HttpDownload的实现（ASIHTTP和NSConnection两种方式）

ASIHTTPRequest是第三方包，使用前需要导入的包：MobileCoreServices、SystemConfiguration、CFNetwork、libz。

这里写的HttpDownload类可以实现用参数选择两种方式中一种来实现HTTP下载。并且通过callMethod函数实现回调。

下面是HttpDownload.h

#import <Foundation/Foundation.h>

#import "ASIHTTPRequest.h"

#define DOWNLOAD_SYSTEM 1

#define DOWNLOAD_ASIHTTPREQUEST 2



@interface HttpDownload : NSObject<ASIHTTPRequestDelegate,NSURLConnectionDataDelegate>

{

    //回调的方法

    SEL callMethod;

    //代理

    id delegate;

    NSURLConnection *mConnection;

    NSInteger mType;

    //用于存放下载到的二进制数据

    NSMutableData *mData;

}

@property (nonatomic,retain) NSMutableData *mData;



-(void)downloadFromUrl:(NSString *)url delegate:(id)delegate selector:(SEL)selector type:(NSInteger)type;



@end

下面是HttpDownload.m

m

#import "HttpDownload.h"

@implementation HttpDownload

@synthesize mData;

//在初始化函数中为mData分配空间

-(id)init

{

    if (self=[super init]) {

        mData=[[NSMutableData alloc] init];

    }

    return self;

}

//dealloc时对mData进行内存回收

-(void)dealloc

{

    self.mData=nil;

    [super dealloc];

}

//参数一表示下载地址，参数二表示回调对象地址，参数3表示回调函数地址，参数四是下载类型

-(void)downloadFromUrl:(NSString *)url delegate:(id)newdelegate selector:(SEL)selector type:(NSInteger)type

{

    delegate=newdelegate;

    callMethod=selector;

    //关于类型的宏定义

    // #define DOWNLOAD_SYSTEM 1

    // #define DOWNLOAD_ASIHTTPREQUEST 2

    if (type==DOWNLOAD_ASIHTTPREQUEST) {

        ASIHTTPRequest *request=[ASIHTTPRequest requestWithURL:[NSURL URLWithString:url]];

        request.delegate=self;

        //启动异步下载

        [request startAsynchronous];

        //后面继续执行requestfinish或者requestFail方法

    }

    else if(type==DOWNLOAD_SYSTEM){

        if (mConnection) {

            [mConnection cancel];

            [mConnection release];

        }

        mConnection=[[NSURLConnection alloc] initWithRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:url]] delegate:self];

        //后面执行connection:系列函数

    }

    else{

        NSLog(@"暂没实现");

    }

}

//得到回应，即将开始开始接收数据时

-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response

{

    //清空mData

    [mData setLength:0];

}

//得到数据时

-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data

{

    //将数据存到mData

    [mData appendData:data];

}



-(void)connectionDidFinishLoading:(NSURLConnection *)connection

{

    //检查代理是否可用以及是否实现方法callMethod

    if(delegate && [delegate respondsToSelector:callMethod]){

        //调用对象delegate的方法callMethod传的参数为self

        [delegate performSelector:callMethod withObject:self];

        //下面这个不能用，因为成员变量delegate是id类型的。

        //[delegate callMethod:self];

    }

}

-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error

{

    NSLog(@"系统下载失败");



}

-(void)requestFinished:(ASIHTTPRequest *)request

{

    [mData setLength:0];

    [mData appendData:[request responseData]];

    //检查代理是否可用以及是否实现方法callMethod

    if(delegate && [delegate respondsToSelector:callMethod]){

        //调用对象delegate的方法callMethod传的参数为self

        [delegate performSelector:callMethod withObject:self];

        //[delegate callMethod:self];

    }

}

-(void)requestFailed:(ASIHTTPRequest *)request

{

    NSLog(@"第三方下载失败");

}

@end