成功連線至藍牙裝置後，每個裝置都有連線的 BluetoothSocket。您現在可以在裝置間分享資訊。使用 BluetoothSocket 時，資料的一般轉移程序如下：
分別使用
getInputStream()和getOutputStream()取得用於透過通訊端處理傳輸的InputStream和OutputStream。使用
read(byte[])和write(byte[])將資料讀取並寫入串流。
當然需要考量實作詳情。請特別注意，您應該使用專屬執行緒從串流讀取及寫入串流。由於 read(byte[]) 和 write(byte[]) 方法都會封鎖呼叫，因此這一點相當重要。read(byte[]) 方法會封鎖，直到有待從串流讀取的內容為止。write(byte[]) 方法通常不會封鎖，但如果遠端裝置呼叫 read(byte[]) 的速度不夠快，且中繼緩衝區因此已滿，則該方法可能會封鎖流量控制。因此，您應在執行緒中設計主要迴圈，以便從 InputStream 讀取。您可以在執行緒中另外使用公開方法，來啟動對 OutputStream 的寫入作業。
範例
以下範例說明如何在兩部透過藍牙連線的裝置之間傳輸資料：
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);
}
}
}
}
在建構函式取得必要的串流後，執行緒會等待資料透過 InputStream 傳送。當 read(byte[]) 傳回來自串流的資料時，系統會使用父項類別的成員 Handler，將資料傳送至主要活動。執行緒會等待更多從 InputStream 讀取的位元組。
如要傳送傳出資料，請從主要活動呼叫執行緒的 write() 方法，然後傳入要傳送的位元組。這個方法會呼叫 write(byte[]) 以將資料傳送至遠端裝置。如果在呼叫 write(byte[]) 時擲回 IOException，執行緒會將浮動式訊息傳送至主要活動，向使用者說明裝置無法將指定位元組傳送到其他 (已連線) 裝置。
執行緒的 cancel() 方法可讓您隨時關閉 BluetoothSocket，藉此終止連線。使用藍牙連線後，請一律呼叫此方法。
如需藍牙 API 的使用示範，請參閱 GitHub 上的藍牙即時通訊範例應用程式。