严重例外：AsyncTask＃4 java.lang.RuntimeException：执行doInBackground时发生错误

编程问答 2022-08-15

问题描述

请帮助我，我不知道该如何解决，我的代码错误并显示如下：

2020-08-24 15:29:36.424 25891-26358/com.cryptbrn.treasify E/AndroidRuntime: FATAL EXCEPTION: AsyncTask #4
    Process: com.cryptbrn.treasify,PID: 25891
    java.lang.RuntimeException: An error occurred while executing doInBackground()
        at android.os.AsyncTask$3.done(AsyncTask.java:353)
        at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:383)
        at java.util.concurrent.FutureTask.setException(FutureTask.java:252)
        at java.util.concurrent.FutureTask.run(FutureTask.java:271)
        at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636)
        at java.lang.Thread.run(Thread.java:764)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference
        at org.json.JSONTokener.nextCleanInternal(JSONTokener.java:116)
        at org.json.JSONTokener.nextValue(JSONTokener.java:94)
        at org.json.JSONObject.<init>(JSONObject.java:159)
        at org.json.JSONObject.<init>(JSONObject.java:176)
        at com.cryptbrn.treasify.fragment.LocationFragment$ParserTask.doInBackground(LocationFragment.java:252)
        at com.cryptbrn.treasify.fragment.LocationFragment$ParserTask.doInBackground(LocationFragment.java:245)
        at android.os.AsyncTask$2.call(AsyncTask.java:333)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245) 
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162) 
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636) 
        at java.lang.Thread.run(Thread.java:764) 
2020-08-24 15:29:36.478 25891-25950/com.cryptbrn.treasify V/FA: Recording user engagement,ms: 5494
2020-08-24 15:29:36.520 25891-25950/com.cryptbrn.treasify V/FA: Activity paused,time: 607133467
2020-08-24 15:29:36.626 25891-25985/com.cryptbrn.treasify D/OpenGLRenderer: endAllActiveAnimators on 0x78542af000 (RippleDrawable) with handle 0x7854112e80
2020-08-24 15:29:38.098 25891-26121/com.cryptbrn.treasify W/OkHttpClient: A connection to https://firebasestorage.googleapis.com/ was leaked. Did you forget to close a response body?
2020-08-24 15:29:38.098 25891-26121/com.cryptbrn.treasify W/OkHttpClient: A connection to https://firebasestorage.googleapis.com/ was leaked. Did you forget to close a response body?
2020-08-24 15:29:38.098 25891-26121/com.cryptbrn.treasify W/OkHttpClient: A connection to https://maps.googleapis.com/ was leaked. Did you forget to close a response body?
2020-08-24 15:29:38.532 25891-25950/com.cryptbrn.treasify D/FA: Application going to the background

LocationFragment.java 

package com.cryptbrn.treasify.fragment;

import android.Manifest;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.location.Location;
import android.os.AsyncTask;
import android.os.Bundle;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.core.app.ActivityCompat;
import androidx.fragment.app.Fragment;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.cryptbrn.treasify.InsertPostActivity;
import com.cryptbrn.treasify.JsonParser;
import com.cryptbrn.treasify.R;
import com.google.android.gms.location.FusedLocationProviderClient;
import com.google.android.gms.location.LocationServices;
import com.google.android.gms.maps.CameraUpdate;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.MapView;
import com.google.android.gms.maps.MapsInitializer;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.android.gms.tasks.Task;
import com.google.android.material.floatingactionbutton.FloatingActionButton;

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

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.HashMap;
import java.util.List;

/**
 * A simple {@link Fragment} subclass.
 * Use the {@link LocationFragment#newInstance} factory method to
 * create an instance of this fragment.
 */
public class LocationFragment extends Fragment implements OnMapReadyCallback {

    GoogleMap mMap;
    MapView mapView;
    FusedLocationProviderClient fusedLocationProviderClient;
    double currentLat = 0,currentLong = 0;

    // TODO: Rename parameter arguments,choose names that match
    // the fragment initialization parameters,e.g. ARG_ITEM_NUMBER
    private static final String ARG_PARAM1 = "param1";
    private static final String ARG_PARAM2 = "param2";

    // TODO: Rename and change types of parameters
    private String mParam1;
    private String mParam2;

    public LocationFragment() {
        // Required empty public constructor
    }

    /**
     * Use this factory method to create a new instance of
     * this fragment using the provided parameters.
     *
     * @param param1 Parameter 1.
     * @param param2 Parameter 2.
     * @return A new instance of fragment LocationFragment.
     */
    // TODO: Rename and change types and number of parameters
    public static LocationFragment newInstance(String param1,String param2) {
        LocationFragment fragment = new LocationFragment();
        Bundle args = new Bundle();
        args.putString(ARG_PARAM1,param1);
        args.putString(ARG_PARAM2,param2);
        fragment.setArguments(args);
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        if (getArguments() != null) {
            mParam1 = getArguments().getString(ARG_PARAM1);
            mParam2 = getArguments().getString(ARG_PARAM2);
        }
    }

    @Override
    public View onCreateView(LayoutInflater inflater,ViewGroup container,Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        View view = inflater.inflate(R.layout.fragment_location,container,false);

        fusedLocationProviderClient = LocationServices.getFusedLocationProviderClient(getActivity());

        if (ActivityCompat.checkSelfPermission(getActivity(),Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_GRANTED){
            getCurrentLocation();
        }else {
            ActivityCompat.requestPermissions(getActivity(),new String[]{Manifest.permission.ACCESS_FINE_LOCATION},44);
        }

        FloatingActionButton btnBank = (FloatingActionButton) view.findViewById(R.id.btn_flea);
        btnBank.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String url = "https://maps.googleapis.com/maps/api/..." +
                        "?location=" + currentLat + "," + currentLong +
                        "&radius=5000" + "&type=" + "kfc"+
                        "&sensor=true" + "&key=" + getResources().getString(R.string.google_api_key);

                new PlaceTask().execute(url);
            }
        });

        FloatingActionButton btnFlea = (FloatingActionButton) view.findViewById(R.id.btn_bank);
        btnFlea.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String url = "https://maps.googleapis.com/maps/api/..." +
                        "?location=" + currentLat + "," + currentLong +
                        "&radius=5000" + "&type=" + "bank_sampah"+
                        "&sensor=true" + "&key=" + getResources().getString(R.string.google_api_key);

                new PlaceTask().execute(url);
            }
        });

        FloatingActionButton button = (FloatingActionButton) view.findViewById(R.id.btn_list);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(getActivity(),InsertPostActivity.class);
                startActivity(intent);
            }
        });




        return view;
    }

    private void getCurrentLocation() {
        Task<Location> task = fusedLocationProviderClient.getLastLocation();
        task.addOnSuccessListener(new OnSuccessListener<Location>() {
            @Override
            public void onSuccess(Location location) {
                if (location != null){
                    currentLat = location.getLatitude();
                    currentLong = location.getLongitude();



                }
            }
        });

    }

    @Override
    public void onViewCreated(@NonNull View view,@Nullable Bundle savedInstanceState) {
        super.onViewCreated(view,savedInstanceState);
        mapView = view.findViewById(R.id.mapView);

        if(mapView != null){
            mapView.onCreate(null);
            mapView.onResume();
            mapView.getMapAsync(this);
        }



    }

    @Override
    public void onMapReady(GoogleMap googleMap) {
        MapsInitializer.initialize(getContext());
        mMap = googleMap;

        mMap.animateCamera(CameraUpdateFactory.newLatLngZoom(
                new LatLng(currentLat,currentLong),40
        ));


    }

    @Override
    public void onRequestPermissionsResult(int requestCode,@NonNull String[] permissions,@NonNull int[] grantResults) {
        if (requestCode == 44){
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED){
                getCurrentLocation();
            }
        }
    }

    private class PlaceTask extends AsyncTask<String,Integer,String> {
        @Override
        protected String doInBackground(String... strings) {
            String data = null;
            try {
                data = downloadUrl(strings[0]);
            } catch (IOException e) {
                e.printStackTrace();
            }
            return data;
        }

        @Override
        protected void onPostExecute(String s) {
            new ParserTask().execute(s);
        }
    }

    private String downloadUrl(String string) throws IOException {
        URL url = new URL(string);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.connect();
        InputStream stream = connection.getInputStream();
        BufferedReader reader = new BufferedReader(new InputStreamReader(stream));
        StringBuilder builder = new StringBuilder();
        String line = "";
        while ((line = reader.readLine()) != null){
            builder.append(line);
        }
        String data = builder.toString();
        reader.close();
        return data;

    }

    private class ParserTask extends AsyncTask<String,List<HashMap<String,String>>> {
        @Override
        protected List<HashMap<String,String>> doInBackground(String... strings) {
            JsonParser jsonParser = new JsonParser();
            List<HashMap<String,String>> mapList = null;
            JSONObject object = null;
            try {
                object = new JSONObject(strings[0]);
                mapList = jsonParser.parseResult(object);
            }catch (JSONException e){
                e.printStackTrace();
            }
            return mapList;
        }


        @Override
        protected void onPostExecute(List<HashMap<String,String>> hashMaps) {
            mMap.clear();
            for (int i=0; i<hashMaps.size(); i++){
                HashMap<String,String> hashMapList = hashMaps.get(i);
                double lat = Double.parseDouble(hashMapList.get("lat"));
                double lng = Double.parseDouble(hashMapList.get("lng"));
                String name = hashMapList.get("name");
                LatLng latLng = new LatLng(lat,lng);
                MarkerOptions options = new MarkerOptions();
                options.position(latLng);
                options.title(name);
                mMap.addMarker(options);
            }

        }
    }
}

JsonParser.java 

package com.cryptbrn.treasify;

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

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

public class JsonParser {
    private HashMap<String,String> parseJsonObject(JSONObject object){
        HashMap<String,String> dataList = new HashMap<>();
        try {
            String name = object.getString("name");
            String latitude = object.getJSONObject("geometry")
                    .getJSONObject("location").getString("lat");
            String longitude = object.getJSONObject("geometry")
                    .getJSONObject("location").getString("lng");
            dataList.put("name",name);
            dataList.put("lat",latitude);
            dataList.put("lng",longitude);
        } catch (JSONException e) {
            e.printStackTrace();
        }

        return dataList;
    }

    private List<HashMap<String,String>> parseJsonArray(JSONArray jsonArray){
        List<HashMap<String,String>> dataList = new ArrayList<>();
        for (int i=0; i<jsonArray.length(); i++){
            try {
                HashMap<String,String> data = parseJsonObject((JSONObject) jsonArray.get(i));
                dataList.add(data);
            } catch (JSONException e){
                e.printStackTrace();
            }
        }
        return dataList;
    }


    public List<HashMap<String,String>> parseResult (JSONObject object){
        JSONArray jsonArray = null;
        try {
            jsonArray = object.getJSONArray("result");

        }catch (JSONException e){
            e.printStackTrace();
        }

        return parseJsonArray(jsonArray);
    }
}

我只关注YouTube上的教程，以在mapview上显示附近的位置，我关注了所有教程，但是应用程序强制关闭。我发现有同样问题的人，请帮助我。

解决方法

这很简单NullPointerException，这里可能存在某种例外情况

private class PlaceTask extends AsyncTask<String,Integer,String> {
        @Override
        protected String doInBackground(String... strings) {
            String data = null;
            try {
                data = downloadUrl(strings[0]);
            } catch (IOException e) {
                e.printStackTrace(); // HERE exception
            }
            return data; // HERE IT IS NULL
        }

        @Override
        protected void onPostExecute(String s) {
            new ParserTask().execute(s); // Here you pass null to ParserTask()
        }
    }

您应该调试应用程序并检查为什么downloadUrl引发异常

也许最好是熟悉RestApi库Retrofit https://square.github.io/retrofit/ 它将使您的生活变得如此轻松：）

androidandroidandroid-asynctaskandroid-mapviewgoogle-nearbygoogle-places-api

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