any other modifiers, use
true如果另一个修饰键也按下（例如，Ctrl+Shift），也会出现这种情况。如果要检查是否单独按下 Shift 而没有任何其他修饰符，请使用
if (Control.ModifierKeys == Keys.Shift)
Note that even this will be trueif another non-modifier is down (Eg, Shift+A). If you want to check whether Shift and onlyShift is pressed, you'll have to use an API call.
请注意，true如果另一个非修饰符被关闭（例如，Shift+A），即使这样也会如此。如果要检查是否按下了Shift 并且仅按下了 Shift，则必须使用 API 调用。
If you're in a class that inherits Control(such as a form), you can remove the Controlqualifier. (staticproperties don't need qualifiers in inherited classes)
如果您在继承的类Control（例如表单）中，则可以删除Control限定符。（static属性在继承的类中不需要限定符）
