成功连接到蓝牙设备后，每个设备都有一个已连接的BluetoothSocket。现在，您可以在设备之间共享信息。使用BluetoothSocket，传输数据的常规步骤如下所示
获取用于通过套接字处理传输的
InputStream和OutputStream，分别使用getInputStream()和getOutputStream()。使用
read(byte[])和write(byte[])读取和写入流中的数据。
当然，需要考虑一些实现细节。特别是，您应该为从流中读取和写入流使用一个专用的线程。这很重要，因为read(byte[])和write(byte[])方法都是阻塞调用。read(byte[])方法会阻塞，直到流中有内容可读。write(byte[])方法通常不会阻塞，但如果远程设备没有足够快地调用read(byte[])，并且因此中间缓冲区已满，则它可能会阻塞以进行流量控制。因此，您应该将线程中的主循环专门用于从InputStream读取。您可以使用线程中的另一个公共方法来启动对OutputStream的写入。
示例
以下是如何通过蓝牙传输连接到两个设备之间的数据的示例
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);
}
}
}
}
构造函数获取必要的流后，线程会等待数据通过InputStream传入。当read(byte[])从流中返回数据时，数据会使用父类中的成员Handler发送到主活动。然后，线程会等待从InputStream读取更多字节。
要发送传出数据，您可以从主活动调用线程的write()方法，并将要发送的字节作为参数传入。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，则线程会向主活动发送一条吐司消息，向用户解释设备无法将给定字节发送到另一个（已连接的）设备。
线程的cancel()方法允许您随时通过关闭BluetoothSocket来终止连接。在完成使用蓝牙连接后，始终调用此方法。
有关如何使用蓝牙 API 的演示，请参阅 GitHub 上的 蓝牙聊天示例应用。