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一、异步下载图片ImageViewDownloader
图?下载是iOS开发中常?的功能，但系统并未提供图?下载类。 为了便于后续使?，可以将图?下载封装到?个类?? （ImageDownloader）
新建SingleViewApplication，使用默认的Storyboard，向其中添加一个Button一个ImageView并关联属性、添加事件。点击Button实现异步下载并显示图片。AsynImageDownloader类封装了下载图片的方法。
使用代理进行AsynImageDownloader与ViewController中的传值(UIImage)
AsynImageDownloaderDelegate.h
#import <Foundation/Foundation.h>
@class UIImage;
@class AsynImageDownloader;
@protocol AsynImageDownloaderDelegate <NSObject>
- (void)AsynImageDownloader:(AsynImageDownloader *)downloader isLoading:(UIImage *)image;
封装图片下载的方法
AsynImageDownloader.h
#import <Foundation/Foundation.h>
#import "AsynImageDownloaderDelegate.h"
@interface AsynImageDownloader : NSObject<NSURLConnectionDataDelegate>
@property (nonatomic, assign) id<AsynImageDownloaderDelegate> delegate;
@property (nonatomic, retain) NSURLConnection *connection;
- (instancetype)initWithImageURL:(NSString *)imageURL;
@end
AsynImageDownloader.m
#import "AsynImageDownloader.h"
#import <UIKit/UIKit.h>
@interface AsynImageDownloader ()
@property (nonatomic, retain) NSMutableData *receiveData;
@end
@implementation AsynImageDownloader
- (instancetype)initWithImageURL:(NSString *)imageURL
{
self = [super init];
if (self) {
//1.URL
NSURL *url = [NSURL URLWithString:imageURL];
//2.request
NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0];
//3.connection OBJ
self.connection = [NSURLConnection connectionWithRequest:request delegate:self];
}
return self;
}
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
self.receiveData = [NSMutableData data];
}
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
[_receiveData appendData:data];
UIImage *image = [UIImage imageWithData:_receiveData];
if ([_delegate respondsToSelector:@selector(AsynImageDownloader:isLoading:)]) {
[_delegate AsynImageDownloader:self isLoading:image];
}
}
@end
创建对象并显示图片，遵守协议、设置代理
ViewController.m
#import "ViewController.h"
#import "AsynImageDownloader.h"
#import "AsynImageDownloaderDelegate.h"
#define kPicURL @"http://image.zcool.com.cn/56/13/1308200901454.jpg"
@interface ViewController ()<NSURLConnectionDataDelegate, AsynImageDownloaderDelegate>
@property (nonatomic, retain) NSMutableData *receiveData;
@property (retain, nonatomic) IBOutlet UIImageView *imgView;
- (IBAction)asynDownloaderPic:(UIButton *)sender;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#pragma mark -- AsynImageDownloaderDelegate --
- (void)AsynImageDownloader:(AsynImageDownloader *)downloader isLoading:(UIImage *)image
{
self.imgView.image = image;
}
#pragma mark -- 异步下载图片 --
- (IBAction)asynDownloadPic:(UIButton *)sender {
AsynImageDownloader *downloader = [[AsynImageDownload alloc] initWithImageURL:kPicURL];
downloader.delegate = self;
}
- (void)dealloc {
[_imgView release];
[super dealloc];
}
@end
二、KVO(Key-Value-Observer 键值观察者)
1、KVO简介
KVO是观察者设计模式的?种具体实现
在 Cocoa 的模型-视图-控制器 (Model-view-controller)架构里，控制器负责让视图和模型同步。这一共有两步：当 model 对象改变的时候，视图应该随之改变以反映模型的变化；当用户和控制器交互的时候，模型也应该做出相应的改变。
KVO 能帮助我们让视图和模型保持同步。控制器可以观察视图依赖的属性变化。MVC中M与C通信，M发?变化通知C。其中M是被 观察者，C是观察者。
KVO触发机制：?个对象（观察者），监测另?对象（被观察者）的某属性是否发?变化，若被监测的属性发?的更改，会触发观察者的?个?法（?法名固定，类似代理?法）
KVO详细介绍及使用：http://objccn.io/issue-7-3/
2、KVO使?步骤：
1、注册观察者（为被观察者指定观察者以及被观察属性）
2、实现回调?法
3、触发回调?法（被观察属性发?更改）
4、移除观察者
3、使用示例
示例一
给Person类的name属性添加观察者。name发?变化 时，让self.view的背景颜?随机改变。界面包含一个UITextField、一个UIButton。使用SingleViewApplication创建，在Storyboard中添加控件
YFPerson.h
#import <Foundation/Foundation.h>
@interface YFPerson : NSObject
@property (nonatomic, retain) NSString *name;
@end
ViewController.m
#import "ViewController.h"
#import "YFPerson.h"
@interface ViewController ()
@property (nonatomic, retain) YFPerson *person;
@property (retain, nonatomic) IBOutlet UITextField *textField;
- (IBAction)didClickButton:(UIButton *)sender;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.person = [[YFPerson alloc] init];
//1.注册观察者(为被观察者_person添加一个观察者self并设置其观察的属性)
[_person addObserver:self forKeyPath:@"name" options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld context:nil];
[_person release];
// Do any additional setup after loading the view, typically from a nib.
}
- (IBAction)didClickButton:(UIButton *)sender {
//3.1改变Person.name
_person.name = _textField.text;
}
//3.2被观察者属性改变触发以下方法
//2.实现回调方法
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context
{
NSLog(@"被观察者的路径:%@",keyPath);
NSLog(@"被观察者:%@", object); //object为被观察者
NSLog(@"被监测的属性所有状态下的值:%@", change); //change {kind=1; new=""; old="<null>"}
NSLog(@"在注册观察者时，context的值:%@", context); //context
//判断新值和旧值
if (![change[@"new"]isEqualToString:change[@"old"]]) {
self.view.backgroundColor = [UIColor colorWithRed:arc4random()%256/255.0 green:arc4random()%256/255.0 blue:arc4random()%256/255.0 alpha:1.0];
}
}
- (void)dealloc {
//4.移除观察者
[_person removeObserver:self forKeyPath:@"name" context:nil];
[_textField release];
[super dealloc];
}
@end
示例二
KVO监测Model图?下载
https://github.com/zooyf/KVO-Monitoring-Model-Picture-Download
附，第三方框架
文件下载
如果文件比较小，下载方式会比较多
直接用NSData的+ (id)dataWithContentsOfURL:(NSURL *)url;
利用NSURLConnection发送一个HTTP请求去下载
如果是下载图片，还可以利用SDWebImage框架
文件压缩解压框架
第三方解压缩框架——SSZipArchive
下载地址：https://github.com/samsoffes/ssziparchive
注意：需要引入libz.dylib框架
// Unzipping
NSString *zipPath = @"path_to_your_zip_file";
NSString *destinationPath = @"path_to_the_folder_where_you_want_it_unzipped";
[SSZipArchive unzipFileAtPath:zipPath toDestination:destinationPath];
// Zipping
NSString *zippedPath = @"path_where_you_want_the_file_created";
NSArray *inputPaths = [NSArray arrayWithObjects:
[[NSBundle mainBundle] pathForResource:@"photo1" ofType:@"jpg"],
[[NSBundle mainBundle] pathForResource:@"photo2" ofType:@"jpg"]
nil];
[SSZipArchive createZipFileAtPath:zippedPath withFilesAtPaths:inputPaths];
部分文件的MIMEType
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原文地址：http://my.oschina.net/zooyf/blog/503528
