android - How can display ListView using an ArrayAdapter class and runOnUiThread method in my MainActivity? -

i new android please bare me , in advance advice. when try run app following error:

  java.lang.classcastexception: com.protogeo.moves.demos.apps.mainactivity$6 cannot cast android.content.context             @ com.protogeo.moves.demos.apps.storylineadapter.<init>(storylineadapter.java:28)             @ com.protogeo.moves.demos.apps.mainactivity$6.run(mainactivity.java:285) 

my main activity code looks this:

public class mainactivity extends fragmentactivity implements onclicklistener{ ...     public void updateresponse(final string message) {         runonuithread(new runnable() {      @override     public void run() {         //medittextresponse.settext(message);         storylineadapter adapter = new storylineadapter(this, r.layout.item_storyline, summary);        // medittextresponse.setadapter(adapter);         medittextresponse.setadapter(adapter); 

...

my arrayadapter code looks this:

 public class storylineadapter extends arrayadapter<summarydata>{     private context context;     private arraylist<summarydata> summary;      public storylineadapter(context context, int item_storyline, arraylist<summarydata> objects) {         super( context, item_storyline, objects);         this.context = context;         this.runnable = runnable;         this.summary = objects;      }        @override     public view getview(int position, view convertview, viewgroup parent){          layoutinflater inflater = ((activity) context).getlayoutinflater();         view view = inflater.inflate(r.layout.item_storyline, parent, false);              summary = summary.get(position);         textview tv = (textview) view.findviewbyid(r.id.textview1);         tv.settext(summary.getactivity());          return view;     } }