Android应用程序因NPE而崩溃

I've made a question and answer application using Android Studio, however it keeps crashing. There are no errors shown on the side (it flags up green), but it crashes after the first time I try and submit an answer. I've found out that it's thrown a null pointer exception in the onClick method. I've had a look about and tried the solutions I could find but have been unable to fix this error so far. Below is the code from the crashing page. Any help would be appreciated.I've made a question and answer application usi