以編程方式連接到藍牙設備

Question

我正在為新的車輛安全應用程序編寫程序。 該應用程序允許用戶通過其手機應用程序控制鎖定/解鎖操作。 假設用戶的手機藍牙最初是關閉的。 如果是這樣，當他打開應用程序時，手機藍牙適配器應該會自動打開，並且應該與固定在車輛上的藍牙模塊連接。 根據我所做的代碼，手機BT適配器的編程啟用工作正常。 但是與車輛 BT 模塊的連接不會發生。

但是如果用戶在手機藍牙適配器已經打開的情況下打開應用程序，則車輛和手機之間的連接會自動建立。

我需要知道為什么以編程方式打開 BT 適配器時不會發生連接。

注意 - 手機和車載藍牙模塊已配對。 藍牙模塊mac地址在編碼中是硬編碼的。 編碼如下。 我只粘貼了必要的部分。 我希望每個需要了解和解決我的問題的人都在這里。 我發布代碼的方式非常混亂。 對於那個很抱歉。 希望很清楚。 我是新手。

    private static final UUID MY_UUID =
      UUID.fromString("00001101-0000-1000-8000-00805F9B34FB");

  // Insert bluetooth devices MAC address
  private static String address = "00:19:5D:EF:03:79";


  /** Called when the activity is first created. */
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

  setContentView(R.layout.main); 
  btAdapter = BluetoothAdapter.getDefaultAdapter();
    btAdapter.enable();


  @Override
  public void onResume() {
    super.onResume();

    btAdapter.enable();

     // Set up a pointer to the remote node using it's address.
    BluetoothDevice device = btAdapter.getRemoteDevice(address);

    // Two things are needed to make a connection:
    //   A MAC address, which we got above.
    //   A Service ID or UUID.  In this case we are using the
    //     UUID for SPP.


    try {
      btSocket = device.createRfcommSocketToServiceRecord(MY_UUID);
    } catch (IOException e) {
      errorExit("Fatal Error", "In onResume() and socket create failed: " + e.getMessage() + ".");
    }

    // Make sure Discovery isn't going on when you attempt to connect and pass your message.

    btAdapter.cancelDiscovery();

    // Establish the connection.  This will block until it connects.

    try {
      btSocket.connect();

    } catch (IOException e) {
      try {
        btSocket.close();
      } catch (IOException e2) {
        errorExit("Fatal Error", "In onResume() and unable to close socket during connection failure" + e2.getMessage() + ".");
      }
    }

    // Create a data stream so we can talk to server.

    try {
      outStream = btSocket.getOutputStream();
    } catch (IOException e) {
      errorExit("Fatal Error", "In onResume() and output stream creation failed:" + e.getMessage() + ".");
    }
  }

Answer 1

可能存在計時問題，onCreate 和 onResume 的調用順序非常短。 在沒有開啟BT的情況下，可能會在BT服務上線前調用onResume中的代碼。

我的建議：嘗試通過將代碼放入 Runnable 來延遲啟動幾秒鍾。

private Handler mHandler = new Handler();

public void onCreate() {

     [...]

     mHandler.postDelayed(new Runnable() {
         @Override
         public void run() {
             btAdapter.enable();
              // Set up a pointer to the remote node using it's address.
             BluetoothDevice device = btAdapter.getRemoteDevice(address);
             // Two things are needed to make a connection:
             //   A MAC address, which we got above.
             //   A Service ID or UUID.  In this case we are using the
             //     UUID for SPP.
             try {
                 btSocket = device.createRfcommSocketToServiceRecord(MY_UUID);
             } catch (IOException e) {
                 errorExit("Fatal Error", "In onResume() and socket create failed: " +                  e.getMessage() + ".");                
             }

             // Make sure Discovery isn't going on when you attempt to connect and pass your message.

             btAdapter.cancelDiscovery();

             // Establish the connection.  This will block until it connects.

             try {
               btSocket.connect();

             } catch (IOException e) {
               try {
                 btSocket.close();
               } catch (IOException e2) {
                 errorExit("Fatal Error", "In onResume() and unable to close socket during connection failure" + e2.getMessage() + ".");
               }
             }

             // Create a data stream so we can talk to server.

             try {
               outStream = btSocket.getOutputStream();
             } catch (IOException e) {
               errorExit("Fatal Error", "In onResume() and output stream creation failed:" + e.getMessage() + ".");
             }
     }, 5000); // 5 second delay

     [...]

警告：如果您在啟動后立即退出應用程序，這將非常糟糕。 將 runnable 放在成員變量中並在 onDestroy() 中調用 mHandler.removeCallback(Runnable)。