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 = 0;
    self.totalLength = 0;
    //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 = 0;
    self.totalLength = 0;
    //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