ios专题 - 异步下载加下载进度显示

【罗国强原创】

今天被刺激了，愤概地要写下这边博文。

说到http异步下载，首先要知道其中的关键类。

关键类是NSURLConnection  NSURLRequest NSMutableURLRequest

委托是 NSURLConnectionDownloadDelegate NSURLConnectionDataDelegate NSURLConnectionDelegate

首先，我们要实现最基本的下载功能。

LQAsynDownload.h

//
//  LQAsynDownload.h
//  lgTest
//
//  Created by yons on 14-2-14.
//  Copyright (c) 2014年 GQ. All rights reserved.
//

#import <Foundation/Foundation.h>

@interface LQAsynDownload : NSObject<NSURLConnectionDataDelegate>

@property (strong) NSURL *httpURL;

+ (LQAsynDownload *) initWithURL:(NSURL *) url;

- (void) startAsyn;

@end

LQAsynDownload.m

//
//  LQAsynDownload.m
//  lgTest
//
//  Created by yons on 14-2-14.
//  Copyright (c) 2014年 GQ. All rights reserved.
//

#import "LQAsynDownload.h"

@interface LQAsynDownload()

@property (assign) long long contentLength;

@property (assign) long long receiveLength;

@property (strong) NSMutableData *receiveData;

@property (strong) NSString *fileName;

@property (strong) NSURLConnection *theConnection;

@property (strong) NSURLRequest *theRequest;

@end

@implementation LQAsynDownload

@synthesize receiveData = _receiveData, fileName = _fileName,
            theConnection=_theConnection, theRequest=_theRequest;

+ (LQAsynDownload *) initWithURL:(NSURL *) url{
    LQAsynDownload *asynDownload = [[LQAsynDownload alloc] init];
    asynDownload.theRequest=[NSURLRequest requestWithURL:url
              cachePolicy:NSURLRequestUseProtocolCachePolicy
                     timeoutInterval:60.0];
    // create the connection with the request
    // and start loading the data
    return asynDownload;
}

- (void) startAsyn{
    _contentLength=;
    _receiveLength=;
    self.receiveData = [[NSMutableData alloc] init];
    self.theConnection = [[NSURLConnection alloc] initWithRequest:self.theRequest delegate:self];
}

//接收到http响应
- (void) connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{
    _contentLength = [response expectedContentLength];
    _fileName = [response suggestedFilename];
    NSLog(@"data length is %lli", _contentLength);
}

//传输数据
-(void) connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{
    _receiveLength += data.length;
    [_receiveData appendData:data];
    NSLog(@"data recvive is %lli", _receiveLength);
}

//错误
- (void) connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{
    [self releaseObjs];
    NSLog(@"%@",error.description);
}

- (void) releaseObjs{
    self.receiveData = nil;
    self.fileName = nil;
    self.theRequest = nil;
    self.theConnection = nil;
}

//成功下载完毕
- (void) connectionDidFinishLoading:(NSURLConnection *)connection{
    //数据写入doument
    //获取完整目录名字
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:];
    NSString *savePath = [NSString stringWithFormat:@"%@/%@",documentsDirectory, _fileName];
    //创建文件
    [_receiveData writeToFile:savePath atomically:YES];
    [self releaseObjs];
}

@end

最简单的功能调用代码：

LQAsynDownload *dwn = [LQAsynDownload initWithURL:[[NSURL alloc] initWithString:@"http://t2.baidu.com/it/u=0,3067863433&fm=19&gp=0.jpg"]];
[dwn startAsyn];

查查模拟器，神啊，MM靓图出现了

情人节努力的补充礼物，哈哈。

关键点分析：

其实就是实现NSURLConnectionData委托的几个方法：

这个方法是客户端接收到回应后的调用方法，算是下载的开始。

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

跟着就是接收数据的方法

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

还有一个遇到错误时的处理方法

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

最后是下载成功调用的方法

- (void) connectionDidFinishLoading:(NSURLConnection *)connection

接着实现，下载进度查看。

在原代码基础上增加2个block 属性。

LQAsynDownload.h

 //
 //  LQAsynDownload.h
 //  lgTest
 //
 //  Created by yons on 14-2-14.
 //  Copyright (c) 2014年 GQ. All rights reserved.
 //

 #import <Foundation/Foundation.h>

11 typedef void (^initProgress)(long long initValue);
12
13 typedef void (^loadedData)(long long loadedLength);

 @interface LQAsynDownload : NSObject<NSURLConnectionDataDelegate>

 @property (strong) NSURL *httpURL;

19 @property (copy) void (^initProgress)(long long initValue);
20
21 @property (copy) void (^loadedData)(long long loadedLength);

 + (LQAsynDownload *) initWithURL:(NSURL *) url;

 - (void) startAsyn;

 @end

LQAsynDownload.m

 //
 //  LQAsynDownload.m
 //  lgTest
 //
 //  Created by yons on 14-2-14.
 //  Copyright (c) 2014年 GQ. All rights reserved.
 //

 #import "LQAsynDownload.h"

 @interface LQAsynDownload()

 @property (assign) long long contentLength;

 @property (assign) long long receiveLength;

 @property (strong) NSMutableData *receiveData;

 @property (strong) NSString *fileName;

 @property (strong) NSURLConnection *theConnection;

 @property (strong) NSURLRequest *theRequest;

 @end

 @implementation LQAsynDownload

 @synthesize receiveData = _receiveData, fileName = _fileName,
             theConnection=_theConnection, theRequest=_theRequest;

 + (LQAsynDownload *) initWithURL:(NSURL *) url{
     LQAsynDownload *asynDownload = [[LQAsynDownload alloc] init];
     asynDownload.theRequest=[NSURLRequest requestWithURL:url
               cachePolicy:NSURLRequestUseProtocolCachePolicy
                      timeoutInterval:60.0];
     // create the connection with the request
     // and start loading the data
     return asynDownload;
 }

 - (void) startAsyn{
     _contentLength=;
     _receiveLength=;
     self.receiveData = [[NSMutableData alloc] init];
     self.theConnection = [[NSURLConnection alloc] initWithRequest:self.theRequest delegate:self];
 }

 //接收到http响应
 - (void) connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{
     _contentLength = [response expectedContentLength];
     _fileName = [response suggestedFilename];
53     if (self.initProgress != nil) {
54         self.initProgress(_contentLength);
55     }
     NSLog(@"data length is %lli", _contentLength);
 }

 //传输数据
 -(void) connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{
     _receiveLength += data.length;
     [_receiveData appendData:data];
63     if (self.loadedData != nil) {
64         self.loadedData(data.length);
65     }
     NSLog(@"data recvive is %lli", _receiveLength);
 }

 //错误
 - (void) connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{
     [self releaseObjs];
     NSLog(@"%@",error.description);
 }

 - (void) releaseObjs{
     self.receiveData = nil;
     self.fileName = nil;
     self.theRequest = nil;
     self.theConnection = nil;
 }

 //成功下载完毕
 - (void) connectionDidFinishLoading:(NSURLConnection *)connection{
     //数据写入doument
     //获取完整目录名字
     NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
     NSString *documentsDirectory = [paths objectAtIndex:];
     NSString *savePath = [NSString stringWithFormat:@"%@/%@",documentsDirectory, _fileName];
     //创建文件
     [_receiveData writeToFile:savePath atomically:YES];
     [self releaseObjs];
 }

 @end

调用代码：

 LQAsynDownload *dwn = [LQAsynDownload initWithURL:[[NSURL alloc] initWithString:@"http://a.hiphotos.baidu.com/image/w%3D2048/sign=fae75ab5d63f8794d3ff4f2ee6230ff4/faedab64034f78f09f9423fe7b310a55b3191c1b.jpg"]];

     dwn.initProgress = ^(long long initValue){
         _sum = initValue;
         NSLog(@"%lli",initValue);
         _rcv = ;
         dispatch_async(dispatch_get_main_queue(), ^{
             self.pv.progress = 0.0;
             self.pv.hidden = NO;
         });
     };

     dwn.loadedData = ^(long long loadedLength){
         dispatch_async(dispatch_get_main_queue(), ^{
             if (_rcv == _sum) {
                 self.pv.hidden = YES;
             } else {
                 _rcv += loadedLength;
                 self.pv.progress = _rcv/_sum;
             }
         });
     };

     [dwn startAsyn];

真相：

情人节第二个礼物：

以前觉得很神奇的野，用心去试试，会觉得很简单，不是吗？