android - listenUsingRfcommWithServiceRecord(...) 返回 null

Question

我的蓝牙服务器在尝试创建蓝牙服务器套接字时崩溃。我已经在谷歌上搜索了很多，找到了几个我尝试过的答案，但没有任何效果。我在几个不同的设备上尝试了代码，但到处都出现相同的错误。

...
private class AcceptThread extends Thread {
    private final BluetoothServerSocket mmServerSocket;

    public AcceptThread() {
        // Use a temporary object that is later assigned to mmServerSocket,
        // because mmServerSocket is final
        BluetoothServerSocket tmp = null;
        try {
            // MY_UUID is the app's UUID string, also used by the client code
            tmp = mBluetoothAdapter.listenUsingRfcommWithServiceRecord(Var.SERVICE_NAME, UUID.fromString("a70aec2c-19e4-4804-8e3c-557de4e3f558"));
        } catch (IOException e) {
            e.printStackTrace();
        }
        mmServerSocket = tmp;
    }

    public void run() {
        BluetoothSocket socket = null;
        // Keep listening until exception occurs or a socket is returned
        while (true) {
            try {
                socket = mmServerSocket.accept();
            } catch (IOException e) {
                break;
            }
...

错误信息:

08-01 16:14:48.361: E/AndroidRuntime(32417): FATAL EXCEPTION: Thread-8045
08-01 16:14:48.361: E/AndroidRuntime(32417): Process: ... .bluetoothserver, PID: 32417
08-01 16:14:48.361: E/AndroidRuntime(32417): java.lang.NullPointerException
08-01 16:14:48.361: E/AndroidRuntime(32417):    at ... .bluetoothserver.communication.BluetoothChat$AcceptThread.run(BluetoothChat.java:103)

08-01 16:14:48.731: E/BluetoothSocket(32417): bindListen, fail to get port number, exception: java.io.IOException: read failed, socket might closed or timeout, read ret: -1

这里有什么问题？以下行中的 tmp 为空:

tmp = mBluetoothAdapter.listenUsingRfcommWithServiceRecord(Var.SERVICE_NAME, UUID.fromString("a70aec2c-19e4-4804-8e3c-557de4e3f558"));

Answer 1

listenUsingRfcommWithServiceRecord 失败并引发 IOException，该异常被忽略并且 AcceptThread 仍然启动。 mmServerSocket 设置为空。

这应该可以解决:

private class Server_Connect_Thread extends Thread {
private final BluetoothServerSocket mmServerSocket;
private boolean running = true;
public Server_Connect_Thread() {
BluetoothServerSocket tmp = null;
try {
    tmp = bluetooth_adapter.listenUsingRfcommWithServiceRecord("NAME", uuid);
} catch (IOException e) {
    bluetooth_show_message("Bluetooth Error! listenUsingRfcommWithServiceRecord failed. Reason:" + e);
    running = false;
}
mmServerSocket = tmp;
}

public void run() {
while (running) {
    try {
        socket = mmServerSocket.accept();
    } catch (IOException e) {
        bluetooth_show_message("Bluetooth Error! Accepting a connection failed. Reason:" + e);
        break;
    }
...
}

您得到的 IOException 经常发生，例如当其他设备未能及时连接时，或者您连接到错误的蓝牙设备时。就我而言，这是我邻居的电视机。