Question

i getting NPE on my listview..so when i click button, its show the data that i have set on another form..

here is my custom adapter code :

public class AdapterListPemesananMenu extends BaseAdapter {
    public static ArrayList<MenuInputClass> searchArrayList;

    private LayoutInflater mInflater;

    public AdapterListPemesananMenu(Context context, ArrayList<MenuInputClass> results) {
        searchArrayList = results;
        mInflater = LayoutInflater.from(context);
    }   


    public AdapterListPemesananMenu(OnClickListener onClickListener,
            ArrayList<MenuInputClass> searchResults) {
        // TODO Auto-generated constructor stub
    } 


    public int getCount() {
        return searchArrayList.size(); *********************the NPE is here
    }

    public Object getItem(int position) {
        return searchArrayList.get(position);
    }

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

    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder holder;
        if (convertView == null) {
            convertView = mInflater.inflate(R.layout.list_pemesananmenu_row, null);
            holder = new ViewHolder();
            holder.txtName = (TextView) convertView.findViewById(R.id.txtNamaMasuk);
            holder.txtCityState = (TextView) convertView
                    .findViewById(R.id.txtJumlahMasuk);


            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        holder.txtName.setText(searchArrayList.get(position).getNama_menu());
        holder.txtCityState.setText(searchArrayList.get(position)
                .getJumlah_menu());


        return convertView;
    }

    static class ViewHolder {
        TextView txtName;
        TextView txtCityState;

    }
}

this is my activity code:

public class SingleListView_Activity extends Activity{

    Button order;       
    public static ListView list_pemesanan;    
    public static String nama_menu;
    TextView namamenu;
    public static String jumlah_menu;
    EditText jumlahmenu;  
    //public static ArrayList<MenuInputClass> searchResults = GetSearchResults();

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.single_list_view);  

        ListView list_single_list_view=(ListView)findViewById(R.id.list_single);    
        list_pemesanan = (ListView)findViewById(R.id.list);
        namamenu=(TextView)findViewById(R.id.nama_menu2);
        jumlahmenu = (EditText)findViewById(R.id.txtJumlahOrder);

        order=(Button)findViewById(R.id.btn_order);
        //when this button on click its set the data to my another form
        order.setOnClickListener(new OnClickListener() { 
                @Override
                public void onClick(View v) {                                             

                     ArrayList<MenuInputClass> searchResults = GetSearchResults();              
                      ListPemesanan_Activity.list_pemesanan.setAdapter(new AdapterListPemesananMenu(this,searchResults));   

                }

             });


    }

     private ArrayList<MenuInputClass> GetSearchResults(){
     //this is the data that i set
         ArrayList<MenuInputClass> results = new ArrayList<MenuInputClass>();

         MenuInputClass sr = new MenuInputClass();      
         sr.setJumlah_menu("asdas");
         sr.setNama_menu("2");
         results.add(sr);                
         return results;
        }
}

logcat :

10-23 04:33:19.759: E/AndroidRuntime(14459): FATAL EXCEPTION: main
10-23 04:33:19.759: E/AndroidRuntime(14459): java.lang.NullPointerException
10-23 04:33:19.759: E/AndroidRuntime(14459):    at list_pemesananmenu_view.AdapterListPemesananMenu.getCount(AdapterListPemesananMenu.java:35)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at android.widget.ListView.setAdapter(ListView.java:479)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at list_pemesananmenu_view.SingleListView_Activity$1.onClick(SingleListView_Activity.java:123)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at android.view.View.performClick(View.java:2538)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at android.view.View$PerformClick.run(View.java:9152)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at android.os.Handler.handleCallback(Handler.java:587)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at android.os.Handler.dispatchMessage(Handler.java:92)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at android.os.Looper.loop(Looper.java:130)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at android.app.ActivityThread.main(ActivityThread.java:3693)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at java.lang.reflect.Method.invokeNative(Native Method)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at java.lang.reflect.Method.invoke(Method.java:507)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:907)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:665)
10-23 04:33:19.759: E/AndroidRuntime(14459):    at dalvik.system.NativeStart.main(Native Method)
10-23 04:33:19.769: E/(195): Dumpstate > /data/log/dumpstate_app_error
10-23 04:33:20.059: E/AudioPolicyManager(129): stopOutput stream = 1 , mHardwareOutput = 1, output = 1 

anyhelp would be appreciated…THANK YOU!!

Answer 1

order.setOnClickListener(new OnClickListener() { 
   @Override
   public void onClick(View v) {                                             
      ArrayList<MenuInputClass> searchResults = GetSearchResults();              
      ListPemesanan_Activity.list_pemesanan.setAdapter(new AdapterListPemesananMenu(this,searchResults));   
   }
});

In the above code, you are calling new AdapterListPemesananMenu(OnClickListener onClickListener, ArrayList searchResults);

“this” refers to OnClickListener, not the activity in this case, since you are inside the new OnClickListener() block.

That constructor doesn’t initialize your searchArrayList. searchArrayList only gets initialized in your constructor that takes (Context, ArrayList).

If you wanted to keep the rest of the code the same, you can probably do

ListPemesanan_Activity.list_pemesanan.setAdapter(new AdapterListPemesananMenu(getApplicationContext(), searchResults));   

and also get rid of the AdapterListPemesananMenu constructor that takes OnClickListener as a parameter to avoid confusion.

That’s the quick fix/analysis of the NPE, there may be better ways to rearrange your code for what you are trying to achieve.