java - 长时间运行后 Volley 在服务中崩溃

Question

正在实现一项服务以从服务器获取更新，如下所示:

public class Myupdates extends Service {

    private static final String TAG = "AutoUpdates";
    private static final int started = 0;
    static SQLiteDatabase db;
    private boolean isRunning = false;

    private CountDownTimer timer;

    @Override
    public void onCreate() {
        this.db = openOrCreateDatabase("db", Context.MODE_PRIVATE, null);
        //Log.i(TAG, "Service onCreate");
        isRunning = true;
    }

    int mCount = 1;

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {

        //Log.i(TAG, "Service onStartCommand");

        //Creating new thread for my service
        //Always write your long running tasks in a separate thread, to avoid ANR
        new Thread(new Runnable() {
            @Override
            public void run() {

                if (isRunning) {

                    new Timer().scheduleAtFixedRate(new TimerTask() {
                        @Override
                        public void run() {
                            updates();
                        }
                    }, 0, 30000);

                }
                //Stop service once it finishes its task
                //stopSelf();
            }
        }).start();

        return Service.START_STICKY;
    }

    @Override
    public IBinder onBind(Intent arg0) {
        //Log.i(TAG, "Service onBind");
        return null;
    }

    @Override
    public void onDestroy() {

        isRunning = false;

        //Log.i(TAG, "Service onDestroy");
    }

    /*
        HANDLE ADVERTS
    */
    protected void updates() {
        /*
            JSON
         */
        final JSONObject json = new JSONObject();
        final JSONObject manJson = new JSONObject();
        try {
            manJson.put("userid", "4444");
            manJson.put("version", "6.0");
            final String j = json.put("UPDATE", manJson).toString();
            final String base_url = "https://myweburl.com";
            // Instantiate the RequestQueue.
            RequestQueue queue = Volley.newRequestQueue(this);
            // Request a string response from the provided URL.
            StringRequest stringRequest = new StringRequest(Request.Method.POST, base_url, new Response.Listener<String>() {
                @Override
                public void onResponse(String response) {
                    //Log.i(TAG, "received "+response);
                    try {
                        JSONObject object = (JSONObject) new JSONTokener(response).nextValue();
                        String update = object.getString("UPDATE");
                    } catch (JSONException e) {
                        return;
                    }
                    return;
                }
            }, new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                    //perform operation here after getting error
                    return;
                }
            }) {
                @Override
                protected Map<String, String> getParams() {
                    Map<String, String> params = new HashMap<String, String>();
                    //pack message into json
                    try {
                        params.put("data", j.toString());
                    } catch (Exception e) {
                        //Log.i(TAG,"Map error: Unable to compile post");
                    }
                    return params;
                }

                @Override
                public Map<String, String> getHeaders() throws AuthFailureError {
                    Map<String, String> params = new HashMap<String, String>();
                    params.put("Content-Type", "application/x-www-form-urlencoded");
                    return params;
                }
            };
            // Add the request to the RequestQueue.
            queue.add(stringRequest);
            // ends here
            return;
        } catch (Exception e) {
            //Log.i(TAG,"ERROR: Unable to get setup settings");
        } // end exception write
        return;
    }

}

但是，在服务长时间运行后，应用程序崩溃并出现以下错误:

03-08 00:19:41.570 11239-11253/com.mobiledatabook.com.dialcode E/AndroidRuntime: FATAL EXCEPTION: Timer-0 Process: com.mobiledatabook.com.dialcode, PID: 11239 java.lang.OutOfMemoryError: pthread_create (stack size 16384 bytes) failed: Try again at java.lang.VMThread.create(Native Method) at java.lang.Thread.start(Thread.java:1029) at com.android.volley.RequestQueue.start(RequestQueue.java:152) at com.android.volley.toolbox.Volley.newRequestQueue(Volley.java:66) at com.android.volley.toolbox.Volley.newRequestQueue(Volley.java:78) at com.mobiledatabook.com.dialcode.Myupdates.iDialAutoUpdates(Myupdates.java:128) at com.mobiledatabook.com.dialcode.Myupdates$1$1.run(Myupdates.java:74) at java.util.Timer$TimerImpl.run(Timer.java:284)

Error: java.lang.OutOfMemoryError.

有人可以帮助我改进这段代码，以避免在长时间运行服务后应用程序崩溃吗？

Answer 1

发生这种情况是因为您通过传递 Activity context 多次创建了 RequestQueue 实例。您应该使用 Application 类创建一次实例，然后在需要时一次又一次地使用它。像这样创建一个应用程序类，

public class AppController extends Application {
    private static AppController sInstance;
    private RequestQueue mRequestQueue;

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

    sInstance = this;
    }

    public static synchronized AppController getInstance() {
    return sInstance;
    }

    public RequestQueue getRequestQueue() {

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

            return mRequestQueue;
        }

}

然后像这样使用它

RequestQueue queue=AppController.getInstance().getRequestQueue();

注意:通过一次又一次地将上下文传递给请求队列，您正在填满您的 ram，这会在无法分配更多空间时导致 OutOfMemoryException

如android官方文档所述here ,

一个关键概念是 RequestQueue 必须用 Application 上下文而不是 Activity 上下文实例化。这确保了 RequestQueue 将在您的应用程序的整个生命周期内持续存在，而不是在每次重新创建 Activity 时都重新创建(例如，当用户旋转设备时)。