You have different options, depending on what your goals are and how in-depth the feedback is that you want to get.
Analytics will tell you what they have done, but they won't tell you why they have done it, and being able to understand why an action was (or was not) taken is often what will give you the insight necessary to address the actual issue. Implementing analytics in your application might or might not be easy, depending on many factors.
User testing will give you feedback without having to worry about users not wanting to type in a question. Depending on the feedback that you need and your userbase, a user test can be as simple as hanging out in a coffee shop with gift cards and gathering feedback (quick and dirty, cheap) to actually recruiting users and talking to them as they do something with your mobile app (a more standard usability study, but takes more time and you should compensate your users for their time giving you their feedback).
A survey can give you some feedback. A survey should be easy to respond to. The easier that it is for your users to respond to your survey, the higher your response rate is. Part of that is the length of the survey (number of questions), part of that is the type of response you expect (choosing one answer from a list of five is faster than typing). To help increase your response rate, you can provide some kind of incentive for completing it. The longer your survey is, the better the incentive should be; for a short survey, a simple entry into a drawing for a $50 gift card will help you get a better response rate. There's the overhead of getting responses from a representative group of users, and the time necessary to analyze the data (which is obviously dependent on how many questions you ask), so this can be somewhat quick and somewhat cheap, but isn't necessarily either of those. If you don't have experience in running a survey, your survey should be very short and you should do a little bit of reading up on survey best practices. The University of Wisconsin at Madison has some survey best practices for their service. (I'm not affiliated with them, I just think that this is a pretty good list of best practices.)
Each of these options has their strengths and weaknesses. You'll have to choose which one best meets your needs and can address the questions that you have in the time that you have available.