iOS激情详解之异步请求图片加载

//
//  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