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覆蓋表單是執(zhí)行以下操作的半透明啟動屏幕：

• 覆蓋控件或表單
• 防止用戶與重疊控件進(jìn)行交互
• 覆蓋控件，即使它更改其大小或在屏幕上的位置
• 在單獨的線程中運行，并且不阻塞主線程和操作線程
• 允許您在重疊控件上顯示自定義消息和按鈕

注意：運行Overlay Form module in the XtraEditors MainDemo來查看正在使用的表單，單擊功能區(qū)中的Open Solution獲取源代碼。

顯示覆蓋表單

調(diào)用 方法來在控件或表單上顯示覆蓋表單，該方法返回一個句柄，您可以將其傳遞給 方法以關(guān)閉表單。

下面的代碼顯示在應(yīng)用程序執(zhí)行長時間運行的操作時如何在當(dāng)前表單上顯示覆蓋表單。

C#

using DevExpress.XtraSplashScreen;
//...
IOverlaySplashScreenHandle ShowProgressPanel() {
return SplashScreenManager.ShowOverlayForm(this);
}
void CloseProgressPanel(IOverlaySplashScreenHandle handle) {
if(handle != null)
SplashScreenManager.CloseOverlayForm(handle);
}
//...
IOverlaySplashScreenHandle handle = null;
try {
handle = ShowProgressPanel();
// Launch a long-running operation while
// the Overlay Form overlaps the current form.
}
finally {
CloseProgressPanel(handle);
}

VB.NET

Imports DevExpress.XtraSplashScreen
'...
Private Function ShowProgressPanel() As IOverlaySplashScreenHandle
Dim handle As IOverlaySplashScreenHandle = SplashScreenManager.ShowOverlayForm(Me)
Return handle
End Function

Private Sub CloseProgressPanel(ByVal handle As IOverlaySplashScreenHandle)
If handle IsNot Nothing Then SplashScreenManager.CloseOverlayForm(handle)
End Sub
'...
Dim Handle As IOverlaySplashScreenHandle = Nothing
Try
Handle = ShowProgressPanel()
'Launch a long-running operation while 
'the Overlay Form overlaps the main form.
Finally
CloseProgressPanel(Handle)
End Try

警告：您只能在已初始化（創(chuàng)建其句柄）的控件/表單上顯示覆蓋表單；否則將拋出，請參見 。

自定義覆蓋表單

方法允許您顯示具有以下參數(shù)的覆蓋表單：

• — 顯示表單之前的延遲。
• — 背景顏色。
• — 不透明表單。
• , — 用于顯示和隱藏表單的淡入淡出效果。
• — 動畫的類型（等待指示符）：
  • — 旋轉(zhuǎn)的圖像，默認(rèn)圖像取決于皮膚。 使用屬性指定默認(rèn)圖像的大小，默認(rèn)圖像大小取決于重疊控件的大小，Image屬性指定一個自定義圖像。
    屬性指定旋轉(zhuǎn)周期和單旋轉(zhuǎn)幀數(shù)。
  • — 使用屬性指定點數(shù)，點的大小以及點之間的距離。
• — 一個用于繪制表單的OverlayWindowPainterBase后代，請參閱部分中的示例。
• — 應(yīng)用于表單的名稱，默認(rèn)的等待指示器，淡入淡出效果和顏色取決于皮膚，默認(rèn)外觀對應(yīng)于重疊控件的外觀
• — 指定是否使用DirectX渲染覆蓋表單，要將DirectX用于所有兼容的DevExpress控件，請在中啟用Use DirectX選項，有關(guān)更多信息，請參閱以下主題： 。

所有這些參數(shù)都是可選的。 如果省略參數(shù)，則使用默認(rèn)值。 不帶選項的方法使用靜態(tài)（在VB中共享）默認(rèn)選項。

下面的代碼顯示了如何顯示帶有自定義參數(shù)的覆蓋表單。

C#

using DevExpress.XtraSplashScreen;

OverlayWindowOptions options = new OverlayWindowOptions(
startupDelay: 1000,
backColor: Color.Red,
opacity: 0.5,
fadeIn: false,
fadeOut: false,
imageSize: new Size(64, 64)
);
IOverlaySplashScreenHandle handle1 = SplashScreenManager.ShowOverlayForm(gridControl1, options);

IOverlaySplashScreenHandle handle2 = SplashScreenManager.ShowOverlayForm(
owner: gridControl1,
startupDelay: 1000,
backColor: Color.Red,
opacity: 127,
fadeIn: false,
fadeOut: false,
imageSize: new Size(64, 64)
);

VB.NET

Imports DevExpress.XtraSplashScreen

Dim options As New OverlayWindowOptions(
startupDelay:=1000,
backColor:=Color.Red,
opacity:=0.5,
fadeIn:=False,
fadeOut:=False,
imageSize:=New Size(64, 64)
)
Dim formHandle1 As IOverlaySplashScreenHandle = SplashScreenManager.ShowOverlayForm(gridControl1, options)

Dim formHandle2 As IOverlaySplashScreenHandle = SplashScreenManager.ShowOverlayForm(
owner:=gridControl1,
startupDelay:=1000,
backColor:=Color.Red,
opacity:=127,
fadeIn:=False,
fadeOut:=False,
imageSize:=New Size(64, 64)
)

自定義Painter

您可以按以下方式呈現(xiàn)重疊表單：

• 繼承自O(shè)verlayWindowPainterBase類
• 重寫Draw方法
• 將創(chuàng)建的對象作為參數(shù)傳遞給ShowOverlayForm方法

下面的代碼段顯示了如何顯示自定義消息，如下圖所示：

C#

using DevExpress.XtraSplashScreen;
using DevExpress.Utils.Drawing;
using System.Drawing;
//...
class CustomOverlayPainter : OverlayWindowPainterBase
{
// Defines the string’s font.
static readonly Font drawFont;
static CustomOverlayPainter() {
drawFont = new Font("Tahoma", 18);
}
protected override void Draw(OverlayWindowCustomDrawContext context)
{
//The Handled event parameter should be set to true. 
//to disable the default drawing algorithm. 
context.Handled = true;
//Provides access to the drawing surface. 
GraphicsCache cache = context.DrawArgs.Cache;
//Adjust the TextRenderingHint option
//to improve the image quality.
cache.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias;
//Overlapped control bounds. 
Rectangle bounds = context.DrawArgs.Bounds;
//Draws the default background. 
context.DrawBackground();
//Specify the string that will be drawn on the Overlay Form instead of the wait indicator.
String drawString = "Please wait...";
//Get the system's black brush.
Brush drawBrush = Brushes.Black;
//Calculate the size of the message string.
SizeF textSize = cache.CalcTextSize(drawString, drawFont);
//A point that specifies the upper-left corner of the rectangle where the string will be drawn.
PointF drawPoint = new PointF(
bounds.Left + bounds.Width / 2 - textSize.Width / 2,
bounds.Top + bounds.Height / 2 - textSize.Height / 2
);
//Draw the string on the screen.
cache.DrawString(drawString, drawFont, drawBrush, drawPoint);
}
}
//...
IOverlaySplashScreenHandle handle = SplashScreenManager.ShowOverlayForm(this, customPainter: new CustomOverlayPainter());

VB.NET

Imports DevExpress.Utils.Drawing
Imports DevExpress.XtraSplashScreen
Imports System.Drawing
'...
Class CustomOverlayPainter
Inherits OverlayWindowPainterBase
'Defines the string’s font.
Shared ReadOnly drawFont As Font

Shared Sub New()
drawFont = New Font("Tahoma", 18)
End Sub

Protected Overrides Sub Draw(context As OverlayWindowCustomDrawContext)
'The Handled event parameter should be set to true 
'to disable the default drawing algorithm.
context.Handled = True
'Provides access to the drawing surface. 
Dim cache As GraphicsCache = context.DrawArgs.Cache
'Adjust the TextRenderingHint option 
’to improve the image quality. 
cache.TextRenderingHint = System.Drawing.Text.TextRenderingHint.AntiAlias
'Overlapped control bounds.
Dim bounds As Rectangle = context.DrawArgs.Bounds
'Draws the default background. 
context.DrawBackground()
'Create the string to draw. 
Dim drawString As String = "Please wait..."
'Get the system black brush. 
Dim drawBrush As Brush = Brushes.Black
'Calculate the size of the message string. 
Dim textSize As SizeF = cache.CalcTextSize(drawString, drawFont)
'A point that specifies the upper-left corner of the rectangle where the string should be drawn.
Dim drawPoint As PointF = New PointF(bounds.Left + bounds.Width / 2 - textSize.Width / 2, bounds.Top + bounds.Height / 2 - textSize.Height / 2)
'Draw the string on the screen.
cache.DrawString(drawString, drawFont, drawBrush, drawPoint)
End Sub
End Class
'...
Dim handle As IOverlaySplashScreenHandle = SplashScreenManager.ShowOverlayForm(Me, customPainter:=New CustomOverlayPainter())

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