IOS-网络（大文件下载）

一、不合理方式

 //
 //  ViewController.m
 //  IOS_0131_大文件下载
 //
 //  Created by ma c on 16/1/31.
 //  Copyright © 2016年 博文科技. All rights reserved.
 //

 #import "ViewController.h"

 @interface ViewController ()<NSURLConnectionDataDelegate>

 //进度条
 @property (weak, nonatomic) IBOutlet UIProgressView *progressView;
 //存数据
 @property (nonatomic, strong) NSMutableData *fileData;
 //文件总长度
 @property (nonatomic, assign) long long totalLength;

 @end

 @implementation ViewController

 - (void)viewDidLoad {
     [super viewDidLoad];

     self.view.backgroundColor = [UIColor cyanColor];
 }

 - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
 {
     [self download];
 }

 - (void)download
 {
     //1.NSURL
     NSURL *url = [NSURL URLWithString:@"http://localhost:8080/MJServer/resources/videos/minion_01.mp4"];
     //2.请求
     NSURLRequest *request = [NSURLRequest requestWithURL:url];
     //3.下载(创建完conn后会自动发起一个异步请求)
     [NSURLConnection connectionWithRequest:request delegate:self];

     //[[NSURLConnection alloc] initWithRequest:request delegate:self];
     //[[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:YES];
     //NSURLConnection *conn = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:NO];
     //[conn start];
 }
 #pragma mark - NSURLConnectionDataDelegate的代理方法
 //请求失败时调用
 - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
 {
     NSLog(@"didFailWithError");
 }
 //接收到服务器响应就会调用
 - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
 {
     //NSLog(@"didReceiveResponse");
     self.fileData = [NSMutableData data];

     //取出文件的总长度
     //NSHTTPURLResponse *resp = (NSHTTPURLResponse *)response;
     //long long fileLength = [resp.allHeaderFields[@"Content-Length"] longLongValue];

     self.totalLength = response.expectedContentLength;
 }
 //当接收到服务器返回的实体数据时就会调用（这个方法根据数据的实际大小可能被执行多次）
 - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
 {
     //拼接数据
     [self.fileData appendData:data];

     //设置进度条（0~1）
     self.progressView.progress = (double)self.fileData.length / self.totalLength;

     NSLog(@"didReceiveData -> %ld",self.fileData.length);
 }
 //加载完毕时调用（服务器的数据完全返回后）
 - (void)connectionDidFinishLoading:(NSURLConnection *)connection
 {
     //NSLog(@"connectionDidFinishLoading");
     //拼接文件路径
     NSString *cache = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
     NSString *file = [cache stringByAppendingPathComponent:@"minion_01.mp4"];
     //NSLog(@"%@",file);

     //写到沙盒之中
     [self.fileData writeToFile:file atomically:YES];
 }

 @end

二、内存优化

 //
 //  ViewController.m
 //  IOS_0201_大文件下载（合理方式）
 //
 //  Created by ma c on 16/2/1.
 //  Copyright © 2016年 博文科技. All rights reserved.
 //

 #import "ViewController.h"

 @interface ViewController ()<NSURLConnectionDataDelegate>

 ///用来写数据的句柄对象
 @property (nonatomic, strong) NSFileHandle *writeHandle;
 ///文件总大小
 @property (nonatomic, assign) long long totalLength;
 ///当前已写入文件大小
 @property (nonatomic, assign) long long currentLength;

 @end

 @implementation ViewController

 - (void)viewDidLoad {
     [super viewDidLoad];

     self.view.backgroundColor = [UIColor cyanColor];

 }

 - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
 {
     [self download];
 }

 - (void)download
 {
     //1.NSURL
     NSURL *url = [NSURL URLWithString:@"http://localhost:8080/MJServer/resources/videos/minion_02.mp4"];
     //2.请求
     NSURLRequest *request = [NSURLRequest requestWithURL:url];
     //3.下载(创建完conn后会自动发起一个异步请求)
     [NSURLConnection connectionWithRequest:request delegate:self];

 }
 #pragma mark - NSURLConnectionDataDelegate的代理方法
 //请求失败时调用
 - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
 {

 }
 //接收到服务器响应时调用
 - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
 {
     //文件路径
     NSString *cache = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
     NSString *file = [cache stringByAppendingPathComponent:@"minion_02.mp4"];
     NSLog(@"%@",file);
     //创建一个空文件到沙盒中
     NSFileManager *fileManager = [NSFileManager defaultManager];
     [fileManager createFileAtPath:file contents:nil attributes:nil];

     //创建一个用来写数据的文件句柄
     self.writeHandle = [NSFileHandle fileHandleForWritingAtPath:file];

     //文件总大小
     self.totalLength = response.expectedContentLength;

 }
 //接收到服务器数据时调用（根据文件大小，调用多次）
 - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
 {
     //移动到文件结尾
     [self.writeHandle seekToEndOfFile];
     //写入数据
     [self.writeHandle writeData:data];
     //累计文件长度
     self.currentLength += data.length;
     NSLog(@"下载进度-->%lf",(double)self.currentLength / self.totalLength);

 }
 //从服务器接收数据完毕时调用
 - (void)connectionDidFinishLoading:(NSURLConnection *)connection
 {

     self.currentLength = ;
     self.totalLength = ;
     //关闭文件
     [self.writeHandle closeFile];
     self.writeHandle = nil;

 }
 @end

三、断点续传

 //
 //  ViewController.m
 //  IOS_0201_大文件下载（合理方式）
 //
 //  Created by ma c on 16/2/1.
 //  Copyright © 2016年 博文科技. All rights reserved.
 //

 #import "ViewController.h"

 @interface ViewController ()<NSURLConnectionDataDelegate>

 ///用来写数据的句柄对象
 @property (nonatomic, strong) NSFileHandle *writeHandle;
 ///连接对象
 @property (nonatomic, strong) NSURLConnection *conn;

 ///文件总大小
 @property (nonatomic, assign) long long totalLength;
 ///当前已写入文件大小
 @property (nonatomic, assign) long long currentLength;

 - (IBAction)btnClick:(UIButton *)sender;
 @property (weak, nonatomic) IBOutlet UIButton *btnClick;

 @property (weak, nonatomic) IBOutlet UIProgressView *progressView;

 @end

 @implementation ViewController

 - (void)viewDidLoad {
     [super viewDidLoad];

     self.view.backgroundColor = [UIColor cyanColor];
     //设置进度条起始状态
     self.progressView.progress = 0.0;

 }

 #pragma mark - NSURLConnectionDataDelegate的代理方法
 //请求失败时调用
 - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
 {

 }
 //接收到服务器响应时调用
 - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
 {
     if (self.currentLength) return;
     //文件路径
     NSString *cache = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
     NSString *file = [cache stringByAppendingPathComponent:@"minion_02.mp4"];
     NSLog(@"%@",file);
     //创建一个空文件到沙盒中
     NSFileManager *fileManager = [NSFileManager defaultManager];
     [fileManager createFileAtPath:file contents:nil attributes:nil];

     //创建一个用来写数据的文件句柄
     self.writeHandle = [NSFileHandle fileHandleForWritingAtPath:file];

     //文件总大小
     self.totalLength = response.expectedContentLength;

 }
 //接收到服务器数据时调用（根据文件大小，调用多次）
 - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
 {
     //移动到文件结尾
     [self.writeHandle seekToEndOfFile];
     //写入数据
     [self.writeHandle writeData:data];
     //累计文件长度
     self.currentLength += data.length;
     //设置进度条进度
     self.progressView.progress = (double)self.currentLength / self.totalLength;

     NSLog(@"下载进度-->%lf",(double)self.currentLength / self.totalLength);

 }
 //从服务器接收数据完毕时调用
 - (void)connectionDidFinishLoading:(NSURLConnection *)connection
 {

     self.currentLength = ;
     self.totalLength = ;
     //关闭文件
     [self.writeHandle closeFile];
     self.writeHandle = nil;
     //下载完成后，状态取反
     self.btnClick.selected = !self.btnClick.isSelected;
 }

 - (IBAction)btnClick:(UIButton *)sender {
     //状态取反
     sender.selected = !sender.isSelected;
     if (sender.selected) {  //继续下载
         //1.NSURL
         NSURL *url = [NSURL URLWithString:@"http://localhost:8080/MJServer/resources/videos/minion_02.mp4"];
         //2.请求
         NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];

         //设置请求头
         NSString *range = [NSString stringWithFormat:@"bytes=%lld-",self.currentLength];
         [request setValue:range forHTTPHeaderField:@"Range"];

         //3.下载(创建完conn后会自动发起一个异步请求)
         self.conn = [NSURLConnection connectionWithRequest:request delegate:self];

     } else {  //暂停下载
         [self.conn cancel];
         self.conn = nil;

     }

 }
 @end