没有从服务器中获取图像到我的Android中的ListView

Question

我想显示带有来自服务器的图像的项目，这些图像来自服务器，但有异常...我在依赖项中也添加了Volly，但不知道为什么它不会来。这是我的子菜单活动

import android.app.ProgressDialog;
import android.content.Intent;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.HashMap;

import android.app.ProgressDialog;
import android.content.Intent;
import android.graphics.Color;
import android.graphics.drawable.ColorDrawable;
import android.os.AsyncTask;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleAdapter;
import android.widget.TextView;
import android.widget.Toast;
import com.android.volley.*;
import com.android.volley.toolbox.JsonArrayRequest;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
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 SubMenu  extends AppCompatActivity {

    // Log tag
    private static final String TAG = SubMenu.class.getSimpleName();
    // Movies json url
    private static final String url = "http://cloud.granddubai.com/broccoli/menu_typeitem.php";
    private ProgressDialog pDialog;
    private List<Movie> movieList = new ArrayList<Movie>();
    private ListView listView;
    private CustomListAdapter adapter;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_sub_menu);
        listView = (ListView) findViewById(R.id.list1);
        adapter = new CustomListAdapter(this, movieList);
        listView.setAdapter(adapter);
        pDialog = new ProgressDialog(this);
        // Showing progress dialog before making http request
        pDialog.setMessage("Loading...");
        pDialog.show();
        // changing action bar color
        getActionBar().setBackgroundDrawable(
                new ColorDrawable(Color.parseColor("#1b1b1b")));
        // Creating volley request obj
        JsonArrayRequest movieReq = new JsonArrayRequest(url,
                new com.android.volley.Response.Listener<JSONArray>() {
                    @Override
                    public void onResponse(JSONArray response) {
                        Log.d(TAG, response.toString());
                        hidePDialog();
                        // Parsing json
                        for (int i = 0; i < response.length(); i++) {
                            try {
                                JSONObject obj = response.getJSONObject(i);
                                Movie movie = new Movie();
                                movie.setTitle(obj.getString("name"));
                                movie.setThumbnailUrl(obj.getString("image"));
                                //  movie.setRating(((Number) obj.get("rating"))
                                //      .doubleValue());
                                //movie.setYear(obj.getInt("releaseYear"));
                                // Genre is json array
                                JSONArray genreArry = obj.getJSONArray("genre");
                                ArrayList<String> genre = new ArrayList<String>();
                                for (int j = 0; j < genreArry.length(); j++) {
                                    genre.add((String) genreArry.get(j));
                                }
                                //  movie.setGenre(genre);
                                // adding movie to movies array
                                movieList.add(movie);
                            } catch (JSONException e) {
                                e.printStackTrace();
                            }
                        }
                        // notifying list adapter about data changes
                        // so that it renders the list view with updated data
                        adapter.notifyDataSetChanged();
                    }
                }, new com.android.volley.Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                VolleyLog.d(TAG, "Error: " + error.getMessage());
                hidePDialog();
            }
        });
        // Adding request to request queue
        AppController.getInstance().addToRequestQueue(movieReq);
    }
    @Override
    public void onDestroy() {
        super.onDestroy();
        hidePDialog();
    }
    private void hidePDialog() {
        if (pDialog != null) {
            pDialog.dismiss();
            pDialog = null;
        }
    }
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }
}

这是我的电影。

 import java.util.ArrayList;
public class Movie {
    private String title, thumbnailUrl;
    private double rating;
    private ArrayList<String> genre;
    public Movie() {
    }

    public Movie(String name, String thumbnailUrl, int year, double rating,
                 ArrayList<String> genre) {
        this.title = name;
        this.thumbnailUrl = thumbnailUrl;
        //this.year = year;
    //  this.rating = rating;
        //this.genre = genre;
    }
    public String getTitle() {
        return title;
    }
    public void setTitle(String name) {
        this.title = name;
    }
    public String getThumbnailUrl() {
        return thumbnailUrl;
    }
    public void setThumbnailUrl(String thumbnailUrl) {
        this.thumbnailUrl = thumbnailUrl;
    }
//  public int getYear() {return year;}
//  public void setYear(int year) {
    //  this.year = year;
    //}
//  public double getRating() {
    //  return rating;
    //}
//  public void setRating(double rating) {
    //  this.rating = rating;
    //}
    //public ArrayList<String> getGenre() {
        //return genre;
    //}
//  public void setGenre(ArrayList<String> genre) {
        //this.genre = genre;
    //}
}

这是我的CustomListAdapter

import android.app.Activity;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;
import com.android.volley.toolbox.ImageLoader;
import com.android.volley.toolbox.NetworkImageView;
import java.util.List;
//import info.androidhive.customlistviewvolley.app.AppController;
//import info.androidhive.customlistviewvolley.model.Movie;
public class CustomListAdapter extends BaseAdapter {
    private Activity activity;
    private LayoutInflater inflater;
    private List<Movie> movieItems;
    ImageLoader imageLoader = AppController.getInstance().getImageLoader();
    public CustomListAdapter(Activity activity, List<Movie> movieItems) {
        this.activity = activity;
        this.movieItems = movieItems;
    }
    @Override
    public int getCount() {
        return movieItems.size();
    }
    @Override
    public Object getItem(int location) {
        return movieItems.get(location);
    }
    @Override
    public long getItemId(int position) {
        return position;
    }
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        if (inflater == null)
            inflater = (LayoutInflater) activity
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        if (convertView == null)
            convertView = inflater.inflate(R.layout.list_item1, null);
        if (imageLoader == null)
            imageLoader = AppController.getInstance().getImageLoader();
        NetworkImageView thumbNail = (NetworkImageView) convertView
                .findViewById(R.id.imgs);
        TextView title = (TextView) convertView.findViewById(R.id.type1);
        //TextView rating = (TextView) convertView.findViewById(R.id.rating);
        //TextView genre = (TextView) convertView.findViewById(R.id.genre);
        //TextView year = (TextView) convertView.findViewById(R.id.releaseYear);
        // getting movie data for the row
        Movie m = movieItems.get(position);
        // thumbnail image
        thumbNail.setImageUrl(m.getThumbnailUrl(), imageLoader);
        // title
        title.setText(m.getTitle());
        // rating
        //rating.setText("Rating: " + String.valueOf(m.getRating()));
        // genre
        //String genreStr = "";
        //for (String str : m.getGenre()) {
        //  genreStr += str + ", ";
    //  }
    //  genreStr = genreStr.length() > 0 ? genreStr.substring(0,
        //      genreStr.length() - 2) : genreStr;
        //genre.setText(genreStr);
        // release year
    //  year.setText(String.valueOf(m.getYear()));
        return convertView;
    }
}

这是我的appcontroller.java

import android.app.Application;
import android.text.TextUtils;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.toolbox.ImageLoader;
import com.android.volley.toolbox.Volley;
public class AppController extends Application {
    public static final String TAG = AppController.class.getSimpleName();
    private RequestQueue mRequestQueue;
    private ImageLoader mImageLoader;
    private static AppController mInstance;
    @Override
    public void onCreate() {
        super.onCreate();
        mInstance = this;
    }
    public static synchronized AppController getInstance() {
        return mInstance;
    }
    public RequestQueue getRequestQueue() {
        if (mRequestQueue == null) {
            mRequestQueue = Volley.newRequestQueue(getApplicationContext());
        }
        return mRequestQueue;
    }
    public ImageLoader getImageLoader() {
        getRequestQueue();
        if (mImageLoader == null) {
            mImageLoader = new ImageLoader(this.mRequestQueue,
                    new LruBitmapCache());
        }
        return this.mImageLoader;
    }
    public <T> void addToRequestQueue(Request<T> req, String tag) {
        // set the default tag if tag is empty
        req.setTag(TextUtils.isEmpty(tag) ? TAG : tag);
        getRequestQueue().add(req);
    }
    public <T> void addToRequestQueue(Request<T> req) {
        req.setTag(TAG);
        getRequestQueue().add(req);
    }
    public void cancelPendingRequests(Object tag) {
        if (mRequestQueue != null) {
            mRequestQueue.cancelAll(tag);
        }
    }
}

另一件事我无法将这两个导入我的项目

//import info.androidhive.customlistviewvolley.app.AppController;
//import info.androidhive.customlistviewvolley.model.Movie;

这是我的list_item1.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    >
    <!-- Product id (pid) - will be DDEN - used to pass to other activity -->

    <com.android.volley.toolbox.NetworkImageView
        android:id="@+id/imgs"
        android:layout_width="80dp"
        android:layout_height="80dp"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true" />
    <TextView
            android:id="@+id/idq"
            android:layout_width="30dp"
            android:layout_height="30dp"/>
        <TextView
            android:id="@+id/type1"
            android:textSize="20dp"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"/>
    </LinearLayout>

这是我的JSON响应postmant

[
  {
    "id": "1",
    "name": "Bianca Pizza",
    "image": "http://cloud.granddubai.com/broccoli/uploads/"
  },
  {
    "id": "2",
    "name": "Cheese Pizza",
    "image": "http://cloud.granddubai.com/broccoli/uploads/Cheese.png"
  },
  {
    "id": "3",
    "name": "Chicken BBQ Pizza:",
    "image": "http://cloud.granddubai.com/broccoli/uploads/Chicken BBQ.png"
  },
  {
    "id": "4",
    "name": "Deluxe Pizza",
    "image": "http://cloud.granddubai.com/broccoli/uploads/Deluxe.png"
  },
  {
    "id": "5",
    "name": "Greek Pizza",
    "image": "http://cloud.granddubai.com/broccoli/uploads/Greek.png"
  },
  {
    "id": "6",
    "name": "Hawaiian Pizza",
    "image": "http://cloud.granddubai.com/broccoli/uploads/Hawaiian.png"
  },
  {
    "id": "7",
    "name": "Meat Lovers Pizza",
    "image": "http://cloud.granddubai.com/broccoli/uploads/Meat Lovers.png"
  },
  {
    "id": "8",
    "name": "Pepperoni Pizza",
    "image": ""
  },
  {
    "id": "9",
    "name": "Shrimp Pizza",
    "image": ""
  },
  {
    "id": "10",
    "name": "Vegetable Pizza",
    "image": ""
  },
  {
    "id": "11",
    "name": "Original Italian Pizza",
    "image": ""
  },
  {
    "id": "12",
    "name": "Beef Strips Pasta",
    "image": ""
  },
  {
    "id": "13",
    "name": "Chicken Pasta",
    "image": ""
  },
  {
    "id": "14",
    "name": "Meat Balls Pasta",
    "image": "http://cloud.granddubai.com/broccoli/uploads/Meat Lovers.png"
  },
  {
    "id": "15",
    "name": "Sausage Pasta",
    "image": "http://cloud.granddubai.com/broccoli/uploads/Sausage.png"
  },
  {
    "id": "16",
    "name": "Shrimp Pasta",
    "image": "http://cloud.granddubai.com/broccoli/uploads/Shrimp.png"
  },
  {
    "id": "17",
    "name": "Vegetable Pasta",
    "image": "http://cloud.granddubai.com/broccoli/uploads/Vegetable.png"
  },
  {
    "id": "18",
    "name": "Pesto Pasta",
    "image": "http://cloud.granddubai.com/broccoli/uploads/Pesto.png"
  },
  {
    "id": "19",
    "name": "Chicken Lasagna",
    "image": ""
  },
  {
    "id": "20",
    "name": "Meat Lasagna",
    "image": ""
  },
  {
    "id": "21",
    "name": "Vegetable Lasagna",
    "image": ""
  },
  {
    "id": "22",
    "name": "Caesar Salad",
    "image": "http://cloud.granddubai.com/broccoli/uploads/Caesar.png"
  },
  {
    "id": "23",
    "name": "Chicken Caesar Salad",
    "image": "http://cloud.granddubai.com/broccoli/uploads/Chicken Caesar.png"
  },
  {
    "id": "24",
    "name": "Garden Salad",
    "image": "http://cloud.granddubai.com/broccoli/uploads/Garden.png"
  },
  {
    "id": "25",
    "name": "Greek Salad",
    "image": ""
  },
  {
    "id": "26",
    "name": "Pasta Salad",
    "image": "http://cloud.granddubai.com/broccoli/uploads/Pasta Salad.png"
  },
  {
    "id": "27",
    "name": "Sunny Side up ",
    "image": ""
  },
  {
    "id": "28",
    "name": "Omelette ",
    "image": ""
  },
  {
    "id": "29",
    "name": "Scrambled Eggs",
    "image": ""
  },
  {
    "id": "30",
    "name": "Scrambled Egg with toppings",
    "image": ""
  },
  {
    "id": "31",
    "name": "Coffee",
    "image": ""
  },
  {
    "id": "32",
    "name": "Fresh Juice",
    "image": ""
  },
  {
    "id": "36",
    "name": "Water 500ml",
    "image": ""
  },
  {
    "id": "35",
    "name": "Pepsi Can",
    "image": ""
  },
  {
    "id": "37",
    "name": "Soup",
    "image": ""
  },
  {
    "id": "38",
    "name": "Special Offer Family Pack",
    "image": ""
  }
]

这是我的logcat：

E/AndroidRuntime: FATAL EXCEPTION: main
                  Process: com.example.zeba.broccoli, PID: 23142
                  java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.zeba.broccoli/com.example.zeba.broccoli.SubMenu}: java.lang.NullPointerException: Attempt to invoke virtual method 'com.android.volley.toolbox.ImageLoader com.example.zeba.broccoli.AppController.getImageLoader()' on a null object reference
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3190)
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3300)
                      at android.app.ActivityThread.access$1000(ActivityThread.java:211)
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1705)
                      at android.os.Handler.dispatchMessage(Handler.java:102)
                      at android.os.Looper.loop(Looper.java:145)
                      at android.app.ActivityThread.main(ActivityThread.java:6946)
                      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:1404)
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199)
                   Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'com.android.volley.toolbox.ImageLoader com.example.zeba.broccoli.AppController.getImageLoader()' on a null object reference
                      at com.example.zeba.broccoli.CustomListAdapter.<init>(CustomListAdapter.java:23)
                      at com.example.zeba.broccoli.SubMenu.onCreate(SubMenu.java:83)
                      at android.app.Activity.performCreate(Activity.java:6575)
                      at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1134)
                      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3143)
                      at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3300) 
                      at android.app.ActivityThread.access$1000(ActivityThread.java:211) 
                      at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1705) 
                      at android.os.Handler.dispatchMessage(Handler.java:102) 
                      at android.os.Looper.loop(Looper.java:145) 
                      at android.app.ActivityThread.main(ActivityThread.java:6946) 
                      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:1404) 
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199) 

这是我的清单文件

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.zeba.broccoli">
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
    <application
        android:allowBackup="true"
        android:icon="@mipmap/logo"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name"
            android:theme="@style/AppTheme.NoActionBar">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".RegistrationForm"
            android:label="@string/title_activity_registration_form"
            android:theme="@style/AppTheme.NoActionBar" />
        <activity
            android:name=".Login"
            android:label="@string/title_activity_login"
            android:theme="@style/AppTheme.NoActionBar" />
        <activity
            android:name=".Home"
            android:label="@string/title_activity_home"
            android:theme="@style/AppTheme.NoActionBar" />
        <activity
            android:name=".Menu_Detail"
            android:label="@string/title_activity_menu__detail"
            android:theme="@style/AppTheme.NoActionBar" />
        <activity
            android:name=".TypeMenu"
            android:label="Menu"
            android:theme="@style/AppTheme.NoActionBar" />
        <activity
            android:name=".SubMenu"
            android:label="@string/title_activity_sub_menu"
            android:theme="@style/AppTheme.NoActionBar">

            <activity
                android:name="AppController"
                android:label="@string/title_activity_sub_menu"
                android:theme="@style/AppTheme.NoActionBar"></activity>
            <activity
                android:name=".Movie"
                android:label="@string/title_activity_sub_menu"
                android:theme="@style/AppTheme.NoActionBar"></activity>
            <activity
                android:name=".CustomListAdapter"
                android:label="@string/title_activity_sub_menu"
                android:theme="@style/AppTheme.NoActionBar"></activity>
            <activity
                android:name=".LruBitmapCache"
                android:label="@string/title_activity_sub_menu"
                android:theme="@style/AppTheme.NoActionBar"></activity>
        </activity>

Answer 1

在清单中添加

android:name="com.example.zeba.broccoli.AppController" 

详细说明

您的代码不知道您正在扩展应用程序，也不会调用初始化无效变量的otreate，以便这样做，您需要在清单

中明确说明。

示例：

    <application
    android:allowBackup="true"
    android:icon="@mipmap/logo"
    android:name="com.example.zeba.broccoli.AppController" 
    android:label="@string/app_name"
    android:supportsRtl="true"
    android:theme="@style/AppTheme">