多线程05-cell照片下载

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////  HMAppsViewController.m//  01-cell图片下载（了解）////  Created by apple on 14-9-18.//  Copyright (c) 2014年 heima. All rights reserved.//#define HMAppImageFile(url) [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:[url lastPathComponent]]#import "HMAppsViewController.h"#import "HMApp.h"@interface HMAppsViewController ()/** *  所有的应用数据 */@property (nonatomic, strong) NSMutableArray *apps;/** *  存放所有下载操作的队列 */@property (nonatomic, strong) NSOperationQueue *queue;/** *  存放所有的下载操作（url是key，operation对象是value） */@property (nonatomic, strong) NSMutableDictionary *operations;/** *  存放所有下载完的图片 */@property (nonatomic, strong) NSMutableDictionary *images;@end@implementation HMAppsViewController#pragma mark - 懒加载- (NSMutableArray *)apps{    if (!_apps) {        // 1.加载plist        NSString *file = [[NSBundle mainBundle] pathForResource:@"apps" ofType:@"plist"];        NSArray *dictArray = [NSArray arrayWithContentsOfFile:file];        // 2.字典 --> 模型        NSMutableArray *appArray = [NSMutableArray array];        for (NSDictionary *dict in dictArray) {            HMApp *app = [HMApp appWithDict:dict];            [appArray addObject:app];        }        // 3.赋值        self.apps = appArray;//        _apps = appArray;    }    return _apps;}- (NSOperationQueue *)queue{    if (!_queue) {        self.queue = [[NSOperationQueue alloc] init];    }    return _queue;}- (NSMutableDictionary *)operations{    if (!_operations) {        self.operations = [[NSMutableDictionary alloc] init];    }    return _operations;}- (NSMutableDictionary *)images{    if (!_images) {        self.images = [[NSMutableDictionary alloc] init];    }    return _images;}#pragma mark - 初始化方法- (void)viewDidLoad{    [super viewDidLoad];    // 这里仅仅是block对self进行了引用，self对block没有任何引用    [UIView animateWithDuration:2.0 animations:^{        self.view.frame = CGRectMake(0, 0, 100, 100);    }];}- (void)didReceiveMemoryWarning{    [super didReceiveMemoryWarning];    // 移除所有的下载操作缓存    [self.queue cancelAllOperations];    [self.operations removeAllObjects];    // 移除所有的图片缓存    [self.images removeAllObjects];}#pragma mark - Table view data source- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section{    return self.apps.count;}- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath{    static NSString *ID = @"app";    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:ID];    if (!cell) {        cell = [[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:ID];    }    // 取出模型    HMApp *app = self.apps[indexPath.row];    // 设置基本信息    cell.textLabel.text = app.name;    cell.detailTextLabel.text = app.download;    // 先从images缓存中取出图片url对应的UIImage    UIImage *image = self.images[app.icon];    if (image) { // 说明图片已经下载成功过（成功缓存）        cell.imageView.image = image;    } else { // 说明图片并未下载成功过（并未缓存过）        // 获得caches的路径, 拼接文件路径        NSString *file = HMAppImageFile(app.icon);        // 先从沙盒中取出图片        NSData *data = [NSData dataWithContentsOfFile:file];        if (data) { // 沙盒中存在这个文件            cell.imageView.image = [UIImage imageWithData:data];        } else { // 沙盒中不存在这个文件            // 显示占位图片            cell.imageView.image = [UIImage imageNamed:@"placeholder"];            // 下载图片            [self download:app.icon indexPath:indexPath];        }    }    return cell;}/** *  下载图片 * *  @param imageUrl 图片的url */- (void)download:(NSString *)imageUrl indexPath:(NSIndexPath *)indexPath{    // 取出当前图片url对应的下载操作（operation对象）    NSBlockOperation *operation = self.operations[imageUrl];    if (operation) return;    // 创建操作，下载图片    __weak typeof(self) appsVc = self;    operation = [NSBlockOperation blockOperationWithBlock:^{        NSURL *url = [NSURL URLWithString:imageUrl];        NSData *data = [NSData dataWithContentsOfURL:url]; // 下载        UIImage *image = [UIImage imageWithData:data]; // NSData -> UIImage        // 回到主线程        [[NSOperationQueue mainQueue] addOperationWithBlock:^{            // 存放图片到字典中            if (image) {                appsVc.images[imageUrl] = image;#warning 将图片存入沙盒中                // UIImage --> NSData --> File（文件）                NSData *data = UIImagePNGRepresentation(image);                // 获得caches的路径, 拼接文件路径//                NSString *file = [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:[imageUrl lastPathComponent]];                [data writeToFile:HMAppImageFile(imageUrl) atomically:YES];//                UIImageJPEGRepresentation(<#UIImage *image#>, 1.0)            }            // 从字典中移除下载操作 (防止operations越来越大，保证下载失败后，能重新下载)            [appsVc.operations removeObjectForKey:imageUrl];            // 刷新表格            [appsVc.tableView reloadRowsAtIndexPaths:@[indexPath] withRowAnimation:UITableViewRowAnimationNone];        }];    }];    // 添加操作到队列中    [self.queue addOperation:operation];    // 添加到字典中 (这句代码为了解决重复下载)    self.operations[imageUrl] = operation;}/** *  当用户开始拖拽表格时调用 */- (void)scrollViewWillBeginDragging:(UIScrollView *)scrollView{    // 暂停下载    [self.queue setSuspended:YES];}/** *  当用户停止拖拽表格时调用 */- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate{    // 恢复下载    [self.queue setSuspended:NO];}@end