Заполнение списка Android с помощью массива Json по URL

Question

Я работаю над этим приложением для школьного проекта. Основой приложения является использование volley для извлечения json-массива из URL-адреса, а затем его использование для заполнения списка. Звучит просто, но у меня самая большая головная боль, поскольку я новичок в разработке приложений. Поэтому после многочисленных уроков и бесчисленных ошибок мне удалось все решить. Но теперь, когда я запускаю приложение, все, что я получаю, это пустой экран. В моем журнале не отображаются ошибки.

Log: 
10-27 18:49:39.662 1997-1997/com.example.sahan.volley2 I/art: Not late-  
enabling -Xcheck:jni (already on) 
10-27 18:49:39.964 1997-2018/com.example.sahan.volley2   
D/OpenGLRenderer: Use EGL_SWAP_BEHAVIOR_PRESERVED: true 
10-27 18:49:39.967 1997-1997/com.example.sahan.volley2 D/:    
HostConnection::get() New Host Connection established 0xa5432140, tid 
1997 
10-27 18:49:39.979 1997-1997/com.example.sahan.volley2 D/Atlas: 
Validating map... 
10-27 18:49:40.156 1997-2018/com.example.sahan.volley2 
I/OpenGLRenderer: Initialized EGL, version 1.4 
10-27 18:49:40.210 1997-2018/com.example.sahan.volley2 
D/OpenGLRenderer: Enabling debug mode 0 
10-27 18:49:40.243 1997-2018/com.example.sahan.volley2 W/EGL_emulation: 
eglSurfaceAttrib not implemented 
10-27 18:49:40.243 1997-2018/com.example.sahan.volley2  
W/OpenGLRenderer: Failed to set EGL_SWAP_BEHAVIOR on surface 
0xa5480b60, error=EGL_SUCCESS 
10-27 18:49:40.696 1997-2018/com.example.sahan.volley2 W/EGL_emulation: 
eglSurfaceAttrib not implemented 
10-27 18:49:40.696 1997-2018/com.example.sahan.volley2 
W/OpenGLRenderer: Failed to set EGL_SWAP_BEHAVIOR on surface 
0xa5480b80, error=EGL_SUCCESS 
10-27 18:49:40.718 1997-1997/com.example.sahan.volley2 I/Choreographer: 
Skipped 43 frames! The application may be doing too much work on its  
main thread. 
10-27 18:49:40.932 1997-1997/com.example.sahan.volley2 D/Volley: [1] 
2.onErrorResponse: MainActivity 

***** ****** MainActivity.java

package com.example.sahan.volley2; 

import android.os.Bundle; 
import android.support.design.widget.FloatingActionButton; 
import android.support.design.widget.Snackbar; 
import android.support.v7.app.AppCompatActivity; 
import android.support.v7.widget.Toolbar; 
import android.view.View; 
import android.view.Menu; 
import android.view.MenuItem; 

import com.example.sahan.volley2.Adapter.CustomListAdapter; 
import com.example.sahan.volley2.app.AppController; 
import com.example.sahan.volley2.Model.lot; 

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

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

import android.app.Activity; 
import android.app.ProgressDialog; 
import android.graphics.Color; 
import android.graphics.drawable.ColorDrawable; 
import android.os.Bundle; 
import android.util.Log; 
import android.view.Menu; 
import android.widget.ListView; 

import com.android.volley.Response; 
import com.android.volley.VolleyError; 
import com.android.volley.VolleyLog; 
import com.android.volley.toolbox.JsonArrayRequest; 

public class MainActivity extends Activity { 
// Log tag 
private static final String TAG = MainActivity.class.getSimpleName(); 

//json url 
private static final String url =  
"http://localhost/smartpark/get_info.php"; 
private ProgressDialog pDialog; 
private List<lot> lotList = new ArrayList<lot>(); 
private ListView listView; 
private CustomListAdapter adapter; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
super.onCreate(savedInstanceState); 
setContentView(R.layout.activity_main); 

listView = (ListView) findViewById(R.id.list); 
adapter = new CustomListAdapter(this, lotList); 
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 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); 
         lot lot = new lot(); 
         lot.setLot(obj.getString("lot")); 
         lot.setSpaces(obj.getString("spaces")); 
         lot.setRates(obj.getString("rates")); 

         // adding movie to movies array 
         lotList.add(lot); 

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

       } 

       // notifying list adapter about data changes 
       // so that it renders the list view with updated data 
       adapter.notifyDataSetChanged(); 
      } 
     }, new 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; 
} 

} 

****** ****** CustomListAdapter

package com.example.sahan.volley2.Adapter; 

/** 
* Created by Sahan on 2015-10-27. 
*/ 
import com.example.sahan.volley2.R; 
import com.example.sahan.volley2.app.AppController; 
import com.example.sahan.volley2.Model.lot; 

import java.util.List; 

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; 

public class CustomListAdapter extends BaseAdapter { 
private Activity activity; 
private LayoutInflater inflater; 
private List<lot> lotItems; 
ImageLoader imageLoader = AppController.getInstance().getImageLoader(); 

public CustomListAdapter(Activity activity, List<lot> lotItems) { 
this.activity = activity; 
this.lotItems = lotItems; 
} 

@Override 
public int getCount() { 
return lotItems.size(); 
} 

@Override 
public Object getItem(int location) { 
return lotItems.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_row, null); 

if (imageLoader == null) 
    imageLoader = AppController.getInstance().getImageLoader(); 
TextView lot = (TextView) convertView.findViewById(R.id.lot); 
TextView spaces = (TextView) convertView.findViewById(R.id.spaces); 
TextView rates = (TextView) convertView.findViewById(R.id.rates); 

// getting movie data for the row 
lot m = lotItems.get(position); 

// title 
lot.setText(m.getLot()); 

// rating 
spaces.setText("Spaces: " + String.valueOf(m.getSpaces())); 


// release year 
rates.setText(String.valueOf(m.getRates())); 

return convertView; 
} 
} 

** ** AppController.java ****

package com.example.sahan.volley2.app; 

/** 
* Created by Sahan on 2015-10-27. 
*/ 
import com.example.sahan.volley2.utils.LruBitmapCache; 
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); 
} 
} 
} 

**** lot.java ****

package com.example.sahan.volley2.app; 

/** 
* Created by Sahan on 2015-10-27. 
*/ 
import com.example.sahan.volley2.utils.LruBitmapCache; 
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); 
} 
} 
} 

**** LruBitmapCache ****

package com.example.sahan.volley2.utils; 

/** 
* Created by Sahan on 2015-10-27. 
*/ 
import com.android.volley.toolbox.ImageLoader.ImageCache; 

import android.graphics.Bitmap; 
import android.support.v4.util.LruCache; 

public class LruBitmapCache extends LruCache<String, Bitmap> implements 
ImageCache { 
public static int getDefaultLruCacheSize() { 
final int maxMemory = (int) (Runtime.getRuntime().maxMemory()/1024); 
final int cacheSize = maxMemory/8; 

return cacheSize; 
} 

public LruBitmapCache() { 
this(getDefaultLruCacheSize()); 
} 

public LruBitmapCache(int sizeInKiloBytes) { 
super(sizeInKiloBytes); 
} 

@Override 
protected int sizeOf(String key, Bitmap value) { 
return value.getRowBytes() * value.getHeight()/1024; 
} 

@Override 
public Bitmap getBitmap(String url) { 
return get(url); 
} 

@Override 
public void putBitmap(String url, Bitmap bitmap) { 
put(url, bitmap); 
} 
} 

**** AndroidManifest.xml ****

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
package="com.example.sahan.volley2" > 

<uses-permission android:name="android.permission.INTERNET" /> 

<application 
android:name="com.example.sahan.volley2.app.AppController" 
android:allowBackup="true" 
android:icon="@mipmap/ic_launcher" 
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> 
</application> 

**** activity_main.xml *** *

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout  
xmlns:android="http://schemas.android.com/apk/res/android" 
xmlns:tools="http://schemas.android.com/tools" 
xmlns:app="http://schemas.android.com/apk/res-auto" 
android:layout_width="match_parent" 
android:layout_height="match_parent" 
android:paddingLeft="@dimen/activity_horizontal_margin" 
android:paddingRight="@dimen/activity_horizontal_margin" 
android:paddingTop="@dimen/activity_vertical_margin" 
android:paddingBottom="@dimen/activity_vertical_margin" 
app:layout_behavior="@string/appbar_scrolling_view_behavior" 
tools:showIn="@layout/activity_main" tools:context=".MainActivity"> 

<ListView 
android:id="@+id/list" 
android:layout_width="fill_parent" 
android:layout_height="wrap_content" 
android:divider="@color/list_divider" 
android:dividerHeight="1dp" 
android:listSelector="@drawable/list_row_selector" /> 

**** list_row.xml ****

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout 
xmlns:android="http://schemas.android.com/apk/res/android" 
android:layout_width="fill_parent" 
android:layout_height="wrap_content" 
android:background="@drawable/list_row_selector" 
android:padding="8dp" > 


<!-- Lot Title --> 
<TextView 
android:id="@+id/lot" 
android:layout_width="wrap_content" 
android:layout_height="wrap_content" 
android:textSize="@dimen/lot" 
android:textStyle="bold" /> 

<!-- Rating --> 
<TextView 
android:id="@+id/spaces" 
android:layout_width="fill_parent" 
android:layout_height="wrap_content" 
android:layout_below="@id/lot" 
android:layout_marginTop="1dip" 
android:textSize="@dimen/spaces" /> 

<!-- Genre --> 
<TextView 
android:id="@+id/rates" 
android:layout_width="fill_parent" 
android:layout_height="wrap_content" 
android:layout_below="@id/spaces" 
android:layout_marginTop="5dp" 
android:textColor="@color/rates" 
android:textSize="@dimen/rates" /> 

**** build.gradle ****

apply plugin: 'com.android.application' 
android { 
compileSdkVersion 23 
buildToolsVersion "23.0.1" 

defaultConfig { 
applicationId "com.example.sahan.volley2" 
minSdkVersion 15 
targetSdkVersion 23 
versionCode 1 
versionName "1.0" 
multiDexEnabled true 
} 
buildTypes { 
release { 
    minifyEnabled false 
    proguardFiles getDefaultProguardFile('proguard-android.txt'),  'proguard-rules.pro' 
} 
} 
} 

dependencies { 
//compile fileTree(dir: 'libs', include: ['*.jar']) 
testCompile 'junit:junit:4.12' 
compile 'com.android.support:appcompat-v7:23.0.1' 
compile 'com.android.support:design:23.0.1' 
compile 'com.mcxiaoke.volley:library-aar:1.0.0' 
} 

Answer 1

Похоже, ваш Lot.java такой же, как AppController.java по какой-то причине. Ваш класс Лот должен выглядеть примерно так:

public class Lot { 
    private String mString; 
    private String mSpaces; 
    private String mRates; 

    public Lot() { 
    } 

    public String getString() { 
     return mString; 
    } 

    public void setString(String string) { 
     mString = string; 
    } 

    public String getSpaces() { 
     return mSpaces; 
    } 

    public void setSpaces(String spaces) { 
     mSpaces = spaces; 
    } 

    public String getRates() { 
     return mRates; 
    } 

    public void setDirector(String rates) { 
     mRates = rates; 
    } 

} 

Этот класс Лот являются узлы/элементы, которые вы храните в вашей MainActivity-х

private List<Lot> lotList = new ArrayList<Lot>();