IOS开发之——下载-断点续传(05)

本文介绍: 一概述HTTP Rang e 概念断点续传逻辑断点续传示例二 HTTP Rang e 概念通过设置请求头Range 可以指定每次从网络下载数据包的大小2.1 Range示例示例说明 bytes=0-499从0到499的头500个字节 bytes=500-999从500到999的第二个500字节 bytes=500-从500字节以后的所有字节 bytes=-500最后500个字节 bytes=500-599,800-899同时指定几个范围2.2 R

通过设置请求头Range可以指定每次从网络下载数据包的大小

示例	说明
bytes=0-499	从0到499的头500个字节
bytes=500-999	从500到999的第二个500字节
bytes=500-	从500字节以后的所有字节
bytes=-500	最后500个字节
bytes=500-599,800-899	同时指定几个范围

#import "ViewController.h"
#import  "DACircularProgressView.h"

@interface ViewController ()&lt;NSURLConnectionDataDelegate>
@property(nonatomic,strong) NSFileHandle *writeHandle;
@property(nonatomic,assign) long long totalLength;
@property(nonatomic,assign) long long currentLength;

@property(nonatomic,weak) DACircularProgressView *circleView;
@property(nonatomic,strong) NSURLConnection *conn;
@property (weak, nonatomic) IBOutlet UIButton *btn;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    DACircularProgressView *circleView=[[DACircularProgressView alloc]init];
    circleView.frame=CGRectMake(120, 100, 100, 100);
    circleView.progressTintColor=[UIColor redColor];
    circleView.trackTintColor=[UIColor orangeColor];
    circleView.progress=0.01;
    [self.view addSubview:circleView];
    self.circleView=circleView;
    
}
- (IBAction)downloadAndPause:(UIButton *)sender
{
    //状态取反
    sender.selected=!sender.isSelected;
    if (sender.selected) { //继续
        NSLog(@"继续");
        //1-URL
        NSURL *url=[NSURL URLWithString:@"http://localhost:8080//MJServer/resources/videos.zip"];
        //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
       self.conn= [NSURLConnection connectionWithRequest:request delegate:self];
    }else{ //暂停
        NSLog(@"暂停");
        [self.conn cancel];
        self.conn=nil;
    }
}

//-请求失败时调用(请求超时，网络异常)
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    NSLog(@"didFailWithError--");
}
//-接收到服务器的响应聚会调用
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    NSLog(@"didReceiveResponse--");
    if (self.currentLength)return;
    //文件路径
    NSString *caches=[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES)lastObject];
    NSString *filePath=[caches stringByAppendingPathComponent:@"videos.zip"];
    
    //创建一个空的文件到沙盒中
    NSFileManager *mgr=[NSFileManager defaultManager];
    [mgr createFileAtPath:filePath contents:nil attributes:nil];
    //创建一个用来写数据的句柄
    self.writeHandle=[NSFileHandle fileHandleForWritingAtPath:filePath];
    
   //获得文件的总大小
    self.totalLength=response.expectedContentLength;

}
//当接收到服务器返回到实体数据时调用(具体内容，这个内容可被调用多次)
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
  //移动到文件的最后面
    [self.writeHandle seekToEndOfFile];
    //写入数据到沙盒中
    [self.writeHandle writeData:data];
    self.currentLength+=data.length;
    NSLog(@"下载进度：%f",(double)self.currentLength/self.totalLength);
    self.circleView.progress=(double)self.currentLength/self.totalLength;
    
}
//加载完毕后调用(服务器的数据已经完全返回后)
-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSLog(@"connectionDidFinishLoading--");
    self.currentLength=0;
    self.totalLength=0;
    [self.btn setHidden:TRUE];
    
    //关闭文件
    [self.writeHandle closeFile];
    self.writeHandle=nil;
}
@end