Google Cloud Messaging - Check if device is already registered

Question

I just set up GCM in my Android App. But I have the problem that I don't know how to check if the device is already registered. I work with the new google play services library.

The register part looks like this:

@Override
        protected String doInBackground(String... arg0) {
            String msg = "";
            try {
                if (gcm == null) {
                    gcm = GoogleCloudMessaging.getInstance(context_app);
                }
                regid = gcm.register(SENDER_ID);
                msg = "Dvice registered, registration ID=" + regid;
                Log.d("111", msg);
                sendRegistrationIdToBackend(regid);

            } catch (IOException ex) {
                msg = "Error :" + ex.getMessage();
            }
            return msg;
        }

How can I modify this that it checks if the device is already registered?

Answer 1

将注册ID存储在databade表或共享首选项中，并在应用启动时..检查其是否为null

Answer 2

Google has provided very clear documentation with code.You should use following code:

// Make sure the device has the proper dependencies.
        GCMRegistrar.checkDevice(this);
 // Make sure the manifest was properly set - comment out this line
        // while developing the app, then uncomment it when it's ready.
        GCMRegistrar.checkManifest(this);
 registerReceiver(mHandleMessageReceiver,
                new IntentFilter(DISPLAY_MESSAGE_ACTION));
        final String regId = GCMRegistrar.getRegistrationId(this);
        if (regId.equals("")) {
            // Automatically registers application on startup.
            GCMRegistrar.register(this, SENDER_ID);
        } else {
            // Device is already registered on GCM, check server.
            if (GCMRegistrar.isRegisteredOnServer(this)) {
                // Skips registration.
                mDisplay.append(getString(R.string.already_registered) + "\n");
            } else {
                // Try to register again, but not in the UI thread.
                // It's also necessary to cancel the thread onDestroy(),
                // hence the use of AsyncTask instead of a raw thread.
                final Context context = this;
                mRegisterTask = new AsyncTask<Void, Void, Void>() {

                    @Override
                    protected Void doInBackground(Void... params) {
                        boolean registered =
                                ServerUtilities.register(context, regId);
                        // At this point all attempts to register with the app
                        // server failed, so we need to unregister the device
                        // from GCM - the app will try to register again when
                        // it is restarted. Note that GCM will send an
                        // unregistered callback upon completion, but
                        // GCMIntentService.onUnregistered() will ignore it.
                        if (!registered) {
                            GCMRegistrar.unregister(context);
                        }
                        return null;
                    }

                    @Override
                    protected void onPostExecute(Void result) {
                        mRegisterTask = null;
                    }

                };
                mRegisterTask.execute(null, null, null);
            }
        }
@Override
    protected void onDestroy() {
        if (mRegisterTask != null) {
            mRegisterTask.cancel(true);
        }
        unregisterReceiver(mHandleMessageReceiver);
        GCMRegistrar.onDestroy(this);
        super.onDestroy();
    }
  private final BroadcastReceiver mHandleMessageReceiver =
            new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String newMessage = intent.getExtras().getString(EXTRA_MESSAGE);
            mDisplay.append(newMessage + "\n");
        }
    };

Answer 3

when you get registration Id, Store it in SharedPreferences, for example:

SharedPreferences shp = context.getSharedPreferences("anyNameYouLike",MODE_PRIVATE);
SharedPreferences.Editor editor=shp.edit();
editor.putString("RegID",registrationID).commit;

In the next time before you register check the "anyNameYouLike" if it contain field called RegID Like this:

private boolean isRegistered(Context context){
SharedPreferences shp = context.getSharedPreferences("anyNameYouLike",PRIVATE_MODE);
return shp.contains("RegID");
}