使用UIPageControl的例子如前面所示。但光以控件形式使用 UIPageControl还是不好用，因为虽然用户能通过手指扫动UIPageControl控件进行翻页，但UIPageControl控件在屏幕上所占的区域还是太小了，如果用户在整个屏幕都能通过扫动来进行翻页就更好了，这无疑大大增强的用户的体验。
这需要我们增加一个UIView控件，让它占据屏幕的整个区域。让UIView能识别用户手指扫动的手势，即几个touchesXXX方法。这样用户在屏幕上滑动手指时，实际上会被UIView捕捉为扫动手势。
首先，我们来实现这个UIView。新建类 SwipeView。SwipeView借鉴了《iPhone开发秘籍》中 Henry Yu 的实现，甚至我们都不需要做多少改变。
#import <UIKit/UIKit.h>
#import <QuartzCore/QuartzCore.h>
@interface SwipeView : UIView {
CGPoint startTouchPosition;
NSString *direction;
UIViewController *host;
}
- (void) setHost: (UIViewController *) aHost;
@end
#import "SwipeView.h"
@implementation SwipeView
- (id)initWithFrame:(CGRect)frame {
if ((self = [super initWithFrame:frame])) {
// Initializationcode
}
return self;
}
- (void) setHost: (UIViewController *) aHost
{
host = aHost;
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
startTouchPosition = [touch locationInView:self];
direction = NULL;
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch =touches.anyObject;
CGPoint currentTouchPosition =[touch locationInView:self];
#defineHORIZ_SWIPE_DRAG_MIN 12
#defineVERT_SWIPE_DRAG_MAX 4
if (fabsf(startTouchPosition.x -currentTouchPosition.x) >=
HORIZ_SWIPE_DRAG_MIN &&
fabsf(startTouchPosition.y - currentTouchPosition.y) <=
VERT_SWIPE_DRAG_MAX)
{
// Horizontal Swipe
if (startTouchPosition.x <currentTouchPosition.x) {
direction = kCATransitionFromLeft;
}
else
direction = kCATransitionFromRight;
}
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
if (host!=nil && direction) {
SEL sel=NSSelectorFromString(@"swipeTo:");
if([host respondsToSelector:sel]) {
[host performSelector:sel withObject:direction];
}
}
}
@end
首先，打开我们前面所做的工程UsingPageControl。
在UsingPageControlVeiwController中导入头文件SwipeView.h。将UsingPageControlViewController中的pageView修改为SwipeView类型。
同时在pageView的初始化时使用SwipeView的initWithFrame方法，并调用setHost:方法：
pageView=[[SwipeView alloc]initWithFrame:contentFrame];
[pageView setHost:self];
接下来，我们需要在SwipeView的Host类UsingPageControlVeiwController实现指定的swipeTo:方法:
// SwipeView 的协议（委托）方法
- (void) swipeTo: (NSString *) aDirection
{
NSLog(@"swipe to");
int to=previousPage;
if ([aDirection isEqualToString:kCATransitionFromRight])
{
to++;
}else {
to--;
}
if (to>=0 && to<=2) {
// pageCtrl的值改变并调用pageTuren方法
[self transitionPage:previousPage toPage:to];
previousPage=pageCtr.currentPage=to;
}
}