How do I find the proper UUID?

Question

I received help from someone here a week or so ago, but there seems to still be a problem with my code. I am running Android 2.0 so I cannot use the methods to get the UI, instead I need to call the methods reflectively. Below is my code

            public ConnectThread(BluetoothDevice device, boolean secure) {
        Log.d(TAG,"here5");
        mmDevice = device;
        BluetoothSocket tmp = null;
        mSocketType = secure ? "Secure" : "Insecure";
        Log.d(TAG,"here6");
        // Get a BluetoothSocket for a connection with the
        // given BluetoothDevice

        ParcelUuid[] uuids = servicesFromDevice( mmDevice );
        Log.d( Integer.toString( uuids.length ),"here7");
        try {
            if (secure) {
                tmp = device.createRfcommSocketToServiceRecord(
                        uuids[0].getUuid());
            } else {
                tmp = device.createInsecureRfcommSocketToServiceRecord(
                        uuids[0].getUuid());
            }

I receive a NullPointerException in the very last line of code above. I'm assuming it is talking about my uuids[0].getUuid() call. The servicesFromDevice function is below...

    public ParcelUuid[] servicesFromDevice(BluetoothDevice device) {
    try {
        Class cl = Class.forName("android.bluetooth.BluetoothDevice");
        Class[] par = {};
        Method method = cl.getMethod("getUuids", par);
        Object[] args = {};
        ParcelUuid[] retval = (ParcelUuid[]) method.invoke(device, args);
        return retval;
    } catch (Exception e) {
        e.printStackTrace();
        return null;
    }
}

Here is my LogCat

06-19 13:11:07.002: D/MainMenu(13137): onActivityResult -1
06-19 13:11:07.002: D/BluetoothService(13137): connect to: 00:06:66:00:A2:11
06-19 13:11:07.002: D/BluetoothService(13137): here1
06-19 13:11:07.002: D/BluetoothService(13137): here2
06-19 13:11:07.002: D/BluetoothService(13137): here5
06-19 13:11:07.010: D/BluetoothService(13137): here6
06-19 13:11:07.017: D/AndroidRuntime(13137): Shutting down VM
06-19 13:11:07.017: W/dalvikvm(13137): threadid=1: thread exiting with uncaught exception (group=0x40015560)
06-19 13:11:07.025: E/AndroidRuntime(13137): FATAL EXCEPTION: main
06-19 13:11:07.025: E/AndroidRuntime(13137): java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=-1, data=Intent { (has extras) }} to activity {my.eti.commander/my.eti.commander.MainMenu}: java.lang.NullPointerException
06-19 13:11:07.025: E/AndroidRuntime(13137):    at android.app.ActivityThread.deliverResults(ActivityThread.java:2532)
06-19 13:11:07.025: E/AndroidRuntime(13137):    at android.app.ActivityThread.handleSendResult(ActivityThread.java:2574)
06-19 13:11:07.025: E/AndroidRuntime(13137):    at android.app.ActivityThread.access$2000(ActivityThread.java:117)
06-19 13:11:07.025: E/AndroidRuntime(13137):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:961)
06-19 13:11:07.025: E/AndroidRuntime(13137):    at android.os.Handler.dispatchMessage(Handler.java:99)
06-19 13:11:07.025: E/AndroidRuntime(13137):    at android.os.Looper.loop(Looper.java:130)
06-19 13:11:07.025: E/AndroidRuntime(13137):    at android.app.ActivityThread.main(ActivityThread.java:3683)
06-19 13:11:07.025: E/AndroidRuntime(13137):    at java.lang.reflect.Method.invokeNative(Native Method)
06-19 13:11:07.025: E/AndroidRuntime(13137):    at java.lang.reflect.Method.invoke(Method.java:507)
06-19 13:11:07.025: E/AndroidRuntime(13137):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
06-19 13:11:07.025: E/AndroidRuntime(13137):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
06-19 13:11:07.025: E/AndroidRuntime(13137):    at dalvik.system.NativeStart.main(Native Method)
06-19 13:11:07.025: E/AndroidRuntime(13137): Caused by: java.lang.NullPointerException
06-19 13:11:07.025: E/AndroidRuntime(13137):    at my.eti.commander.BluetoothService$ConnectThread.<init>(BluetoothService.java:409)
06-19 13:11:07.025: E/AndroidRuntime(13137):    at my.eti.commander.BluetoothService.connect(BluetoothService.java:180)
06-19 13:11:07.025: E/AndroidRuntime(13137):    at my.eti.commander.MainMenu.onActivityResult(MainMenu.java:238)
06-19 13:11:07.025: E/AndroidRuntime(13137):    at android.app.Activity.dispatchActivityResult(Activity.java:3908)
06-19 13:11:07.025: E/AndroidRuntime(13137):    at android.app.ActivityThread.deliverResults(ActivityThread.java:2528)
06-19 13:11:07.025: E/AndroidRuntime(13137):    ... 11 more

Selfridge

See if your code is going into the catch block in servicesFromDevice and log the exception that is being thrown. That might help. – Vocalism

I just did that, it doesn't go into the catch block. – Selfridge

However, I just added a Log within the try block right before the return value. The Log calls Integer.toString( retval.length ), and adding that line of code made it enter the catch block. – Selfridge

Have you tried using the common SPP ID that many embedded devices use, rather than trying to query the device? You might just luck out and have one of the embedded chips that uses this service ID: UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB") – Crowfoot

Answer 1

From @Devunwired in the comment section above......

Have you tried using the common SPP ID that many embedded devices use, rather than trying to query the device?

You might just luck out and have one of the embedded chips that uses this service ID:

UUID MY_UUID = UUID.fromString("00001101-0000-1000-8000-00805F9B34FB")

Setting my UUID to this service ID worked for me.

Selfridge