This document discusses several key aspects of UIView in iOS, including: 1. UIView defines a rectangular region on the screen for drawing and handling touch events. 2. Core Animation layers are used to improve performance by reusing rendered content through layer transformations and animations. 3. Views have properties like frame, bounds, and alpha that control their appearance and layout. Touch events are handled through the responder chain.

1. UIVIEW
употреба, хитрости и задължения
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2. UIVIEW
• defines a rectangular region on the screen
• drawing and touch events
• placement and sizing of other views
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3. CONTAINER VIEW
• resizing behavior Групиране
• hiding a view
• alpha (transparency)
• mathematical transform to the coordinate system
• responder chain (touches)
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4. UIVIEW AND CALAYER
CHAPTER 1
View and Window Architecture
Figure 1-1 Architecture of the views in a sample application
UIView UIWindow
UIImageView
UIToolbar UIBarButtonItem
(internal view)
UIKit views Core Animation layers
The use of Core Animation layer objects has important implications for performance. The actual drawing
code of a view object is called as little as possible, and when the code is called, the results are cached by
Core Animation and reused as much as possible later. Reusing already-‐rendered content eliminates the
Всяко View е изгранено от CALayer
expensive drawing cycle usually needed to update views. Reuse of this content is especially important during
animations, where the existing content can be manipulated. Such reuse is much less expensive than creating
new content.
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5. CALAYER
Quartz 2D
Reuse
Drawing
Hardware
buffers
Performance Render
Animation
Transform
matrices
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6. CHAPTER 1
CUSTOM DRAWING
View and Window Architecture
Figure 1-7 UIKit interactions with your view objects
iPhone OS
Your Application
Touch Framework
touches
setNeedsLayout
Mark redraw
Touches
UIKit setNeedsDisplay
frame, alpha, etc.
layoutSubviews
• Buffers setNeedsDisplay
• Images frame, alpha, etc.
• Attributes
• Geometry drawRect
• Animations
Compositor Draw images, text, etc.
Graphics hardware
The following steps break the event sequence in Figure 1-‐7 (page 23) down even further and explain what
happens at each stage and how you might want your application to react in response.
1. The user touches the screen.
2. APPLE: Avoid custom drawing!
The hardware reports the touch event to the UIKit framework.
3. The UIKit framework packages the touch into a UIEvent object and dispatches it to the appropriate
view. (For a detailed explanation of how UIKit delivers events to your views, see Event Handling Guide
for iOS.)
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7. CHAPTER 1
View and Window Architecture
CHAPTER 1
Overview of Quartz 2D
UIKIT Figure 1-‐4 shows this coordinate system r
windows and views define their own loca
to the view or window origin instead of r
Figure 1-4 Coordinate system orient
Figure 1-5
Quartz 2D UIKit
Modifying the coordinate system creates a mirrored image.
y (0,0)
x
(0,0)
x
(0,0)
y
x
Default Coordinates Modified Coordinates
• drawing - own coordinate system
y
• geometry changes - superview’s
coordinate system.
flipped_coordinates.eps
Cocoa Drawing
Apple Computer, Inc.
February 9, 2006 Because every view and window defines
Thursday, January 5, 12 coordinate system is in effect at any given

8. UIVIEW АМИНАЦИИ
• frame, bounds, center
• transform — rotate or scale the view.
• alpha
• backgroundColor
• contentStretch
• //autoresizingMask
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9. FRAME & BOUNDS
Frame rectangle Bounds rectangle
(40,40) (0,0)
Center
(160,230) 380 380
240
240
coordinates in coordinates
superview in self
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10. РАЗТЯГАНЕ НА КОНТЕНТ
CHAPTER 1
View and Window Architecture
Stretchable Views
You can designate a portion of a view as stretchable so that when the size of the view changes only the
content in the stretchable portion is affected. You typically use stretchable areas for buttons or other views
where part of the view defines a repeatable pattern. The stretchable area you specify can allow for stretching
Core Animation layer
along one or both axes of the view. Of course, when stretching a view along two axes, the edges of the view
must also define a repeatable pattern to avoid any distortion. Figure 1-‐3 shows how this distortion manifests
stretchable area - contentStretch property
itself in a view. The color from each of the view’s original pixels is replicated to fill the corresponding area in
the larger view.
Figure 1-3 Stretching the background of a button
(0,0)
(1,1)
UIViewContentModeScaleToFill
UIViewContentModeScaleAspectFit
UIViewContentModeScaleAspectFill
You specify the stretchable area of a view using the contentStretch property. This property accepts a
rectangle whose values are normalized to the range 0.0 to 1.0. When stretching the view, the system
multiplies these normalized values by the view’s current bounds and scale factor to determine which pixel
or pixels need to be stretched. The use of normalized values alleviates the need for you to update the
contentStretch property every time the bounds of your view change.
The view’s content mode also plays a role in determining how the view’s stretchable area is used. Stretchable
areas are only used when the content mode would cause the view’s content to be scaled. This means that
stretchable views are supported only with the UIViewContentModeScaleToFill,
UIViewContentModeScaleAspectFit, and UIViewContentModeScaleAspectFill content modes. If
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11. ПРИМЕРИ
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12. РЕЦИКЛИРАНЕ НА КОНТЕНТ
Първоначално
Bitmap
изобразяване
Render content
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13. TOUCHES
User input Touch Framework UIKit
UIEvent
UIView UIView
UIView
(superview) (superview)
Responder chain
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14. PERFORMANCE
• ViewControllers - колко и за какво се използват
• Избягвайте да чертаете сами
• Използвайте contentModes & AutoResizingMask
• aView.opaque = YES; когато е възможно
• Scrolling optimisation
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15. CUSTOM VIEWS
• initWithFrame: Не забравяй!
• dealloc
• autoresizingMask
• addGestureRecognizer: or touchesBegan:withEvent:
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16. APPENDIX A
The iOS Environment
APPLICATION SANDBOX
Figure A-1 Sandbox directories in iOS
App Sandbox
MyApp.app
Documents
App
Library
...
tmp
...
App Sandbox
App ...
App Sandbox
App ...
Important: The purpose of a sandbox is to limit the damage that a compromised app can cause to the
system. Sandboxes do not prevent attacks from happening to a particular app and it is still your responsibility
to code defensively to prevent attacks. For example, if your app does not validate user input and there is an
exploitable buffer overflow in your input-‐handling code, an attacker could still hijack your app or cause it to
crash. The sandbox only prevents the hijacked app from affecting other apps and other parts of the system.
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