.NET中的KeyDown和KeyPress有什么区别？

Question

KeyDown和KeyPress事件有.net什么区别？

Answer 1

这显然有很多误解!

KeyDown和之间唯一的实际区别KeyPress是KeyPress传递按键产生的角色,只有在有按键时才会调用.

换句话说,如果你按下A键盘,你将得到以下一系列事件:

1. KeyDown:KeyCode = Keys.A,KeyData = Keys.A,Modifiers = Keys.None
2. KeyPress:KeyChar ='a'
3. KeyUp:KeyCode = Keys.A

但如果你按Shift+ A,你会得到:

1. KeyDown:KeyCode = Keys.ShiftKey,KeyData = Keys.ShiftKey,Shift,Modifiers = Keys.Shift
2. KeyDown:KeyCode = Keys.A,KeyData = Keys.A | Keys.Shift,Modifiers = Keys.Shift
3. KeyPress:KeyChar ='A'
4. KeyUp:KeyCode = Keys.A
5. KeyUp:KeyCode = Keys.ShiftKey

如果你按住键一段时间,你会得到类似的东西:

1. KeyDown:KeyCode = Keys.ShiftKey,KeyData = Keys.ShiftKey,Shift,Modifiers = Keys.Shift
2. KeyDown:KeyCode = Keys.ShiftKey,KeyData = Keys.ShiftKey,Shift,Modifiers = Keys.Shift
3. KeyDown:KeyCode = Keys.ShiftKey,KeyData = Keys.ShiftKey,Shift,Modifiers = Keys.Shift
4. KeyDown:KeyCode = Keys.ShiftKey,KeyData = Keys.ShiftKey,Shift,Modifiers = Keys.Shift
5. KeyDown:KeyCode = Keys.ShiftKey,KeyData = Keys.ShiftKey,Shift,Modifiers = Keys.Shift
6. KeyDown:KeyCode = Keys.A,KeyData = Keys.A | Keys.Shift,Modifiers = Keys.Shift
7. KeyPress:KeyChar ='A'
8. KeyDown:KeyCode = Keys.A,KeyData = Keys.A | Keys.Shift,Modifiers = Keys.Shift
9. KeyPress:KeyChar ='A'
10. KeyDown:KeyCode = Keys.A,KeyData = Keys.A | Keys.Shift,Modifiers = Keys.Shift
11. KeyPress:KeyChar ='A'
12. KeyDown:KeyCode = Keys.A,KeyData = Keys.A | Keys.Shift,Modifiers = Keys.Shift
13. KeyPress:KeyChar ='A'
14. KeyDown:KeyCode = Keys.A,KeyData = Keys.A | Keys.Shift,Modifiers = Keys.Shift
15. KeyPress:KeyChar ='A'
16. KeyUp:KeyCode = Keys.A
17. KeyUp:KeyCode = Keys.ShiftKey

该通知KeyPress发生在之间 KeyDown和KeyUp,不以后KeyUp,因为很多其他的答案中所指出的,即KeyPress当没有产生的字符不叫,而KeyDown当键被按下重复,也出乎很多其他的答案.

不直接导致调用的键的示例KeyPress:

• Shift,Ctrl,Alt
• F1 通过 F12
• 方向键

该键的例子也导致调用KeyPress:

• A通过Z,0通过9等
• Spacebar
• Tab (KeyChar ='\ t',ASCII 9)
• Enter (KeyChar ='\ r',ASCII 13)
• Esc (KeyChar ='\ x1b',ASCII 27)
• Backspace (KeyChar ='\ b',ASCII 8)

对于好奇,KeyDown大致关联到WM_KEYDOWN,KeyPress到WM_CHAR和KeyUp到WM_KEYUP. WM_KEYDOWN 可以被称为少于密钥重复次数,但它发送重复计数,IIRC,WinForms用于每次重复生成一个KeyDown.

Answer 2

非字符键不会引发KeyPress事件; 但是,非字符键确实引发了KeyDown和KeyUp事件.

http://msdn.microsoft.com/en-us/library/system.windows.forms.control.keypress.aspx

Answer 3

KeyPress仅由可打印字符触发,并在KeyDown事件后触发.根据键入延迟设置,可能有多个KeyDown和KeyPress事件,但只有一个KeyUp事件.

KeyDown
KeyPress
KeyUp

Answer 4

KeyPress是比KeyDown(和KeyUp)更高级别的抽象.KeyDown和KeyUp是硬件相关的:键盘上键的实际动作.KeyPress更像是"我从键盘上收到了一个角色".