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Я решил эту проблему. Проблема в методе.registerGCMInBackground()GoogleCloudMessaging.getInstance() ожидает.ApplicationContext

    private void registerGCMInBackground(final String userId) {
    new AsyncTask() {
        @Override
        protected String doInBackground(Void... params) {
            String msg = "";
            Log.d("Register GCM", "started");
            try {
                if (gcm == null) {
                    //PROBLEM SOLVED HERE
                    gcm = GoogleCloudMessaging.getInstance(getApplicationContext());
                    Log.d("GCM", gcm.toString());
                }



                regid = gcm.register(SENDER_ID); //////NULL POINTER EXCEPTION
                msg = "Device registered, registration ID=" + regid;



                // You should send the registration ID to your server over HTTP
                sendRegistrationIdToBackend(userId, regid);

                // For this demo: we don't need to send it because the device will send
                // upstream messages to a server that echo back the message using the
                // 'from' address in the message.

                // Persist the regID - no need to register again.
                storeRegistrationId(context, regid);
            } catch (IOException ex) {
                return "Error :" + ex.getMessage();
                // If there is an error, don't just keep trying to register.
                // Require the user to click a button again, or perform
                // exponential back-off.
            }
            return regid;
        }

-------- Решенная проблема --------------

У меня проблемы с регистрацией моего устройства Android наGCM (Google Cloud Messaging). Я'м, используя пример изРазработчики Google, Используя пример Google Developer, я обеспечил следующее:

добавление последней библиотеки Play Servicesдобавление последней версии JAR Play Servicesправильный файл манифестас установленным на устройстве Play Services APKиспользуя номер проекта в качестве SENDER_ID

Кажется, такая же проблема, как этаВопрос, К сожалению до сих пор не ответил. Я'получаю исключение нулевого указателя по следующей строке:

regid = gcm.register(SENDER_ID);

Вот мой код проблемы:Пример деятельности

     static final String TAG = "GCM";
    public static final String EXTRA_MESSAGE = "message";
    public static final String PROPERTY_REG_ID = "registration_id";
    private static final String PROPERTY_APP_VERSION = "appVersion";
    private static final int PLAY_SERVICES_RESOLUTION_REQUEST = 9000;
    String SENDER_ID = "xxxxxxxxxxxxxxx";
    GoogleCloudMessaging gcm;
    AtomicInteger msgId = new AtomicInteger();
    Context context;

    @Override
    protected void onCreate(Bundle savedInstanceState) {

            super.onCreate(savedInstanceState);
            setContentView(R.layout.registration);

            final Button register = (Button) findViewById(R.id.btn_register);

            register.setOnClickListener(new View.OnClickListener() {

                @Override
                public void onClick(View v) {

                     EditText mobilePhoneNumber = (EditText) findViewById(R.id.et_phonenumber);

                    if(!mobilePhoneNumber.getText().toString().isEmpty()){
                    User user = new User();
                    user.setMobilePhoneNumber(mobilePhoneNumber.getText().toString());

                     EditText firstName = (EditText) findViewById(R.id.et_firstName);
                    user.setFirstName(firstName.getText().toString());

                     EditText lastName = (EditText) findViewById(R.id.et_lastName);
                    user.setLastName(lastName.getText().toString());

                     EditText email = (EditText) findViewById(R.id.et_email);
                    user.setEmail(email.getText().toString());
                    Log.d("email: ", user.getEmail().toString());

                    if (android.os.Build.VERSION.SDK_INT>14) {
                        StrictMode.ThreadPolicy policy = new StrictMode.ThreadPolicy.Builder()
                                .permitAll().build();
                        StrictMode.setThreadPolicy(policy);
                    }

                    UserService userService = new UserService();
                    String path = userService.createNewUser(user);




                    Log.d("Location: ", path);
                    Toast.makeText(getApplicationContext(), 
                            path, Toast.LENGTH_LONG).show();

                    String userID = path.replace("/user/", "");
                    userID = userID.replace("/users/", "");
                    Log.d("UserID:::", userID);
                    Log.d("User Service", "register in Background started");
                    if(checkPlayServices()){
                    registerGCMInBackground(userID);
                    }

                    }
                    else{
                        Toast.makeText(getApplicationContext(), 
                                "Please enter your Mobile Phone Number", Toast.LENGTH_LONG).show();
                    }           
                }
            });

    private void registerGCMInBackground(final String userId) {
        new AsyncTask() {
            @Override
            protected String doInBackground(Void... params) {
                String msg = "";
                Log.d("Register GCM", "started");
                try {
                    if (gcm == null) {
                        gcm = GoogleCloudMessaging.getInstance(context);
                        Log.d("GCM", gcm.toString());
                    }



                    regid = gcm.register(SENDER_ID); //////NULL POINTER EXCEPTION
                    msg = "Device registered, registration ID=" + regid;



                    // You should send the registration ID to your server over HTTP
                    sendRegistrationIdToBackend(userId, regid);

                    // For this demo: we don't need to send it because the device will send
                    // upstream messages to a server that echo back the message using the
                    // 'from' address in the message.

                    // Persist the regID - no need to register again.
                    storeRegistrationId(context, regid);
                } catch (IOException ex) {
                    return "Error :" + ex.getMessage();
                    // If there is an error, don't just keep trying to register.
                    // Require the user to click a button again, or perform
                    // exponential back-off.
                }
                return regid;
            }

            @Override
            protected void onPostExecute(String msg) {

            }
        }.execute(null, null, null);
    }

Вот мой консольный вывод:Console OutputI '

Я занимаюсь этим два дня. :( Большое спасибо!