依靠NSOutputStream,NSURLSession,NSURLSessionDataTask创建一个支持断点下载的任务
//
// ViewController.m
// BreakPointDownload
//
// Created by hq on 16/4/18.
// Copyright © 2016年 hanqing. All rights reserved.
//
#import "ViewController.h"
#import "NSString+Hash.h"
//定义文件等下载路径cache路径
#define HQFilePath NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES).firstObject
#define HQFileURLString @"http://xxx/resources/videos/minion_01.mp4"
//定义我们的文件名,直接只用url因为每个url对应一个文件是唯一的
#define HQFileName HQFileURLString.md5String
@interface ViewController () <NSURLSessionDataDelegate>
@property (weak, nonatomic) IBOutlet UILabel *downloadStatus;
@property (weak, nonatomic) IBOutlet UIProgressView *pro;
@property (weak, nonatomic) IBOutlet UILabel *downSize;
@property (weak, nonatomic) IBOutlet UIButton *loadBut;
//文件等总大小
@property(nonatomic,assign) NSInteger fileTotalSize;
//当前文件下载了多少
@property(nonatomic,assign) NSInteger fileCurrentSize;
@property(nonatomic,strong) NSOutputStream *outputStream;
@property(nonatomic,strong) NSURLSessionDataTask *task;
- (IBAction)butClicked:(UIButton *)sender;
@property(nonatomic,strong) NSOperationQueue *queue;
@end
@implementation ViewController
-(NSURLSessionDataTask *)task{
if (!_task) {
NSURLSession *session=[NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[[NSOperationQueue alloc] init]];
NSMutableURLRequest *request=[NSMutableURLRequest requestWithURL:[NSURL URLWithString:HQFileURLString]];
//指定从哪个位置继续下载
[request setValue:[NSString stringWithFormat:@"bytes=%ld-",[self getCurrentDownloadSize]] forHTTPHeaderField:@"Range"];
_task=[session dataTaskWithRequest:request];
}
return _task;
}
-(NSOutputStream *)outputStream{
if (!_outputStream) {
_outputStream=[[NSOutputStream alloc]initToFileAtPath:[HQFilePath stringByAppendingPathComponent:HQFileName] append:YES];
}
return _outputStream;
}
- (void)viewDidLoad {
[super viewDidLoad];
NSString *plistPath=[HQFilePath stringByAppendingPathComponent:@"fileSize.plist"];
//获取文件的总大小
NSInteger totalSize=[[NSDictionary dictionaryWithContentsOfFile:plistPath][HQFileName] integerValue];
if (totalSize==0) {
self.downSize.hidden=YES;
self.pro.progress=0;
}
else{
self.downSize.hidden=NO;
self.downSize.text=[NSString stringWithFormat:@"%.0f％",1.0*[self getCurrentDownloadSize]/totalSize*100];
self.pro.progress=1.0*[self getCurrentDownloadSize]/totalSize;
}
if (totalSize==[self getCurrentDownloadSize]&&totalSize!=0) {
self.downloadStatus.hidden=NO;
self.loadBut.enabled=NO;
[self.loadBut setTitle:@"开始下载" forState:UIControlStateNormal];
}
NSLog(@"%@",[HQFilePath stringByAppendingPathComponent:HQFileName]);
}
- (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
}
- (IBAction)butClicked:(UIButton *)sender {
if ([self.loadBut.titleLabel.text isEqualToString:@"开始下载"]) {
[self.task resume];
[self.loadBut setTitle:@"暂停" forState:UIControlStateNormal];
}
else if([self.loadBut.titleLabel.text isEqualToString:@"暂停"]){
[self.task suspend];
[self.loadBut setTitle:@"继续下载" forState:UIControlStateNormal];
}
else{
[self.task resume];
[self.loadBut setTitle:@"暂停" forState:UIControlStateNormal];
}
}
-(void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSHTTPURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler{
[self.outputStream open];
//必须开启才能接收服务端的请求
completionHandler(NSURLSessionResponseAllow);
//表示服务器当前能返回给我们的文件等大小
self.fileTotalSize=[response.allHeaderFields[@"Content-Length"] integerValue]+[self getCurrentDownloadSize];
//把文件的总大小写入我们的plist文件，key就用我们的文件名
NSString *plistPath=[HQFilePath stringByAppendingPathComponent:@"fileSize.plist"];
NSMutableDictionary *dict=[NSMutableDictionary dictionaryWithContentsOfFile:plistPath];
if (dict==nil) {
dict=[NSMutableDictionary dictionary];
}
//用我们的md5的url当作key
dict[HQFileName]=@(self.fileTotalSize);
[dict writeToFile:plistPath atomically:YES];
}
-(void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data{
[self.outputStream write:[data bytes] maxLength:data.length];
self.fileCurrentSize=[self getCurrentDownloadSize];
[[NSOperationQueue mainQueue] addOperationWithBlock:^{
self.downSize.hidden=NO;
self.pro.progress=(1.0*self.fileCurrentSize/self.fileTotalSize);
self.downSize.text=[NSString stringWithFormat:@"%.0f%%",(1.0*self.fileCurrentSize/self.fileTotalSize)*100];
}];
NSLog(@"%ld",self.fileCurrentSize);
}
-(void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error{
if (error) {
return;
}
[[NSOperationQueue mainQueue] addOperationWithBlock:^{
self.downloadStatus.hidden=NO;
self.loadBut.enabled=NO;
[self.loadBut setTitle:@"开始下载" forState:UIControlStateNormal];
}];
[self.outputStream close];
self.outputStream=nil;
self.task=nil;
}
//判断文件现在已经下载了多少
-(NSInteger) getCurrentDownloadSize{
NSDictionary *dict=[[NSFileManager defaultManager] attributesOfItemAtPath:[HQFilePath stringByAppendingPathComponent:HQFileName] error:nil];
return [dict[@"NSFileSize"] integerValue];
}
@end