如何通过按钮删除recyclerview适配器中的最后一项？

Question

我有一个 recyclerview，当我单击一个不在 recyclerview 中的按钮时，我想删除其中的最后一项。我想删除该项目并通知适配器该项目已删除，以便我可以输入另一个项目。顺便说一句，我输入的项目是通过edittext和一个按钮。

activity_main.xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.brecyclerview.MainActivity"
    android:orientation="vertical">

    <EditText
        android:id="@+id/edit_ten"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10"
        android:hint="Score"
        android:inputType="numberSigned|number" />

    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

        <Button
            android:id="@+id/btn_add"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:onClick="btn_add"
            android:text="Add"
            tools:ignore="OnClick" />

        <Button
            android:id="@+id/btn_undo"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:onClick="btn_undo"
            android:text="Undo"
            tools:ignore="OnClick" />

        <Button
            android:id="@+id/btn_new"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:onClick="btn_new"
            android:text="New Game" />
    </LinearLayout>

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recycleViewContainer"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentStart="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        tools:itemCount="8" />

</LinearLayout>

list_item.xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <RelativeLayout
        android:id="@+id/singleRow"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="8dp">

        <ImageView
            android:id="@+id/userImg"
            android:src="@mipmap/ic_launcher"
            android:layout_width="60dp"
            android:layout_height="60dp" />

        <TextView
            android:id="@+id/pNametxt"
            android:text="User Name"
            android:textSize="20sp"
            android:layout_marginTop="6dp"
            android:maxLines="1"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_alignParentTop="true"
            android:layout_toRightOf="@+id/userImg"
            android:layout_toEndOf="@+id/userImg"
            android:layout_marginLeft="8dp"
            android:layout_marginStart="8dp" />

    </RelativeLayout>

    <View
        android:layout_below="@+id/singleRow"
        android:layout_width="match_parent"
        android:layout_height="1dp"
        android:background="#f2f2f2" />

</RelativeLayout>

MainActivity.java：

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {
    int total = 0;
    Button button;
    Button button1;
    Button button2;
    EditText editText;
    TextView personName;
    RecyclerView recyclerView;
    RecyclerView.Adapter mAdapter;
    RecyclerView.LayoutManager layoutManager;

    List<PersonUtils> personUtilsList;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button = (Button)findViewById(R.id.btn_add);
        button1 = (Button)findViewById(R.id.btn_undo);
        button2 = (Button)findViewById(R.id.btn_new);
        editText = (EditText)findViewById(R.id.edit_ten);
        personName = (TextView)findViewById(R.id.pNametxt);

        recyclerView = (RecyclerView) findViewById(R.id.recycleViewContainer);
        recyclerView.setHasFixedSize(true);
        layoutManager = new LinearLayoutManager(getApplicationContext());
        recyclerView.setLayoutManager(layoutManager);
        personUtilsList = new ArrayList<>();
        mAdapter = new CustomRecyclerAdapter(this, personUtilsList);

        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (v == button2) {
                    MainActivity.this.finish();

                    startActivity(new Intent(MainActivity.this, MainActivity.class));
                }}});

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                for (int i = 0; i<personUtilsList.size(); i++)
                {
                    total = personUtilsList.get(i).getPersonName();
                }
                total += Integer.parseInt(editText.getText().toString());

                personUtilsList.add(new PersonUtils(total));
                recyclerView.setAdapter(mAdapter);
                mAdapter.notifyDataSetChanged();
                editText.setText("");
            }});
        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                for (int i = 0; i<personUtilsList.size(); i++)
                {

                    personUtilsList.remove(i).getPersonName();
                personUtilsList.remove(new PersonUtils(total));
                recyclerView.setAdapter(mAdapter);
                mAdapter.notifyDataSetChanged();
            }}
        });
    }}

CustomRecyclerAdapter.java：

import android.content.Context;
import android.preference.PreferenceScreen;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;

import androidx.recyclerview.widget.RecyclerView;

import java.util.List;

public class CustomRecyclerAdapter extends RecyclerView.Adapter<CustomRecyclerAdapter.ViewHolder> {
    private Context context;
    private List<PersonUtils> personUtils;

    public CustomRecyclerAdapter(Context context, List personUtils) {
        this.context = context;
        this.personUtils = personUtils;
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.list_item, parent, false);
        ViewHolder viewHolder = new ViewHolder(v);
        return viewHolder;
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        holder.itemView.setTag(personUtils.get(position));

        PersonUtils pu = personUtils.get(position);

       holder.pName.setText(String.valueOf(pu.getPersonName()));
    }

    @Override
    public int getItemCount() {
        return (personUtils.size()>8)?8:personUtils.size();
    }

    public static class ViewHolder extends RecyclerView.ViewHolder{
        public TextView pName;
        final Button deleteButton;

        public ViewHolder(final View itemView) {
            super(itemView);

            pName = (TextView) itemView.findViewById(R.id.pNametxt);
            deleteButton = (Button) itemView.findViewById(R.id.btn_undo);
        }
}}

PersonUtils.java：

public class PersonUtils {
    private Integer personName;

    public static void remove(int index) {
    }

    public Integer getPersonName() {
        return personName;
    }

    public void setPersonName(Integer personName) {
        this.personName = personName;
    }

    public PersonUtils(Integer personName) {
        this.personName = personName;
    }
}

我希望删除 recyclerview 中的最后一项（整数）并通知适配器，以便我可以在需要时编辑该值。

Answer 1

您可以在适配器中添加一个方法来删除列表中的最后一项：

public ViewHolder removeLastItem() {
    if (personUtils == null || personUtils.isEmpty()) return;

    personUtils.removeAt(personUtils.getSize()-1);
    notifyDataSetChanged();
}

当按钮被点击时，只需调用：

adapter.removeLastItem()

Answer 2

检查您是否在最后一个索引中，然后删除该项目并使用notifyItemRemoved 通知任何注册的观察者：

if(currentPosition == 0){
   listOfItems.removeAt(currentPosition)

   notifyItemRemoved(currentPosition)  
}