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PONullpointerException error in android gridview
 

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  1. PONullpointerException error in android gridview
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    <p>I have to develop an one android application.</p> <p>Here i have to create custom gridview adapter class.</p> <p>But am getting following error:</p> <pre><code> 06-14 14:56:26.676: E/AndroidRuntime(797): Caused by: java.lang.NullPointerException 06-14 14:56:26.676: E/AndroidRuntime(797): at com.bestinuk.adapter.CategoriesAdapter.getCount(CategoriesAdapter.java:34) 06-14 14:56:26.676: E/AndroidRuntime(797): at android.widget.GridView.setAdapter(GridView.java:180) 06-14 14:56:26.676: E/AndroidRuntime(797): at com.example.androidbestinuk.HomePage.onCreate(HomePage.java:43) </code></pre> <p>i have wrote the adapter class like below:</p> <pre><code> public class CategoriesAdapter extends BaseAdapter { private Activity activity; </code></pre> <p>List categories; private static LayoutInflater inflater=null;</p> <pre><code>public CategoriesAdapter(Activity a, List&lt;Category&gt; categories) { activity = a; this.categories=categories; inflater = (LayoutInflater)activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE); } public int getCount() { return categories.size(); } public Object getItem(int position) { return position; } public long getItemId(int position) { return position; } public View getView(int position, View convertView, ViewGroup parent) { View vi=convertView; if(convertView==null) vi = inflater.inflate(R.layout.list_item, null); ImageView thumb_image=(ImageView)vi.findViewById(R.id.categoryimage); TextView title = (TextView)vi.findViewById(R.id.categorytitle); // title Category categorylist = (Category) getItem(position); title.setText(categorylist.getmCategoryName()); thumb_image.setImageBitmap(categorylist.getmCategoryImage()); return vi; } } </code></pre> <p>Here why am getting abovr error ???</p> <p>How can i resolve these error ???</p> <p>please give me solution for these ??? </p> <p><strong>EDIT:</strong></p> <p>yes my list is null.That's why am getting null pointer exception.</p> <p>this is my HomePage.java class:</p> <pre><code> public class HomePage extends Activity { List&lt;Category&gt; categories = new ArrayList&lt;Category&gt;();; GridView category_list; CategoriesAdapter categoryViewAdapter; private ProgressDialog pDialog; static final String URL = "http://dev.mercuryminds.com/xctesting/feed.xml"; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); category_list = (GridView) findViewById(R.id.categorylist); GetXMLTask task = new GetXMLTask(this); task.execute(new String[] { URL }); } //private inner class extending AsyncTask private class GetXMLTask extends AsyncTask&lt;String, Void, Document&gt; { private Activity context; public GetXMLTask(Activity context) { this.context = context; } @Override protected void onPreExecute() { super.onPreExecute(); // Create a progressbar pDialog = new ProgressDialog(HomePage.this); // Set progressbar title pDialog.setTitle("BestinUk"); // Set progressbar message pDialog.setMessage("Loading..."); pDialog.setIndeterminate(false); // Show progressbar pDialog.show(); } @Override protected Document doInBackground(String... urls) { Document dom = null; String xml = null; for (String url : urls) { xml = getXmlFromUrl("http://dev.mercuryminds.com/xctesting/feed.xml"); dom= XMLfunctions.XMLfromString(xml); } return dom; } @Override protected void onPostExecute(Document dom) { Category categoryBean = null; if(dom !=null) { Element root = dom.getDocumentElement(); NodeList categoryNL = root.getElementsByTagName("Category"); if(categoryNL.getLength() &gt; 0){ for (int i=0;i&lt;categoryNL.getLength();i++){ Node categoryNode = categoryNL.item(i); Element categoryElmt = null; if(categoryNode.hasAttributes()){ categoryBean = new Category(); categoryElmt = (Element)categoryNode; categoryBean.setmCategoryName(categoryElmt.getAttribute("title")); categoryBean.setmCategoryID(Integer.parseInt(categoryElmt.getAttribute("categoryid"))); categoryBean.setmCategoryImageLink(categoryElmt.getAttribute("image")); categories.add(categoryBean); categoryViewAdapter = new CategoriesAdapter(HomePage.this, categories); category_list.setAdapter(categoryViewAdapter); System.out.println("Category Title is "+ " "+categoryElmt.getAttribute("title")); System.out.println("Category Image is "+ " "+categoryElmt.getAttribute("image")); } ----------- ------------ --------- pDialog.dismiss(); } } </code></pre> <p>Now am getting following error:</p> <pre><code>06-14 16:00:21.076: E/AndroidRuntime(1305): FATAL EXCEPTION: main 06-14 16:00:21.076: E/AndroidRuntime(1305): java.lang.ClassCastException: java.lang.Integer cannot be cast to com.example.androidbestinuk.Category 06-14 16:00:21.076: E/AndroidRuntime(1305): at com.bestinuk.adapter.CategoriesAdapter.getView(CategoriesAdapter.java:56) </code></pre> <p>This is my 56th line:</p> <pre><code> Category categorylist = (Category) getItem(position); </code></pre> <p>what's wrong in my code ??? please give me solution ???</p> <p>i got the output after add the below line:</p> <pre><code> Category categorylist = categories.get(position); </code></pre>
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    1. COMay be your `categories` is not being set with an instance in your constructor. Who is creating the instance of `CategoriesAdapter` ?
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    2. COcheck xml ids in `R.layout.list_item`
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