成功连接到蓝牙设备后，每个设备都有一个已连接的 BluetoothSocket。您现在可以在设备之间共享信息。使用 BluetoothSocket 传输数据的一般步骤如下：
分别使用
getInputStream()和getOutputStream()获取用于处理通过套接字传输的InputStream和OutputStream。使用
read(byte[])和write(byte[])读取和写入数据到流。
当然，还有需要考虑的实现细节。特别是，您应该使用专用线程从流中读取数据并向其写入数据。这一点很重要，因为 read(byte[]) 和 write(byte[]) 方法都是阻塞调用。read(byte[]) 方法会一直阻塞，直到流中有内容可供读取。write(byte[]) 方法通常不会阻塞，但如果远程设备调用 read(byte[]) 的速度不够快，导致中间缓冲区变满，它可能会因流量控制而阻塞。因此，您应该将线程中的主循环专门用于从 InputStream 读取数据。您可以在线程中使用一个单独的公共方法来启动对 OutputStream 的写入。
示例
以下是演示如何在通过蓝牙连接的两个设备之间传输数据的示例：
Kotlin
private const val TAG = "MY_APP_DEBUG_TAG" // Defines several constants used when transmitting messages between the // service and the UI. const val MESSAGE_READ: Int = 0 const val MESSAGE_WRITE: Int = 1 const val MESSAGE_TOAST: Int = 2 // ... (Add other message types here as needed.) class MyBluetoothService( // handler that gets info from Bluetooth service private val handler: Handler) { private inner class ConnectedThread(private val mmSocket: BluetoothSocket) : Thread() { private val mmInStream: InputStream = mmSocket.inputStream private val mmOutStream: OutputStream = mmSocket.outputStream private val mmBuffer: ByteArray = ByteArray(1024) // mmBuffer store for the stream override fun run() { var numBytes: Int // bytes returned from read() // Keep listening to the InputStream until an exception occurs. while (true) { // Read from the InputStream. numBytes = try { mmInStream.read(mmBuffer) } catch (e: IOException) { Log.d(TAG, "Input stream was disconnected", e) break } // Send the obtained bytes to the UI activity. val readMsg = handler.obtainMessage( MESSAGE_READ, numBytes, -1, mmBuffer) readMsg.sendToTarget() } } // Call this from the main activity to send data to the remote device. fun write(bytes: ByteArray) { try { mmOutStream.write(bytes) } catch (e: IOException) { Log.e(TAG, "Error occurred when sending data", e) // Send a failure message back to the activity. val writeErrorMsg = handler.obtainMessage(MESSAGE_TOAST) val bundle = Bundle().apply { putString("toast", "Couldn't send data to the other device") } writeErrorMsg.data = bundle handler.sendMessage(writeErrorMsg) return } // Share the sent message with the UI activity. val writtenMsg = handler.obtainMessage( MESSAGE_WRITE, -1, -1, mmBuffer) writtenMsg.sendToTarget() } // Call this method from the main activity to shut down the connection. fun cancel() { try { mmSocket.close() } catch (e: IOException) { Log.e(TAG, "Could not close the connect socket", e) } } } }
Java
public class MyBluetoothService { private static final String TAG = "MY_APP_DEBUG_TAG"; private Handler handler; // handler that gets info from Bluetooth service // Defines several constants used when transmitting messages between the // service and the UI. private interface MessageConstants { public static final int MESSAGE_READ = 0; public static final int MESSAGE_WRITE = 1; public static final int MESSAGE_TOAST = 2; // ... (Add other message types here as needed.) } private class ConnectedThread extends Thread { private final BluetoothSocket mmSocket; private final InputStream mmInStream; private final OutputStream mmOutStream; private byte[] mmBuffer; // mmBuffer store for the stream public ConnectedThread(BluetoothSocket socket) { mmSocket = socket; InputStream tmpIn = null; OutputStream tmpOut = null; // Get the input and output streams; using temp objects because // member streams are final. try { tmpIn = socket.getInputStream(); } catch (IOException e) { Log.e(TAG, "Error occurred when creating input stream", e); } try { tmpOut = socket.getOutputStream(); } catch (IOException e) { Log.e(TAG, "Error occurred when creating output stream", e); } mmInStream = tmpIn; mmOutStream = tmpOut; } public void run() { mmBuffer = new byte[1024]; int numBytes; // bytes returned from read() // Keep listening to the InputStream until an exception occurs. while (true) { try { // Read from the InputStream. numBytes = mmInStream.read(mmBuffer); // Send the obtained bytes to the UI activity. Message readMsg = handler.obtainMessage( MessageConstants.MESSAGE_READ, numBytes, -1, mmBuffer); readMsg.sendToTarget(); } catch (IOException e) { Log.d(TAG, "Input stream was disconnected", e); break; } } } // Call this from the main activity to send data to the remote device. public void write(byte[] bytes) { try { mmOutStream.write(bytes); // Share the sent message with the UI activity. Message writtenMsg = handler.obtainMessage( MessageConstants.MESSAGE_WRITE, -1, -1, mmBuffer); writtenMsg.sendToTarget(); } catch (IOException e) { Log.e(TAG, "Error occurred when sending data", e); // Send a failure message back to the activity. Message writeErrorMsg = handler.obtainMessage(MessageConstants.MESSAGE_TOAST); Bundle bundle = new Bundle(); bundle.putString("toast", "Couldn't send data to the other device"); writeErrorMsg.setData(bundle); handler.sendMessage(writeErrorMsg); } } // Call this method from the main activity to shut down the connection. public void cancel() { try { mmSocket.close(); } catch (IOException e) { Log.e(TAG, "Could not close the connect socket", e); } } } }
构造函数获取所需的流后，线程等待通过 InputStream 传入数据。当 read(byte[]) 从流返回数据时，数据会使用父类中的成员 Handler 发送到主 activity。然后，线程等待从 InputStream 读取更多字节。
要发送传出数据，您可以从主 activity 调用线程的 write() 方法并传入要发送的字节。此方法会调用 write(byte[]) 将数据发送到远程设备。如果在调用 write(byte[]) 时抛出 IOException，线程会向主 activity 发送 Toast 消息，向用户解释设备无法将给定字节发送到其他（已连接）设备。
线程的 cancel() 方法可让您随时通过关闭 BluetoothSocket 来终止连接。完成使用蓝牙连接后，请务必调用此方法。
要了解蓝牙 API 的使用演示，请参阅 GitHub 上的 Bluetooth Chat 示例应用。