user interface - Android Fixed Tabs on a Processing PApplet -

i developing android app based on processing

i show 2 fixed tabs content when menu button pressed.
tab1 contain settings , maybe button
tab2 should have listview show list of presets. trying create 2 textviews sake of simplicity.
trying approach of ketai library ketailist
there's inner class extends tabhost inside papplet class extended application:

 public class myprocessingapp extends papplet {    public void setup() {   }   public void draw() {   }    public void keypressed() {       if (key == coded) {       if (keycode == keyevent.keycode_menu) {         tabhost th = new gbtab(this);       }     }   }    public class gbtab extends tabhost {     private papplet parent;     tabhost self;     tabwidget tab1, tab2;     linearlayout layout;      public gbtab(papplet _parent) {        super(_parent.getapplicationcontext());       parent = _parent;       init();     }      public void init() {       println("gbtab init");       self = this;       layout = new linearlayout(parent);       tabspec settingsspec = self.newtabspec("settings").setcontent(       new tabcontentfactory() {         public view createtabcontent(string tag) {           textview tv = new textview(parent);           tv.settext("settings!");           return tv;         }       }       )         .setindicator("settings");       self.addtab(settingsspec);       tabspec presetsspec = self.newtabspec("presets").setcontent(       new tabcontentfactory() {         public view createtabcontent(string tag) {           textview tv = new textview(parent);           tv.settext("presets!");           return tv;         }       }       )         .setindicator("presets");       self.addtab(presetsspec);       self.setcurrenttab(0);        parent.runonuithread(new runnable() {         public void run() {           parent.addcontentview(self, new viewgroup.layoutparams(           viewgroup.layoutparams.fill_parent,            viewgroup.layoutparams.fill_parent));         }       }       );     }   } } 

this code gives nullpointerexception when adding tab tabhost.

self.addtab(settingsspec); 

since self null.
valid approach?

thank you

how second answer (24 votes) in this? says since not using tabactivity need call self.setup(); before adding tabs