执行ValueEventListener时活动崩溃

时间:2019-02-16 17:09:34

标签: java android firebase firebase-realtime-database

每次我运行此活动时,我的应用都会由于某种原因而崩溃。正如我在调试模式下所发现的那样,问题似乎出在onStart方法上。

public class TimesListActivity extends AppCompatActivity {
private ListView listView;
DatabaseReference mDatabaseReference;
List<Message>messageList;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_times_list);
    listView = findViewById(R.id.list_view);
    mDatabaseReference = FirebaseDatabase.getInstance().getReference("messages");
    messageList = new ArrayList<Message>();

}

@Override
protected void onStart() {
    super.onStart();

    mDatabaseReference.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            for(DataSnapshot mDataSnapshot  : dataSnapshot.getChildren()) {
                Message message = mDataSnapshot.getValue(Message.class);
                messageList.add(message);
            }
            TimeMessageAdapter messageAdapter = new TimeMessageAdapter(TimesListActivity.this, messageList);
            listView.setAdapter(messageAdapter);
        }

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

执行活动时,崩溃日志将打印出以下内容     com.google.firebase.database.DatabaseException: Class com.example.[username].[app name].Message does not define a no-argument constructor. If you are using ProGuard, make sure these constructors are not stripped.

0 个答案:

没有答案