$20000000是一个32位值, $20000000;表示在按键的同时有alt 类似的: Ctrl : $10000000; Shift: $08000000; 以下来自win32 sdk的帮助lKeyDataValue of lParam. Specifies the repeat count, scan code, extended-key flag, context code, previous key-state flag, and transition-state flag, as shown in the following table: Value Description 0-15 Specifies the repeat count. The value is the number of times the keystroke is repeated as a result of the user holding down the key. 16-23 Specifies the scan code. The value depends on the original equipment manufacturer (OEM). 24 Specifies whether the key is an extended key, such as the right-hand ALT and CTRL keys that appear on an enhanced 101- or 102-key keyboard. The value is 1 if it is an extended key; otherwise, it is 0. 25-28 Reserved; do not use. 29 Specifies the context code. The value is always 0 for a WM_KEYDOWN message. 30 Specifies the previous key state. The value is 1 if the key is down before the message is sent, or it is 0 if the key is up. 31 Specifies the transition state. The value is always 0 for a WM_KEYDOWN message.
$20000000;表示在按键的同时有alt
类似的:
Ctrl : $10000000;
Shift: $08000000;
以下来自win32 sdk的帮助lKeyDataValue of lParam. Specifies the repeat count, scan code, extended-key flag, context code, previous key-state flag, and transition-state flag, as shown in the following table: Value Description
0-15 Specifies the repeat count. The value is the number of times the keystroke is repeated as a result of the user holding down the key.
16-23 Specifies the scan code. The value depends on the original equipment manufacturer (OEM).
24 Specifies whether the key is an extended key, such as the right-hand ALT and CTRL keys that appear on an enhanced 101- or 102-key keyboard. The value is 1 if it is an extended key; otherwise, it is 0.
25-28 Reserved; do not use.
29 Specifies the context code. The value is always 0 for a WM_KEYDOWN message.
30 Specifies the previous key state. The value is 1 if the key is down before the message is sent, or it is 0 if the key is up.
31 Specifies the transition state. The value is always 0 for a WM_KEYDOWN message.