java - Android Shared Preference TinyDB putListObject 函数

Question

我正在尝试使用 TinyDB 的 putListObject 函数将对象列表保存到共享首选项，但我收到了 Wrong 2nd argument type 错误。我可以很好地使用 putObject 函数，错误仅在我使用 putListObject 函数时出现。

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玩家类别:

public class Player {

    private String name = "";
    private int score = 0;

    public Player(String name, int score) {
        this.name = name;
        this.score = score;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getScore() {
        return score;
    }

    public void setScore(int score) {
        this.score = score;
    }
}

putListObject 函数:

 public void putListObject(String key, ArrayList<Object> objArray){
        checkForNullKey(key);
        Gson gson = new Gson();
        ArrayList<String> objStrings = new ArrayList<String>();
        for(Object obj : objArray){
            objStrings.add(gson.toJson(obj));
        }
        putListString(key, objStrings);
    }

我是如何使用这个函数的:

ArrayList<Player> playerList = new ArrayList<Player>();

TinyDB tinydb = new TinyDB(this);
tinydb.putListObject("players", playerList);

我得到的错误:

putListObject (String java.util.ArrayList<java.lang.Object>) in TinyDB cannot be applied to (String java.util.ArrayList<com.example.package.Player>)

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帮助将不胜感激!

Answer 1

kcochibili TinyDB的开发者在github上回答了这个问题。他说，您必须在触发 putListObject 之前将自定义对象转换为对象。

放置自定义对象 ArrayList 的示例:

ArrayList<Player> players = new ArrayList<Player>();
ArrayList<Object> playerObjects = new ArrayList<Object>();

for(Player a : players){
    playerObjects.add((Object)a);
}

TinyDB tinydb = new TinyDB(this);
tinydb.putListObject("players", playerObjects);

此外，当您想从数据库中获取值时，它会给出 ArrayList< Object >。因此，您可能希望将它们转换回您的自定义对象。

一个示例:

TinyDB tinydb = new TinyDB(this);
ArrayList<Object> playerObjects = tinydb.getListObject("players", Player.class);
ArrayList<Player> players = new ArrayList<Player>();

for(Object objs : playerObjects){
    players.add((Player)objs);
}

您可以通过转换使用所有自定义对象。我更喜欢的另一种方法是，将所有自定义对象的 get 和 put 方法添加到 TinyDB 类中。例如:

public void putListPlayer(String key, ArrayList<Player> playerList){
    checkForNullKey(key);
    Gson gson = new Gson();
    ArrayList<String> objStrings = new ArrayList<String>();
    for(Player player: playerList){
        objStrings.add(gson.toJson(player));
    }
    putListString(key, objStrings);
}

//No need Class<?> mClass parameter. Because we know it is Player!
public ArrayList<Player> getListPlayer(String key){
    Gson gson = new Gson(); 

    ArrayList<String> objStrings = getListString(key);
    ArrayList<Player> playerList =  new ArrayList<Player>();

    for(String jObjString : objStrings){
        Player player  = gson.fromJson(jObjString,  Player.class);
        playerList.add(player);
    }
    return playerList;
}