我想要显示带有图像的项目，这些图像来自服务器到我的ListView但是我得到了异常...我已经在我的依赖项中添加了volly但不知道它为什么不来...... 这是我的SubMenu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Movie.java类
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);
}
}
}
还有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>
这是我对postmant的json回复
[
{
"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>
答案 0 :(得分：0)
添加
android:name="com.example.zeba.broccoli.AppController"
给你
精心制作
你的代码不知道你正在扩展应用程序并且没有调用初始化null变量的oncreate，为了做到这一点，你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">