Download Important New Concepts In WPF

Important New Concepts In WPF
Orlando Robertson
Brown Bag Seminar
Windows Presentation Foundation Unleashed
Introduction
This chapter introduces concepts beyond .NET
programming
New Concepts
– Logical Trees
– Visual Trees
Extended Concepts
– Dependency Properties
– Routed Events
– Commands
Review UI applications needed for programming
Logical & Visual Trees
Logical Trees are objects to create UIs in WPF
Important because every aspect in WPF is
associated to Logical Trees
Visual Trees are considered an expanded logical
tree exposing visual components
Visual Trees expose elements derived from
System.Windows.Media.Visual &Visual3D
Logical & Visual Trees
Logical & Visual Trees
Logical & Visual Trees
Visual Trees & Logical Trees are needed for
applications separating look and logic
Logical Trees can be traversed using class
System.Windows.LogicalTreeHelper
Visual Trees can be traversed using class
System.Windows.VisualTreeHelper
Dependency Properties
Dependency Property is a new WPF property type used
to enable styling, automatic data binding, animation
Dependency Properties provide change notifications
from declarative markup
– Also property value inheritance & multiple provider support
Styling and Animation are done with dependency
properties
A Dependency Property Implementation
Dependency Properties are .NET properties connected
to extra WPF infrastructure
Represented by System.Windows.DependencyProperty
Created by calling DependencyProperty.Register
Options for passing metadata, callbacks, coercing
values, validating values
.NET property wrappers are bypassed at run-time when
setting Dependency Properties in XAML
Change Notification
Change Notifications allows WPF to automatically
trigger actions when dependency properties change
– Property Trigger, Data Trigger, Event Trigger
Property Trigger allows custom changes when property
values change without procedural code
Data Trigger works for all .NET properties, not just
dependency properties
Event Trigger declaratively specifies actions for raised
events
– Used for animation and sound applications
Property Value Inheritance
Property Value Inheritance refers to flow of
property values down the element tree
Child elements inherit properties of the parent
element unless overridden
Elements deriving from Freezable may inherit
values from the parent element
Support for Multiple Providers
WPF executes a 5 step process to calculate the final
value of dependency properties using change
notifications
Step 1 Determine Base Value
– Applies a precedence order for property providers
Step 2 Evaluate
– Evaluate expressions from step 1
Step 3 Apply Animations
– Apply animation values to current properties
Support for Multiple Providers
Step 4 Coerce
– Passes the resulting property values to a
CoerceValueCallback delegate
Step 5 Validate
– Passes the coerced property values to a
ValidateValueCallback delegate
Attached Properties
Attached Properties are special dependency
properties assigned to arbitrary objects
Objects that don’t have a dependency property
of it’s own can be attached and used for property
value inheritance
Ex. Assigning a FontSize to a StackPanel
Routed Events
Routed Events traverse thru visual and logical
trees without the need for custom code
Provides the service of encapsulation of
application from visual trees
Allows for embedded complex content and visual
trees
A Routed Event Implementation
Routed Events are static public fields
Routed Events are represented by
RoutedEvents
Created by calling
EventManger.RegisterRoutedEvent
Routing Strategies & Event Handlers
RoutingStrategy enumeration: Tunneling,
Bubbling, Direct
Tunneling raises the routed event at the root
then to each element toward the source element
Bubbling raises the routed event at the source
element then to each element toward the root
Direct raises the routed event at the source
element only
Routing Strategies & Event Handlers
Routed Event handlers are similar to .NET event
handlers
1st Parameter is System.Object sender
2nd Parameter is RoutedEventArgs e
RoutedEventArgs derived from EventArgs
Routed Events in Action
UIElement class defines routed events for keyboard,
mouse, stylus input
Many of the bubbling events are paired with tunneling
events
Naming convention of tunneling events are prefixed with
Preview
– Tunneling Event: PreviewMouseMove
– Bubbling Event: MouseMove
Event pairing provides the option of canceling or
modifying a bubbling event
Attached Events
Attached Events provide tunneling and bubbling
of routed events to elements that don’t define the
event
Similar to attached properties
Routed events can be used as attached events
Commands
Commands represent independent actions from the UI
Multiple commands can be exposed with the use of
events
WPF reduces the amount of code needed to support
commands
WPF provides flexibility to change UIs supporting
commands without breaking back-end logic
Built-In Commands
WPF defines many commands ready for use
ApplicationCommands: Cut, Paste
ComponentCommands: MoveUp, MoveDown
MediaCommands: ChannelUp, ChannelDown
NavigationCommands: Search, Refresh
EditingCommands: AlignLeft, AlignCenter
These commands are instances of RoutedUICommand
– Implements ICommand & Supports Bubbling
Executing Commands w/ Input Gestures
Input Gestures can be bound to commands by
adding a KeyBinding or MouseBinding to the
elements InputBindings collection
Ex Help command provides auto binding to
keyboard shortcuts
– Default: F1 Key
Input Gestures can assign F2 key to execute
Help command
Controls w/ Built-In Command Bindings
Some controls in WPF have their own command
bindings
– Ex TextBox control bound to Cut, Paste
Built-In Commands can be bound by WPF
controls
– Button bound to a TextBox Built-In command
WPF’s built-in commands becomes important
– Buttons and TextBoxes can gain rich interaction
A Tour of the Class Hierarchy
Conclusion
We learned the major WPF applications for the
.NET Framework
Reviewed types of properties, types of events,
trees, declarative code, procedural code
We now have an understanding of WPF controls
and developing WPF UIs.
References
“Windows Presentation Foundation Unleashed”,
Adam Nathan with Daniel Lehenbauer
Software Requirements
– Windows that support .NET 3.0: XP SP2, Vista
– .NET Framework 3.0
Software Recommended
– Windows SDK (http://msdn.com)
– Visual Studio 2005 or later