我应该如何在 Firebase 实时数据库中设置作为键值类型的 getter 和 setter？

Question

我有这个 Firebase 实时数据库

当我想显示它时出现错误：

com.google.firebase.database.DatabaseException：无法将 java.util.ArrayList 类型的值转换为字符串

如果数据库中没有 "players" 子项，则显示效果很好。错误在此行event = ds.getValue(Event.class); 中的MyEvents.java 类中。 这是我的 Event.java 类，带有 getter、setter 和构造函数

package com.example.vilniausfutbolas;

import com.google.firebase.database.IgnoreExtraProperties;

@IgnoreExtraProperties
public class Event {

    public String team_name;
    public String date;
    public String time;
    public String location;
    public Integer quantity;
    public Double price;
    public String additional;
    public String players;
    public String refused_players;
    public String event_id;

    public Event() {
        // Default constructor required for calls to DataSnapshot.getValue(Event.class)
    }

    public Event(String userId, String team_name, String date, String time, String location, Integer quantity, Double price, String additional, String players, String refused_players, String event_id) {

        this.team_name = team_name;
        this.date = date;
        this.time = time;
        this.location = location;
        this.quantity = quantity;
        this.price = price;
        this.additional = additional;
        this.players = players;
        this.refused_players = refused_players;
        this.event_id = event_id;
    }


    public String getTeam_name() {
        return team_name;
    }

    public void setTeam_name(String team_name) {
        this.team_name = team_name;
    }

    public String getDate() {
        return date;
    }

    public void setDate(String date) {
        this.date = date;
    }

    public String getTime() {
        return time;
    }

    public void setTime(String time) {
        this.time = time;
    }

    public String getLocation() {
        return location;
    }

    public void setLocation(String location) {
        this.location = location;
    }

    public Integer getQuantity() {
        return quantity;
    }

    public void setQuantity(Integer quantity) {
        this.quantity = quantity;
    }

    public Double getPrice() {
        return price;
    }

    public void setPrice(Double price) {
        this.price = price;
    }

    public String getAdditional() {
        return additional;
    }

    public void setAdditional(String additional) {
        this.additional = additional;
    }

    public String getPlayers() {
        return players;
    }

    public void setPlayers(String players) {
        this.players = players;
    }

    public String getRefused_players() {
        return refused_players;
    }

    public void setRefused_players(String refused_players) {
        this.refused_players = refused_players;    }

    public String getEvent_id() {
        return event_id;
    }

    public void setEvent_id(String event_id) {
        this.event_id = event_id;
    }
}

所以我想问题是由于错误而正确设置players getter 和 setter。或者也许还有其他方法可以处理players 子对象，我可以在一个对象中显示event，并使用Event.java 类的一个构造函数？

也许我应该为players 孩子创建单独的课程？

Answer 1

在您的数据库中，players 字段是 list，而不是 String。因此，您应该在 Event.java 模型类中将 players 声明为一个列表，如下所示： public List<String> players;
然后在您的构造函数中替换相同的内容。然后用这段代码替换getter和setter：

public List<String> getPlayers() {
   return players;
}

public void setPlayers(List<String> players) {
    this.players = players;
}

或者，最好让 Android Studio 自动生成构造函数、getter 和 setter。