作品鏈接：
http://www.lxweimin.com/users/1e0f5e6f73f6/top_articles

• 1.第一種

NSURL *url = [NSURL URLWithString:@"圖片請(qǐng)求路徑"];
    NSData *data = [NSData dataWithContentsOfURL:url];
    self.imagView.image = [UIImage imageWithData:data];

• 2.第二種 NSURLConnection

 NSURL *url = [NSURL URLWithString:@"圖片請(qǐng)求路徑"];
    
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    
    [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse * _Nullable response, NSData * _Nullable data, NSError * _Nullable connectionError) {
        
        self.imagView.image = [UIImage imageWithData:data];

• 3.下載視頻 代理方法

- (void)viewDidLoad {
    [super viewDidLoad];
    NSURL *url = [NSURL URLWithString:@"請(qǐng)求路徑"];
    //2.創(chuàng)建請(qǐng)求對(duì)象
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    //3.設(shè)置代理,發(fā)送請(qǐng)求
    [NSURLConnection connectionWithRequest:request delegate:self];
}


pragma mark  NSURLConnectionDataDelegate 

聲明文件數(shù)據(jù) 已下載大小和總文件大小
// 文件數(shù)據(jù)
@property (nonatomic, strong) NSMutableData *fileData;
//當(dāng)前已經(jīng)下載文件的大小
@property (nonatomic, assign) NSInteger currentLength;
//下載文件的總大小
@property (nonatomic, assign) NSInteger totalLength;
/*
 1.接收到服務(wù)器響應(yīng)的適合調(diào)用 1次
 */
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    // 創(chuàng)建data
    self.fileData = [NSMutableData data];
    
    //拿到文件的總大小
    self.totalLength = response.expectedContentLength;
    
    NSLog(@"%zd",self.totalLength);
}

/*
 2.接收到服務(wù)器返回的數(shù)據(jù),會(huì)調(diào)用多次
 */
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    // 拼接數(shù)據(jù)
    [self.fileData appendData:data];
   
    
    self.currentLength = self.fileData.length;
//     NSLog(@"%zd---%zd",data.length,self.currentLength);
    
    NSLog(@"%f",1.0 * self.currentLength / self.totalLength);// 此時(shí)數(shù)據(jù)是在內(nèi)存中，直接退出的話(huà)，再次啟動(dòng)數(shù)據(jù)消失
}

/*
 3.當(dāng)請(qǐng)求完成之后調(diào)用該方法
 */
-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSLog(@"connectionDidFinishLoading");
    
    //保存下載的文件到沙河
    NSString *caches = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
    
    //拼接文件全路徑
    NSString *fullPath = [caches stringByAppendingPathComponent:@"XXOO.mp4"];
    
    //寫(xiě)入數(shù)據(jù)到文件
    [self.fileData writeToFile:fullPath atomically:YES];
    NSLog(@"%@",fullPath);
//    self.imagView.image = [UIImage imageWithData:self.fileData];
}
/*
 4.當(dāng)請(qǐng)求失敗的適合調(diào)用該方法,如果失敗那么error有值
 */
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    NSLog(@"didFailWithError");
}