问为什么调试报告在单击微调器时会记录“尝试完成输入事件，但输入事件接收器已被释放”？

EN

package club.bms.keshav.readersreserve;

import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Spinner;

import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

import java.util.ArrayList;
import java.util.List;

public class TempActivity extends AppCompatActivity implements AdapterView.OnItemSelectedListener {
    private List<CharSequence> userList = new ArrayList<>();
    private ArrayAdapter<CharSequence> adapter;
    private Spinner spinner;
    private static final String TAG = "TempActivity";
    private String temp;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_temp);
        userList.clear();
        DatabaseReference rootReference = FirebaseDatabase.getInstance().getReference();
        rootReference.child(ConstantFields.DATABASE_USER_LIST).addValueEventListener(new ValueEventListener() {
            String temp;
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                for(DataSnapshot dataSnapshot1: dataSnapshot.getChildren())
                {
                    temp = dataSnapshot1.child(ConstantFields.DATABASE_USER_NAME).getValue(String.class);
                    userList.add(temp);
                }
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
            }
        });

        spinner = (Spinner) findViewById(R.id.tempSpinner);
        adapter = new ArrayAdapter<>(this, android.R.layout.simple_list_item_1, userList);
        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
        spinner.setAdapter(adapter);
        spinner.setPrompt("SELECT THE CURRENT HOLDER OF THE BOOK");
        Log.d(TAG, "onCreate: Adapter Set");
        spinner.setOnItemSelectedListener(this);
    }


    @Override
    public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
        Log.d(TAG, "onItemSelected: ");
    }

    @Override
    public void onNothingSelected(AdapterView<?> parent) {
        Log.d(TAG, "onNothingSelected: ");
    }
}

W/InputEventReceiver: Attempted to finish an input event but the input event receiver has already been disposed.