ApplicationContext 类
指定有关应用程序线程的上下文信息。
**命名空间:**System.Windows.Forms
**程序集:**System.Windows.Forms（在 system.windows.forms.dll 中）
语法
声明
Public Class ApplicationContext
Implements IDisposable
用法
Dim instance As ApplicationContext
public class ApplicationContext : IDisposable
public ref class ApplicationContext : IDisposable
public class ApplicationContext implements IDisposable
public class ApplicationContext implements IDisposable
备注
可以使用 ApplicationContext 类重定义导致消息循环退出的环境。默认情况下，ApplicationContext 侦听应用程序主 Form 上的 Closed，然后退出线程的消息循环。
示例
下面的代码示例显示两个窗体，并在两个窗体都关闭时退出应用程序。在应用程序启动和退出时，它会记住每个窗体的位置。此示例演示如何使用 ApplicationContext 和 Application.Run(context) 方法在启动应用程序时显示多个窗体。
类 MyApplicationContext 从 ApplicationContext 继承，并跟踪每个窗体关闭的时间，然后在这两个窗体均关闭时退出当前线程。该类为用户存储每个窗体的位置。窗体位置数据存储在标题为 Appdata.txt 的文件中，该文件在 UserAppDataPath 确定的位置中创建。
给定 ApplicationContext 的情况下，Main 方法调用 Application.Run(context) 启动应用程序。
Imports System
Imports System.Drawing
Imports System.Windows.Forms
Imports System.ComponentModel
Imports System.Text
Imports System.IO
' A simple form that represents a window in our application
Public Class AppForm1
Inherits System.Windows.Forms.Form
Public Sub New()
MyBase.New()
Me.Size = New System.Drawing.Size(300, 300)
Me.Text = "AppForm1"
End Sub
End Class
' A simple form that represents a window in our application
Public Class AppForm2
Inherits System.Windows.Forms.Form
Public Sub New()
MyBase.New()
Me.Size = New System.Drawing.Size(300, 300)
Me.Text = "AppForm2"
End Sub
End Class
' The class that handles the creation of the application windows
Public Class MyApplicationContext
Inherits ApplicationContext
Private formCount As Integer
Private form1 As AppForm1
Private form2 As AppForm2
Private form1Position As Rectangle
Private form2Position As Rectangle
Private userData As FileStream
Public Sub New()
MyBase.New()
formCount = 0
' Handle the ApplicationExit event to know when the application is exiting.
AddHandler Application.ApplicationExit, AddressOf OnApplicationExit
Try
' Create a file that the application will store user specific data in.
userData = New FileStream(Application.UserAppDataPath + "\appdata.txt", FileMode.OpenOrCreate)
Catch e As IOException
' Inform the user that an error occurred.
MessageBox.Show("An error occurred while attempting to show the application." + _
"The error is:" + e.ToString())
' Exit the current thread instead of showing the windows.
ExitThread()
End Try
' Create both application forms and handle the Closed event
' to know when both forms are closed.
form1 = New AppForm1()
AddHandler form1.Closed, AddressOf OnFormClosed
AddHandler form1.Closing, AddressOf OnFormClosing
formCount = formCount + 1
form2 = New AppForm2()
AddHandler form2.Closed, AddressOf OnFormClosed
AddHandler form2.Closing, AddressOf OnFormClosing
formCount = formCount + 1
' Get the form positions based upon the user specific data.
If (ReadFormDataFromFile()) Then
' If the data was read from the file, set the form
' positions manually.
form1.StartPosition = FormStartPosition.Manual
form2.StartPosition = FormStartPosition.Manual
form1.Bounds = form1Position
form2.Bounds = form2Position
End If
' Show both forms.
form1.Show()
form2.Show()
End Sub
Private Sub OnApplicationExit(ByVal sender As Object, ByVal e As EventArgs)
' When the application is exiting, write the application data to the
' user file and close it.
WriteFormDataToFile()
Try
' Ignore any errors that might occur while closing the file handle.
userData.Close()
Catch
End Try
End Sub
Private Sub OnFormClosing(ByVal sender As Object, ByVal e As CancelEventArgs)
' When a form is closing, remember the form position so it
' can be saved in the user data file.
If TypeOf sender Is AppForm1 Then
form1Position = CType(sender, Form).Bounds
ElseIf TypeOf sender Is AppForm2 Then
form2Position = CType(sender, Form).Bounds
End If
End Sub
Private Sub OnFormClosed(ByVal sender As Object, ByVal e As EventArgs)
' When a form is closed, decrement the count of open forms.
' When the count gets to 0, exit the app by calling
' ExitThread().
formCount = formCount - 1
If (formCount = 0) Then
ExitThread()
End If
End Sub
Private Function WriteFormDataToFile() As Boolean
' Write the form positions to the file.
Dim encoding As UTF8Encoding = New UTF8Encoding()
Dim rectConv As RectangleConverter = New RectangleConverter()
Dim form1pos As String = rectConv.ConvertToString(form1Position)
Dim form2pos As String = rectConv.ConvertToString(form2Position)
Dim dataToWrite As Byte() = encoding.GetBytes("~" + form1pos + "~" + form2pos)
Try
' Set the write position to the start of the file and write
userData.Seek(0, SeekOrigin.Begin)
userData.Write(dataToWrite, 0, dataToWrite.Length)
userData.Flush()
userData.SetLength(dataToWrite.Length)
Return True
Catch
' An error occurred while attempting to write, return false.
Return False
End Try
End Function
Private Function ReadFormDataFromFile() As Boolean
' Read the form positions from the file.
Dim encoding As UTF8Encoding = New UTF8Encoding()
Dim data As String
If (userData.Length <> 0) Then
Dim dataToRead(userData.Length) As Byte
Try
' Set the read position to the start of the file and read.
userData.Seek(0, SeekOrigin.Begin)
userData.Read(dataToRead, 0, dataToRead.Length)
Catch e As IOException
Dim errorInfo As String = e.ToString()
' An error occurred while attempt to read, return false.
Return False
End Try
' Parse out the data to get the window rectangles
data = encoding.GetString(dataToRead)
Try
' Convert the string data to rectangles
Dim rectConv As RectangleConverter = New RectangleConverter()
Dim form1pos As String = data.Substring(1, data.IndexOf("~", 1) - 1)
form1Position = CType(rectConv.ConvertFromString(form1pos), Rectangle)
Dim form2pos As String = data.Substring(data.IndexOf("~", 1) + 1)
form2Position = CType(rectConv.ConvertFromString(form2pos), Rectangle)
Return True
Catch
' Error occurred while attempting to convert the rectangle data.
' Return false to use default values.
Return False
End Try
Else
' No data in the file, return false to use default values.
Return False
End If
End Function
End Class
Public Module MyApplication
Public Sub Main()
' Create the MyApplicationContext, that derives from ApplicationContext,
' that manages when the application should exit.
Dim context As MyApplicationContext = New MyApplicationContext()
' Run the application with the specific context. It will exit when
' all forms are closed.
Application.Run(context)
End Sub
End Module
using System;
using System.Drawing;
using System.Windows.Forms;
using System.ComponentModel;
using System.Text;
using System.IO;
namespace MyApplication
{
// A simple form that represents a window in our application
public class AppForm2 : System.Windows.Forms.Form {
public AppForm2(){
this.Size = new System.Drawing.Size(300,300);
this.Text = "AppForm2";
}
}
// A simple form that represents a window in our application
public class AppForm1 : System.Windows.Forms.Form {
public AppForm1(){
this.Size = new System.Drawing.Size(300,300);
this.Text = "AppForm1";
}
}
// The class that handles the creation of the application windows
class MyApplicationContext : ApplicationContext {
private int formCount;
private AppForm1 form1;
private AppForm2 form2;
private Rectangle form1Position;
private Rectangle form2Position;
private FileStream userData;
private MyApplicationContext() {
formCount = 0;
// Handle the ApplicationExit event to know when the application is exiting.
Application.ApplicationExit += new EventHandler(this.OnApplicationExit);
try {
// Create a file that the application will store user specific data in.
userData = new FileStream(Application.UserAppDataPath + "\\appdata.txt", FileMode.OpenOrCreate);
} catch(IOException e) {
// Inform the user that an error occurred.
MessageBox.Show("An error occurred while attempting to show the application." +
"The error is:" + e.ToString());
// Exit the current thread instead of showing the windows.
ExitThread();
}
// Create both application forms and handle the Closed event
// to know when both forms are closed.
form1 = new AppForm1();
form1.Closed += new EventHandler(OnFormClosed);
form1.Closing += new CancelEventHandler(OnFormClosing);
formCount++;
form2 = new AppForm2();
form2.Closed += new EventHandler(OnFormClosed);
form2.Closing += new CancelEventHandler(OnFormClosing);
formCount++;
// Get the form positions based upon the user specific data.
if (ReadFormDataFromFile()) {
// If the data was read from the file, set the form
// positions manually.
form1.StartPosition = FormStartPosition.Manual;
form2.StartPosition = FormStartPosition.Manual;
form1.Bounds = form1Position;
form2.Bounds = form2Position;
}
// Show both forms.
form1.Show();
form2.Show();
}
private void OnApplicationExit(object sender, EventArgs e) {
// When the application is exiting, write the application data to the
// user file and close it.
WriteFormDataToFile();
try {
// Ignore any errors that might occur while closing the file handle.
userData.Close();
} catch {}
}
private void OnFormClosing(object sender, CancelEventArgs e) {
// When a form is closing, remember the form position so it
// can be saved in the user data file.
if (sender is AppForm1)
form1Position = ((Form)sender).Bounds;
else if (sender is AppForm2)
form2Position = ((Form)sender).Bounds;
}
private void OnFormClosed(object sender, EventArgs e) {
// When a form is closed, decrement the count of open forms.
// When the count gets to 0, exit the app by calling
// ExitThread().
formCount--;
if (formCount == 0) {
ExitThread();
}
}
private bool WriteFormDataToFile(){
// Write the form positions to the file.
UTF8Encoding encoding = new UTF8Encoding();
RectangleConverter rectConv = new RectangleConverter();
String form1pos = rectConv.ConvertToString(form1Position);
String form2pos = rectConv.ConvertToString(form2Position);
byte[] dataToWrite = encoding.GetBytes("~" + form1pos + "~" + form2pos);
try {
// Set the write position to the start of the file and write
userData.Seek(0,SeekOrigin.Begin);
userData.Write(dataToWrite, 0, dataToWrite.Length);
userData.Flush();
userData.SetLength(dataToWrite.Length);
return true;
} catch {
// An error occurred while attempting to write, return false.
return false;
}
}
private bool ReadFormDataFromFile(){
// Read the form positions from the file.
UTF8Encoding encoding = new UTF8Encoding();
String data;
if (userData.Length != 0) {
byte[] dataToRead = new Byte[userData.Length];
try {
// Set the read position to the start of the file and read.
userData.Seek(0, SeekOrigin.Begin);
userData.Read(dataToRead, 0, dataToRead.Length);
} catch (IOException e) {
String errorInfo = e.ToString();
// An error occurred while attempt to read, return false.
return false;
}
// Parse out the data to get the window rectangles
data = encoding.GetString(dataToRead);
try {
// Convert the string data to rectangles
RectangleConverter rectConv = new RectangleConverter();
String form1pos = data.Substring(1,data.IndexOf("~",1)-1);
form1Position = (Rectangle)rectConv.ConvertFromString(form1pos);
String form2pos = data.Substring(data.IndexOf("~",1)+1);
form2Position = (Rectangle)rectConv.ConvertFromString(form2pos);
return true;
} catch {
// Error occurred while attempting to convert the rectangle data.
// Return false to use default values.
return false;
}
} else {
// No data in the file, return false to use default values.
return false;
}
}
[STAThread]
static void Main(string[] args) {
// Create the MyApplicationContext, that derives from ApplicationContext,
// that manages when the application should exit.
MyApplicationContext context = new MyApplicationContext();
// Run the application with the specific context. It will exit when
// all forms are closed.
Application.Run(context);
}
}
}
#using <System.dll>
#using <System.Drawing.dll>
#using <System.Windows.Forms.dll>
using namespace System;
using namespace System::Drawing;
using namespace System::Windows::Forms;
using namespace System::ComponentModel;
using namespace System::Text;
using namespace System::IO;
// A simple form that represents a window in our application
public ref class AppForm2: public System::Windows::Forms::Form
{
public:
AppForm2()
{
this->Size = System::Drawing::Size( 300, 300 );
this->Text = "AppForm2";
}
};
// A simple form that represents a window in our application
public ref class AppForm1: public System::Windows::Forms::Form
{
public:
AppForm1()
{
this->Size = System::Drawing::Size( 300, 300 );
this->Text = "AppForm1";
}
};
// The class that handles the creation of the application windows
ref class MyApplicationContext: public ApplicationContext
{
private:
int formCount;
AppForm1^ form1;
AppForm2^ form2;
System::Drawing::Rectangle form1Position;
System::Drawing::Rectangle form2Position;
FileStream^ userData;
public:
MyApplicationContext()
{
formCount = 0;
// Handle the ApplicationExit event to know when the application is exiting.
Application::ApplicationExit += gcnew EventHandler( this, &MyApplicationContext::OnApplicationExit );
try
{
// Create a file that the application will store user specific data in.
userData = gcnew FileStream( String::Concat( Application::UserAppDataPath, "\\appdata.txt" ),FileMode::OpenOrCreate );
}
catch ( IOException^ e )
{
// Inform the user that an error occurred.
MessageBox::Show( "An error occurred while attempting to show the application. The error is: {0}", dynamic_cast<String^>(e) );
// Exit the current thread instead of showing the windows.
ExitThread();
}
// Create both application forms and handle the Closed event
// to know when both forms are closed.
form1 = gcnew AppForm1;
form1->Closed += gcnew EventHandler( this, &MyApplicationContext::OnFormClosed );
form1->Closing += gcnew CancelEventHandler( this, &MyApplicationContext::OnFormClosing );
formCount++;
form2 = gcnew AppForm2;
form2->Closed += gcnew EventHandler( this, &MyApplicationContext::OnFormClosed );
form2->Closing += gcnew CancelEventHandler( this, &MyApplicationContext::OnFormClosing );
formCount++;
// Get the form positions based upon the user specific data.
if ( ReadFormDataFromFile() )
{
// If the data was read from the file, set the form
// positions manually.
form1->StartPosition = FormStartPosition::Manual;
form2->StartPosition = FormStartPosition::Manual;
form1->Bounds = form1Position;
form2->Bounds = form2Position;
}
// Show both forms.
form1->Show();
form2->Show();
}
void OnApplicationExit( Object^ /*sender*/, EventArgs^ /*e*/ )
{
// When the application is exiting, write the application data to the
// user file and close it.
WriteFormDataToFile();
try
{
// Ignore any errors that might occur while closing the file handle.
userData->Close();
}
catch ( Exception^ )
{
}
}
private:
void OnFormClosing( Object^ sender, CancelEventArgs^ /*e*/ )
{
// When a form is closing, remember the form position so it
// can be saved in the user data file.
if ( dynamic_cast<AppForm1^>(sender) != nullptr )
form1Position = (dynamic_cast<Form^>(sender))->Bounds;
else
if ( dynamic_cast<AppForm1^>(sender) != nullptr )
form2Position = (dynamic_cast<Form^>(sender))->Bounds;
}
void OnFormClosed( Object^ /*sender*/, EventArgs^ /*e*/ )
{
// When a form is closed, decrement the count of open forms.
// When the count gets to 0, exit the app by calling
// ExitThread().
formCount--;
if ( formCount == 0 )
{
ExitThread();
}
}
bool WriteFormDataToFile()
{
// Write the form positions to the file.
UTF8Encoding^ encoding = gcnew UTF8Encoding;
RectangleConverter^ rectConv = gcnew RectangleConverter;
String^ form1pos = rectConv->ConvertToString( form1Position );
String^ form2pos = rectConv->ConvertToString( form2Position );
array<Byte>^dataToWrite = encoding->GetBytes( String::Concat( "~", form1pos, "~", form2pos ) );
try
{
// Set the write position to the start of the file and write
userData->Seek( 0, SeekOrigin::Begin );
userData->Write( dataToWrite, 0, dataToWrite->Length );
userData->Flush();
userData->SetLength( dataToWrite->Length );
return true;
}
catch ( Exception^ )
{
// An error occurred while attempting to write, return false.
return false;
}
}
bool ReadFormDataFromFile()
{
// Read the form positions from the file.
UTF8Encoding^ encoding = gcnew UTF8Encoding;
String^ data;
if ( userData->Length != 0 )
{
array<Byte>^dataToRead = gcnew array<Byte>(userData->Length);
try
{
// Set the read position to the start of the file and read.
userData->Seek( 0, SeekOrigin::Begin );
userData->Read( dataToRead, 0, dataToRead->Length );
}
catch ( IOException^ e )
{
String^ errorInfo = dynamic_cast<String^>(e);
// An error occurred while attempt to read, return false.
return false;
}
// Parse out the data to get the window rectangles
data = encoding->GetString( dataToRead );
try
{
// Convert the String* data to rectangles
RectangleConverter^ rectConv = gcnew RectangleConverter;
String^ form1pos = data->Substring( 1, data->IndexOf( "~", 1 ) - 1 );
form1Position = *safe_cast<Rectangle^>(rectConv->ConvertFromString( form1pos ));
String^ form2pos = data->Substring( data->IndexOf( "~", 1 ) + 1 );
form2Position = *safe_cast<Rectangle^>(rectConv->ConvertFromString( form2pos ));
return true;
}
catch ( Exception^ )
{
// Error occurred while attempting to convert the rectangle data.
// Return false to use default values.
return false;
}
}
else
{
// No data in the file, return false to use default values.
return false;
}
}
};
[STAThread]
int main()
{
// Create the MyApplicationContext, that derives from ApplicationContext,
// that manages when the application should exit.
MyApplicationContext^ context = gcnew MyApplicationContext;
// Run the application with the specific context. It will exit when
// all forms are closed.
Application::Run( context );
}
package MyApplication;
import System.*;
import System.Drawing.*;
import System.Windows.Forms.*;
import System.ComponentModel.*;
import System.Text.*;
import System.IO.*;
// A simple form that represents a window in our application
public class AppForm2 extends System.Windows.Forms.Form
{
public AppForm2()
{
this.set_Size(new System.Drawing.Size(300, 300));
this.set_Text("AppForm2");
} //AppForm2
} //AppForm2
// A simple form that represents a window in our application
public class AppForm1 extends System.Windows.Forms.Form
{
public AppForm1()
{
this.set_Size(new System.Drawing.Size(300, 300));
this.set_Text("AppForm1");
} //AppForm1
} //AppForm1
// The class that handles the creation of the application windows
class MyApplicationContext extends ApplicationContext
{
private int formCount;
private AppForm1 form1;
private AppForm2 form2;
private Rectangle form1Position;
private Rectangle form2Position;
private FileStream userData;
private MyApplicationContext()
{
formCount = 0;
// Handle the ApplicationExit event to know
// when the application is exiting.
Application.add_ApplicationExit(new EventHandler(
this.OnApplicationExit));
try {
// Create a file that the application will store
// user specific data in.
userData = new FileStream(Application.get_UserAppDataPath()
+ "\\appdata.txt", FileMode.OpenOrCreate);
}
catch (IOException e) {
// Inform the user that an error occurred.
MessageBox.Show("An error occurred while attempting to show the "
+ " application. The error is:" + e.ToString());
// Exit the current thread instead of showing the windows.
ExitThread();
}
// Create both application forms and handle the Closed event
// to know when both forms are closed.
form1 = new AppForm1();
form1.add_Closed(new EventHandler(OnFormClosed));
form1.add_Closing(new CancelEventHandler(OnFormClosing));
formCount++;
form2 = new AppForm2();
form2.add_Closed(new EventHandler(OnFormClosed));
form2.add_Closing(new CancelEventHandler(OnFormClosing));
formCount++;
// Get the form positions based upon the user specific data.
if (ReadFormDataFromFile()) {
// If the data was read from the file, set the form
// positions manually.
form1.set_StartPosition(FormStartPosition.Manual);
form2.set_StartPosition(FormStartPosition.Manual);
form1.set_Bounds(form1Position);
form2.set_Bounds(form2Position);
}
// Show both forms.
form1.Show();
form2.Show();
} //MyApplicationContext
private void OnApplicationExit(Object sender, EventArgs e)
{
// When the application is exiting, write the application data to the
// user file and close it.
WriteFormDataToFile();
try {
// Ignore any errors that might occur while closing the file handle.
userData.Close();
}
catch (System.Exception exp) {
}
} //OnApplicationExit
private void OnFormClosing(Object sender, CancelEventArgs e)
{
// When a form is closing, remember the form position so it
// can be saved in the user data file.
if (sender instanceof AppForm1) {
form1Position = ((Form)sender).get_Bounds();
}
else {
if (sender instanceof AppForm2) {
form2Position = ((Form)sender).get_Bounds();
}
}
} //OnFormClosing
private void OnFormClosed(Object sender, EventArgs e)
{
// When a form is closed, decrement the count of open forms.
// When the count gets to 0, exit the app by calling
// ExitThread().
formCount--;
if (formCount == 0) {
ExitThread();
}
} //OnFormClosed
private boolean WriteFormDataToFile()
{
// Write the form positions to the file.
UTF8Encoding encoding = new UTF8Encoding();
RectangleConverter rectConv = new RectangleConverter();
String form1Pos = rectConv.ConvertToString(form1Position);
String form2Pos = rectConv.ConvertToString(form2Position);
ubyte dataToWrite[] = encoding.GetBytes("~" + form1Pos + "~"
+ form2Pos);
try {
// Set the write position to the start of the file and write
userData.Seek(0, SeekOrigin.Begin);
userData.Write(dataToWrite, 0, dataToWrite.length);
userData.Flush();
userData.SetLength(dataToWrite.length);
return true;
}
catch (System.Exception exp) {
// An error occurred while attempting to write, return false.
return false;
}
} //WriteFormDataToFile
private boolean ReadFormDataFromFile()
{
// Read the form positions from the file.
UTF8Encoding encoding = new UTF8Encoding();
String data;
if (userData.get_Length() != 0) {
ubyte dataToRead[] = new ubyte[(int)userData.get_Length()];
try {
// Set the read position to the start of the file and read.
userData.Seek(0, SeekOrigin.Begin);
userData.Read(dataToRead, 0, dataToRead.length);
}
catch (IOException e) {
String errorInfo = e.ToString();
// An error occurred while attempt to read, return false.
return false;
}
// Parse out the data to get the window rectangles
data = encoding.GetString(dataToRead);
try {
// Convert the string data to rectangles
RectangleConverter rectConv = new RectangleConverter();
String form1Pos = data.Substring(1, data.IndexOf("~", 1) - 1);
form1Position =
(Rectangle)(rectConv.ConvertFromString(form1Pos));
String form2Pos = data.Substring(data.IndexOf("~", 1) + 1);
form2Position =
(Rectangle)(rectConv.ConvertFromString(form2Pos));
return true;
}
catch (System.Exception exp) {
// Error occurred while attempting to convert the rectangle data.
// Return false to use default values.
return false;
}
}
else {
// No data in the file, return false to use default values.
return false;
}
} //ReadFormDataFromFile
/** @attribute STAThread()
*/
public static void main(String[] args)
{
// Create the MyApplicationContext, that derives from
// ApplicationContext, that manages when the application should exit.
MyApplicationContext context = new MyApplicationContext();
// Run the application with the specific context. It will exit when
// all forms are closed.
Application.Run(context);
} //main
} //MyApplicationContext
继承层次结构
System.Object
System.Windows.Forms.ApplicationContext
线程安全
此类型的任何公共静态（Visual Basic 中的 Shared）成员都是线程安全的，但不保证所有实例成员都是线程安全的。
平台
Windows 98、Windows 2000 SP4、Windows CE、Windows Millennium Edition、Windows Mobile for Pocket PC、Windows Mobile for Smartphone、Windows Server 2003、Windows XP Media Center Edition、Windows XP Professional x64 Edition、Windows XP SP2、Windows XP Starter Edition
.NET Framework 并不是对每个平台的所有版本都提供支持。有关受支持版本的列表，请参见系统要求。
版本信息
.NET Framework
受以下版本支持：2.0、1.1、1.0