DatabaseException：无法将java.lang.String类型的对象转换为类型java.lang.String

Question

我的firebase数据结构

我的主要活动代码......

public class MainActivity extends AppCompatActivity {

ListView reviewListView;
DatabaseReference reviewDatabaseReference;
//FirebaseReview1 fr;
CustomReviewAdapter adapter;
ArrayList<UserReview> userReviews = new ArrayList<>();
TextView text;
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    try {
        reviewListView = (ListView) findViewById(R.id.reviewList);
        //reviewDatabaseReference = FirebaseDatabase.getInstance().getReference();
        //Query q = reviewDatabaseReference.child("Reviews").child("Mobile").child("Apple").child("iPhone 8 Plus").orderByChild("time");
        //fr = new FirebaseReview1(q);

        adapter = new CustomReviewAdapter(this,retrieve());
        reviewListView.setAdapter(adapter);


    }catch (Exception e){
        Toast.makeText(getApplicationContext(),e.toString(),Toast.LENGTH_SHORT).show();
    }

}


private void fetchReviewData(DataSnapshot dataSnapshot){
    try{
    userReviews.clear();
    for(DataSnapshot ds: dataSnapshot.getChildren()){
        UserReview userReview1 = ds.getValue(UserReview.class);
        userReviews.add(userReview1);
    }}catch (Exception e){
        text = (TextView)findViewById(R.id.text);
        text.setText(e.toString());
        Toast.makeText(getApplicationContext(),e.toString(),Toast.LENGTH_SHORT).show();
    }
}
public ArrayList<UserReview> retrieve()
{
    try {
        reviewDatabaseReference = FirebaseDatabase.getInstance().getReference();
        Query q = reviewDatabaseReference.child("Reviews").child("Mobile").child("Apple").child("iPhone 8 Plus").orderByChild("time");
        q.addChildEventListener(new ChildEventListener() {
            @Override
            public void onChildAdded(DataSnapshot dataSnapshot, String s) {
                fetchReviewData(dataSnapshot);
            }

            @Override
            public void onChildChanged(DataSnapshot dataSnapshot, String s) {
                fetchReviewData(dataSnapshot);
            }

            @Override
            public void onChildRemoved(DataSnapshot dataSnapshot) {

            }

            @Override
            public void onChildMoved(DataSnapshot dataSnapshot, String s) {

            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });
    }catch (Exception e){
        Toast.makeText(getApplicationContext(),e.toString(), Toast.LENGTH_SHORT).show();
    }
    return userReviews;
}

我的UserReview类

public class UserReview {
String phone;
String name;
String rate;
String title;
String review;
String time;

public UserReview(){}
public UserReview(String phone,String name,String rate,String title,String review,String time){
    this.phone = phone;
    this.name = name;
    this.rate = rate;
    this.title = title;
    this.review = review;
    this.time = time;
}
public String getPhone() { return phone; }
public String getName() {
    return name;
}
public String getRate() {return rate;}
public String getTitle() {
    return title;
}
public String getReview() {
    return review;
}
public String getTime() {return time;}
}

我的CustomeAdapter

public class CustomReviewAdapter extends BaseAdapter{

Context c;
ArrayList<UserReview> userReviews;

public CustomReviewAdapter(Context c, ArrayList<UserReview> userReviews){
    this.c = c;
    this.userReviews = userReviews;
}

@Override
public int getCount() {
    return userReviews.size();
}

@Override
public Object getItem(int position) {
    return userReviews.get(position);
}

@Override
public long getItemId(int position) {
    return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {

    if(convertView == null){
        convertView = LayoutInflater.from(c).inflate(R.layout.review_list,parent,false);
    }
    TextView starTextView = (TextView)convertView.findViewById(R.id.starTextView);
    TextView titleTextView = (TextView)convertView.findViewById(R.id.titleTextView);
    TextView nameTextView = (TextView)convertView.findViewById(R.id.nameTextView);
    TextView reviewTextView = (TextView)convertView.findViewById(R.id.reviewTextView);

    UserReview ur = (UserReview)this.getItem(position);

    starTextView.setText(ur.getRate());
    titleTextView.setText(ur.getTitle());
    nameTextView.setText(ur.getName());
    reviewTextView.setText(ur.getReview());

    return convertView;
}
}

我正在尝试检索数据，但却出错

  

DatabaseException：无法将java.lang.String类型的对象转换为类型java.lang.String以键入

Answer 1

由于您正在收听onChildAdded，因此快照中只包含一个孩子。因此，fetchData并不需要遍历快照的孩子。

private void fetchReviewData(DataSnapshot dataSnapshot){
    UserReview userReview = dataSnapshot.getValue(UserReview.class);
    userReviews.add(userReview);
}