java - 创建 Intent 时，方法 getParcelableExtra() 返回 null

Question

我在创建 Intent 以及使用 getParcelableExtra() 方法将对象移交到该对象时遇到问题。该项目的目标是创建回收者 View 。如果选择了回收器中的某个项目，则会启动新 Intent 并应显示更详细的数据。

因为数据是从外部 MySQL 数据库获取的，所以我使用 Volley 来处理大部分网络内容。

回收器是在 Volley onResponse() 方法内实现的，该方法首先在应用程序启动 (onCreate) 时调用。到目前为止，一切正常，回收器已加载并正确显示。

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(interface)。在这个方法中，我创建了一个 onItemClickListener，这就是它变得丑陋的地方。onItemClickListener 打开项目的更详细 View ，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() 按预期工作并获取食物类的正确对象。但 getParcelableExtra() 每次都返回 NULL。因此启动 Intent 中不会显示任何值。

食品类别:

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);

}
}

有人知道是什么导致 getParcelableExtra() 返回 null 吗？

提前感谢您的帮助!

Answer 1

正如我上面评论的，writeToParcel() 是有问题的。包裹的写入和读取顺序应相同。

请引用以下页面:

What is Parcelable in android

Using Parcelable

Understanding Androids Parcelable - Tutorial