Question

我使用intentService在每个特定时间段定期更新新闻... 当我尝试通过getResources从字符串资源获取URL时，应用程序崩溃并返回null

这是IntentService

import com.android.volley.Request;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonObjectRequest;
import com.example.jerry.studentunion.R;

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

import announcements.Announcement;
import announcements.AnnouncementsBag;
public class AnnouncementIntentService extends IntentService {

    private final Resources URL = getResources();  //line 24 
    private JsonObjectRequest jsObjRequest=  null;
    private AnnouncementsBag announcementData = new AnnouncementsBag();

    public AnnouncementIntentService() {
        super("AnnouncementIntentService");

        jsObjRequest = new JsonObjectRequest(Request.Method.GET,
                "Place Holder for URL ",
                null,
                new Response.Listener<JSONObject>() {
// The Listeners goes here
                });
        jsObjRequest.setShouldCache(false);


    }


    @Override
    protected void onHandleIntent(Intent intent) {
        Log.d("BroadCast", "SecondStep");
        Intent broadCastAction = new Intent();


        broadCastAction.setAction(GlobalBroadcast.ANNOUNCEMENT_START_UPDATING_ACTION);
        sendBroadcast(broadCastAction);
        CustomRequestQueue.getInstance(getApplicationContext())
                .addToRequestQueue(jsObjRequest);
    }

}

完整的logcat崩溃错误

09-06 00:44:25.350  15831-15831/com.example.jerry.studentunion E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to instantiate service util.AnnouncementIntentService: java.lang.NullPointerException
        at android.app.ActivityThread.handleCreateService(ActivityThread.java:2650)
        at android.app.ActivityThread.access$1600(ActivityThread.java:156)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1422)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:153)
        at android.app.ActivityThread.main(ActivityThread.java:5299)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
        at dalvik.system.NativeStart.main(Native Method)
 Caused by: java.lang.NullPointerException
        at android.content.ContextWrapper.getResources(ContextWrapper.java:89)
        at util.AnnouncementIntentService.<init>(AnnouncementIntentService.java:24)
        at java.lang.Class.newInstanceImpl(Native Method)
        at java.lang.Class.newInstance(Class.java:1319)
        at android.app.ActivityThread.handleCreateService(ActivityThread.java:2647)
            at android.app.ActivityThread.access$1600(ActivityThread.java:156)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1422)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:153)
            at android.app.ActivityThread.main(ActivityThread.java:5299)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
            at dalvik.system.NativeStart.main(Native Method)

我使用广播接收器在BOOT_COMPLETED操作时使用警报管理器启动此服务。

Answer 1

在您发布的代码中，您实际上并未使用调用URL的字段getResources()，因此您可以轻松删除它。

但是，如果您需要获取IntentService中的资源，只需在实际需要时调用getResources()，然后将其存储在本地变量中，如下所示：

....

@Override
protected void onHandleIntent(Intent intent) {
    Resources resources = getResources();
}

...

您获得NullPointerException的原因是因为您在getResources()创建之前拨打了IntentService。如果您坚持将其存储在字段中，则可以通过覆盖onCreate()并将来电置于getResources()来完成此操作。

IntentService中的getResources返回null

1 个答案: