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如何创建半透明窗口

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翻译:
chenziteng
最后由 hamishwillee 在 14 Sep 2012 编辑

概述

本文描述了如何在支持EColor16MA显示模式的设备上创建半透明窗口。

前提条件

设备必须支持EColor16MA显示模式。使用以下代码可以检查设备支持的显示模式。

if(CCoeEnv::Static()->ScreenDevice()->DisplayMode()==EColor16MA)
{
// 支持EColor16MA
}

方案

本方案最初由william.edwards在UIQ论坛的"半透明窗口"系列文章中阐明 (UIQ论坛已经关闭,但仍然可以使用Google搜索"Semi-Transparent Windows #1"和"Semi-Transparent Windows #2",然后查看缓存的网页).

void CControlOnTopCtrl::ConstructL(const TRect& aRect, RWindowGroup* aWindowGroup)
{
TRect rc(aRect);
TInt w = rc.Width();
TInt h = rc.Height();
 
CreateWindowL(aWindowGroup);
for (TInt i = 0; i < 2; i++)
{
w /= 2;
h /= 2;
}
 
SetUniqueHandle(EMyCueControl);
 
TRect rc_new(w, h, w+15, h+15);
SetRect(rc_new);
// begin by chen, code from William's post
// we need to set the display mode to ensure that it has an
// alpha-component specified. However, the system may instead return
// another display mode. We don't have to pay much attention, as the
// call to SetTransparencyAlphaChannel will check wether the Window
// Server and the window's display mode support this kind of
// transparency
Window().SetRequiredDisplayMode(EColor16MA);
TRgb backgroundColour = KRgbWhite; // for example
if(KErrNone == Window().SetTransparencyAlphaChannel())
{
// we now have a semi-transparent window,
// so we have to not clear the window region in an
// opaque colour before drawing it each time;
// 0 alpha is completely transparent,
// 255 alpha is completely opaque
backgroundColour.SetAlpha(0);
}
Window().SetBackgroundColor(backgroundColour);
// end by chen
ActivateL();
}

该代码已经在S60第五版仿真器和一台支持EColor16MA显示模式的设备上验证通过, 以下是仿真器屏幕截图 (透明窗口上的红点):

Semi-transparent03.PNG Semi-transparent04.PNG

完整的示例程序: HelloWorld(Semi-transparent).zip

This page was last modified on 14 September 2012, at 09:02.
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