NSString * str = @"http://img.tupianzj.com/uploads/allimg/160601/9-160601091U8.jpg";
  
  [NSThread detachNewThreadSelector:@selector(downLoadImage:) toTarget:self withObject:str];

//在子線程下載圖片,發(fā)送同步連接請(qǐng)求數(shù)據(jù)//子線程中系統(tǒng)不會(huì)幫我們生成自動(dòng)釋放池,需要我們手動(dòng)添加
- (void)downLoadImage:(NSString *)imageURLStr
{    
@autoreleasepool {  
      NSURL * url = [NSURL URLWithString:imageURLStr];        
NSURLRequest * request = [NSURLRequest requestWithURL:url];     
   NSData * data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];      
  UIImage * image = [UIImage imageWithData:data];    
    //注意:對(duì)于界面的刷新,交給主線程來處理,通過調(diào)用方法,回到主線程   
     //performSelectorOnMainThread: 在主線程完成相應(yīng)的任務(wù),      
  [self performSelectorOnMainThread:@selector(refreshUI:) withObject:image waitUntilDone:NO];  //waitUntilDone: YES等待這個(gè)方法執(zhí)行完再執(zhí)行(refreshUI:) NO:不等
  }    
 }
//主線程刷新UI
- (void)refreshUI:(UIImage *)Aimage{  
  self.image.image = Aimage;
}