Android Volley Probleme

Question

ich diesen Fehler haben, wenn ich meine app android Volley laufen versuchen:

E/AndroidRuntime: FATAL EXCEPTION: main 
       Process: umaya.edu.androidvolley, PID: 1857 
       java.lang.RuntimeException: Unable to start activity ComponentInfo{umaya.edu.androidvolley/umaya.edu.androidvolley.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'com.android.volley.Request com.android.volley.RequestQueue.add(com.android.volley.Request)' on a null object reference 
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325) 
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387) 
        at android.app.ActivityThread.access$800(ActivityThread.java:151) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303) 
        at android.os.Handler.dispatchMessage(Handler.java:102) 
        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) 
       Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'com.android.volley.Request com.android.volley.RequestQueue.add(com.android.volley.Request)' on a null object reference 

MainActivity

Das ist meine Tätigkeit Haupt

ist

package umaya.edu.androidvolley; 

import android.support.v7.app.AppCompatActivity; 
import android.os.Bundle; 
import android.widget.TextView; 

import com.android.volley.Request; 
import com.android.volley.RequestQueue; 
import com.android.volley.Response; 
import com.android.volley.VolleyError; 
import com.android.volley.toolbox.StringRequest; 

public class MainActivity extends AppCompatActivity { 
    //creamos todas las variables 
    private TextView txt; 
    //Variables de volley 
    private RequestQueue queue; 
    private final String url = "http://mywebpage.com"; 
    private StringRequest stringRequest; 
    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 
     //inicializamos 
     txt = (TextView) findViewById(R.id.mtxt); 
     //Pedimos la respuesta dle servidor desde la url tomada como string 
     StringRequest stringRequest = new StringRequest(Request.Method.GET, url, 
       new Response.Listener<String>() { 
        @Override 
        public void onResponse(String response) { 
         // obtenemos la respuesta del servidor 
         txt.setText(response); 
        } 
       }, new Response.ErrorListener() { 
      @Override 
      public void onErrorResponse(VolleyError error) { 
       txt.setText("That didn't work!"); 
      } 
     }); 

     //agregamos la peticion 
     queue.add(stringRequest); 

    } 
} 

ich gelesen habe Dieser Fehler, und die fähige Lösungen sagt, dass in meinem Manifest hinzufügen Android: Name = "AppController" in , aber wenn ich versuche, in Code eingeben, senden Sie mir einen Fehler.

AndroidMainifest.xml

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
    package="umaya.edu.androidvolley"> 
    <uses-permission android:name="android.permission.INTERNET"></uses-permission> 
    <application 
     android:name="umaya.edu.androidvolley.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"> 
      <intent-filter> 
       <action android:name="android.intent.action.MAIN" /> 

       <category android:name="android.intent.category.LAUNCHER" /> 
      </intent-filter> 
     </activity> 
    </application> 

</manifest> 

Answer 1

Ihre Warteschlange ist null, weil Sie es als Singelton

public class MyApplication extends Application { 

    public static final String TAG = MyApplication.class.getSimpleName(); 

    private RequestQueue mRequestQueue; 

    private static MyApplication mInstance; 



    @Override 
    public void onCreate() { 
     super.onCreate(); 
     mInstance = this; 
    } 

    public static synchronized MyApplication getInstance() { 
     return mInstance; 
    } 

    public RequestQueue getRequestQueue() { 
     if (mRequestQueue == null) { 
      mRequestQueue = Volley.newRequestQueue(getApplicationContext()); 
     } 

     return mRequestQueue; 
    } 

    public <T> void addToRequestQueue(Request<T> req, String tag) { 
     req.setTag(TextUtils.isEmpty(tag) ? TAG : tag); 
     getRequestQueue().add(req); 
    } 

    public <T> void addToRequestQueue(Request<T> req) { 
     req.setTag(TAG); 
     req.setShouldCache(false); 
     getRequestQueue().add(req); 
    } 

    public void cancelPendingRequests(Object tag) { 
     if (mRequestQueue != null) { 
      mRequestQueue.cancelAll(tag); 
     } 
    } 


} 

dann eine Anfrage machen und einfach fügen Sie es in die Warteschlange Instanz initialisieren müssen

JsonObjectRequest jsObjRequest = new JsonObjectRequest 
      (Request.Method.POST, url_register, jso, new Response.Listener<JSONObject>() { 
       @Override 
       public void onResponse(JSONObject response) { 


      }, new Response.ErrorListener() { 
       @Override 
       public void onErrorResponse(VolleyError error) { 

       } 
      }); 
    MyApplication.getInstance().addToRequestQueue(jsObjRequest); 
} 

und Sie müssen Ihren Mann aktualisieren ifest mit diesem

<application 
     android:name=".utils.MyApplication" 
     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:launchMode="singleTask" 
      android:screenOrientation="portrait" />