覆蓋表單

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立即下載DevExpress WinForms

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ShowOverlayForm(Control) 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 CloseOverlayForm(IOverlaySplashScreenHandle)方法來關(guān)閉表單。

下面的代碼顯示在應用程序執(zhí)行長時間運行的操作時如何在當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 。

疊加表單手柄

您也可以使用句柄的Close()方法來關(guān)閉疊加表單。

 顯示疊加表單時，聚焦控件將失去焦點，當Overlay Form關(guān)閉時，此控件將重新獲得焦點。QueueFocus(Control)和QueueFocus(IntPtr)方法允許您指定在關(guān)閉Overlay Form時應該聚焦的控件，傳遞來防止所有控件都有焦點。

 您也可以使用QueueCloseUpAction(Action)方法來指定當Overlay Form關(guān)閉時應該執(zhí)行的動作。

C#：

void ReloadData() {
using(var handle = SplashScreenManager.ShowOverlayForm(gridControl)) {
handle.QueueFocus(IntPtr.Zero);
ReloadDataCore();
}
}

VB.NET ：

Private Sub ReloadData()
Using handle = SplashScreenManager.ShowOverlayForm(gridControl)
handle.QueueFocus(IntPtr.Zero)
ReloadDataCore()
End Using
End Sub

自定義覆蓋表單

 ShowOverlayForm(Control, OverlayWindowOptions方法允許您顯示具有以下參數(shù)的覆蓋表單：

• StartupDelay ——顯示表單之前的延遲。
• BackColor —— 背景顏色。
• Opacity —— 不透明表單。
• FadeIn, FadeOut —— 用于顯示和隱藏表單的淡入淡出效果。
• AnimationType —— 動畫的類型（等待指示符）：
  • Image ——旋轉(zhuǎn)的圖像，默認圖像取決于皮膚。 使用ImageSize屬性指定默認圖像的大小，默認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。
    RotationParameters屬性指定旋轉(zhuǎn)周期和單旋轉(zhuǎn)幀數(shù)。
  • Line —— 使用LineAnimationParameters屬性指定點數(shù)，點的大小以及點之間的距離。
• DisableInput——重疊表單是否接收焦點并禁用重疊控件上的用戶輸入，關(guān)閉疊加表單后，它將焦點返回到控件。
• CustomPainter —— 一個用于繪制表單的OverlayWindowPainterBase后代。
• SkinName —— 應用于表單的skin名稱，默認的等待指示器，淡入淡出效果和顏色取決于皮膚，默認外觀對應于重疊控件的外觀
• UseDirectX —— 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Project Settings中啟用Use DirectX選項。

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

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OverlayWindowPainterBase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())