ios大文件下载之开始和暂停

  1 #import "HMViewController.h"
  2 
  3 @interface HMViewController ()
  4 @property (weak, nonatomic) IBOutlet UIProgressView *progressView;
  5 /**
  6  *  写数据的文件句柄
  7  */
  8 @property (nonatomic, strong) NSFileHandle *writeHandle;
  9 /**
 10  *  当前已下载数据的长度
 11  */
 12 @property (nonatomic, assign) long long currentLength;
 13 /**
 14  *  完整文件的总长度
 15  */
 16 @property (nonatomic, assign) long long totalLength;
 17 
 18 /**
 19  * 连接对象
 20  */
 21 @property (nonatomic, strong) NSURLConnection *conn;
 22 
 23 /**
 24  * 是否在下载
 25  */
 26 @property (nonatomic, assign, getter = isDownloading) BOOL downloading;
 27 
 28 - (IBAction)start:(UIButton *)button;
 29 @end
 30 
 31 @implementation HMViewController
 32 
 33 - (void)viewDidLoad
 34 {
 35     [super viewDidLoad];
 36     
 37 }
 38 
 39 // 按钮文字: "开始", "暂停"
 40 - (IBAction)start:(UIButton *)button { // self.currentLength == 200
 41     if (self.isDownloading) { // 暂停下载
 42         self.downloading = NO;
 43         
 44         [button setTitle:@"开始" forState:UIControlStateNormal];
 45         
 46         // 取消当前的请求
 47         [self.conn cancel];
 48         self.conn = nil;
 49     } else { // 开始下载
 50         self.downloading = YES;
 51         
 52         [button setTitle:@"暂停" forState:UIControlStateNormal];
 53         
 54         NSURL *url = [NSURL URLWithString:@"http://192.168.1.200:8080/MJServer/resources/jre.zip"];
 55         // 默认就是GET请求
 56         NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
 57         // 设置请求头信息
 58         NSString *value = [NSString stringWithFormat:@"bytes=%lld-", self.currentLength];
 59         [request setValue:value forHTTPHeaderField:@"Range"];
 60         self.conn = [NSURLConnection connectionWithRequest:request delegate:self];
 61     }
 62 }
 63 
 64 #pragma mark - NSURLConnectionDataDelegate 代理方法
 65 /**
 66  *  1. 当接受到服务器的响应(连通了服务器)就会调用
 67  */
 68 - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
 69 {
 70 #warning 一定要判断
 71     if (self.totalLength) return;
 72     
 73     // 0.文件的存储路径
 74     NSString *caches = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
 75     NSString *filepath = [caches stringByAppendingPathComponent:@"jre.zip"];
 76     
 77     // 1.创建一个空的文件到沙盒中
 78     NSFileManager *mgr = [NSFileManager defaultManager];
 79     // 刚创建完毕的大小是0字节
 80     [mgr createFileAtPath:filepath contents:nil attributes:nil];
 81     
 82     // 2.创建写数据的文件句柄
 83     self.writeHandle = [NSFileHandle fileHandleForWritingAtPath:filepath];
 84     
 85     // 3.获得完整文件的长度
 86     self.totalLength = response.expectedContentLength;
 87 }
 88 
 89 /**
 90  *  2. 当接受到服务器的数据就会调用(可能会被调用多次, 每次调用只会传递部分数据)
 91  */
 92 - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
 93 {
 94     // 累加长度
 95     self.currentLength += data.length;
 96     
 97     // 显示进度
 98     double progress = (double)self.currentLength / self.totalLength;
 99     self.progressView.progress = progress;
100     
101     // 移动到文件的尾部
102     [self.writeHandle seekToEndOfFile];
103     // 从当前移动的位置(文件尾部)开始写入数据
104     [self.writeHandle writeData:data];
105 }
106 
107 /**
108  *  3. 当服务器的数据接受完毕后就会调用
109  */
110 - (void)connectionDidFinishLoading:(NSURLConnection *)connection
111 {
112     NSLog(@"connectionDidFinishLoading----");
113     
114     // 清空属性值
115     self.currentLength = 0;
116     self.totalLength = 0;
117     
118     // 关闭连接(不再输入数据到文件中)
119     [self.writeHandle closeFile];
120     self.writeHandle = nil;
121 }
122 
123 /**
124  *  请求错误(失败)的时候调用(请求超时\断网\没有网, 一般指客户端错误)
125  */
126 - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
127 {
128     
129 }
130 @end