Question

我正在尝试从Java客户端向iOS应用程序发送图像。我需要尽快发送图像以获得高fps。我尝试使用套接字，但速度太慢，所以现在我从客户端上传到服务器并使用应用程序下载它。这适用于使用Java接收器，但不适用于应用程序。在应用程序上查看时，图像刚出现黑色，因为图像一次又一次地保存。在java中，图像刷新，你可以看到帧，但在iOS中它只是总是黑色。无论如何我可以解决这个问题吗？或者我是否需要找到更好的方式来传输图像？谢谢！

我的上传代码：

public static BufferedImage resize(BufferedImage img, int newW, int newH) {
    int w = img.getWidth();
    int h = img.getHeight();
    BufferedImage dimg = new BufferedImage(newW, newH, img.getType());
    Graphics2D g = dimg.createGraphics();
    g.setRenderingHint(RenderingHints.KEY_INTERPOLATION,
            RenderingHints.VALUE_INTERPOLATION_BILINEAR);
    g.drawImage(img, 0, 0, newW, newH, 0, 0, w, h, null);
    g.dispose();
    return dimg;
}

public void uploadToServer() {

    String server = "ip";
    int port = 21;
    String user = "user";
    String pass = "pass";

    FTPClient ftpClient = new FTPClient();
    try {

        ftpClient.connect(server, port);
        ftpClient.login(user, pass);
        ftpClient.enterLocalPassiveMode();

        ftpClient.setFileType(FTP.BINARY_FILE_TYPE);

        ByteArrayOutputStream os = new ByteArrayOutputStream();

        int w = 765;
        int h = 503;
        double d = .75;

        ImageIO.write(
                resize(client.methods.getClientImage(), (int) (w * d),
                        (int) (h * d)), "JPG", os);

        InputStream inputStream = new ByteArrayInputStream(os.toByteArray());

        String secondRemoteFile = "public_html/iRS/client_img.jpg";

        // System.out.println("Start uploading file");
        OutputStream outputStream = ftpClient
                .storeFileStream(secondRemoteFile);

        byte[] bytesIn = new byte[4096];
        int read = 0;

        while ((read = inputStream.read(bytesIn)) != -1) {
            outputStream.write(bytesIn, 0, read);
        }

        inputStream.close();
        outputStream.close();
        ftpClient.completePendingCommand();

    } catch (IOException ex) {
        System.out.println("Error: " + ex.getMessage());
        ex.printStackTrace();
    } finally {
        try {
            if (ftpClient.isConnected()) {
                ftpClient.logout();
                ftpClient.disconnect();
                Tools.log("Disconnected");
            }
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
}

下载代码：

- (void) refreshImage {
        client.image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL   URLWithString:@"url"]]]; ;
}

Answer 1

如果你只需要几毫秒就不要存储在文件中。将文件下载到NSData并将其传递给UIImage。这是我的HTTP客户端类的一些示例代码。以下方法启动下载任务：

- (NSURLSessionTask *) startGetTaskForURL: (NSURL *) url {
    NSLog(@"startGetTaskForUrl: %@", url);
    NSURLSessionTask *task = [self.session dataTaskWithURL:url];
    NSMutableData *data = [NSMutableData data];
    [task resume];
    [self.runningTasks setObject:data forKey:task];
    return task;
}

每次有可用数据时，都会调用以下委托方法。这里的数据是在创建任务时创建的NSMutableData中收集的：

- (void) URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data {
    NSString *dataString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    NSLog(@"HTTPClient: Data task received data: %@", dataString);
    NSMutableData *runningData = [self dataForTask:dataTask];
    if (!runningData) {
        NSLog(@"No data found for task");
        return;
    }
    [runningData appendData: data];
}

下载任务完成后，将调用以下委托方法：

- (void) URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error {
    NSLog(@"HTTPClient: Task completed with error: %@", error);
    [self.delegate sessionTask:task completedWithError:error data:[self dataForTask:task]];
}

不断刷新UIImage

1 个答案: