iOS优化内存的横向ScrollView

来源：互联网发布：塞班s60v5 软件下载编辑：程序博客网时间：2024/06/07 18:23

原理就是ScrollView中同时只有1、2、3张图片，每次翻动结束后，重新设置这三张图片，如1、2、3，原来是2，向右翻动结束减速后将1、2、3换成2、3、4，由于是结束滚动后替换的，所以看上去跟平滑滚动是一样的

#import "ViewController.h"@implementation ViewController{    UIScrollView *_mainScrollView;    NSMutableArray *_imagePathArray;    NSInteger _currentIndex;    CGFloat _width;    CGFloat _height;}- (void)viewDidLoad{    [super viewDidLoad];    _width = self.view.frame.size.width;    _height = self.view.frame.size.height;    self.view.backgroundColor = [UIColor whiteColor];    _mainScrollView = [[UIScrollView alloc] init];    _mainScrollView.frame = CGRectMake(0, 0, _width , _height);    _mainScrollView.delegate = self;    _mainScrollView.pagingEnabled = YES;    _mainScrollView.bounces = NO;    _mainScrollView.showsHorizontalScrollIndicator = NO;    _mainScrollView.contentSize = CGSizeMake(_width*3, _height);    [self.view addSubview:_mainScrollView];        _imagePathArray = [[NSMutableArray alloc] init];    for(int i=1;i<7;i++)    {        NSString *path = [NSString stringWithFormat:@"%@/%d.jpg",[[NSBundle mainBundle] resourcePath],i];        [_imagePathArray addObject:path];    }        _currentIndex = 0;        [self loadImageView];}- (void)loadImageView{    // 移除之前加载的    for(UIView *view in _mainScrollView.subviews)    {        [view removeFromSuperview];    }        // 当前页        UIImage *currentImage = [[UIImage alloc] initWithContentsOfFile:[_imagePathArray objectAtIndex:_currentIndex]];    UIImageView *currentImageView = [[UIImageView alloc] initWithImage:currentImage];    currentImageView.frame = CGRectMake(_width, 0, _width, _height);    [_mainScrollView addSubview:currentImageView];        // 左侧页    UIImage *preImage = [[UIImage alloc] initWithContentsOfFile:_currentIndex-1<0?[_imagePathArray lastObject]:[_imagePathArray objectAtIndex:_currentIndex-1]];    UIImageView *preImageView = [[UIImageView alloc] initWithImage:preImage];    preImageView.frame = CGRectMake(0, 0, _width, _height);    [_mainScrollView addSubview:preImageView];        // 右侧页    UIImage *nextImage = [[UIImage alloc] initWithContentsOfFile:_currentIndex+1==_imagePathArray.count?[_imagePathArray firstObject]:[_imagePathArray objectAtIndex:_currentIndex+1]];    UIImageView *nextImageView = [[UIImageView alloc] initWithImage:nextImage];    nextImageView.frame = CGRectMake(_width*2, 0, _width, _height);    [_mainScrollView addSubview:nextImageView];            [_mainScrollView setContentOffset:CGPointMake(_width, 0)];}//翻页- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView{    NSLog(@"scrollView.contentOffset.x = %.0f",scrollView.contentOffset.x);    int index = scrollView.contentOffset.x/_width;    if(index == 0)    {        _currentIndex = _currentIndex-1<0?_imagePathArray.count-1:_currentIndex-1;        [self loadImageView];    }    if(index == 2)    {        _currentIndex = _currentIndex+1==_imagePathArray.count?0:_currentIndex+1;        [self loadImageView];    }}@end

0 0