如何修复这个RecyclerView代码？

Question

这是RecyclerView代码，但有一些错误。 请帮我把它变成一个有效的代码。 我对RecyclerView一无所知，所以对此的一个很好的解释也非常有用。

我需要的只是一个有效的RecyclerView。

MainActivity.java

package com.slack.weeklychallengeone;

import android.app.AlertDialog; import android.os.Bundle; import android.support.v7.app.AppCompatActivity; import android.support.v7.widget.LinearLayoutManager; import android.support.v7.widget.RecyclerView;

import com.slack.weeklychallengeone.Utils.Model; import com.slack.weeklychallengeone.Utils.MyAdapter;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

    private ArrayList<Model> mArrayList;
    private MyAdapter mAdapter;


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

        initViews();
        loadData();

    }


    private void initViews(){
        RecyclerView mRecyclerView = findViewById(R.id.recyler_view);
        mRecyclerView.setHasFixedSize(true);
        RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(this);
        mRecyclerView.setLayoutManager(layoutManager);
    }






    private void loadData(){

        mArrayList = new ArrayList<>();

        mArrayList.add(new Model("Constraint Layout"));
        mArrayList.add(new Model("Linear Layout"));
        mArrayList.add(new Model("Relative Layout"));
        mArrayList.add(new Model("Card View"));
        mArrayList.add(new Model("Scroll Views"));
        mArrayList.add(new Model("Grid View"));



        mAdapter = new MyAdapter(mArrayList);
        //mRecyclerViews.setAdapter(mAdapter);

    }



}

activity_main.xml中

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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=".MainActivity">


    <android.support.v7.widget.RecyclerView
        android:id="@+id/recyler_view"
        android:layout_width="match_parent"
        android:scrollbars="vertical"
        android:layout_height="match_parent">

    </android.support.v7.widget.RecyclerView>



</RelativeLayout>

MyAdapter.java

package com.slack.weeklychallengeone.Utils;

import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import com.slack.weeklychallengeone.R;

import java.util.ArrayList;

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {

    private ArrayList<Model> mArrayList;


    public MyAdapter(ArrayList<Model> mArrayList) {
        this.mArrayList = mArrayList;
    }

    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.row_layout, parent, false);
        return new MyViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
        holder.tv_name.setText(mArrayList.get(position).getName());
    }

    @Override
    public int getItemCount() {
        return mArrayList.size();
    }


    class MyViewHolder extends RecyclerView.ViewHolder{
        private TextView tv_name;
        MyViewHolder(View view) {
            super(view);

            tv_name = view.findViewById(R.id.tv_name);

        }
    }


}

row_layout.xml

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:card_view="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

        <TextView
            android:layout_marginBottom="4dp"
            android:layout_marginTop="4dp"
            android:padding="6dp"
            android:gravity="center_horizontal"
            android:id="@+id/tv_name"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textStyle="bold"
            android:textColor="@android:color/primary_text_light"
            android:textSize="18sp"
            android:text="Name or Title"/>


</LinearLayout>

Model.java

package com.slack.weeklychallengeone.Utils;

public class Model {
    private String name;

    public Model(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

}

Answer 1

您忘记将 Adapter 设置为 mRecyclerViews

检查 loadData() 方法

检查此行 //mRecyclerViews.setAdapter(mAdapter);

试试这个

private void loadData(){

        mArrayList = new ArrayList<>();

        mArrayList.add(new Model("Constraint Layout"));
        mArrayList.add(new Model("Linear Layout"));
        mArrayList.add(new Model("Relative Layout"));
        mArrayList.add(new Model("Card View"));
        mArrayList.add(new Model("Scroll Views"));
        mArrayList.add(new Model("Grid View"));



        mAdapter = new MyAdapter(mArrayList);
        mRecyclerViews.setAdapter(mAdapter);

    }

修改

您需要声明您的 mRecyclerView; 全球，例如 mArrayList 和 mAdapter

private ArrayList<Model> mArrayList;
private MyAdapter mAdapter;
RecyclerView mRecyclerView;

Answer 2

在您的代码mRecyclerView中未全局声明。请检查我的代码。希望这会有所帮助。

package com.slack.weeklychallengeone;

import android.app.AlertDialog; 
import android.os.Bundle; 
import android.support.v7.app.AppCompatActivity; 
import android.support.v7.widget.LinearLayoutManager; 
import android.support.v7.widget.RecyclerView;

import com.slack.weeklychallengeone.Utils.Model; 
import com.slack.weeklychallengeone.Utils.MyAdapter;

import java.util.ArrayList;

public class MainActivity extends AppCompatActivity {

    private ArrayList<Model> mArrayList;
    private MyAdapter mAdapter;
    RecyclerView mRecyclerView;

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

        initViews();
        loadData();
    }

    private void initViews(){
        mArrayList = new ArrayList<>();
        mRecyclerView = findViewById(R.id.recyler_view);
        mRecyclerView.setHasFixedSize(true);
        RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(this);
        mRecyclerView.setLayoutManager(layoutManager);
        mAdapter = new MyAdapter(mArrayList);
        mRecyclerViews.setAdapter(mAdapter);

    }

    private void loadData(){

        mArrayList = new ArrayList<>();

        mArrayList.add(new Model("Constraint Layout"));
        mArrayList.add(new Model("Linear Layout"));
        mArrayList.add(new Model("Relative Layout"));
        mArrayList.add(new Model("Card View"));
        mArrayList.add(new Model("Scroll Views"));
        mArrayList.add(new Model("Grid View"));

       mAdapter.notifyDataSetChanged()

    }
}