I am working on Project 5: Temperature Readings. Everything seem to be working okay except for the data display on the Android. I can see the correct temperature displayed periodically but a dialog window keeps coming up and covering the data which reads “Bad arguments to < The operation < cannot accept theargumens: [*empty-strings*], 
The android connects properly to the android. provides the correct initial display to connect to the HC06 and does connect, but gives the above error message. The Serial Monitor provides the correct temperature also.
I tried a different Android and after I connect to the arduino I get that same error message but if I continue to touch the display that error message goes away and the module works perfectly. I still would like to know if anyone has an idea why that error message occurs initially and every time I have to activate the display. It is annoying to have to do this all the time. I am happy that the module does work as advertised, except for that anomaly.
Again I tried another android, since I have several that I use for developing projects and on this one it worked perfectly. No error messages. It must have been something with incompatibility with the the other androids. This can be closed now.
I’m sorry for not responding to your question and taking so long to get back to you, but I was without internet for the last couple of days during a trip.
I’m glad you have made the project work. The project worked fine on our android smartphones, it was probably some compatibility issues.
I’ll close this question.