iOS激情详解之异步请求图片加载

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////  RootViewController.m//  ImageDownLoader-01////  Created by WDX on 15/9/14.//  Copyright (c) 2015年 WDongXu. All rights reserved.#import "RootViewController.h"// 加载图片// 一,获取照片#define kImageUrl @"http://img3.douban.com/view/event_poster/median/public/10f53a2ad8b38c5.jpg"@interface RootViewController ()<NSURLConnectionDataDelegate,NSURLConnectionDelegate> // 遵守协议//声明一个可变的data接受收据@property (nonatomic, retain)NSMutableData *data;// 链接声明 方便终止请求@property (nonatomic, retain)NSURLConnection *connection;// 创建个ImageView属性 下面的修改一下,用属性表示 self.@property (nonatomic, retain)UIImageView *imageView;@end@implementation RootViewController-  (void)dealloc{    [_connection cancel];    [_data release];    [_connection release];    [_imageView release];    [super dealloc];}- (void)viewDidLoad {    [super viewDidLoad];    // Do any additional setup after loading the view.    [self setUpData];    self.imageView = [[UIImageView alloc] initWithFrame:(CGRectMake(100, 100, 100, 100))];    self.imageView.backgroundColor = [UIColor redColor];    [self.view addSubview:self.imageView];    [_imageView release];}

// 二,异步请求一张图片- (void)setUpData{    // 1,创建一个NSURL    NSURL *url = [NSURL URLWithString:kImageUrl];    // 2, 用url对象创建一个请求    NSMutableURLRequest *requst = [NSMutableURLRequest requestWithURL:url cachePolicy:(NSURLRequestUseProtocolCachePolicy) timeoutInterval:30.0];    [requst setHTTPMethod:@"GET"];    // 3, 用请求 创建一个链接 使用代理方法    self.connection = [NSURLConnection connectionWithRequest:requst delegate:self];    // 4,开启链接    [self.connection start];}// 代理方法- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{    // 初始化data    self.data = [NSMutableData data];}- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{    // 拼接data    [self.data appendData:data];}

-(void)connectionDidFinishLoading:(NSURLConnection *)connection{    // 加载完成    self.imageView.image = [UIImage imageWithData:self.data];    // ***************写入沙盒***************************    // 写入data 起一个名字 newImage.png    NSArray *documentsArr = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);    NSString *documents = documentsArr[0];    // 拼接路径    NSString *imagePath = [documents stringByAppendingPathComponent:@"newImage.png"];    // 把data写入    [self.data writeToFile:imagePath atomically:YES];    NSLog(@"%@", imagePath);}

#import <Foundation/Foundation.h>// 1,创建协议@protocol ImageDownLoaderDelegate<NSObject>// 2,声明两个方法// 成功- (void) imageDownSucceedWithData:(NSData *)data;// 失败- (void) imageDownFaildeWithData:(NSError *)error;@end@interface ImageDownLoader : NSObject// 3,声明代理属性@property (nonatomic ,assign)id<ImageDownLoaderDelegate> delegate;// 声明一个初始化方法- (id) initWithImageUrl:(NSString *)imageUrl delegate:(id<ImageDownLoaderDelegate>)delegate;- (void)start;- (void)cancel;@end

#import "ImageDownLoader.h"// 属性要想写.m里面 写一个延展@interface ImageDownLoader ()<NSURLConnectionDataDelegate,NSURLConnectionDelegate>//声明一个可变的data接受收据  直接复制粘贴过来@property (nonatomic, retain)NSMutableData *data;// 链接声明 方便终止请求@property (nonatomic, retain)NSURLConnection *connection;@end@implementation ImageDownLoader- (void)dealloc{    // 终止请求最好写在控制器里面    // [_connection cancel];    [_connection release];    [_data release];    [super dealloc];}// 实现声明的一个初始化方法- (id) initWithImageUrl:(NSString *)imageUrl delegate:(id<ImageDownLoaderDelegate>)delegate{    self = [super init];    if (self) {        // 设置代理        _delegate = delegate;        // 进行图片的请求        // 1,创建一个NSURL        NSURL *url = [NSURL URLWithString:imageUrl];        // 2, 用url对象创建一个请求        NSMutableURLRequest *requst = [NSMutableURLRequest requestWithURL:url cachePolicy:(NSURLRequestUseProtocolCachePolicy) timeoutInterval:30.0];        [requst setHTTPMethod:@"GET"];        // 3, 用请求创建一个链接(使用代理方法)        self.connection = [NSURLConnection connectionWithRequest:requst delegate:self];        // 4,开启链接        // 最好用这个类的对象 可以控制开始 或者终止增加灵活性        // [self.connection start];    }    return self;}// 代理方法- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{    // 初始化data    self.data = [NSMutableData data];}- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{    // 拼接data    [self.data appendData:data];}-(void)connectionDidFinishLoading:(NSURLConnection *)connection{    // 加载完成 使用代理 把data传给控制器 (因为imageView在控制器创建)    // 外面设置了代理 并且实现了代理中的方法    // 才能让代理去干活    if (_delegate != nil && [_delegate respondsToSelector:@selector(imageDownSucceedWithData:)]) {        [_delegate imageDownSucceedWithData:self.data];    }}-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{    if (_delegate != nil && [_delegate respondsToSelector:@selector(imageDownFaildeWithData:)]) {        [_delegate imageDownFaildeWithData:error];    }}- (void)start{    [self.connection start];}- (void)cancel{    [self.connection cancel];}@end

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