#import "UIImageView+WebCache.h"
#import "ImageDownloader.h"@implementation UIImageView (WebCache)- (void)setImageWithUrl:(NSString *)urlStr andPlaceHolderImage:(UIImage *)image andIsScrolling:(BOOL)isScroll
{self.image = image;//文件夹位置NSString *dirPath = [NSHomeDirectory() stringByAppendingString:@"/Library/Caches/images"];NSFileManager *fm = [NSFileManager defaultManager];//判断文件夹是否存在BOOL isDir = YES;if (![fm fileExistsAtPath:dirPath isDirectory:&isDir]) {//创建文件夹
        [fm createDirectoryAtPath:dirPath withIntermediateDirectories:YES attributes:nil error:nil];}//取得文件名称NSString *fileName = [[urlStr componentsSeparatedByString:@"/"]lastObject];//取得文件路径NSString *filePath = [dirPath stringByAppendingFormat:@"/%@",fileName];//先从本地找该图片是否存在，如果存在直接从本地加载图片，否则从网络获取if ([fm fileExistsAtPath:filePath]) {self.image = [UIImage imageWithContentsOfFile:filePath];NSLog(@"从本地加载");self.layer.borderWidth = 2;return;}//如果tableview滚动，则不去加载图片if (isScroll) {return;}//如果该url已经存在manager中，即当前url已经对应有一个下载线程在下载该图片，则不需要再次启动线程下载该图片if ([[ImageDownloaderManager sharedManager]checkImageDownloaderIsExist:urlStr]) {return;}for (ImageDownloader *downloader in [[ImageDownloaderManager sharedManager]allDownloaders]) {if (downloader.imageView == self) {NSLog(@"----取消下载之前的！");[downloader cancel];[[ImageDownloaderManager sharedManager]removeDownloaderWithUrl:downloader.urlStr];break;}}self.layer.borderWidth = 0;NSLog(@"----新的下载");//从网络获取__weak typeof(self)wSelf = self;__block typeof(filePath)wFilePath = filePath;ImageDownloader *downloader = [[ImageDownloader alloc]init];downloader.imageView = self;//以urlstr为key值保存imagedownloader
    [[ImageDownloaderManager sharedManager]addDownloader:downloader withUrl:urlStr];[downloader startDownImageWithUrl:urlStr whenSuccess:^(id responseData) {//设置自身image为网络请求返回的数据wSelf.image = [UIImage imageWithData:responseData];wSelf.layer.borderWidth = 0;//本地缓存[((NSData *)responseData) writeToFile:wFilePath atomically:YES];[[ImageDownloaderManager sharedManager]removeDownloaderWithUrl:urlStr];NSLog(@"成功：%ld",[[ImageDownloaderManager sharedManager] count]);} andFailure:^(NSString *errorDesc) {[[ImageDownloaderManager sharedManager]removeDownloaderWithUrl:urlStr];NSLog(@"失败：%ld",[[ImageDownloaderManager sharedManager] count]);}];
}@end

#import "ViewController.h"
#import "UIImageView+WebCache.h"@interface ViewController ()<UITableViewDataSource,UITableViewDelegate>
{UITableView *_tableView;NSMutableArray *_dataArr;
}
@end// 主界面菜单
#define MAINMENU_URL @"%@/HandheldKitchen/api/more/tblcalendaralertinfo!getHomePage.do?phonetype=2&page=1&pageRecord=30&user_id=&is_traditional=0"
//最新主机地址和端口
#define kHost_And_Port @"http://121.40.54.251:80"@implementation ViewController- (void)viewDidLoad {[super viewDidLoad];_tableView = [[UITableView alloc]initWithFrame:self.view.bounds style:UITableViewStylePlain];_tableView.delegate = self;_tableView.dataSource = self;[self.view addSubview:_tableView];//请求网络数据dispatch_async(dispatch_get_global_queue(0, 0), ^{_dataArr = [[NSMutableArray alloc]init];NSString *urlStr = [NSString stringWithFormat:MAINMENU_URL,kHost_And_Port];//同步网络请求NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:urlStr]];if (data) {//解析数据NSDictionary *rootDic = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:nil];for (NSDictionary *dic in rootDic[@"data"]) {[_dataArr addObject:dic[@"imagePathLandscape"]];}//主线程刷新dispatch_async(dispatch_get_main_queue(), ^{[_tableView reloadData];});}});
}#pragma mark -TableViewDelegate
- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{return _dataArr.count;
}- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{static NSString *cellIde = @"Cell";UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:cellIde];if (!cell) {cell = [[UITableViewCell alloc]initWithStyle:UITableViewCellStyleDefault reuseIdentifier:cellIde];//添加imgViewUIImageView *imgView = [[UIImageView alloc]initWithFrame:CGRectMake(200, 5, 80, 80)];[cell.contentView addSubview:imgView];imgView.tag = 100;if (indexPath.row == 0) {cell.backgroundColor = [UIColor redColor];}}UIImageView *imgView = (UIImageView *)[cell.contentView viewWithTag:100];//isDecelerating是否减速中，isDragging是否被拖拽中，满足其中一个，则tableview没有静止[imgView setImageWithUrl:_dataArr[indexPath.row] andPlaceHolderImage:[UIImage imageNamed:@"1.png"] andIsScrolling:_tableView.isDecelerating || _tableView.isDragging];cell.textLabel.text = [NSString stringWithFormat:@"第%ld个",indexPath.row];return cell;
}- (CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath
{return 90;
}- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView
{//tableview静止，加载图片
    [self downloadScreenCellImages];
}- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate
{//decelerate是否即将减速，若为yes则会出发didenddecelerate方法，否则不会，所以没有减速时需要加载当前屏幕范围内的图片//不存在减速即tableview已经静止if (!decelerate) {[self downloadScreenCellImages];}
}//加载当前屏幕范围内可见cell的图片
- (void)downloadScreenCellImages
{//获取当前屏幕可见cellNSArray *cells = [_tableView visibleCells];for (UITableViewCell *cell in cells) {UIImageView *imgView = (UIImageView *)[cell.contentView viewWithTag:100];//获取cell所对应的indexpathNSIndexPath *indexPath = [_tableView indexPathForCell:cell];[imgView setImageWithUrl:_dataArr[indexPath.row] andPlaceHolderImage:[UIImage imageNamed:@"1.png"] andIsScrolling:NO];}
}- (void)didReceiveMemoryWarning {[super didReceiveMemoryWarning];// Dispose of any resources that can be recreated.
}@end