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Windows Forms
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Windows Forms Overview about describe the structure of a Windows Forms application (application entry point, forms, components and controls); Introduce deployment over networks. It provides about Visual Studio, Application Structure, Form border; Form properties.
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Nội dung Text: Windows Forms
- Windows Forms
- Overview
• Describe the structure of a Windows Forms application
– application entry point
– forms
– components and controls
• Introduce deployment over networks
2
- Windows Forms
• Windows Forms are classes for building UIs
– forms, controls, dialogs, etc.
– part of the .NET Framework Library
– core classes in System.Windows.Forms namespace
• Possible uses include:
– stand-alone Windows applications
– web services front-ends
– intranet “smart clients”
3
- Visual Studio
• Visual Studio .NET provides development environment
– starter templates, drag-and-drop editing, property grid, etc.
4
- Application Structure
• Windows Forms application has three main pieces
– the application itself
– forms in the application
– controls and components on the forms
Label
Application myForm "Hello, World!"
mainForm label1
button1 Button
"OK"
5
- Application
• Application class represents the application itself
– Run method processes UI events delivered by Windows
– provides access to application environment
ExecutablePath, CommonAppDataPath, UserAppDataPath, etc.
– no instances, all members are static
class MyApp
{
public static void Main()
{
MyForm form = new MyForm();
start application Application.Run(form);
}
}
6
- Form
• Form class represents window, provides appropriate services
– properties: Size, Location, Controls, ShowInTaskbar
– methods: Show, Close, SetDesktopLocation
– events: Load, Click, Closing
• Common to derive from Form to create custom form
define custom form class MyForm : Form
{
public MyForm()
{
this.ShowInTaskbar = false;
set properties this.Location = new Point(10, 10);
this.Size = new Size(100, 100);
}
}
7
- Form border
• Forms can look like windows, dialogs, or tools
– controlled using FormBorderStyle property
– set ShowInTaskbar property to false for tool windows
– window border styles show the icon from the Icon property
8
- Form properties
• Form has many properties
– used to customize appearance and behavior
public class Form : ContainerControl
{
public IButtonControl AcceptButton { get; set; }
public IButtonControl CancelButton { get; set; }
public bool HelpButton { get; set; }
public Icon Icon { get; set; }
public String Text { get; set; }
public Size MaximumSize { get; set; }
properties public Size MinimumSize { get; set; }
public MainMenu Menu { get; set; }
public bool ShowInTaskbar { get; set; }
public FormBorderStyle FormBorderStyle { get; set; }
...
}
9
- Form as container
• Form manages a list of controls
– stored in Controls collection property
all forms inherit class MyForm : Form
Controls collection {
Button button1 = new Button();
Label label1 = new Label ();
public MyForm()
{
...
this.Controls.Add(button1);
add to collection this.Controls.Add(label1 );
}
...
}
myForm
Controls button1 label1
10
- Form layout
• Form determines layout for controls it manages
– recalculates as needed, such as when user resizes form
– tries to accommodate control preferences for size and location
– uses Anchor and Dock property of each control
– can override OnLayout method to do custom layout
resize
11
- Controls
• Controls are visual components derived from Control class
– common controls supplied
Object
Component
Control
ButtonBase DataGrid ScrollableControl
Button DateTimePicker ContainerControl
CheckBox
GroupBox Form
RadioButton
Label PropertyGrid
UserControl
MonthCalendar
ListControl
ComboBox PictureBox Panel
TabPage
ListBox ProgressBar
Splitter
StatusBar
12
- Control properties
• Controls supply many properties
– used to customize appearance and behavior
public class MyForm : Form
{
private Button button1;
public MyForm()
{
button1 = new Button();
button1.Name = "OK button";
set properties button1.Text = "OK";
...
}
}
13
- Control events
• Controls offer events
– click
– mouse or keyboard activity
– property value change
– paint
– etc.
public class Control : Component ...
{
public event EventHandler Click;
public event EventHandler Enter;
public event EventHandler TextChanged;
events public event KeyPressEventHandler KeyPress;
public event MouseEventHandler MouseDown;
public event PaintEventHandler Paint;
...
}
14
- Event handlers
• Several types of event handler delegates
– generic EventHandler used for many events
– specific types for some events such as mouse and keyboard
• Event handlers have 2 arguments
– control that generated event
– event details in EventArgs or derived object
delegate void EventHandler (object sender, EventArgs e);
delegate void MouseEventHandler (object sender, MouseEventArgs e);
delegate void KeyPressEventHandler(object sender, KeyPressEventArgs e);
the control that event details
generated the event
15
- EventArgs
• Event handlers pass event details to handler
– passed in EventArgs or derived class object
generic base class public class EventArgs
so no event data {
}
info specific to class MouseEventArgs : EventArgs
mouse event {
public MouseButtons Button { get; }
public int Clicks { get; }
public int X { get; }
public int Y { get; }
...
}
info specific to class KeyPressEventArgs : EventArgs
keyboard event {
public char KeyChar { get; }
...
}
16
- Event registration
• Clients can register for events
– define method with signature required by delegate
– create delegate instance and add to event
public class MyForm : Form
{
private Button button1;
define
void button1_Click(object sender, EventArgs args)
method {
...
}
public MyForm()
{
...
register button1.Click += new EventHandler(this.button1_Click);
...
}
}
17
- Components
• Components are non-visual elements useful in UI
– e.g. Timer, FileSystemWatcher, EventLog, etc.
– extend System.ComponentModel.Component
components
in toolbox
shown in component
tray when added to form
18
- Threading
• Control should only be accessed by the creating thread
– messages from different threads subject to interleaving
– resulting race conditions can lead to inconsistent behavior
• Control class provides methods for thread-switching
– see docs for InvokeRequired, Invoke, BeginInvoke
window message queue
dequeue
owning other
thread thread
access
Login access
window Name:
controls Password:
OK Cancel
19
- No-touch deployment
• Windows forms applications can be deployed automatically
– client uses browser to access executable
– needed assemblies downloaded and stored in download cache
– program runs locally
– executable downloaded only if changed since last run
Client GET /App.exe HTTP/1.1
Server
cache App.exe App.exe
20
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