Question

我正在使用ActionBarSherlock来使用viewpager呈现标签。每个选项卡都有自己的片段。还使用回调接口创建了一个外部异步任务，因此我可以多次使用它。

成功输出响应但是当调用asynctask到fragment时，它会抛出nullpointerexception。我试图从View中引用LinearLayout并动态添加更多视图。这是我关于StackOverFlow的第一个问题，请告诉我任何其他细节。

LogCat错误：

08-01 11:02:00.364: W/System.err(23359): java.lang.NullPointerException
08-01 11:02:00.364: W/System.err(23359):    at in.clairvoyant.comicswala.JustAddedFragment.onTaskComplete(JustAddedFragment.java:78)
08-01 11:02:00.364: W/System.err(23359):    at in.clairvoyant.utils.AsyncTask.onPostExecute(AsyncTask.java:54)
08-01 11:02:00.364: W/System.err(23359):    at android.os.AsyncTask.finish(AsyncTask.java:631)
08-01 11:02:00.364: W/System.err(23359):    at android.os.AsyncTask.access$600(AsyncTask.java:177)
08-01 11:02:00.364: W/System.err(23359):    at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
08-01 11:02:00.364: W/System.err(23359):    at android.os.Handler.dispatchMessage(Handler.java:99)
08-01 11:02:00.364: W/System.err(23359):    at android.os.Looper.loop(Looper.java:137)
08-01 11:02:00.364: W/System.err(23359):    at android.app.ActivityThread.main(ActivityThread.java:4744)
08-01 11:02:00.364: W/System.err(23359):    at java.lang.reflect.Method.invokeNative(Native Method)
08-01 11:02:00.364: W/System.err(23359):    at java.lang.reflect.Method.invoke(Method.java:511)
08-01 11:02:00.364: W/System.err(23359):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
08-01 11:02:00.364: W/System.err(23359):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
08-01 11:02:00.364: W/System.err(23359):    at dalvik.system.NativeStart.main(Native Method)
08-01 11:02:00.364: W/System.err(23359): java.lang.NullPointerException
08-01 11:02:00.364: W/System.err(23359):    at android.widget.ArrayAdapter.init(ArrayAdapter.java:310)
08-01 11:02:00.364: W/System.err(23359):    at android.widget.ArrayAdapter.<init>(ArrayAdapter.java:153)
08-01 11:02:00.364: W/System.err(23359):    at in.clairvoyant.comicswala.FeaturedGridViewAdapter.<init>(FeaturedGridViewAdapter.java:23)
08-01 11:02:00.364: W/System.err(23359):    at in.clairvoyant.comicswala.JustAddedFragment.onTaskComplete(JustAddedFragment.java:115)
08-01 11:02:00.364: W/System.err(23359):    at in.clairvoyant.utils.AsyncTask.onPostExecute(AsyncTask.java:54)
08-01 11:02:00.364: W/System.err(23359):    at android.os.AsyncTask.finish(AsyncTask.java:631)
08-01 11:02:00.364: W/System.err(23359):    at android.os.AsyncTask.access$600(AsyncTask.java:177)
08-01 11:02:00.374: W/System.err(23359):    at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
08-01 11:02:00.374: W/System.err(23359):    at android.os.Handler.dispatchMessage(Handler.java:99)
08-01 11:02:00.374: W/System.err(23359):    at android.os.Looper.loop(Looper.java:137)
08-01 11:02:00.374: W/System.err(23359):    at android.app.ActivityThread.main(ActivityThread.java:4744)
08-01 11:02:00.374: W/System.err(23359):    at java.lang.reflect.Method.invokeNative(Native Method)
08-01 11:02:00.374: W/System.err(23359):    at java.lang.reflect.Method.invoke(Method.java:511)
08-01 11:02:00.374: W/System.err(23359):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
08-01 11:02:00.374: W/System.err(23359):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
08-01 11:02:00.374: W/System.err(23359):    at dalvik.system.NativeStart.main(Native Method)

AsyncTaskClass下面：

public class AsyncTask extends android.os.AsyncTask<String, Integer, Object> {


    private Context context;
    private AsyncTaskListener<Object> listener;
    private Object mobj;

    String response = "{\"success\":\"true\",\"bannerList\":[{\"bannerId\":1,\"bannerURL\":\"http://guardianlv.com/wp-content/uploads/2014/05/Katrina-Kaif-Is-Dating-Ranbir-Kapoor.jpg\",\"bannerContentType\":1,\"productContentID\":1},{\"bannerId\":2,\"bannerURL\":\"http://guardianlv.com/wp-content/uploads/2014/05/Katrina-Kaif-Is-Dating-Ranbir-Kapoor.jpg\",\"bannerContentType\":2,\"productContentID\":2},{\"bannerId\":3,\"bannerURL\":\"http://guardianlv.com/wp-content/uploads/2014/05/Katrina-Kaif-Is-Dating-Ranbir-Kapoor.jpg\",\"bannerContentType\":2,\"productContentID\":3},{\"bannerId\":4,\"bannerURL\":\"http://guardianlv.com/wp-content/uploads/2014/05/Katrina-Kaif-Is-Dating-Ranbir-Kapoor.jpg\",\"bannerContentType\":4,\"productContentID\":4}],\"categories\":[{\"catName\":\"Recomended\",\"catType\":1,\"catId\":1,\"productCount\":13,\"products\":[{\"productId\":1,\"productName\":\"ChachaChoudharyKaDanda\",\"publishesName\":\"Diamond\",\"productType\":1,\"productSeries\":\"ChachaChoudhary\",\"units\":35,\"actualPrice\":20,\"discountedPrice\":10,\"discountPercentage\":50,\"offerName\":\"Recommended\",\"offerId\":1,\"imageURL\":\"http://guardianlv.com/wp-content/uploads/2014/05/Katrina-Kaif-Is-Dating-Ranbir-Kapoor.jpg\",\"rating\":3,\"downloads\":2,\"language\":1,\"genre\":[{\"genreId\":1},{\"genreId\":2}]},{\"productId\":2,\"productName\":\"ChachaChoudharyAndRocket\",\"publishesName\":\"Diamond\",\"productType\":1,\"productSeries\":\"ChachaChoudhary\",\"units\":35,\"actualPrice\":20,\"discountedPrice\":20,\"discountPercentage\":50,\"offerName\":\"Recommended\",\"offerId\":1,\"imageURL\":\"http://guardianlv.com/wp-content/uploads/2014/05/Katrina-Kaif-Is-Dating-Ranbir-Kapoor.jpg\",\"rating\":2,\"downloads\":12,\"language\":1,\"genre\":[{\"genreId\":1},{\"genreId\":2}]},{\"productId\":3,\"productName\":\"ChachaChoudharyAndRaka\",\"publishesName\":\"Diamond\",\"productType\":1,\"productSeries\":\"ChachaChoudhary\",\"units\":25,\"actualPrice\":50,\"discountedPrice\":25,\"discountPercentage\":50,\"offerName\":\"NewLaunch\",\"offerId\":1,\"imageURL\":\"http://guardianlv.com/wp-content/uploads/2014/05/Katrina-Kaif-Is-Dating-Ranbir-Kapoor.jpg\",\"rating\":3,\"downloads\":2,\"language\":1,\"genre\":[{\"genreId\":1},{\"genreId\":2}]}]}],\"categories\":[{\"catName\":\"SpecialPackage\",\"catType\":2,\"catId\":2,\"productCount\":19,\"products\":[{\"productId\":20,\"productName\":\"ChachaChoudhary\",\"publishesName\":\"Diamond\",\"productType\":2,\"productSeries\":\"ChachaChoudhary\",\"units\":12,\"actualPrice\":30,\"discountedPrice\":25,\"discountPercentage\":25,\"offerName\":\"Recommended\",\"offerId\":1,\"imageURL\":\"http://guardianlv.com/wp-content/uploads/2014/05/Katrina-Kaif-Is-Dating-Ranbir-Kapoor.jpg\",\"rating\":3,\"downloads\":2,\"language\":1,\"genre\":[{\"genreId\":1},{\"genreId\":2}]},{\"productId\":21,\"productName\":\"PinkiSeries\",\"publishesName\":\"Diamond\",\"productType\":2,\"productSeries\":\"Pinki\",\"units\":5,\"actualPrice\":20,\"discountedPrice\":15,\"discountPercentage\":25,\"offerName\":\"Recommended\",\"offerId\":1,\"imageURL\":\"http://guardianlv.com/wp-content/uploads/2014/05/Katrina-Kaif-Is-Dating-Ranbir-Kapoor.jpg\",\"rating\":2,\"downloads\":12,\"language\":1,\"genre\":[{\"genreId\":1},{\"genreId\":2}]},{\"productId\":22,\"productName\":\"BabluandRocket\",\"publishesName\":\"Diamond\",\"productType\":2,\"productSeries\":\"Bablu\",\"units\":11,\"actualPrice\":20,\"discountedPrice\":15,\"discountPercentage\":25,\"offerName\":\"ExclusiveLaunch\",\"offerId\":2,\"imageURL\":\"http://guardianlv.com/wp-content/uploads/2014/05/Katrina-Kaif-Is-Dating-Ranbir-Kapoor.jpg\",\"rating\":3,\"downloads\":2,\"language\":1,\"genre\":[{\"genreId\":1},{\"genreId\":2}]}]}]}";

    public AsyncTask(Context context2, Object object,
            AsyncTaskListener<Object> listener) {
        this.context = context2;
        this.mobj = object;
        this.listener = listener;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected Object doInBackground(String... params) {

        Gson gson = new Gson();
        try {
            mobj = gson.fromJson(response, mobj.getClass());

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

        System.out.println("Response in string>>> " + mobj.toString());
        return mobj;
    }

    @Override
    protected void onProgressUpdate(Integer... values) {
        super.onProgressUpdate(values);
    }

    @Override
    protected void onPostExecute(Object result) {

        System.out.println("INSIDE POST EXECUTE METHOD>>>>>> "+result.toString() );
        try {

            if(null != listener) {
                listener.onTaskComplete(result);
            } else {
                System.out.println("Listener is Null");
            }

            System.out.println("API response>>" + result.toString());

        } catch (Exception e) {

            e.printStackTrace();
        }
        super.onPostExecute(result);
    }
}

JustAddedFragment Class：

public class JustAddedFragment extends SherlockFragment implements AsyncTaskListener<Object> {

    // response string temporary
    String response = "{\"success\":\"true\",\"bannerList\":[{\"bannerId\":1,\"bannerURL\":\"http://guardianlv.com/wp-content/uploads/2014/05/Katrina-Kaif-Is-Dating-Ranbir-Kapoor.jpg\",\"bannerContentType\":1,\"productContentID\":1},{\"bannerId\":2,\"bannerURL\":\"http://guardianlv.com/wp-content/uploads/2014/05/Katrina-Kaif-Is-Dating-Ranbir-Kapoor.jpg\",\"bannerContentType\":2,\"productContentID\":2},{\"bannerId\":3,\"bannerURL\":\"http://guardianlv.com/wp-content/uploads/2014/05/Katrina-Kaif-Is-Dating-Ranbir-Kapoor.jpg\",\"bannerContentType\":2,\"productContentID\":3},{\"bannerId\":4,\"bannerURL\":\"http://guardianlv.com/wp-content/uploads/2014/05/Katrina-Kaif-Is-Dating-Ranbir-Kapoor.jpg\",\"bannerContentType\":4,\"productContentID\":4}],\"categories\":[{\"catName\":\"Recomended\",\"catType\":1,\"catId\":1,\"productCount\":13,\"products\":[{\"productId\":1,\"productName\":\"ChachaChoudharyKaDanda\",\"publishesName\":\"Diamond\",\"productType\":1,\"productSeries\":\"ChachaChoudhary\",\"units\":35,\"actualPrice\":20,\"discountedPrice\":10,\"discountPercentage\":50,\"offerName\":\"Recommended\",\"offerId\":1,\"imageURL\":\"http://guardianlv.com/wp-content/uploads/2014/05/Katrina-Kaif-Is-Dating-Ranbir-Kapoor.jpg\",\"rating\":3,\"downloads\":2,\"language\":1,\"genre\":[{\"genreId\":1},{\"genreId\":2}]},{\"productId\":2,\"productName\":\"ChachaChoudharyAndRocket\",\"publishesName\":\"Diamond\",\"productType\":1,\"productSeries\":\"ChachaChoudhary\",\"units\":35,\"actualPrice\":20,\"discountedPrice\":20,\"discountPercentage\":50,\"offerName\":\"Recommended\",\"offerId\":1,\"imageURL\":\"http://guardianlv.com/wp-content/uploads/2014/05/Katrina-Kaif-Is-Dating-Ranbir-Kapoor.jpg\",\"rating\":2,\"downloads\":12,\"language\":1,\"genre\":[{\"genreId\":1},{\"genreId\":2}]},{\"productId\":3,\"productName\":\"ChachaChoudharyAndRaka\",\"publishesName\":\"Diamond\",\"productType\":1,\"productSeries\":\"ChachaChoudhary\",\"units\":25,\"actualPrice\":50,\"discountedPrice\":25,\"discountPercentage\":50,\"offerName\":\"NewLaunch\",\"offerId\":1,\"imageURL\":\"http://guardianlv.com/wp-content/uploads/2014/05/Katrina-Kaif-Is-Dating-Ranbir-Kapoor.jpg\",\"rating\":3,\"downloads\":2,\"language\":1,\"genre\":[{\"genreId\":1},{\"genreId\":2}]}]}],\"categories\":[{\"catName\":\"SpecialPackage\",\"catType\":2,\"catId\":2,\"productCount\":19,\"products\":[{\"productId\":20,\"productName\":\"ChachaChoudhary\",\"publishesName\":\"Diamond\",\"productType\":2,\"productSeries\":\"ChachaChoudhary\",\"units\":12,\"actualPrice\":30,\"discountedPrice\":25,\"discountPercentage\":25,\"offerName\":\"Recommended\",\"offerId\":1,\"imageURL\":\"http://guardianlv.com/wp-content/uploads/2014/05/Katrina-Kaif-Is-Dating-Ranbir-Kapoor.jpg\",\"rating\":3,\"downloads\":2,\"language\":1,\"genre\":[{\"genreId\":1},{\"genreId\":2}]},{\"productId\":21,\"productName\":\"PinkiSeries\",\"publishesName\":\"Diamond\",\"productType\":2,\"productSeries\":\"Pinki\",\"units\":5,\"actualPrice\":20,\"discountedPrice\":15,\"discountPercentage\":25,\"offerName\":\"Recommended\",\"offerId\":1,\"imageURL\":\"http://guardianlv.com/wp-content/uploads/2014/05/Katrina-Kaif-Is-Dating-Ranbir-Kapoor.jpg\",\"rating\":2,\"downloads\":12,\"language\":1,\"genre\":[{\"genreId\":1},{\"genreId\":2}]},{\"productId\":22,\"productName\":\"BabluandRocket\",\"publishesName\":\"Diamond\",\"productType\":2,\"productSeries\":\"Bablu\",\"units\":11,\"actualPrice\":20,\"discountedPrice\":15,\"discountPercentage\":25,\"offerName\":\"ExclusiveLaunch\",\"offerId\":2,\"imageURL\":\"http://guardianlv.com/wp-content/uploads/2014/05/Katrina-Kaif-Is-Dating-Ranbir-Kapoor.jpg\",\"rating\":3,\"downloads\":2,\"language\":1,\"genre\":[{\"genreId\":1},{\"genreId\":2}]}]}]}";
    String jsonString;
    FeaturedGridViewAdapter featuredAdapter;
    LinearLayout justAddedContainer;
    Context context;
    View view, row;
    GridView featuredGridview;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        view = inflater.inflate(R.layout.activity_justadded_fragment, container, false);

        // take the parent container where child views to be added
        justAddedContainer = (LinearLayout) view.findViewById(R.id.just_added_container);
        context = getActivity();
        // inflate the child views (work in a look, lenght will the category count
        row = inflater.inflate(R.layout.category_layout, null);

        // reference to gridviews per child
        featuredGridview = (GridView) row.findViewById(R.id.featured_gridview);
        new AsyncTask(context, new FeaturedModel(), new JustAddedFragment()).execute();
        return view;
    }

    @Override
    public void onSaveInstanceState(Bundle outState) {
        super.onSaveInstanceState(outState);
    }

    public void onTaskComplete(Object result) {

        System.out.println("INSIDE TASK COMPLETE METHOD>>>> "
                + result.toString());

        FeaturedModel featuredModel = new FeaturedModel();
        featuredModel = (FeaturedModel) result;
        System.out.println("featured model length>>> "
                + featuredModel.toString());

        ProductModel productModel = new ProductModel();
        ArrayList<ProductModel> data = new ArrayList<ProductModel>();

        if (featuredModel.isSuccess()) {
            CategoriesModel[] categoriesArray = new CategoriesModel[featuredModel
                    .getCategories().length];
            categoriesArray = featuredModel.getCategories();
            int length1 = categoriesArray.length;
            System.out.println("Length of Category array : " + length1);

            for (int i = 0; i < categoriesArray.length; i++) {

                try {
                    // here getting the nullpointer
                    **justAddedContainer**.addView(row, i, new ViewGroup.LayoutParams(
                            ViewGroup.LayoutParams.MATCH_PARENT,
                            ViewGroup.LayoutParams.WRAP_CONTENT));
                    RobotoTextView categoryName = (RobotoTextView) row
                            .findViewById(R.id.featured_title);
                    RobotoTextView seeAll = (RobotoTextView) row
                            .findViewById(R.id.featured_seeall);
                    categoryName.setText(categoriesArray[i].getCatName());

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

            }

            for (int i = 0; i < categoriesArray.length; i++) {
                ProductModel[] productsArray = new ProductModel[categoriesArray[i]
                        .getProducts().length];
                productsArray = categoriesArray[i].getProducts();

                for (int j = 0; j < productsArray.length; j++) {
                    productModel.setProductName(productsArray[i]
                            .getProductName());
                    productModel.setProductSeries(productsArray[i]
                            .getProductSeries());
                    // productModel.setImageURL(productsArray[i].getImageURL());
                    productModel.setUnits(productsArray[i].getUnits());
                    productModel.setRating(productsArray[i].getRating());
                    productModel.setDownloads(productsArray[i].getDownloads());
                    productModel.setDiscountedPrice(productsArray[i]
                            .getDiscountedPrice());
                    productModel.setActualPrice(productsArray[i]
                            .getActualPrice());
                    productModel.setDiscountPercentage(productsArray[i]
                            .getDiscountPercentage());
                    data.add(productModel);
                    featuredAdapter = new FeaturedGridViewAdapter(context,
                            R.layout.product_view, data);
                    featuredGridview.setAdapter(featuredAdapter);

                }

            }

        } else {
            System.out.println("feature model response is false>>");
        }

    }
}

AsyncTaskListener接口：

public interface AsyncTaskListener<Object> {

    public void onTaskComplete(Object result);
}

Answer 1

new JustAddedFragment（）将创建一个新对象，你应该用JustAddedFragment替换它。这可能会解决你的问题。

 Better Approach:

您应该在您的活动上实现回调接口，然后将其上下文移动到其他类，然后在完成的操作中，您的活动将被通知，您可以从活动中将结果传递给碎片。

通过调用getActivity（）在片段中，您可以获取活动上下文，并可以使用其他操作。

使用外部AsyncTask和接口回调的片段抛出NullPointerException

1 个答案: