我有一个Android应用程序，其最新版本的类型为Android API（29）。用户可以搜索附近的蓝牙设备并连接到它们以发送数据。蓝牙连接是通过应用程序作为客户端进行的。
我从Anroid的文档中复制了许多代码，并对其进行了更改以满足我的需求。该应用程序确实找到了设备，可以正确配对并连接。
问题在于，连接后，当它尝试读取传入流时，在Connected线程的第一个循环上，将引发异常，并且套接字断开连接。
我已经直接连接到设备的正确uuid，以测试通过可能的服务器蓝牙uuid进行的循环是否会干扰rfcomsocket。
我尝试在循环中的连接线程中尝试读取mInputStream.available() > 0，然后再尝试读取，但是看来它也引发了异常。
要测试连接，我激活了笔记本电脑的蓝牙适配器并将其设置为接收文件（作为服务器）。我曾经在Xamarin.Android中拥有此应用程序，而代码也曾以这种方式工作。目前它在Kotlin中运行。
下面的代码介绍了从相应函数调用的Connect和Connected线程。
fun connect(device: BluetoothDevice, uuids: ArrayList<ParcelUuid>) {
if (connectionState == STATE_CONNECTING) {
if (connectThread != null) {
connectThread?.cancel()
connectThread = null
}
}
// Cancel any thread currently running a connection
if (connectedThread != null) {
connectedThread?.cancel()
connectedThread = null
}
connectThread = ConnectThread(device, this, uuids)
connectThread?.start()
}
private inner class ConnectThread(
val device: BluetoothDevice,
service: BTService,
val uuids: ArrayList<ParcelUuid>
) : Thread() {
var socket: BluetoothSocket? = null
init {
service.connectionState = STATE_CONNECTING
}
override fun run() {
// Cancel discovery because it otherwise slows down the connection.
btAdapter?.cancelDiscovery()
for (uuid in uuids) {
try {
val mmSocket: BluetoothSocket? by lazy(LazyThreadSafetyMode.NONE) {
device.createRfcommSocketToServiceRecord(uuid.uuid)
}
mmSocket?.use { thisSocket ->
// Connect to the remote device through the socket. This call blocks
// until it succeeds or throws an exception.
thisSocket.connect()
// The connection attempt succeeded. Perform work associated with
// the connection in a separate thread.
socket = thisSocket
connected(thisSocket)
}
break
} catch (e: IOException) {
// Close the socket
cancel()
// Start the service over to restart listening mode
Log.e(TAG, "unable to connect() to socket.", e)
}
}
}
// Closes the client socket and causes the thread to finish.
fun cancel() {
try {
socket?.close()
} catch (e: IOException) {
Log.e(TAG, "Could not close the client socket", e)
}
}
}
//##################################### #####################################
//#####################################----->Connected<-----#####################################
//##################################### #####################################
// Start the ConnectedThread to begin managing a Bluetooth connection
fun connected(socket: BluetoothSocket) {
// Cancel the thread that completed the connection
if (connectThread != null) {
connectThread?.cancel()
connectThread = null
}
// Cancel any thread currently running a connection
if (connectedThread != null) {
connectedThread?.cancel()
connectedThread = null
}
// Start the thread to manage the connection and perform transmissions
connectedThread = ConnectedThread(socket)
connectedThread?.start()
// Send the name of the connected device back to the UI Activity
MainActivity.settingsFragment?.activity?.runOnUiThread {
(MainActivity.settingsFragment as SettingsFragment).btConnected()
}
}
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
init {
connectionState = STATE_CONNECTED
}
override fun run() {
// Keep listening to the InputStream until an exception occurs.
while (true) {
// Read from the InputStream.
try {
mmInStream.read(mmBuffer)
} catch (e: IOException) {
connectionLost()
Log.d(TAG, "Input stream was disconnected", e)
break
}
//Do something with stream.
}
}
// 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.
return
}
}
// 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)
}
}
}
// Stop all threads.
fun stop() {
if (connectThread != null) {
connectThread?.cancel()
connectThread = null
}
if (connectedThread != null) {
connectedThread?.cancel()
connectedThread = null
}
connectionState = STATE_NONE
}
fun write(bytes: ByteArray) {
if (connectionState != STATE_CONNECTED) {
return
}
val temp: ConnectedThread? = connectedThread
temp?.write(bytes)
}
fun connectionLost() {
MainActivity.settingsFragment?.activity?.runOnUiThread {
(MainActivity.settingsFragment as SettingsFragment).btLost()
}
connectionState = STATE_NONE
}
由于尝试读取时发生崩溃，结果是来自连接线程的IO捕获。我希望它只是在活动连接中循环，如果有数据要发送给我，就可以。
我知道inputStream不会保存在任何地方（这是有意的），但是我怀疑这是问题所在。
编辑1： 从连接开始到连接失败（结束）的调试日志...
2019-08-03 18:30:40.583 24961-25088/com.konkarapas.rcs.full.debug W/BluetoothAdapter: getBluetoothService() called with no BluetoothManagerCallback
2019-08-03 18:30:40.776 24961-25088/com.konkarapas.rcs.full.debug D/BluetoothSocket: close() this: android.bluetooth.BluetoothSocket@39f9369, channel: -1, mSocketIS: android.net.LocalSocketImpl$SocketInputStream@611f1ee, mSocketOS: android.net.LocalSocketImpl$SocketOutputStream@96eb68fmSocket: android.net.LocalSocket@15d7d1c impl:android.net.LocalSocketImpl@94fd25 fd:java.io.FileDescriptor@42f3efa, mSocketState: INIT
2019-08-03 18:30:40.780 24961-25088/com.konkarapas.rcs.full.debug E/BluetoothService: unable to connect() to socket.
java.io.IOException: read failed, socket might closed or timeout, read ret: -1
at android.bluetooth.BluetoothSocket.readAll(BluetoothSocket.java:762)
at android.bluetooth.BluetoothSocket.readInt(BluetoothSocket.java:776)
at android.bluetooth.BluetoothSocket.connect(BluetoothSocket.java:399)
at com.konkarapas.rcs.models.BTService$ConnectThread.run(BluetoothService.kt:172)
2019-08-03 18:30:40.782 24961-25088/com.konkarapas.rcs.full.debug W/BluetoothAdapter: getBluetoothService() called with no BluetoothManagerCallback
2019-08-03 18:30:40.934 24961-25088/com.konkarapas.rcs.full.debug D/BluetoothSocket: close() this: android.bluetooth.BluetoothSocket@5534f08, channel: 4, mSocketIS: android.net.LocalSocketImpl$SocketInputStream@ebd46a1, mSocketOS: android.net.LocalSocketImpl$SocketOutputStream@3a250c6mSocket: android.net.LocalSocket@fdce887 impl:android.net.LocalSocketImpl@f5253b4 fd:java.io.FileDescriptor@cc6abdd, mSocketState: CONNECTED
2019-08-03 18:30:40.938 24961-25088/com.konkarapas.rcs.full.debug D/BluetoothSocket: close() this: android.bluetooth.BluetoothSocket@5534f08, channel: 4, mSocketIS: android.net.LocalSocketImpl$SocketInputStream@ebd46a1, mSocketOS: android.net.LocalSocketImpl$SocketOutputStream@3a250c6mSocket: null, mSocketState: CLOSED
2019-08-03 18:30:40.943 24961-25089/com.konkarapas.rcs.full.debug D/BluetoothService: Input stream was disconnected
java.io.IOException: socket closed
at android.net.LocalSocketImpl$SocketInputStream.read(LocalSocketImpl.java:104)
at android.bluetooth.BluetoothSocket.read(BluetoothSocket.java:555)
at android.bluetooth.BluetoothInputStream.read(BluetoothInputStream.java:88)
at java.io.InputStream.read(InputStream.java:101)
at com.konkarapas.rcs.models.BTService$ConnectedThread.run(BluetoothService.kt:245)
由于错误的uuid，第一个例外是合乎逻辑的。第二个例外是问题。
答案 0 :(得分：1)
您正在使用mmSocket?.use，mmsocket?.let完成后会自动清理（即关闭连接）。如果将其更改为Cross Apply，它不应在连接后自动关闭连接已经完成了。 （对于网络套接字也有完全相同的问题，请像这样修复它）
答案 1 :(得分：0)
因此，在深入研究Kotlin和JVM并进行了大量调试之后，我发现了问题所在。 看来，就像Java一样，Kotlin是按引用传递的。
这意味着当您将非原始（任何自定义类）对象传递给函数时，它只是将该对象引用到函数中。这意味着即使在函数退出之后，对该对象对该函数所做的任何更改也将对“父对象”进行。
问题：
就我而言，这是两个问题。 @Joozd提到的第一个问题是使用mmSocket.use。连接后立即关闭了插座
第二个问题是connected()函数。它是为了关闭ConnectThread并仅保留一个ConnectedThread而创建的。相反，当它关闭ConnectThread中的套接字时，它也关闭了传递给ConnectedThread的套接字。
解决方案：
将mmSocket.use更改为mmSocket.let，以不自动关闭连接。
建立连接后立即删除不必要的功能connected()并移动内容。在连接开始时，无论如何都在connect()函数中进行了空检查。