淺析iPhone SDK開發(fā)基礎(chǔ)之UIPageControl編程
iPhone SDK開發(fā)基礎(chǔ)之UIPageControl編程是本文要介紹的內(nèi)容，當(dāng)用戶界面需要按頁面進(jìn)行顯示時(shí)，使用iOS提供的UIPageControl控件將要顯示的用戶界面內(nèi)容分頁進(jìn)行顯示會(huì)使編程工作變得非?？旖?，如圖3-47所示就是一個(gè)使用UIPageControl控件逐頁進(jìn)行圖片顯示的程序，用戶按下屏幕即可進(jìn)行左右滾動(dòng)顯示，在屏幕的正上方使用白色的點(diǎn)顯示當(dāng)前滾動(dòng)到的頁面位置，如圖：
程序自定義一個(gè)SwipeView類，該類通過子類化UIView類并重載其touchesMoved()方法捕獲用戶滾動(dòng)的方向，類的定義如下。
- // SwipeView.h
- #import <UIKit/UIKit.h>
- #import <QuartzCore/QuartzCore.h>
- @interface SwipeView : UIView {
- CGPoint startTouchPosition;
- NSString *dirString;
- UIViewController *host;
- }
- - (void) setHost: (UIViewController *) aHost;
- @end
- // SwipeView.m
- #import "SwipeView.h"
- @implementation
- SwipeView
- - (id)initWithFrame:(CGRect)frame {
- if ((self = [super initWithFrame:frame])) {
- // Initialization code
- }
- return self;
- }
- - (void) setHost: (UIViewController *) aHost
- {
- host = aHost;
- }
- - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event {
- UITouch *touch = [touches anyObject];
- startTouchPosition = [touch locationInView:self];
- dirString = NULL;
- }
- - (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event {
- UITouch *touch = touches.anyObject;
- CGPoint currentTouchPosition = [touch locationInView:self];
- #define HORIZ_SWIPE_DRAG_MIN 12
- #define VERT_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) {
- dirString = kCATransitionFromLeft;
- }
- else
- dirString = kCATransitionFromRight;
- }
- }
- - (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
- if (dirString) [host swipeTo:dirString];
- }
- @end
在捕獲用戶滾動(dòng)的方向后，SwipeView類通過用戶設(shè)置的host成員變量回調(diào)其swipeTo()方法，host成員變量在類中定義為UIViewController，在編譯時(shí)編譯器會(huì)產(chǎn)生警告，這里不用管它，只需要SwipeView類的使用者設(shè)置host成員變量并實(shí)現(xiàn)swipeTo()方法即可。
SwipeView類的使用者為PageViewController類，該類實(shí)現(xiàn)程序的主界面，在這個(gè)自定義的UIViewController類中實(shí)現(xiàn)swipeTo()方法，代碼如下。
- // PageViewController.m
- - (void) swipeTo: (NSString *) aDirection{
- UIPageControl *pageControl = [[[contentView superview] subviews] lastObject];
- if ([aDirection isEqualToString:kCATransitionFromRight])
- {
- if (currentPage == 5) return;
- [pageControl setCurrentPage:currentPage + 1];
- } else {
- if (currentPage == 0) return;
- [pageControl setCurrentPage:currentPage - 1];
- }
- [self pageTurn:pageControl];
- }
在該回調(diào)方法中根據(jù)用戶滾動(dòng)的方向來設(shè)置UIPageControl的currentPage屬性，如果是向右方滾動(dòng)則頁面計(jì)數(shù)加一，如果用戶滾動(dòng)的方向是向左，則頁面計(jì)數(shù)減一。設(shè)置UIPageControl的currentPage屬性以后，PageViewController對(duì)象再調(diào)用其pageTurn()方法交換頁面顯示內(nèi)容，并將圖片顯示出來，代碼如下。
- - (void) pageTurn: (UIPageControl *) pageControl{
- CATransition *transition;
- int secondPage = [pageControl currentPage];
- if ((secondPage - currentPage) > 0)
- transition = [self getAnimation:@"fromRight"];
- else
- transition = [self getAnimation:@"fromLeft"];
- UIImageView *newView = (UIImageView *)[[contentView subviews] objectAtIndex:0];
- [newView setImage:[UIImage imageNamed:[NSString stringWithFormat:@"ipad_ wallpaper%02d.jpg", secondPage + 1]]];
- [contentView exchangeSubviewAtIndex:0 withSubviewAtIndex:1];
- [[contentView layer] addAnimation:transition forKey:@"transitionView Animation"];
- currentPage = [pageControl currentPage];
- }
在主pageTurn()方法實(shí)現(xiàn)中，PageViewController類通過UIView的exchangeSubview AtIndex()方法實(shí)現(xiàn)頁面內(nèi)容的切換。
小結(jié)：淺析iPhone SDK開發(fā)基礎(chǔ)之UIPageControl編程的內(nèi)容介紹完了，希望通過本文的學(xué)習(xí)能對(duì)你有所幫助！
