Question

我使用了vollay库，将数据发送到服务器。我使用了本教程（here）

当我运行app时，我收到以下代码的错误：ApplicationController.getInstance（）。addToRequestQueue（req）;

错误是：

Attempt to invoke virtual method 'void com.example.divid.holo.ApplicationController.addToRequestQueue(com.android.volley.Request)' on a null object reference

请帮助我，TNX

ApplicationController类：

public class ApplicationController extends Application {

    /**
     * Log or request TAG
     */
    public static final String TAG = "VolleyPatterns";

    /**
     * Global request queue for Volley
     */
    private RequestQueue mRequestQueue;

    /**
     * A singleton instance of the application class for easy access in other places
     */
    private static ApplicationController sInstance;

    @Override
    public void onCreate() {
        super.onCreate();

        // initialize the singleton
        sInstance = this;
    }

    /**
     * @return ApplicationController singleton instance
     */
    public static synchronized ApplicationController getInstance() {
        return sInstance;
    }

    /**
     * @return The Volley Request queue, the queue will be created if it is null
     */
    public RequestQueue getRequestQueue() {
        // lazy initialize the request queue, the queue instance will be
        // created when it is accessed for the first time
        if (mRequestQueue == null) {
            mRequestQueue = Volley.newRequestQueue(getApplicationContext());
        }

        return mRequestQueue;
    }

    /**
     * Adds the specified request to the global queue, if tag is specified
     * then it is used else Default TAG is used.
     * 
     * @param req
     * @param tag
     */
    public <T> void addToRequestQueue(Request<T> req, String tag) {
        // set the default tag if tag is empty
        req.setTag(TextUtils.isEmpty(tag) ? TAG : tag);

        VolleyLog.d("Adding request to queue: %s", req.getUrl());

        getRequestQueue().add(req);
    }

    /**
     * Adds the specified request to the global queue using the Default TAG.
     * 
     * @param req
     * @param tag
     */
    public <T> void addToRequestQueue(Request<T> req) {
        // set the default tag if tag is empty
        req.setTag(TAG);

        getRequestQueue().add(req);
    }

    /**
     * Cancels all pending requests by the specified TAG, it is important
     * to specify a TAG so that the pending/ongoing requests can be cancelled.
     * 
     * @param tag
     */
    public void cancelPendingRequests(Object tag) {
        if (mRequestQueue != null) {
            mRequestQueue.cancelAll(tag);
        }
    }
}

在主要活动中使用它，如下所示：

final String URL = "xxxxxxxxxxxx";
// Post params to be sent to the server
HashMap<String, String> params = new HashMap<String, String>();
params.put("token", "AbCdEfGh123456");

JsonObjectRequest req = new JsonObjectRequest(URL, new JSONObject(params),
       new Response.Listener<JSONObject>() {
           @Override
           public void onResponse(JSONObject response) {
               try {
                   VolleyLog.v("Response:%n %s", response.toString(4));
               } catch (JSONException e) {
                   e.printStackTrace();
               }
           }
       }, new Response.ErrorListener() {
           @Override
           public void onErrorResponse(VolleyError error) {
               VolleyLog.e("Error: ", error.getMessage());
           }
       });

// add the request object to the queue to be executed
ApplicationController.getInstance().addToRequestQueue(req);

Answer 1

在Manifest中定义AppController，如：

 <application
        android:name=".AppController"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:largeHeap="true"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">

使用Vollay库但我得到错误

1 个答案: