Unbekannt Null-Zeiger Fehler android

Question

I gridview in Alertdialog zeigen müssen ... wenn ich diesen Code verwende ich diesen Fehler ...

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.Object android.app.Activity.getSystemService(java.lang.String)' on a null object reference 

Mein maincode ....

GridView grid; 
GridViewAdapter adapter1; 
listView_prev.setOnItemClickListener(new AdapterView.OnItemClickListener() { 
     @Override 
     public void onItemClick(AdapterView<?> arg0, final View arg1, int arg2, long arg3) { 
      //listview click event handling 
      TextView id = (TextView) arg1.findViewById(R.id.textView17); 
      final int id_To_Search = Integer.valueOf(id.getText().toString()); 
      Cursor item=mydb.singlecons(id_To_Search); 
      Cursor att=mydb.attrs(id_To_Search); 
      Cursor picloc=mydb.singleconspic(id_To_Search); 
      att.moveToFirst(); 
      List<String> list = new ArrayList<>(); 
      // Log.d("temp",att.getColumnName(1)); 

      while (!att.isAfterLast()) 
      { 
       int l=att.getColumnCount(); 
       Log.d("length", String.valueOf(l)); 
       for(int i=2;i<l;i++){ 
       Log.d("for","for"); 
        if(att.getString(i)!=null){ 
         String b= att.getColumnName(i)+" "+att.getString(i); 
         list.add(b); 
         Log.d("att",b); 
        } 
       } 
       Log.d("while","while"); 
       att.moveToNext(); 
      } 
      att.close(); 
      Log.d("list", String.valueOf(list)); 
      picloc.moveToFirst(); 

      FilePathStrings = new String[picloc.getCount()]; 
      int i=0; 
      while (!picloc.isAfterLast()){ 
       Log.d("picloc",picloc.getString(2)); 
       FilePathStrings[i]=picloc.getString(2); 
       i++; 
       picloc.moveToNext(); 
      } 

      item.moveToFirst(); 

      AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(Consultation.this); 
      LayoutInflater inflater = getLayoutInflater(); 
      View dialogView = inflater.inflate(R.layout.alert_label_editor, null); 
      dialogBuilder.setView(dialogView); 

      TextView con=(TextView)dialogView.findViewById(R.id.textView29); 
      con.setText("Consultation on "+item.getString(4)); 
      TextView des=(TextView)dialogView.findViewById(R.id.textView28); 
      des.setText(item.getString(2)); 
      TextView pre=(TextView)dialogView.findViewById(R.id.textView31); 
      pre.setText(item.getString(3)); 
      TextView fee=(TextView)dialogView.findViewById(R.id.textView32); 
      fee.setText(item.getString(5)); 
      adapter1 = new GridViewAdapter(FilePathStrings); 

      grid.setAdapter(adapter1); 
      AlertDialog alertDialog = dialogBuilder.create(); 
      alertDialog.show(); 


     } 
    }); 

Gridviewadapter Klasse ...

class GridViewAdapter extends BaseAdapter { 

private Activity activity; 
private String[] filepath; 
private static LayoutInflater inflater = null; 
GridViewAdapter(String[] fpath) { //you need to pass Activity reference here 
    filepath = fpath; 
    activity = activity; 
    inflater = (LayoutInflater) activity 
      .getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
} 
public int getCount() { 
    return filepath.length; 

} 

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.gridview_item, null); 
     ImageView image = (ImageView) vi.findViewById(R.id.image); 
     Bitmap bmp = BitmapFactory.decodeFile(filepath[position]); 
     image.setImageBitmap(bmp); 
     return vi; 
} 

}

Wie kann ich dieses Problem beheben? Ich brauche Bilder mit Alertdialog zeigen ... Wie kann ich dieses Problem beheben ...

Answer 1

Eigentlich Ihr Kontext wie dieser

GridViewAdapter(String[] fpath,Context context) { 
filepath = fpath; 
inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 

} 

Anruf GridViewAdapter in Ihrer Aktivitätsklasse wie diese

null.so zu ändern ist

adapter1 = new GridViewAdapter(FilePathStrings,getApllicationContext()); 

Answer 2

Es wird in den Code selbst deutlich erwähnt ..

GridViewAdapter(Activity activity, String[] fpath) { //you need to pass Activity reference here 
filepath = fpath; 
activity = activity; 
inflater = (LayoutInflater) activity 
     .getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
} 

Siehe die Argumente Activi ty hinzugefügt. Sie müssen diesen Parameter an den Konstruktor übergeben.