当我运行应用程序时，AsyncTask Android nullpointexception

Question

我是一个新手没有足够的信息如何解决这个问题。这里的任何专业知识都会有所帮助。

当我运行应用程序时，

nullpointexception。没有在他们的观点中显示任何内容

这就是我的PHP脚本：

while ($row = mysql_fetch_array($result)) {
    // temp user array
    $product = array();
    $product["image_name"] = $row["image_name"];
    $product["image_type"] = $row["image_type"];


    // push single product into final response array
    array_push($response["products"], $product);
}
// success
$response["success"] = 1;

// echoing JSON response
echo json_encode($response);

我对异步任务的主要活动：

public class SimpleGridPatternViewActivity extends BaseActivity {
String url = "http://192.168.0.23/giveaways/tickets.php";
@SuppressWarnings("unchecked")
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_simple_grid_pattern_view);

    final GridPatternView<BaseAdapter> gridPatternView = (GridPatternView<BaseAdapter>) findViewById(R.id.parchment_view);

    final List<GridPatternItemDefinition> gridPatternItemDefinitions = new ArrayList<GridPatternItemDefinition>();

    FetchDataTask task = new FetchDataTask();

    gridPatternItemDefinitions
            .add(new GridPatternItemDefinition(0, 0, 6, 4));
    gridPatternView
            .addGridPatternGroupDefinition(gridPatternItemDefinitions);
    gridPatternItemDefinitions.clear();

    gridPatternItemDefinitions
            .add(new GridPatternItemDefinition(0, 0, 2, 2));
    gridPatternItemDefinitions
            .add(new GridPatternItemDefinition(2, 0, 2, 2));
    gridPatternItemDefinitions
            .add(new GridPatternItemDefinition(4, 0, 2, 3));
    gridPatternItemDefinitions
            .add(new GridPatternItemDefinition(0, 2, 4, 4));
    gridPatternItemDefinitions
            .add(new GridPatternItemDefinition(4, 3, 2, 3));
    gridPatternView
            .addGridPatternGroupDefinition(gridPatternItemDefinitions);
    gridPatternItemDefinitions.clear();

    gridPatternItemDefinitions
            .add(new GridPatternItemDefinition(0, 0, 2, 3));
    gridPatternItemDefinitions
            .add(new GridPatternItemDefinition(2, 0, 4, 4));
    gridPatternItemDefinitions
            .add(new GridPatternItemDefinition(0, 3, 2, 3));
    gridPatternItemDefinitions
            .add(new GridPatternItemDefinition(2, 4, 2, 2));
    gridPatternItemDefinitions
            .add(new GridPatternItemDefinition(4, 4, 2, 2));
    gridPatternView
            .addGridPatternGroupDefinition(gridPatternItemDefinitions);

    task.execute(url);

    gridPatternView.setAdapter(getProductsAdapter());

}

@Override
public int getLayoutResourceId() {
    return R.layout.list_item_gridpatternview_picture;
}

class FetchDataTask extends AsyncTask<String, Void, String> {

    private String msg;

    @Override
    protected String doInBackground(String... params) {
        if (params == null)
            return null;

        // get url from params
        String url = params[0];

        try {
            // create http connection
            HttpClient client = new DefaultHttpClient();
            HttpGet httpget = new HttpGet(url);

            // connect
            HttpResponse response = client.execute(httpget);

            // get response
            HttpEntity entity = response.getEntity();

            if (entity == null) {
                msg = "No response from server";
                return null;
            }

            // get response content and convert it to json string
            InputStream is = entity.getContent();
            return streamToString(is);
        } catch (IOException e) {
            msg = "No Network Connection";
        }

        return null;
    }

    @Override
    protected void onPostExecute(String arg0) {

        try {
            // convert json string to json array
            JSONArray aJson = new JSONArray(products);
            // create apps list
            List<Model> mModels = new ArrayList<Model>();

            for (int i = 0; i < aJson.length(); i++) {
                JSONObject json = aJson.getJSONObject(i);
                Model mdl = new Model();
                mdl.setImage(json.getString("image_name"));
                mdl.setType(json.getString("image_type"));

                // add the app to apps list
                mModels.add(mdl);
            }

            // notify the activity that fetch data has been complete

        } catch (JSONException e) {
            msg = "Invalid response";

            return;
        }
    }

    /**
     * This function will convert response stream into json string
     * 
     * @param is
     *            respons string
     * @return json string
     * @throws IOException
     */
    public String streamToString(final InputStream is) throws IOException {
        BufferedReader reader = new BufferedReader(
                new InputStreamReader(is));
        StringBuilder sb = new StringBuilder();
        String line = null;

        try {
            while ((line = reader.readLine()) != null) {
                sb.append(line + "\n");
            }
        } catch (IOException e) {
            throw e;
        } finally {
            try {
                is.close();
            } catch (IOException e) {
                throw e;
            }
        }

        return sb.toString();
    }
}

}

我的适配器：

 public class ProductsAdapter extends BaseAdapter {

private final int mLayoutResourceId;

public ProductsAdapter(final int layoutResourceId) {
    super();
    mLayoutResourceId = layoutResourceId;

}

private List<Model> mModels = new ArrayList<Model>();

@Override
public int getCount() {
    return mModels.size();
}

@Override
public Object getItem(final int position) {
    return mModels.get(position);
}

@Override
public long getItemId(final int position) {
    return position;
}

@Override
public boolean hasStableIds() {
    return true;
}

private View getView(final Context context, final View convertView,
        final ViewGroup viewGroup) {
    if (convertView == null) {
        final LayoutInflater layoutInflater = LayoutInflater.from(context);
        final View view = layoutInflater.inflate(mLayoutResourceId,
                viewGroup, false);
        return view;
    }
    return convertView;
}

@Override
public View getView(final int position, final View convertView,
        final ViewGroup parent) {
    final Context context = parent.getContext();
    final View view = getView(context, convertView, parent);

    Model model = (Model) getItem(position);

    final ImageView imageView = (ImageView) view
            .findViewById(R.id.list_item_picture_image_view);

    imageView.setImageBitmap(null);
    Picasso.with(context).load(model.getmUrl()).into(imageView);

    final TextView textView = (TextView) view
            .findViewById(R.id.list_item_picture_text_view);
    textView.setText(model.getImage());
    return view;
}

}