方法 getParcelableExtra() 在创建意图时返回 null

Question

我在创建意图和使用 getParcelableExtra() 方法将对象移交给它时遇到问题。 该项目的目的是创建一个回收站视图。如果选择了来自回收商的项目，则会启动新的意图并应显示更详细的数据。

因为数据是从外部 MySQL 数据库中获取的，所以我使用 Volley 进行大部分网络工作。

回收器在 Volley onResponse() 方法中实现，该方法首先在应用程序启动 (onCreate) 时调用。至此，一切正常，回收站已正确加载并显示。

public class UserAreaActivity extends AppCompatActivity{

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_user_area);

    initializeRecycler();
}

    public void initializeRecycler() {

    operations.getFoodFromDB(getFoodID(), new IDatabaseOperations() {
        @Override
        public void onSuccess(final ArrayList<Food> food_list) {

            mRecyclerView = (RecyclerView) findViewById(R.id.recyclerView);
            mLayoutmanager = new LinearLayoutManager(UserAreaActivity.this);
            mAdapter = new FoodAdapter(food_list);
            mRecyclerView.setLayoutManager(mLayoutmanager);
            mRecyclerView.setAdapter(mAdapter);

            mAdapter.setOnItemClickListener(new FoodAdapter.OnItemClickListener() {
                @Override
                public void OnItemClick(int position) {
                    Intent intent = new Intent(UserAreaActivity.this, FoodProfile.class);
 GETS CORRECT OBJECT----->intent.putExtra("food", food_list.get(position));
                    startActivity(intent);
                }
            });

        }
    });

}

}

如您所见，我为 Volley onResponse 方法创建了一个名为 onSuccess 的接口。在这个方法中，我正在创建一个 onItemClickListener，这就是它变得丑陋的地方。 onItemClickListener 打开项目的更详细视图，但方法 getParcelableExtra() 返回 NULL。无论我做什么，它都不会返回 Food 类的对象。

public class FoodProfile extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(activity_food_profile);

    Food food = getIntent().getParcelableExtra("food");<----RETURNS NULL 


    String price = food.getPrice();
    String name = food.getName();
    String rating = ((Float)food.getRating()).toString();
    String imageRes = food.getmimgId();


    TextView mPrice = (TextView) findViewById(R.id.Price);
    mPrice.setText(price);
    TextView mName = (TextView) findViewById(R.id.Name);
    mName.setText(name);
    TextView mRating = (TextView) findViewById(R.id.Rating);
    mRating.setText(rating);

}

}

因此 putExtra() 可以按预期工作并获得正确的食物类对象。但是 getParcelableExtra() 每次都返回 NULL。因此，启动的意图中不会显示任何值。

食品类：

public class Food implements Parcelable {

public int id;
public String name;
public String category;
public String date;
public int vegan;
public int vegetarian;
public String price;
public String uuid;
public float rating;
public String mimgId;

public Food(int id, String name, String category, int vegan, int vegetarian, String price, String uuid, float rating, String mimgId){
    this.id = id;
    this.name = name;
    this.category = category;
    this.date = date;
    this.vegan = vegan;
    this.vegetarian = vegetarian;
    this.price = price;
    this.uuid = uuid;
    this.rating = rating;
    this.mimgId = mimgId;
}

protected Food(Parcel in) {
    id = in.readInt();
    name = in.readString();
    category = in.readString();
    date = in.readString();
    vegan = in.readInt();
    vegetarian = in.readInt();
    price = in.readString();
    uuid = in.readString();
    rating = in.readFloat();
    mimgId = in.readString();
}

public static final Creator<Food> CREATOR = new Creator<Food>() {
    @Override
    public Food createFromParcel(Parcel in) {
        return new Food(in);
    }

    @Override
    public Food[] newArray(int size) {
        return new Food[size];
    }
};

public int getId() {
    return id;
}

public String getName() {
    if(name != null) {
        name = name.replaceAll(System.getProperty("line.separator"), (""));
    }
    return name;
}

public String getDate() {
    return date;
}

public int isVegan() {
    return vegan;
}

public int isVegetarian() {
    return vegetarian;
}

public String getPrice() {
    return price;
}

public String getUuid() {
    return uuid;
}

public float getRating(){return rating;}

public String getmimgId() {
    return mimgId;
}

@Override
public int describeContents() {
    return 0;
}

@Override
public void writeToParcel(Parcel dest, int flags) {
    dest.writeString(price);
    dest.writeString(name);
    dest.writeString(((Float)rating).toString());
    dest.writeString(mimgId);

}
}

有人知道导致 getParcelableExtra() 返回 null 的原因吗？

提前感谢您的帮助！

Answer 1

正如我上面评论的那样，writeToParcel() 是有问题的。包裹应该按照相同的顺序读写。

请参考以下页面：

What is Parcelable in android

Using Parcelable

Understanding Androids Parcelable - Tutorial