wguzgg

从win2000开始,windows提供了一个新的api   SetLayeredWindowAttributes,可以轻松实现透明窗口,在网上有许多vb,vc,delphi的示例程序,下面我来介绍一下如何使用swt来实现这一效果:

BOOL SetLayeredWindowAttributes(
HWND hwnd, // handle to the layered window
COLORREF crKey, // specifies the color key
BYTE bAlpha, // value for the blend function
DWORD dwFlags // action
);

Windows NT/2000/XP: Included in Windows 2000 and later.
Windows 95/98/Me: Unsupported.
Header: Declared in Winuser.h; include Windows.h.
Library: Use User32.lib.

一些常量:
WS_EX_LAYERED = 0x80000;
LWA_ALPHA = 0x2;
LWA_COLORKEY=0x1
其中dwFlags有LWA_ALPHA和LWA_COLORKEY
LWA_ALPHA被设置的话,通过bAlpha决定透明度.
LWA_COLORKEY被设置的话,则指定被透明掉的颜色为crKey,其他颜色则正常显示.
注:要使使窗体拥有透明效果,首先要有WS_EX_LAYERED扩展属性(旧sdk也没有的).
　
上面是该函数的资料,下面是一段代码示例:
[code:1]
            display = new Display();
            shell = new Shell(display , SWT.NULL);
            shell.setMaximized(false);
            shell.setBackground(display.getSystemColor(SWT.COLOR_BLACK));
            shell.setText("Example");
            shell.setBounds(0 , 700 , 1024 , 68);
           
            //始终最前
            OS.SetWindowPos(shell.handle , OS.HWND_TOPMOST, 0 , 700 , 1024 , 68 , SWT.NULL);

            //透明窗体
            OS.SetWindowLong(shell.handle , OS.GWL_EXSTYLE , OS.GetWindowLong(shell.handle , OS.GWL_EXSTYLE)^0x80000);

            TCHAR lpLibFileName = new TCHAR (0, "User32.dll", true);
            int hInst = OS.LoadLibrary(lpLibFileName);
            if(hInst != 0) {
                String name = "SetLayeredWindowAttributes\0";
                byte [] lpProcName = new byte [name.length ()];
                for (int i=0; i<lpProcName.length; i++) {
                    lpProcName [i] = (byte) name.charAt (i);
                }
                int fun = OS.GetProcAddress(hInst , lpProcName);
                if (fun != 0) {
                    OS.CallWindowProc(fun , shell.handle , 0,50,1);
                }
                OS.FreeLibrary(hInst);
            }
[/code:1]
里面用到的几个类都在org.eclipse.swt.internal.win32下,相信大家看到上面的代码就都清楚该如何做了,我也就不多罗嗦了.