Java 我的应用程序在使用RecyclerView时崩溃

我的应用程序在尝试加载列表后立即崩溃，我搜索并发现一些应用程序出现错误，因为它们没有，但我有：

implementation 'com.android.support:recyclerview-v7:28.0.0-alpha3'
implementation 'com.android.support:cardview-v7:28.0.0-alpha3'

以下是我得到的错误代码：

E/AndroidRuntime: FATAL EXCEPTION: main
              Process: com.yemencar.yemencar, PID: 28558
              java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView$Adapter.notifyDataSetChanged()' on a null object reference
                  at com.yemencar.yemencar.homepageActivity.parseData(homepageActivity.java:144)
                  at com.yemencar.yemencar.homepageActivity.access$000(homepageActivity.java:26)
                  at com.yemencar.yemencar.homepageActivity$1.onResponse(homepageActivity.java:95)
                  at com.yemencar.yemencar.homepageActivity$1.onResponse(homepageActivity.java:91)
                  at com.android.volley.toolbox.JsonRequest.deliverResponse(JsonRequest.java:65)
                  at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:99)
                  at android.os.Handler.handleCallback(Handler.java:789)
                  at android.os.Handler.dispatchMessage(Handler.java:98)
                  at android.os.Looper.loop(Looper.java:164)
                  at android.app.ActivityThread.main(ActivityThread.java:6541)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
E/Surface: queueBuffer: error queuing buffer to SurfaceTexture, -19
E/EGL_emulation: tid 28589: swapBuffers(550): error 0x300d (EGL_BAD_SURFACE)

我正在尝试使用标题创建RecyclerView，这样我就可以放置排序选项并以网格或列表选项的形式查看。这是我的主页活动代码：

package com.yemencar.yemencar;

import android.os.Bundle;
import android.support.v4.view.ViewCompat;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.View;
import android.widget.ProgressBar;
import android.widget.Toast;

import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonArrayRequest;
import com.android.volley.toolbox.Volley;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

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

public class homepageActivity extends AppCompatActivity implements RecyclerView.OnScrollChangeListener {

    //Creating a List of superheroes
    private List<SuperHero> listSuperHeroes;

    //Creating Views
    private RecyclerView recyclerView;
    private RecyclerView.LayoutManager layoutManager;
    private RecyclerView.Adapter adapter;

    //Volley Request Queue
    private RequestQueue requestQueue;

    //The request counter to send ?page=1, ?page=2  requests
    private int requestCount = 1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_homepage);
        ViewCompat.setLayoutDirection(getWindow().getDecorView(),ViewCompat.LAYOUT_DIRECTION_RTL);

        //Initializing Views
        recyclerView = (RecyclerView) findViewById(R.id.recyclerView);
        recyclerView.setHasFixedSize(true);
        layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);

        //Initializing our superheroes list
        listSuperHeroes = new ArrayList<>();
        requestQueue = Volley.newRequestQueue(this);

        //Calling method to get data to fetch data
        getData();

        //Adding an scroll change listener to recyclerview
        recyclerView.setOnScrollChangeListener(this);

        //initializing our adapter
        CardAdapter adapter = new CardAdapter(getHeader(),listSuperHeroes, this);

        //Adding adapter to recyclerview
        recyclerView.setAdapter(adapter);
    }

    public  Header getHeader()
    {
        Header header = new Header();
        header.setHeader("I'm header");
        return header;
    }

    //Request to get json from server we are passing an integer here
    //This integer will used to specify the page number for the request ?page = requestcount
    //This method would return a JsonArrayRequest that will be added to the request queue
    private JsonArrayRequest getDataFromServer(int requestCount) {
        //Initializing ProgressBar
        final ProgressBar progressBar = (ProgressBar) findViewById(R.id.progressBar1);

        //Displaying Progressbar
        progressBar.setVisibility(View.VISIBLE);
        setProgressBarIndeterminateVisibility(true);

        //JsonArrayRequest of volley
        JsonArrayRequest jsonArrayRequest = new JsonArrayRequest(Config.DATA_URL + String.valueOf(requestCount),
                new Response.Listener<JSONArray>() {
                    @Override
                    public void onResponse(JSONArray response) {
                        //Calling method parseData to parse the json response
                        parseData(response);
                        //Hiding the progressbar
                        progressBar.setVisibility(View.GONE);
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        progressBar.setVisibility(View.GONE);
                        //If an error occurs that means end of the list has reached
                        Toast.makeText(homepageActivity.this, "No More Items Available", Toast.LENGTH_SHORT).show();
                    }
                });

        //Returning the request
        return jsonArrayRequest;
    }

    //This method will get data from the web api
    private void getData() {
        //Adding the method to the queue by calling the method getDataFromServer
        requestQueue.add(getDataFromServer(requestCount));
        //Incrementing the request counter
        requestCount++;
    }

    //This method will parse json data
    private void parseData(JSONArray array) throws RuntimeException {
        for (int i = 0; i < array.length(); i++) {
            //Creating the superhero object
            SuperHero superHero = new SuperHero();
            JSONObject json = null;
            try {
                //Getting json
                json = array.getJSONObject(i);

                //Adding data to the superhero object
                superHero.setImageUrl(json.getString(Config.TAG_IMAGE_URL));
                superHero.setName(json.getString(Config.TAG_NAME));
                superHero.setPublisher(json.getString(Config.TAG_PUBLISHER));
            } catch (JSONException e) {
                e.printStackTrace();
            }
            //Adding the superhero object to the list
            listSuperHeroes.add(superHero);
        }
        //Notifying the adapter that data has been added or changed
        Log.d("ADebugTag", "Value: " + listSuperHeroes);

        adapter.notifyDataSetChanged();
    }

    //This method would check that the recyclerview scroll has reached the bottom or not
    private boolean isLastItemDisplaying(RecyclerView recyclerView) {
        if (recyclerView.getAdapter().getItemCount() != 0) {
            int lastVisibleItemPosition = ((LinearLayoutManager) recyclerView.getLayoutManager()).findLastCompletelyVisibleItemPosition();
            if (lastVisibleItemPosition != RecyclerView.NO_POSITION && lastVisibleItemPosition == recyclerView.getAdapter().getItemCount() - 1)
                return true;
        }
        return false;
    }

    //Overriden method to detect scrolling
    @Override
    public void onScrollChange(View v, int scrollX, int scrollY, int oldScrollX, int oldScrollY) {
        //Ifscrolled at last then
        if (isLastItemDisplaying(recyclerView)) {
            //Calling the method getdata again
            getData();
        }
    }
}

package com.yemencar.yemencar；
导入android.os.Bundle；
导入android.support.v4.view.ViewCompat；
导入android.support.v7.app.AppActivity；
导入android.support.v7.widget.LinearLayoutManager；
导入android.support.v7.widget.RecyclerView；
导入android.util.Log；
导入android.view.view；
导入android.widget.ProgressBar；
导入android.widget.Toast；
导入com.android.volley.RequestQueue；
导入com.android.volley.Response；
导入com.android.volley.VolleyError；
导入com.android.volley.toolbox.JsonArrayRequest；
导入com.android.volley.toolbox.volley；
导入org.json.JSONArray；
导入org.json.JSONException；
导入org.json.JSONObject；
导入java.util.ArrayList；
导入java.util.List；
公共类homepageActivity扩展AppCompatActivity实现RecyclerView.OnScrollChangeListener{
//创建超级英雄列表
私人名单超级英雄；
//创建视图
私人回收站；
private RecyclerView.LayoutManager LayoutManager；
专用循环视图适配器；
//截击请求队列
私有请求队列请求队列；
//发送请求的请求计数器？page=1，？page=2请求
private int requestCount=1；
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity_主页）；
ViewCompat.setLayoutDirection（getWindow（）.getDecorView（），ViewCompat.LAYOUT\u DIRECTION\u RTL）；
//初始化视图
recyclerView=（recyclerView）findViewById（R.id.recyclerView）；
recyclerView.setHasFixedSize（true）；
layoutManager=新的LinearLayoutManager（此）；
recyclerView.setLayoutManager（layoutManager）；
//正在初始化我们的超级英雄列表
ListSuperheros=newArrayList（）；
requestQueue=Volley.newRequestQueue（this）；
//调用方法获取数据以获取数据
getData（）；
//向recyclerview添加滚动更改侦听器
recyclerView.setOnScrollChangeListener（此）；
//初始化适配器
CardAdapter=新的CardAdapter（getHeader（），ListSuperheros，this）；
//向recyclerview添加适配器
recyclerView.setAdapter（适配器）；
}
公共头getHeader（）
{
页眉=新页眉（）；
header.setHeader（“我是header”）；
返回头；
}
//请求从服务器获取json我们在这里传递一个整数
//此整数将用于指定请求的页码？page=requestcount
//此方法将返回将添加到请求队列的JsonArrayRequest
私有JsonArrayRequest getDataFromServer（int requestCount）{
//初始化进度条
最终ProgressBar ProgressBar=（ProgressBar）findViewById（R.id.progressBar1）；
//显示进度条
progressBar.setVisibility（View.VISIBLE）；
SetProgressBarInDeterminateVibility（真）；
//JsonArrayRequest截击
JsonArrayRequest JsonArrayRequest=新的JsonArrayRequest（Config.DATA\u URL+String.valueOf（requestCount），
新的Response.Listener（）{
@凌驾
公共void onResponse（JSONArray响应）{
//调用parseData方法来解析json响应
解析数据（响应）；
//隐藏进度条
progressBar.setVisibility（View.GONE）；
}
},
新的Response.ErrorListener（）{
@凌驾
公共无效onErrorResponse（截击错误）{
progressBar.setVisibility（View.GONE）；
//若发生错误，则表示已到达列表末尾
Toast.makeText（homepageActivity.this，“没有更多可用项”，Toast.LENGTH_SHORT.show（）；
}
});
//返回请求
返回jsonArrayRequest；
}
//此方法将从web api获取数据
私有void getData（）{
//通过调用getDataFromServer方法将该方法添加到队列
add（getDataFromServer（requestCount））；
//递增请求计数器
requestCount++；
}
//此方法将解析json数据
私有void parseData（JSONArray数组）引发RuntimeException{
对于（int i=0；ipublic class homepageActivity ... {

    // 1. Change this to a CardAdapter
    private CardAdapter adapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // ...

        // 2. Change this to reference the field adapter.
        adapter = new CardAdapter(getHeader(),listSuperHeroes, this);
    }
}