设备长时间休眠时Android是否会删除局部变量？

Question

In my app i keep some data in local variables and sometimes after opening the app from sleep it reports a null pointer exception on local variable, which was existing before the device went to sleep. Is it possible that the system deletes these variables and how can i resolve this problem?

Answer 1

Probably you meant class fields, instead of local variables. In Android system View Life Cycle views such as Activities and Fragments can be destroyed if system needs more memory and application is in background. When it happens few methods are called. For example when activity is going to be cleared onPause(), onStop() and onDestroy() are called ( more ). You can override these methods and save current application state in SharedPreferences or in database.

Also you would need to check if you are not creating new Activity, if such happens, fields will be empty.