Atomic counter - Null pointer exception !!

General
1

Hi - I am getting below ‘npe’ while trying to call ‘incrementAndGet’ android API for counters (code lines below):

IAtomic<Long> myCounter = Backendless.Counters.of(“merchant_reg_count”, Long.class);
myCounter.incrementAndGet(createRegCounterCb(context, callback));The callback function does not get called - and exception comes prior to that.Am I doing anything wrong ?? Am I required to create/initialize counter before calling ‘incrementAndGet’ ??Also, can’t I see counter values from console ??

java.lang.NullPointerException: Attempt to invoke interface method ‘java.lang.reflect.Type[] java.lang.reflect.ParameterizedType.getActualTypeArguments()’ on a null object reference
at com.backendless.utils.ReflectionUtil.getCallbackGenericType(ReflectionUtil.java:126)
at com.backendless.atomic.AtomicCallback.handleResponse(AtomicCallback.java:47)
at com.backendless.async.message.AsyncMessage$ResponseHandler.handle(AsyncMessage.java:64)
at com.backendless.async.message.AsyncMessage.handleCallback(AsyncMessage.java:41)
at com.backendless.core.AndroidCarrier$1.handleMessage(AndroidCarrier.java:37)
at android.os.Handler.dispatchMessage(Handler.java:98)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5443)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:728)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)

Thanks.

Regards,
Aditya

2

Aditya,

Do you have Backendless.initApp call in your application? The only time I was able to get a NPE if the initApp method is not invoked.

As for console, no, there is no place in console where you can see counters.

Mark

3

Yes, it’s called once in main activity - I do a file upload before fetching counter and that works fine …in fact I call get counter method from the file upload callback function only …below is complete code …

new LoadingCallback<BackendlessFile>(context, AppConstants.imageUpload, true)
{
@Override
public void handleResponse(BackendlessFile file)
{
setImage_url(file.getFileURL());
Log.d(TAG, “Display image uploaded successfully at :” + getImage_url());
// stop progress dialog
super.handleResponse(file);
// If registration scenario, fetch unique ciunter value asynchronously
if(registerCase) {
IAtomic<Long> myCounter = Backendless.Counters.of("merchant_reg_count, Long.class);
myCounter.incrementAndGet(createRegCounterCb(context, callback));
} else {
callback.onSuccess();
}
}

@Override
public void handleFault( BackendlessFault fault ) {
    Log.e(TAG, "Image file upload failed: " + fault.toString());
    // stop progress dialog
    super.handleFault(fault);
    // Image upload failed, but still try for registration
    if(registerCase) {
        Backendless.Counters.incrementAndGet( MERCHANT_REG_COUNTER_NAME, createRegCounterCb(context, callback) );
    } else {
        callback.onFailure(ErrorCodes.FILE_UPLOAD_FAILED);
    }
}

};
Below is reg counter callback function - however, this does not get called and exception comes prior to this.private LoadingCallback<Long> createRegCounterCb(final Context context, final OnResult callback)
{
// start showing in progress dialog also
return new LoadingCallback<Long>(context, AppConstants.registrationCounter, true)
{
@Override
public void handleResponse(Long value)
{
Log.d(TAG, "Unique registration counter value: "+value);
mRegCounter = value;
if(mRegCounter == null || mRegCounter == 0) {
super.handleResponse(value);
callback.onFailure(ErrorCodes.GENERAL_ERROR);
return;
}
Log.d(TAG, “Unique registration counter value :” + mRegCounter);
// Set userid and ‘cashback table name’
setAutoUserId();
setCashbackTable();
// stop progress dialog
super.handleResponse(value);
// Register asynchronously
Backendless.UserService.register(backendUser, createRegCallback(context, callback));
}

    @Override
    public void handleFault( BackendlessFault fault ) {
        Log.e(TAG, "Increment registration counter value failed: " + fault.toString());
        // stop progress dialog
        super.handleFault(fault);
        callback.onFailure(ErrorCodes.GENERAL_ERROR);
    }
};

}

4

Can you tell me which line causes the exception? Are you absolutely sure it is the line fetching the counter value?

5

yes, 100% it comes in between calling incrementAndGet() and before its callback gets called.

I added 3 below debug statement, and I see them - but I do not see debug statement from callback.

Log.d(TAG, “Get IAtomic counter”);
IAtomic<Long> myCounter = Backendless.Counters.of(MERCHANT_REG_COUNTER_NAME, Long.class);
Log.d(TAG, “calling incrementAndGet”);
myCounter.incrementAndGet(createRegCounterCb(displayImg, context, callback));
Log.d(TAG, “returned from incrementAndGet”);

6

I tried vanilla incrementAndGet() - and its working - so some issue with my code.

I am checking and will update. Thanks.

7

I do not understand what your LoadingCallback does. Here, try this in a JAVA program (not android):

public class GetCounter
{
public static void main( String[] args )
{
String APPLICATION_ID = “PUT-YOUR-APP-ID-HERE”;
final String SECRET_KEY = “PUT-YOUR-ANDROID-KEY-HERE”;
Backendless.initApp( APPLICATION_ID, SECRET_KEY, “v1” );

Backendless.Counters.of("merchant_reg_count", Long.class ).incrementAndGet( new AsyncCallback&lt;Long&gt;()
{
  @Override
  public void handleResponse( Long counterValue )
  {
    System.out.println( "got value - " + counterValue );
  }


  @Override
  public void handleFault( BackendlessFault fault )
  {
    System.out.println( "got fault - " + fault.getMessage() );
  }
} );

}
}

8

Hi - The problem got solved. You were right - it was somewhere else, due to a race condition.

Thanks a lot for bearing with me :slight_smile:

9

LoadingCallback is from your ‘Restaurant-to-go’ app :slight_smile: - issue anyways was in my code and not due to LoadingCallback.