第一次运行 Room DB 查询会导致 Activity / Fragment onDestroy()

Question

当我的应用程序运行时，StartFragment 在我的 Room DB 上运行 LiveData 查询以获取 PersonId。第一次数据库调用似乎创建/打开数据库，但 LiveData onChanged() 从未被调用，然后 StartFragment 和 StartActivity 都被销毁。但是在 LogCat 中解释这个没有错误。应用程序自动重启并按预期运行，查询将值返回给 onChanged()。在我的 LogCat 的输出之下。

StartActivity onCreate()
StartFragment onCreate()
StartFragment onCreateView()
StartFragment onStart()
StartFragment queryPersonId()
StartFragmentViewModel queryPersonId_LD()
MyAppDatabase getDatabase()
MyAppDatabase getDatabase() Creating new DB instance...
MyAppDatabase DB INSTANCE not null
MyAppDatabase onOpen()
StartFragment onDestroyView()    <=== why does this happen?
StartFragment onDestroy()
StartActivity onDestroy()
...
app restarts
...
StartActivity onCreate()
StartFragment onCreate()
StartFragment onCreateView()
StartFragment onStart()
StartFragment queryPersonId()
StartFragmentViewModel queryPersonId_LD()
MyAppDatabase getDatabase()     <=== DB instance already created and opened
StartFragment queryPersonId().onChanged(), personId = 1  <== why don't come here above?
...

我的代码如下：

StartFragment.class

private void queryPersonId() {
    mViewModel.queryPersonId_LD().observe(getViewLifecycleOwner(), new Observer<Long>() {
        @Override
        public void onChanged(@Nullable Long personId) {
            // Don't come here first time, but do second time.
        });
    }
}

StartFragmentViewModel.class

public LiveData<Long> queryPersonId_LD() {
    MyRepo repo = new MyRepo(getApplication());
    return repo.getPersonId();
}

MyRepo.class

public MyRepo(Application application) {
    super();
    MyAppDatabase db = MyAppDatabase.getDatabase(application);
    dao = db.getPersonIdDao();
}
public LiveData<Long> getPersonId() {
    return dao.getPersonId();
}

MyAppDatabase.class

if (DB_INSTANCE == null) {
    synchronized (MyAppDatabase.class) {
        if (DB_INSTANCE == null) {
            LogUtil.msg("getDatabase() Creating new DB instance...");
            DB_INSTANCE = Room.databaseBuilder(context.getApplicationContext(),
                    MyAppDatabase.class, Constants.DB_NAME)
                    .addCallback(rdc)
                    .build();
        }
    }
}