Windows 窗体—— 键盘输入工作原理

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方法	注释
PreFilterMessage	此方法在应用程序级截获排队的（也称为已发送的）Windows 消息。
PreProcessMessage	此方法在 Windows 消息处理前在窗体和控件级截获它们。
WndProc	此方法在窗体和控件级处理 Windows 消息。
DefWndProc	此方法在窗体和控件级执行 Windows 消息的默认处理。这提供了窗口的最小功能。
OnNotifyMessage	此方法在消息处理后在窗体和控件级截获它们。若要调用此方法，必须设置 EnableNotifyMessage 样式位。

KeyDown 事件的预处理相关方法:ProcessCmdKey、IsInputKey、ProcessDialogKey

KeyPress 事件的预处理相关方法:IsInputChar、ProcessDialogChar

Control的ProcessCmdKey方法：该方法处理命令键，命令键的优先级高于常规键。命令键的例子包括快捷键和菜单快捷方式

// true:将不调度键消息，而且将不发生键事件
// false:将调用IsInputKey
[SecurityPermission(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.UnmanagedCode), SecurityPermission(SecurityAction.InheritanceDemand, Flags=SecurityPermissionFlag.UnmanagedCode)]
protected virtual bool ProcessCmdKey(ref Message msg, Keys keyData)
{
ContextMenu menu = (ContextMenu) this.Properties.GetObject(PropContextMenu);
return (((menu != null) && menu.ProcessCmdKey(ref msg, keyData, this)) || ((this.parent != null) && this.parent.ProcessCmdKey(ref msg, keyData)));
}

Control的IsInputKey方法：

// true:表示该控件为常规字符，将引发 KeyDown 事件
// false:表示还没有做处理，将会调用ProcessDialogKey进行处理

[UIPermission(SecurityAction.InheritanceDemand, Window=UIPermissionWindow.AllWindows)]
protected virtual bool IsInputKey(Keys keyData)
{
// 1.检查该键是否为需要预处理的特殊键
// Alt需要特殊处理
if ((keyData & Keys.Alt) == Keys.Alt)
{
return false;
}
int num = ;
switch ((keyData & Keys.KeyCode))
{
case Keys.Left:
case Keys.Up:
case Keys.Right:
case Keys.Down:
num = ;
break; case Keys.Tab:
num = ;
break;
}
// 2.检查它是否为应引发KeyDown 事件并且被调度到某个控件的普通字符键
// IsHandleCreated 指示控件是否有与它关联的句柄
return (this.IsHandleCreated && ((((int) ((long) this.SendMessage(0x87, , ))) & num) != ));
}

※预处理的键包括 Tab、Return、ESC 以及向上键、向下键、向左键和向右键。

ProcessDialogKey:此方法在控件内实现特殊功能（如在控件及其父级之间切换焦点）的物理按键。如果中间控件不处理该键，则将调用父控件的 ProcessDialogKey，直至层次结构中的最顶端控件。

// true:将完成预处理，而且将不生成按键事件。
// false:将发生 KeyDown 事件
[UIPermission(SecurityAction.InheritanceDemand, Window=UIPermissionWindow.AllWindows), UIPermission(SecurityAction.LinkDemand, Window=UIPermissionWindow.AllWindows)]
protected virtual bool ProcessDialogKey(Keys keyData)
{
return ((this.parent != null) && this.parent.ProcessDialogKey(keyData));
}

处理键盘消息

ProcessKeyMessage：此方法处理由控件的 WndProc 方法接收的所有键盘消息。

[SecurityPermission(SecurityAction.InheritanceDemand, Flags=SecurityPermissionFlag.UnmanagedCode), SecurityPermission(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.UnmanagedCode)]
protected internal virtual bool ProcessKeyMessage(ref Message m)
{
return (((this.parent != null) && this.parent.ProcessKeyPreview(ref m)) || this.ProcessKeyEventArgs(ref m));
}

ProcessKeyPreview：此方法将键盘消息发送到控件的父控件。如果 ProcessKeyPreview 返回 true，则将不生成键事件；否则将调用 ProcessKeyEventArgs。

[SecurityPermission(SecurityAction.InheritanceDemand, Flags=SecurityPermissionFlag.UnmanagedCode), SecurityPermission(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.UnmanagedCode)]
protected virtual bool ProcessKeyPreview(ref Message m)
{
return ((this.parent != null) && this.parent.ProcessKeyPreview(ref m));
}

ProcessKeyEventArgs：此方法根据需要引发 KeyDown、KeyPress 和 KeyUp 事件。

[SecurityPermission(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.UnmanagedCode), SecurityPermission(SecurityAction.InheritanceDemand, Flags=SecurityPermissionFlag.UnmanagedCode)]
protected virtual bool ProcessKeyEventArgs(ref Message m)
{
KeyEventArgs e = null;
KeyPressEventArgs args2 = null;
IntPtr zero = IntPtr.Zero;
if ((m.Msg == 0x102) || (m.Msg == 0x106))
{
int imeWmCharsToIgnore = this.ImeWmCharsToIgnore;
if (imeWmCharsToIgnore > )
{
imeWmCharsToIgnore--;
this.ImeWmCharsToIgnore = imeWmCharsToIgnore;
return false;
}
args2 = new KeyPressEventArgs((char) ((ushort) ((long) m.WParam)));
// OnKeyPress
this.OnKeyPress(args2);
zero = (IntPtr) args2.KeyChar;
}
else if (m.Msg == 0x286)
{
int num2 = this.ImeWmCharsToIgnore;
if (Marshal.SystemDefaultCharSize == )
{
char ch = '\0';
byte[] lpMultiByteStr = new byte[] { (byte) (((int) ((long) m.WParam)) >> ), (byte) ((long) m.WParam) };
char[] lpWideCharStr = new char[];
int num3 = UnsafeNativeMethods.MultiByteToWideChar(, , lpMultiByteStr, lpMultiByteStr.Length, lpWideCharStr, );
if (num3 <= )
{
throw new Win32Exception();
}
lpWideCharStr = new char[num3];
UnsafeNativeMethods.MultiByteToWideChar(, , lpMultiByteStr, lpMultiByteStr.Length, lpWideCharStr, lpWideCharStr.Length);
if (lpWideCharStr[] != '\0')
{
ch = lpWideCharStr[];
num2 += ;
}
else if ((lpWideCharStr[] == '\0') && (lpWideCharStr.Length >= ))
{
ch = lpWideCharStr[];
num2++;
}
this.ImeWmCharsToIgnore = num2;
args2 = new KeyPressEventArgs(ch);
}
else
{
num2 += - Marshal.SystemDefaultCharSize;
this.ImeWmCharsToIgnore = num2;
args2 = new KeyPressEventArgs((char) ((ushort) ((long) m.WParam)));
}
char keyChar = args2.KeyChar;
// OnKeyPress
this.OnKeyPress(args2);
if (args2.KeyChar == keyChar)
{
zero = m.WParam;
}
else if (Marshal.SystemDefaultCharSize == )
{
string wideStr = new string(new char[] { args2.KeyChar });
byte[] pOutBytes = null;
int num4 = UnsafeNativeMethods.WideCharToMultiByte(, , wideStr, wideStr.Length, null, , IntPtr.Zero, IntPtr.Zero);
if (num4 >= )
{
pOutBytes = new byte[num4];
UnsafeNativeMethods.WideCharToMultiByte(, , wideStr, wideStr.Length, pOutBytes, pOutBytes.Length, IntPtr.Zero, IntPtr.Zero);
int num5 = Marshal.SizeOf(typeof(IntPtr));
if (num4 > num5)
{
num4 = num5;
}
long num6 = ;
for (int i = ; i < num4; i++)
{
num6 = num6 << ;
num6 |= pOutBytes[i];
}
zero = (IntPtr) num6;
}
else if (num4 == )
{
pOutBytes = new byte[num4];
UnsafeNativeMethods.WideCharToMultiByte(, , wideStr, wideStr.Length, pOutBytes, pOutBytes.Length, IntPtr.Zero, IntPtr.Zero);
zero = (IntPtr) pOutBytes[];
}
else
{
zero = m.WParam;
}
}
else
{
zero = (IntPtr) args2.KeyChar;
}
}
else
{
e = new KeyEventArgs(((Keys) ((int) ((long) m.WParam))) | ModifierKeys);
if ((m.Msg == 0x100) || (m.Msg == ))
{
// OnKeyDown
this.OnKeyDown(e);
}
else
{
// OnKeyUp
this.OnKeyUp(e);
}
}
if (args2 != null)
{
m.WParam = zero;
return args2.Handled;
}
if (e.SuppressKeyPress)
{
this.RemovePendingMessages(0x102, 0x102);
this.RemovePendingMessages(0x106, 0x106);
this.RemovePendingMessages(0x286, 0x286);
}
return e.Handled;
}