An ANR or 'application not responding' dialog box will appear whenever an application is not responding. There are several reasons that this may occur, and as an Android developer, you should be familiar with these and know how to avoid or correct them. This is an example of an operational question with which the interviewer seeks to understand how you go about doing this job. Operational, like technical questions, should be responded to directly and succinctly, with little embellishment. The interviewer will ask you a follow-up question if they need additional information.