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我在自定义列表视图中做片段，同时从服务器数据库获取 json 数据到 android 移动它显示一个错误，如 data.java.lang.null 指针异常。请告诉我如何解决这个问题我在下面提到我的代码

       i try this code
    public class MyListFragment1 extends ListFragment {
private static final Context Context = null;
ImageView back;
String url = Main.url;
String Qrimage;
Bitmap bmp;

AppetiserFragment adapter;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    LayoutInflater gridInflater = (LayoutInflater) getActivity()
            .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    View v = gridInflater.inflate(R.layout.applistviewfragment, null);


    ArrayList<HashMap<String, String>> mylist = new ArrayList<HashMap<String, String>>();

    InputStream is = null;
    String result = "";
    JSONObject jArray = null;
    try {
        HttpClient httpClient = new DefaultHttpClient();
        HttpPost httpPost = new HttpPost(url + "test.php");
        HttpResponse response = httpClient.execute(httpPost);
        HttpEntity entity = response.getEntity();
        is = entity.getContent();
    } catch (Exception e) {
        // TODO: handle exception
        Log.e("Log", "Error in Connection" + e.toString());

        // Intent intent = new Intent(ViewQRCode.this, PimCarder.class);

        // startActivity(intent);

    }
    try {
        BufferedReader reader = new BufferedReader(new InputStreamReader(
                is, "iso-8859-1"), 8);
        StringBuilder sb = new StringBuilder();
        String line = null;
        while ((line = reader.readLine()) != null) {
            sb.append(line + "\n");
        }
        is.close();
        result = sb.toString();
        jArray = new JSONObject(result);
        JSONArray json = jArray.getJSONArray("appetiser");
        ListView list = (ListView) v.findViewById(R.id.list);

        adapter = new AppetiserFragment(Context, json);
        list.setAdapter(adapter);


    } catch (Exception e) {
        // TODO: handle exception
        Log.e("log", "Error in Passing data" + e.toString());
    }
}

  }

AppetizerFragment.class

     public class AppetiserFragment extends BaseAdapter {
public static ArrayList<String> arr = new ArrayList<String>();
public static ArrayList<String> itemprice = new ArrayList<String>();
public static ArrayList<Bitmap> image = new ArrayList<Bitmap>();
String url = Main.url;
public Context Context;
String qrimage;
Bitmap bmp, resizedbitmap;
Bitmap[] bmps;
Activity activity = null;
private LayoutInflater inflater;

private ImageView[] mImages;
String[] itemimage;
TextView[] tv;
String itemname, price, desc, itemno;
String[] itemnames, checkeditems, itemnos;
String[] prices;
String[] descs;
HashMap<String, String> map = new HashMap<String, String>();

public AppetiserFragment(Context context, JSONArray imageArrayJson) {
    Context = context;
    System.out.println(imageArrayJson);//here i can print json data
    // (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    // imageLoader=new ImageLoader(activity);
    inflater = LayoutInflater.from(context);
    this.mImages = new ImageView[imageArrayJson.length()];(here after code not runs correctly i thought here only the problem)
    this.bmps = new Bitmap[imageArrayJson.length()];
    this.itemnames = new String[imageArrayJson.length()];
    this.prices = new String[imageArrayJson.length()];
    this.descs = new String[imageArrayJson.length()];
    this.itemnos = new String[imageArrayJson.length()];
    try {

        for (int i = 0; i < imageArrayJson.length(); i++) {
            JSONObject image = imageArrayJson.getJSONObject(i);

            qrimage = image.getString("itemimage");
            itemname = image.getString("itemname");
            itemno = new Integer(i + 1).toString();
            price = image.getString("price");
            desc = image.getString("itemdesc");
            System.out.println(price);
            itemnames[i] = itemname;
            prices[i] = price;
            descs[i] = desc;
            itemnos[i] = itemno;

            byte[] qrimageBytes = Base64.decode(qrimage.getBytes());

            bmp = BitmapFactory.decodeByteArray(qrimageBytes, 0,
                    qrimageBytes.length);
            int width = 100;
            int height = 100;
            resizedbitmap = Bitmap.createScaledBitmap(bmp, width, height,
                    true);
            bmps[i] = bmp;

            mImages[i] = new ImageView(context);
            mImages[i].setImageBitmap(resizedbitmap);

            mImages[i].setScaleType(ImageView.ScaleType.FIT_START);

            // tv[i].setText(itemname);
        }
        System.out.println(map);

    } catch (Exception e) {
        // TODO: handle exception
    }
}

public AppetiserFragment() {
    // TODO Auto-generated constructor stub
}

public int getCount() {
    return mImages.length;
}

public Object getItem(int position) {
    return position;
}

public long getItemId(int position) {
    return position;
}

public View getView(final int position, View convertView, ViewGroup parent) {

    View view = convertView;
    final ViewHolder viewHolder;
    if (view == null) {
        view = inflater.inflate(R.layout.appetiserlistview, null);
        System.out.println("prakash");
        viewHolder = new ViewHolder();
        viewHolder.image = (ImageView) view
                .findViewById(R.id.appetiserimage);
        viewHolder.text = (TextView) view.findViewById(R.id.appetisertext);
        viewHolder.desc = (TextView) view.findViewById(R.id.appetiserdesc);
        viewHolder.price = (TextView) view
                .findViewById(R.id.appetiserprice);
        viewHolder.appitemnum = (TextView) view
                .findViewById(R.id.appitemno);
        // viewHolder.checkbox = (CheckBox) view.findViewById(R.id.bcheck);

        view.setTag(viewHolder);
    } else {
        viewHolder = (ViewHolder) view.getTag();
    }
    viewHolder.image.setImageBitmap(bmps[position]);
    viewHolder.appitemnum.setText(itemnos[position]);
    viewHolder.price.setText(prices[position]);
    viewHolder.desc.setText(descs[position]);
    // viewHolder.checkbox.setTag(itemnames[position]);
    ViewHolder holder = (ViewHolder) view.getTag();
    holder.text.setText(itemnames[position]);

    return view;
}

public void clear() {
    arr.clear();
    itemprice.clear();
    image.clear();
}

static class ViewHolder {

    protected TextView text, price, desc, appitemnum;
    protected ImageView image;
    public static CheckBox checkbox = null;
}

请告诉我如何解决这个问题...请帮助我

4

2 回答 2

1

我看到的第一件事是你忘记初始化你的上下文。

改变这个

 private static final Context Context = null;   //variable name should not be reserved keyword

到

private Context context= null;  
context= getActivity().getApplicationContext();  <<<<<<<<<<<<<<<



adapter = new AppetiserFragment(Context, json);
于 2012-06-08T05:24:08.233 回答
1 
public class mm {
    private static String p;

    static void ll (String h){
        p=h;    
    }

    static String get(){    
        return p;
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub

        ll("Mozambique is a nica country");

        System.out.println(get());
    }
}

注意：- 返回方法应该没有参数。

于 2012-08-18T22:10:51.507 回答