Question

我目前正在努力实施fetching我在class创建的数据parse.com。我想要检索一个名为＆＃34; flyerDataFetch ＆＃34;的对象。及其所有元素都显示在Recyclerview。

中

当我运行并编译程序时，我收到错误：

error:java.lang.NullPointerException at android.view.LayoutInflater.from(LayoutInflater.java:211) 
Error: RecyclerView﹕ No adapter attached; skipping layout.

在尝试填充RecyclerView时，您能否查看我的代码并帮助确定我出错的地方？

MainActivity：

public class HomeScreen extends AppCompatActivity {
    private RecyclerView mRecyclerDrawer;
    private customAdapter mAdapter;
    private Context context;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_home_screen);
        setupDrawer();
        final List<Information> data = new ArrayList<>();
        Parse.initialize(this, "xxxxxxxxxxxxxxxxxxxxx", "xxxxxxxxxxxxxxxxxxxxx");
        ParseQuery<ParseObject> query = ParseQuery.getQuery("flyerDataFetch");
        query.getInBackground("xWMyZ4YEGZ", new GetCallback<ParseObject>() {
            @Override
            public void done(ParseObject parseObject, com.parse.ParseException e) {
                if (e == null) {

                    Information information = new Information();
                    information.partyName = parseObject.getString("partyName");
                    information.partyPromoterName = parseObject.getString("partyCost");
                    information.partyCost = parseObject.getString("partyName");

                    information.flyerPic = parseObject.getParseFile("partyFlyerImage");
                    information.partyPromoterPic = parseObject.getParseFile("partyPromoterImage");

                    data.add(information);
                } else {
                    // something went wrong
                }
                mRecyclerDrawer = (RecyclerView) findViewById(R.id.drawerList);
                mRecyclerDrawer.setLayoutManager(new LinearLayoutManager(context));
                mAdapter = new customAdapter(context, data);
                mRecyclerDrawer.setAdapter(mAdapter);
            }
        });

    }

MyApplication：

 @Override
    public void onCreate() {
        super.onCreate();
        sInstance = this;
        ParseCrashReporting.enable(this);
        Parse.enableLocalDatastore(this);
        Parse.initialize(this, "xxxxxxxxxxxxxxxx", "xxxxxxxxxxxxxxxx");
    }

CustomAdapter：

package com.example.jbobo_000.prac;
import android.content.Context;
import android.content.Intent;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

import com.parse.ParseImageView;

import java.util.Collections;
import java.util.List;

public class customAdapter extends RecyclerView.Adapter<customAdapter.MyViewHolder> {
    List<Information> data = Collections.emptyList();
    private LayoutInflater inflater;
    private Context context;
    public customAdapter (Context context,List<Information>data){
        this.context=context;
        inflater=LayoutInflater.from(context);
        this.data= data;
    }

   @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType){
       View view= inflater.inflate(R.layout.custom_row, parent, false);
       MyViewHolder holder = new MyViewHolder(view);
       return holder;
   }

    @Override
    public void onBindViewHolder(MyViewHolder holder,int position){
        Information current= data.get(position);
        holder.promoterNameText.setText(current.partyPromoterName);
        holder.costText.setText(current.partyCost);
        holder.partyNameText.setText(current.partyName);
        holder.flyerImage.setParseFile(current.flyerPic);
        holder.promoterImage.setParseFile(current.partyPromoterPic);
    }

    @Override
    public int getItemCount(){

        return data.size();
    }


    class MyViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener {
        TextView promoterNameText;
        TextView costText;
        TextView partyNameText;
        ParseImageView flyerImage;
        ParseImageView promoterImage;

        public MyViewHolder(View itemView) {
            super(itemView);
            itemView.setOnClickListener(this);
            promoterImage = (ParseImageView) itemView.findViewById(R.id.promoterPicImage);
            flyerImage = (ParseImageView) itemView.findViewById(R.id.flyertImage);
            costText = (TextView) itemView.findViewById(R.id.costText);
            promoterNameText = (TextView) itemView.findViewById(R.id.promoterNameText);
            partyNameText = (TextView) itemView.findViewById(R.id.partyNameText);
        }

        @Override
        public void onClick(View v) {
            context.startActivity(new Intent(context, partyInformation.class));

        }
    }
}

Information：

package com.example.jbobo_000.prac;
import com.parse.ParseFile;
import com.parse.ParseImageView;

public class Information {
    public ParseFile flyerPic;
    public ParseFile partyPromoterPic;
    public String partyCost;
    public String partyName;
    public String partyPromoterName;



}

Logcat：

06-12 01:52:37.511    5432-5432/com.example.jbobo_000.prac E/RecyclerView﹕ No adapter attached; skipping layout
06-12 01:52:37.766    5432-5432/com.example.jbobo_000.prac D/AndroidRuntime﹕ Shutting down VM
06-12 01:52:37.766    5432-5432/com.example.jbobo_000.prac E/CrashReporting﹕ ParseCrashReporting caught a NullPointerException exception for com.example.jbobo_000.prac. Building report.
06-12 01:52:37.768    5432-5432/com.example.jbobo_000.prac E/CrashReporting﹕ Handling exception for crash
    java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object android.content.Context.getSystemService(java.lang.String)' on a null object reference
            at android.view.LayoutInflater.from(LayoutInflater.java:219)
            at com.example.jbobo_000.prac.customAdapter.<init>(customAdapter.java:25)
            at com.example.jbobo_000.prac.HomeScreen$1.done(HomeScreen.java:57)
            at com.example.jbobo_000.prac.HomeScreen$1.done(HomeScreen.java:38)
            at com.parse.ParseTaskUtils$2$1.run(ParseTaskUtils.java:107)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5254)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
06-12 01:52:37.768    5432-5432/com.example.jbobo_000.prac D/CrashReporting﹕ Generating report file for crash
06-12 01:52:37.843    5432-5432/com.example.jbobo_000.prac D/CrashReporting﹕ Retrieving logcat output...
06-12 01:52:37.871    5432-5432/com.example.jbobo_000.prac D/CrashReporting﹕ Retrieving logcat output...
06-12 01:52:37.889    5432-5432/com.example.jbobo_000.prac D/CrashReporting﹕ Retrieving logcat output...
06-12 01:52:37.965    5432-5432/com.example.jbobo_000.prac W/Settings﹕ Setting stay_on_always has moved from android.provider.Settings.System to android.provider.Settings.Global, returning read-only value.
06-12 01:52:38.164    5432-5432/com.example.jbobo_000.prac V/CrashReporting﹕ About to start ReportSenderWorker from #handleException
06-12 01:52:38.172    5432-5603/com.example.jbobo_000.prac D/CrashReporting﹕ #checkAndSendReports - start
06-12 01:52:38.172    5432-5603/com.example.jbobo_000.prac D/CrashReporting﹕ Looking for error files in /data/data/com.example.jbobo_000.prac/files/com.parse/cr/reports
06-12 01:52:38.175    5432-5603/com.example.jbobo_000.prac D/CrashReporting﹕ Loading file 1434088357768-NullPointerException-1.stacktrace
06-12 01:52:38.185    5432-5603/com.example.jbobo_000.prac I/CrashReporting﹕ Sending file 1434088357768-NullPointerException-1.stacktrace
06-12 01:52:38.186    5432-5603/com.example.jbobo_000.prac D/CrashReporting﹕ Sending crash report to Parse...
06-12 01:52:38.193    5432-5603/com.example.jbobo_000.prac D/CrashReporting﹕ #checkAndSendReports - finish
06-12 01:52:38.265    5432-5432/com.example.jbobo_000.prac E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: com.example.jbobo_000.prac, PID: 5432
    java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object android.content.Context.getSystemService(java.lang.String)' on a null object reference
            at android.view.LayoutInflater.from(LayoutInflater.java:219)
            at com.example.jbobo_000.prac.customAdapter.<init>(customAdapter.java:25)
            at com.example.jbobo_000.prac.HomeScreen$1.done(HomeScreen.java:57)
            at com.example.jbobo_000.prac.HomeScreen$1.done(HomeScreen.java:38)
            at com.parse.ParseTaskUtils$2$1.run(ParseTaskUtils.java:107)
            at android.os.Handler.handleCallback(Handler.java:739)
            at android.os.Handler.dispatchMessage(Handler.java:95)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5254)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
06-12 01:52:38.291    5432-5442/com.example.jbobo_000.prac W/art﹕ Suspending all threads took: 5.494ms

Answer 1

这里是您应该更改的所有内容..首先您没有获得table（Object）flyerDataFetch的所有数据，您只是获取ID为“xWMyZ4YEGZ”的一个特定列数据，您的查询应该是

ParseQuery<ParseObject> query = ParseQuery.getQuery("flyerDataFetch");
    query.findInBackgroud(new FindCallBack<TableClass>(){


        @Override
        public void done(ParseObject List<TableName> list, com.parse.ParseException e) {
            if (e == null) {

       // GENERATE LOOP HERE AND GET ALL DATA OF LIST INTO YOUR LOCAL LIST WHICH YOU ARE PASSING TO ADAPTER OF RECYCLER VIEW
      //I am telling you to add loop so you can learn.. 
                Information information = new Information();
                information.partyName = parseObject.getString("partyName");
                information.partyPromoterName = parseObject.getString("partyCost");
                information.partyCost = parseObject.getString("partyName");

                information.flyerPic = parseObject.getParseFile("partyFlyerImage");
                information.partyPromoterPic = parseObject.getParseFile("partyPromoterImage");

                data.add(information);
            } else {
                // something went wrong
            }

这将获取表中的所有数据并在List中设置，您将传递给适配器。这可能是你的NullPointerException的原因！

另一件事是你获得图像的方式是错误的你实际上需要执行查询并获取bytes []数组，然后你可以在ParseImageView

中设置

Bitmap bmp = BitmapFactory.decodeByteArray(data, 0, data.length, options);
myViewHolder.myImageView.setBitmapImage(bmp);

你也不需要在customAdapter中使用上下文..只需写下这个

private LayoutInflater inflater;

public customAdapter (Context context,List<Information>data){
    inflater=LayoutInflater.from(context);
    this.data= data;
}

也在你的MainActivity类中......改变这个

 mRecyclerDrawer.setLayoutManager(new LinearLayoutManager(context));
mAdapter = new customAdapter(context, data);

到

  mRecyclerDrawer.setLayoutManager(new LinearLayoutManager(this));
mAdapter = new customAdapter(getApplicationContext(), data);

..声明您的以下数据

final List<Information> data = new ArrayList<>();

在onCreate（）方法之前的MainActivity中

..

希望它有所帮助！

Answer 2

context为null。请在调用适配器之前将上下文值设置为活动。添加

setContentView(R.layout.activity_home_screen);
context=this;

使用parse.com提取的数据清空RecyclerView

2 个答案: