Graphics Reference
In-Depth Information
implement any other iOS-specific behavior such as
scroll bouncing
(when a view
elastically snaps back into place after scrolling past its bounds).
Let's use a
CAScrollLayer
to create a very basic
UIScrollView
replacement. We'll
create a custom
UIView
that uses a
CAScrollLayer
as its backing layer, and then use
UIPanGestureRecognizer
to implement the touch handling. The code is shown in
Listing 6.10. Figure 6.11 shows the
ScrollView
being used to pan around a
UIImageView
that is larger than the
ScrollView
frame.
Listing 6.10
Implementing a Scrolling View Using
CAScrollLayer
#import
"ScrollView.h"
#import
<QuartzCore/QuartzCore.h>
@implementation
ScrollView
+ (
Class
)layerClass
{
return
[
CAScrollLayer
class
];
}
- (
void
)setUp
{
//enable clipping
self
.
layer
.
masksToBounds
=
YES
;
//attach pan gesture recognizer
UIPanGestureRecognizer
*recognizer =
nil
;
recognizer = [[
UIPanGestureRecognizer
alloc
]
initWithTarget
:
self
action
:
@selector
(pan:)];
[
self
addGestureRecognizer
:recognizer];
}
- (
id
)initWithFrame:(
CGRect
)frame
{
//this is called when view is created in code
if
((
self
= [
super
initWithFrame
:frame]))
{
[
self
setUp
];
}
return
self
;
}
- (
void
)awakeFromNib
{
//thi
s is called when view is created from a nib
