ApplicationContext Clase

Definición

Espacio de nombres:

System.Windows.Forms

Ensamblado:

System.Windows.Forms.dll

Especifica información contextual sobre un subproceso de aplicación.

public ref class ApplicationContext : IDisposable

public class ApplicationContext : IDisposable

type ApplicationContext = class
    interface IDisposable

Public Class ApplicationContext
Implements IDisposable

Herencia

Object

ApplicationContext

Implementaciones

IDisposable

Ejemplos

En el ejemplo de código siguiente se muestran dos formularios y sale de la aplicación cuando se cierran ambos formularios. Cuando se inicia y sale la aplicación, se recuerda la posición de cada formulario. En este ejemplo se muestra cómo usar , ApplicationContextjunto con el Application.Run(context) método , para mostrar varios formularios cuando se inicia la aplicación.

La clase MyApplicationContext hereda de ApplicationContext y realiza un seguimiento cuando se cierra cada formulario y sale del subproceso actual cuando ambos están. La clase almacena las posiciones de cada formulario para el usuario. Los datos de posición del formulario se almacenan en un archivo titulado Appdata.txt que se crea en la ubicación determinada por UserAppDataPath.

El Main método llama Application.Run(context) a para iniciar la aplicación, según ApplicationContext.

#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 );
}

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);
        }
    }
}

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

Comentarios

Puede usar la ApplicationContext clase para redefinir las circunstancias que hacen que un bucle de mensajes salga. De forma predeterminada, escucha ApplicationContext el Closed evento en el principal Formde la aplicación y, a continuación, sale del bucle de mensajes del subproceso.

Constructores

ApplicationContext()	Inicializa una nueva instancia de la clase ApplicationContext sin contexto.
ApplicationContext(Form)	Inicializa una nueva instancia de la clase ApplicationContext con el objeto Form especificado.

Propiedades

MainForm	Obtiene o establece el Form que se va a utilizar como contexto.
Tag	Obtiene o establece un objeto que contiene datos sobre el control.

Métodos

Dispose()	Libera todos los recursos que usa ApplicationContext.
Dispose(Boolean)	Libera los recursos no administrados que usa ApplicationContext y, de forma opcional, libera los recursos administrados.
Equals(Object)	Determina si el objeto especificado es igual que el objeto actual. (Heredado de Object)
ExitThread()	Termina el bucle de mensajes del subproceso.
ExitThreadCore()	Termina el bucle de mensajes del subproceso.
Finalize()	Intenta liberar recursos y realizar otras operaciones de limpieza antes de que el contexto de la aplicación sea reclamado por la recolección de elementos no utilizados.
GetHashCode()	Sirve como la función hash predeterminada. (Heredado de Object)
GetType()	Obtiene el Type de la instancia actual. (Heredado de Object)
MemberwiseClone()	Crea una copia superficial del Object actual. (Heredado de Object)
OnMainFormClosed(Object, EventArgs)	Llama al método ExitThreadCore(), que provoca el evento ThreadExit.
ToString()	Devuelve una cadena que representa el objeto actual. (Heredado de Object)

Eventos

ThreadExit

Se produce cuando el bucle de mensajes del subproceso debe terminar mediante una llamada a ExitThread().