如何初始化存储在另一个活动中的 Pojo 类中的数组列表? [英] How to initialize arraylist which store in a Pojo class in another activity?

问题描述

我想将数据存储在一个ArrayList中并在另一个类中访问它，但是当我访问arraylist时，arraylist.size()是0.意味着我没有访问同一个数组列表.有人请告诉我我做错了什么.

I want to store the data in a ArrayList and access it in another class,but when when I access the arraylist,the arraylist.size() is 0.Means I didn't access the same arraylist. Somebody please tell me what I doing wrong.

这是我的 POJO 课程

Here is my POJO class

public class item {
   private String name;
   private String body;
   private String profileImage;

public Item(){

}

public Item(String body,String name,String profileImage){
  this.body = body;
  this.name = name;
  this.profileImage = profileImage;
}
//Getter and setter

这是我如何将数据存储在 Class A 中，我检查了它是否成功地将其插入到数组列表中.

Here is how I store the data in Class A,which I checked,is successfully insert it to the arraylist.

A级

 List<Item> items = new ArrayList<>();
 Item item = new Item();
 item.setBody(body);
 item.setName(name);
 item.setProfileImage(profileImage);
 items.add(item);

问题出在Class B，当我访问item.size()时，它返回值0，这意味着我没有访问同一个arraylist.

The problem is in Class B when I access the item.size() it return value 0,means that I didnt access to the same arraylist.

这是我在B班中所做的

List<Item>items = new ArrayList<>();
Log.d("ListSize",String.valueOf(items.size()));

我之前在 RecycleView 中尝试过这个，但这不起作用，因为我的 B 类是 Fragment 活动

I tried this which I done in RecycleView before,but this doesnt work,cause my Class B is a Fragment activity

public Class B(Context mContext, List<Item> items) {
    this.mContext = mContext;
    this.items = items;
}

那么，我在 Class B 中的 Class A 中初始化将数据保存到的 arraylist 的正确方法是什么?

So what is the correct way for me initialize the arraylist which I save data to in Class A in Class B?

推荐答案

像这样改变类:

public class Item implements Parcelable{
   private String name;
   private String body;
   private String profileImage;

public Item(){

}

public Item(Parcel in) {
            name = in.readString();
            body = in.readString();
            profileImage = in.readString();
        }


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


        @Override
        public void writeToParcel(Parcel dest, int flags) {
            dest.writeString(name);
            dest.writeString(body);
            dest.writeString(profileImage);
        }

        @SuppressWarnings("unused")
        public static final Parcelable.Creator<Item> CREATOR = new Parcelable.Creator<Item>() {
            @Override
            public Item createFromParcel(Parcel in) {
                return new Item(in);
            }

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


public Item(String body,String name,String profileImage){
  this.body = body;
  this.name = name;
  this.profileImage = profileImage;
}

现在在A班:

ArrayList<Item> mDATA = new ArrayList<>();

/******   add values in array list  ****/

                Intent i = new Intent(CLASS_A.this, CLASS_B.class);
                i.putParcelableArrayListExtra("ARRAY_DATA", mDATA);
                startActivity(i);

现在在 B 类，获取列表:

Now in Class B, get list:

Intent intent = getIntent();
    ArrayList<Item> mDATAFROMA = new ArrayList<>();
     try {
                    mDATAFROMA = intent.getParcelableArrayListExtra("ARRAY_DATA");
                    Log.d("ListSize",String.valueOf(mDATAFROMA.size()));
                } catch (Exception e) {
                    e.printStackTrace();
                }

对于片段传递，例如:

Bundle args = new Bundle();
        args.putParcelableArrayList("GET_LIST", (ArrayList<? extends Parcelable>) mDATA);
        fragmentDemo.setArguments(args);

在片段获取中:

ArrayList<Item> mDATAFROMA = new ArrayList<>(); 

@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Bundle pb=getArguments();
        mDATAFROMA = pb.getParcelableArrayList("GET_LIST"); 
    }

这篇关于如何初始化存储在另一个活动中的 Pojo 类中的数组列表?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！