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Přehled používání ovládacích prvků ve Windows Forms

  • Článek

Toto téma popisuje základní prvky model Windows Forms aplikace a poskytuje jednoduchý příklad, který používá ovládací prvky a zpracovává události v aplikaci model Windows Forms.

Jednoduché model Windows Forms aplikace

Minimálně model Windows Forms aplikace se skládá z následujících prvků:

  • Jedna nebo více tříd, které jsou odvozeny od System.Windows.Forms.Form.

  • Metoda Main , která vyvolá metodu static (shared v jazyce Visual Basic) Run a předá Form do ní instanci. Metoda Run zpracovává zprávy z operačního systému do aplikace.

Následující příklad kódu ukazuje základní prvky model Windows Forms aplikace.

Option Explicit  
Option Strict  
  
Imports System  
Imports System.Windows.Forms  
  
Public Class MyForm  
   Inherits Form  
  
   Public Sub New()  
      Me.Text = "Hello World"  
   End Sub 'New  
  
   <STAThread()> _  
   Public Shared Sub Main()  
      Dim aform As New MyForm()  
      ' The Application.Run method processes messages from the operating system
      ' to your application. If you comment out the next line of code,
      ' your application will compile and execute, but because it is not in the  
      ' message loop, it will exit after an instance of the form is created.  
      Application.Run(aform)  
   End Sub  
End Class  

using System;  
using System.Windows.Forms;  
  
public class MyForm : Form {  
  
   public MyForm() {  
      this.Text = "Hello World";  
   }  
   [STAThread]  
   public static void Main(string[] args) {  
     MyForm aform = new MyForm();  
// The Application.Run method processes messages from the operating system
// to your application. If you comment out the next line of code,
// your application will compile and execute, but because it is not in the // message loop, it will exit after an instance of the form is created.  
      Application.Run(aform);  
   }  
}

Použití ovládacích prvků v aplikaci model Windows Forms

Následující příklad kódu ukazuje jednoduchou aplikaci, která ukazuje, jak model Windows Forms aplikace používají ovládací prvky a zpracovávají události. Příklad se skládá ze tří tlačítek ve formuláři; každé tlačítko změní barvu pozadí po kliknutí.

Option Explicit  
Option Strict  
  
Imports System  
Imports System.ComponentModel  
Imports System.Windows.Forms  
Imports System.Resources  
Imports System.Drawing  
  
Public Class MyForm  
   Inherits Form  
   Private red As Button  
   Private blue As Button  
   Private green As Button  
  
   Public Sub New()  
      InitializeComponent()  
   End Sub  
  
   Protected Overloads Overrides Sub Dispose(disposing as Boolean)  
      MyBase.Dispose(disposing)  
   End Sub  
  
   ' InitializeComponent is a helper method for the constructor.
   ' It is included for consistency with code that is
   ' auto-generated by the Windows Forms designer in Visual Studio.
   Private Sub InitializeComponent()  
  
      ' Creates three buttons, sets their properties, and attaches  
      ' an event handler to each button.  
      red = New Button()  
      red.Text = "Red"  
      red.Location = New Point(100, 50)  
      red.Size = New Size(50, 50)  
      AddHandler red.Click, AddressOf button_Click  
      Controls.Add(red)  
  
      blue = New Button()  
      blue.Text = "Blue"  
      blue.Location = New Point(100, 100)  
      blue.Size = New Size(50, 50)  
      AddHandler blue.Click, AddressOf button_Click  
      Controls.Add(blue)  
  
      green = New Button()  
      green.Text = "Green"  
      green.Location = New Point(100, 150)  
      green.Size = New Size(50, 50)  
      AddHandler green.Click, AddressOf button_Click  
      Controls.Add(green)  
   End Sub  
  
   ' Event handler.  
   Private Sub button_Click(sender As Object, e As EventArgs)  
      If sender Is red Then  
         Me.BackColor = Color.Red  
      Else  
         If sender Is blue Then  
            Me.BackColor = Color.Blue  
         Else  
            Me.BackColor = Color.Green  
         End If  
      End If
   End Sub  
  
   ' The STAThreadAttribute informs the common language runtime that  
   ' Windows Forms uses the single-threaded apartment model.  
   <STAThread()> _  
   Public Shared Sub Main()  
      Application.Run(New MyForm())  
   End Sub  
End Class  

using System;  
using System.ComponentModel;  
using System.Windows.Forms;  
using System.Resources;  
using System.Drawing;  
  
public class MyForm : Form {  
   private Button red;  
   private Button blue;  
   private Button green;  
  
   public MyForm() : base() {
      InitializeComponent();
   }  
  
   protected override void Dispose(bool disposing) {  
      base.Dispose(disposing);  
   }  
  
// InitializeComponent is a helper method for the constructor.
// It is included for consistency with code that is
// auto-generated by the Windows Forms designer in Visual Studio.
   private void InitializeComponent() {  
  
// A delegate for the click event of a button. The argument to
// the constructor contains a reference to the method that performs the
// event handling logic.  
      EventHandler handler = new EventHandler(button_Click);  
  
// Creates three buttons, sets their properties, and attaches  
// an event handler to each button.  
  
      red = new Button();  
      red.Text = "Red";  
      red.Location = new Point(100, 50);  
      red.Size = new Size(50, 50);  
      red.Click +=handler;  
      Controls.Add(red);  
  
      blue = new Button();  
      blue.Text = "Blue";  
      blue.Location = new Point(100, 100);  
      blue.Size = new Size(50, 50);  
      blue.Click += handler;  
      Controls.Add(blue);  
  
      green = new Button();  
      green.Text = "Green";  
      green.Location = new Point(100, 150);  
      green.Size = new Size(50, 50);  
      green.Click += handler;  
      Controls.Add(green);
      }  
  
   // Event handler.  
   private void button_Click(object sender, EventArgs e) {  
            if (sender == red) this.BackColor = Color.Red ;  
                  else if (sender == blue) this.BackColor = Color.Blue;  
                  else this.BackColor = Color.Green;  
        }  
   // The STAThreadAttribute informs the common language runtime that  
   // Windows Forms uses the single-threaded apartment model.  
  [STAThread]  
   public static void Main(string[] args) {  
   Application.Run(new MyForm());  
   }  
  
}

Viz také