蓝牙传输应用程序在使用 InputStream.read() 后停止，没有错误

Question

我正在尝试使用这些来源使文件传输蓝牙应用程序工作：

http://developer.android.com/guide/topics/connectivity/bluetooth.html

https://android.googlesource.com/platform/development/+/25b6aed7b2e01ce7bdc0dfa1a79eaf009ad178fe/samples/BluetoothChat/

当我尝试以这种方式使用 InputStream.read() 方法获取 InputStream 字节时：

public class ConnectedThread extends Thread {

...(some code here)

public void run(){

        byte[] buffer = new byte[1024];
        int bytes = -1;

        //Keep listening to the InputStream while connected
        while (true){

            try {

                bytes = this.mmInStream.read(buffer);

                //* this part is not reached
                if (bytes==-1){
                    Log.d("NoData:","-1");  
                }

            }
            catch(Exception e){
                Log.d("inStream exception:",e.getMessage());
                break;
            }

        }

    }

...(some code here)

}

代码的下一部分（在这种情况下为"if" 部分）永远不会到达，也不会出现Log.D 调试输出或我在后面添加的任何其他内容。我刚从 LogCat 收到这条消息：

BluetoothSocket read in: android.net.LocalStocketImpl$SocketInputStream@f7e
                b08 len: 1024

要将数据从客户端传输到服务器，我这样做：

public class MainActivity extends Activity {

...(some code here)

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    clientConnect();
    //serverConnect();

}

...(some code here)

public void clientConnect(){

        Set<BluetoothDevice> devices;

        devices = bConfig.getPairedDevices(); 

        if (devices == null){                   
            return;
        }

        if (devices.size() > 0) {           

            BluetoothDevice device = devices.iterator().next();

            ConnectThread connectTransmit = new ConnectThread(device,bConfig.getBluetoothAdapter(),BluetoothConfig.mUUID);
            connectTransmit.start();

            Toast.makeText(this, "connected", Toast.LENGTH_SHORT).show();

            socket = connectTransmit.mmSocket;
            ConnectedThread connectedThread = new ConnectedThread(socket);

            //write file bytes to the connected thread, so the thread can receive its own input written bytes later
            File file_to_transfer = new File(Environment.getExternalStorageDirectory() + "/txtTransfer.txt");           

            //get bytes from our File
            int size = (int) file_to_transfer.length();
            byte[] bytes = new byte[size];

            try {

                //14b are read succesfully, the whole text file 
                BufferedInputStream buf = new BufferedInputStream(new FileInputStream(file_to_transfer));
                buf.read(bytes,0,bytes.length);
                buf.close();                

            }catch (FileNotFoundException e){
                Log.d("FileNotFoundException:",e.getMessage());
            }catch (IOException e){ 
                Log.d("IOException:",e.getMessage());
            }

            //send the data to the server
            connectedThread.start();
            connectedThread.write(bytes);
            //connectedThread.cancel();

        }

    }

...(some code here)

}

AcceptThread（实现的服务器部分）有效，因为当我运行客户端部分连接然后传输数据时，在设备中调试时，服务器部分上的 LogCat 激活并到达运行方法线程，我在其中调用ConnectedThread 实现，但随后它“显然”读取了字节，但它卡在 LogCat 上而没有错误。

请让我知道我可以做些什么来完成读取字节以移动到流程的下一部分。

谢谢

Answer 1

您在等待更多输入时被阻止。

标记为... (some code here) 的部分应在读取循环内，在流结束测试之后。注意如果read() 返回 -1 并不意味着“没有数据”，它意味着流结束，您应该关闭套接字并跳出读取循环。否则，您应该继续处理刚刚读取的数据。目前，您只需阅读并忽略所有输入，直到流结束，这是没有意义的。充其量只能处理最后一个部分缓冲区，并且不知道它持续了多长时间。

Answer 2

在我看来，您应该在阅读之前验证缓冲区中是否有内容。 从流中读取会阻塞操作，因此应用程序将挂起，直到出现某些数据。 How can I check if an InputStream is empty without reading from it?

Answer 3

在您的客户端代码中，您可能应该让 connectedThread 对象存活一段时间。可能是一旦 if 子句关闭并且它超出范围（不太确定 GC 和所有会发生什么），写入就不会发生，并且您的连接没有关闭但也没有使用。

在写入后在 connectedThread 内的 mmOutStream 上调用 flush() 也可能会有所帮助。

就像@EJP 建议的那样，你应该在你的读取循环中放一些东西。

编辑：为了调试，您可以在编写客户端代码后立即添加this.wait(1000);。

Answer 4

尝试将您的运行方法更改为：

public void run(){
    byte[] buffer = new byte[1024];
    int bytesRead = 0;
    final int shortSleepTime = 1000;
    final int longSleepTime = 5000;
    int emptyReadCounter = 0;
    int sleepCounter = 0;
    int currentSleepTime = shortSleepTime;

    //Keep listening to the InputStream while connected
    while (bytesRead >= 0){
        try {

            // if available() returns 0, there is nothing to read yet
            if (this.mmInStream.available() != 0){
                bytesRead = this.mmInStream.read(buffer);

                // Check if we need to reset the sleep counters
                if (emptyReadCounter != 0){
                    emptyReadCounter = 0;
                    sleepCounter = 0;
                    currentSleepTime = shortSleepTime;

                    // We can also do anything else dependent on just waking up
                    // from a sleep cycle in this block
                }


                // Do something with my now full buffer
                // Remember not to process more than 
                // 'bytesRead' bytes from my buffer because the
                // rest could be filled with crap left over from
                // the last iteration
            } else {                
                // Three consecutive empty reads means sleep
                if (emptyReadCounter++ >= 3){                       
                    if (currentSleepTime != longSleepTime && sleepCounter++ >= 3){
                        currentSleepTime = longSleepTime;
                    }
                    Thread.sleep(currentSleepTime);
                }
            }
        }
        catch(Exception e){
            Log.d("inStream exception:",e.getMessage());
            break;
        }
    }
}