使用Cocoa框架中的输入输出流，可以从文件或应用中内存读取数据，也可以向文件/应用中内存写入数据。你可以在基于socket连接的远程服务交换数据中使用。—翻译自苹果文档。

其主要类与方法

image

使用示例：我们从使用输入流从本地文件中读取图片，使用输出流存储读取的图片数据并显示。

1.声明输入/输出流/图片框属性

1
2
3
4


@property(nonatomic, strong) NSInputStream *imageInputStream;
@property(nonatomic, strong) NSOutputStream *imageOutputStream;
@property(nonatomic, strong) IBOutlet UIImageView *imageView;

2.初始化输出流/输入流，清理方法，相关方法调用

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106


- (void)viewDidLoad {
  [super viewDidLoad];
  // Do any additional setup after loading the view, typically from a nib.

  NSString *filePath =
      [[NSBundle mainBundle] pathForResource:@"qq_head" ofType:@"jpg"];
  [self loadImageFile:filePath];
}


#pragma mark---------NSStreamDelegate----------

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

  const NSUInteger kBufferSize = 2048;

  if (aStream == _imageInputStream) {
    NSLog(@"eventcode = %u", eventCode);

    switch (eventCode) {
    case NSStreamEventHasBytesAvailable: {

      uint8_t buf[kBufferSize];
      memset(buf, 0, kBufferSize * sizeof(uint8_t));
      NSInteger numOfBytes =
          [(NSInputStream *)aStream read:buf maxLength:kBufferSize];

      if (numOfBytes > 0) {
        [_imageOutputStream write:(const void *)buf maxLength:numOfBytes];
      }

      break;
    }

    case NSStreamEventEndEncountered: {

      NSLog(@"The end of the stream has been reached.");

      NSData *imageData = [_imageOutputStream
          propertyForKey:NSStreamDataWrittenToMemoryStreamKey];

      if (imageData.length > 0) {
        UIImage *icon = [[UIImage alloc] initWithData:imageData];
        _imageView.image = icon;
      }

      [self cleanUpStream];

      break;
    }

    case NSStreamEventErrorOccurred: {
      NSLog(@"NSStreamEventErrorOccurred!!");

      [self cleanUpStream];
    }
    default:
      break;
    }
  }
}

- (IBAction)loadNewImageFileEvnet:(id)sender {

  NSString *filePath =
      [[NSBundle mainBundle] pathForResource:@"qq_head_1" ofType:@"jpg"];
  [self loadImageFile:filePath];
}

/**
 *  从本地图片文件中初始化输入流，同时初始化输出流。
 *
 *  @param fileName 图片文件全路径
 */
- (void)loadImageFile:(NSString *)fileName {

  if ([[NSFileManager defaultManager] fileExistsAtPath:fileName]) {

    self.imageInputStream = [NSInputStream inputStreamWithFileAtPath:fileName];
    _imageInputStream.delegate = self;
    [_imageInputStream scheduleInRunLoop:[NSRunLoop currentRunLoop]
                                 forMode:NSDefaultRunLoopMode];
    [_imageInputStream open];

    self.imageOutputStream = [NSOutputStream outputStreamToMemory];
    [_imageOutputStream open];
  } else {
    NSLog(@"%@ ---not found the file", fileName);
  }
}

/**
 *  清理输出输入流
 */
- (void)cleanUpStream {

  [_imageInputStream removeFromRunLoop:[NSRunLoop currentRunLoop]
                               forMode:NSDefaultRunLoopMode];
  _imageInputStream.delegate = nil;
  [_imageInputStream close];
  _imageInputStream = nil;

  [_imageOutputStream close];
  _imageOutputStream = nil;
}