Question

当我在Recycler视图中添加新数据项（从Activity to activity获取）时，当前项目已丢失。插入新项目后如何不丢失回收站视图中的当前数据？谢谢。

更新

这是我的代码：

import android.content.Context;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.StaggeredGridLayoutManager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;

public class RecyclerActivity extends AppCompatActivity implements     View.OnClickListener{
    private RecyclerView listRecyclerView;
    private StaggeredGridLayoutManager gaggeredGridLayoutManager;
    private List<GetItemData> getItemDataList = new ArrayList<>();
    private Button btnBack;
    private MyAdapter myAdapter;
    final int[] mfp_photo = {R.drawable.dg, R.drawable.er, R.drawable.ib,
        R.drawable.m, R.drawable.md, R.drawable.mk, R.drawable.r, R.drawable.rf,
        R.drawable.rn, R.drawable.sm};
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_view);
        listRecyclerView = (RecyclerView) findViewById(R.id.recycler_view);
        listRecyclerView.setHasFixedSize(true);

        gaggeredGridLayoutManager = new StaggeredGridLayoutManager(2,StaggeredGridLayoutManager.VERTICAL);
        listRecyclerView.setLayoutManager(gaggeredGridLayoutManager);
        Bundle bundle = getIntent().getExtras();
        GetItemData getItemData = new GetItemData(bundle.getString("Name"), bundle.getString("Age"), bundle.getString("Date of Birth"),
                bundle.getString("Address"), bundle.getString("Gender"), bundle.getInt("list_length"));
            myAdapter = new MyAdapter(getItemDataList, this);
            myAdapter.addItem(getItemData);

        listRecyclerView.setAdapter(myAdapter);
        btnBack = (Button) findViewById(R.id.buttonBack);
        btnBack.setOnClickListener(this);

    }

    @Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.buttonBack:
                Intent intent = new Intent(this, new MainActivity().getClass());
                startActivity(intent);
                break;
            default:break;
        }
    }

    class MyViewHolder extends RecyclerView.ViewHolder {
        public ImageView fp_photo;
        public TextView fp_name;
        public MyViewHolder(View itemView) {
            super(itemView);
            fp_name = (TextView) itemView.findViewById(R.id.fp_name);
            fp_photo = (ImageView) itemView.findViewById(R.id.fp_photo);

        }
    }

    class MyAdapter extends RecyclerView.Adapter<MyViewHolder> {
        Context context;
        private List<GetItemData> getItemDataList_Adapter;

        public MyAdapter(List<GetItemData> getItemDataList_Adapter, Context context) {
            super();
            this.context = context;
            this.getItemDataList_Adapter = getItemDataList_Adapter;

        }

        @Override
        public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            if (parent.getTag() != null) {
                return (MyViewHolder)(parent.getTag());
            } else {
                View view = LayoutInflater.from(context).inflate(R.layout.cardview, parent, false);
                MyViewHolder viewHolder = new MyViewHolder(view);
                return viewHolder;
            }
        }

        @Override
        public void onBindViewHolder(MyViewHolder holder,int position) {
            Random rand = new Random();
            int _rpositon = rand.nextInt(mfp_photo.length);


            holder.fp_photo.setImageResource(mfp_photo[position]);
            holder.fp_name.setText(getItemDataList_Adapter.get(position).getName());

        }

        @Override
        public int getItemCount() {
            return getItemDataList_Adapter.size();
        }
        public void addItem(GetItemData Data) {
            getItemDataList_Adapter.add(Data);
            notifyDataSetChanged();

        }

    }
}

从MainActivity获取数据到此活动，但是当我向RecylerView添加新项目时，现有项目已丢失。

Answer 1

我相信您希望将class.getResource(path)设为全局变量，以使其值可在各个活动中使用。在Android术语中，您试图拥有List<GetItemData> getItemDataList

的应用程序上下文

为此，首先创建一个Application类，例如MyApp.java，

getItemDataList

现在，将此类添加为清单

中的应用程序标记

public class MyApp extends Application {

    private ArrayList<ItemData> dataList;

    public ArrayList<ItemData> getDataList() {
        return dataList;
    }

    public void setDataList(ArrayList<ItemData> dataList) {
        this.dataList = dataList;
    }

    public void addData(ItemData data){
        if(dataList == null){
            dataList = new ArrayList<>();
        }

        dataList.add(data);
    }
}

android:name

在MainActivity中：

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.tony.myapp">

    <application
        android:name=".MyApp"
        .....>

然后，您在RecyclerActivity中需要做的就是，

ItemData itemData = new ItemData("John Doe", "16", 
                                    "15 July 2000",
                                    "Address", "Male", 10);
MyApp myApp = (MyApp) getApplicationContext();
myApp.addData(itemData);

// Logic for going to RecyclerActivity here. 
// No need to pass getItemData as a bundle.

建议

看起来你的Java命名约定已经搞砸了。例如，类和变量名应始终为名词，绝不使用动词。有关详细信息，请参阅Naming Conventions。

插入新项目后如何不丢失回收站视图中的当前数据

更新

1 个答案:

建议