在iPhone上接收圖像（TCP客戶端）

Question

我正在iPhone上編程客戶端。我想發送一些字符串，並從服務器接收圖像。

我發現本教程（http://www.devx.com/wireless/Article/43551），它一直非常有用。它可以工作，如果我想接收字符串，但現在我想收到一個圖像，我不能讓它工作。

這是我的代碼，當iPhone收到數據。這是本教程和JeremyP（http://stackoverflow.com/questions/4613218）這個回答讓混合：

- (void)stream:(NSStream *)stream handleEvent:(NSStreamEvent)eventCode { 

switch(eventCode) { 
    case NSStreamEventHasBytesAvailable: { 
     if (data == nil) { 
      data = [[NSMutableData alloc] init]; 
     } 
     uint8_t buf[102400]; 
     unsigned int len = 0; 
     len = [(NSInputStream *)stream read:buf maxLength:102400]; 

     if(len) {  
      [data appendBytes:(const void *)buf length:len]; 

      // Recibir img 
    uint8_t size; // Let's make sure size is an explicit width. 

      NSInteger totalBytesRead = 0; 
      NSInteger bytesRead = [iStream read: &size maxLength: sizeof size]; 
      while (bytesRead > 0 && totalBytesRead + bytesRead < sizeof size) { 
       totalBytesRead+= bytesRead; 
       bytesRead = [iStream read: &size + totalBytesRead maxLength: (sizeof size) - totalBytesRead]; 
      } 
      if (bytesRead >= 0) { 
       totalBytesRead += bytesRead; 
      } 
      else { 
       // read failure, report error and bail 
      } 
      if (totalBytesRead < sizeof size) { 
       // connection closed before we got the whole size, report and bail 
      } 
      size = ntohl(size); // assume wire protocol uses network byte ordering 

      NSMutableData* buffer = [[NSMutableData alloc] initWithLength: size]; 
      totalBytesRead = 0; 
      bytesRead = [iStream read: [buffer mutableBytes] maxLength: size]; 
      while (bytesRead > 0 && totalBytesRead + bytesRead < size) { 
       totalBytesRead+= bytesRead; 
       bytesRead = [iStream read: [buffer mutableBytes] + totalBytesRead maxLength: size - totalBytesRead]; 
      } 
      if (bytesRead >= 0) { 
       totalBytesRead += bytesRead; 
      } 
      else { 
       // read failure, report error and bail (not forgetting to release buffer) 
      } 
      if (totalBytesRead < size) { 
       // connection closed before we got the whole image, report and bail (not forgetting to release buffer) 
      } 
      else { 
       [buffer setLength: size]; 
      } 

      imgResultado.image = [UIImage imageWithData: buffer]; 
      [buffer release]; 
      [data release];   
      data = nil; 

     } 
     else { 
      NSLog(@"No data."); 
     } 


    } break; 
}} 

它不工作...你能幫助我嗎？

Answer 1

嗯，我是這樣做的，但我不確定是否有更好的方法。

- (void)stream:(NSStream *)stream handleEvent:(NSStreamEvent)eventCode { 
switch(eventCode) { 
    case NSStreamEventHasBytesAvailable: 
    { 
     uint32_t max_size = 1000000; // Max size of the received imaged. 
     NSMutableData* buffer = [[NSMutableData alloc] initWithLength: max_size]; 
     NSInteger totalBytesRead = 0; 
     NSInteger bytesRead = [(NSInputStream *)stream read: [buffer mutableBytes] maxLength: max_size]; 
     if (bytesRead != 0) { 
      while (bytesRead > 0 && totalBytesRead + bytesRead < max_size) { 
       totalBytesRead+= bytesRead; 
       bytesRead = [(NSInputStream *)stream read: [buffer mutableBytes] + totalBytesRead maxLength: max_size - totalBytesRead]; 
      } 
      if (bytesRead >= 0) { 
       totalBytesRead += bytesRead; 
      } 
      else { 
       // read failure, report error and bail (not forgetting to release buffer) 
      } 
      [buffer setLength: totalBytesRead]; 
      imgResultado.image = [UIImage imageWithData: buffer]; 
      [buffer release]; 
     } 
    } break; 
}} 

使用這種方法，接收到的圖像必須小於max_size。 如果你知道更好的方法來做到這一點，請讓我知道！ ;）

Answer 2

如果你想要做的是從服務器上顯示下載圖像，看看這個：

https://github.com/michaelkamprath/iPhoneMK/tree/master/Views/MKNetworkImageView

有很多的內置功能來將處理圖像的iOS爲你下載。也就是說，如果您可以將要下載的實體封裝爲單獨的URL（例如，Web服務器）。

但是，如果您嘗試通過相同的TCP連接發送和接收數據，我強烈建議您更改爲更加REST風格的方法。部分原因是從客戶端實現更容易，部分原因是您不必擔心底層TCP連接（儘可能多）。