تغییر فونت

من در یک برنامه میخوام فونت برنامه رو عوض کنم که یکم ایراد داره کدم اگه امکانش هست کمک کنید/

 package com.ecommerce.app;

import android.app.ActionBar;
import android.app.ActionBar.Tab;
import android.app.FragmentTransaction;
import android.graphics.Typeface;
import android.graphics.drawable.ColorDrawable;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v4.view.ViewPager;
import android.view.MenuItem;


public class Profile extends FragmentActivity implements
        ActionBar.TabListener {
    
    public Typeface headeryek;

    private ViewPager      viewPager;
    private ActionBar      actionBar;
    private ProfileAdapter tabPagerAdapter;
    private String[]       tabs = { "سوال", "خرید" };


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.swipetab);
        
        headeryek = Typeface.createFromAsset(getAssets(), "Yekan.ttf");
        
        viewPager = (ViewPager) findViewById(R.id.pager);
        tabPagerAdapter = new ProfileAdapter(getSupportFragmentManager());
        viewPager.setAdapter(tabPagerAdapter);
        actionBar = getActionBar();
        actionBar.setBackgroundDrawable(new ColorDrawable(getResources().getColor(R.color.header)));
        actionBar.setStackedBackgroundDrawable(new ColorDrawable(getResources().getColor(R.color.header)));
        actionBar.setTitle("راهنما");
        
        ((Object) actionBar).setTypeface(headeryek);
        
        

        getActionBar().setDisplayHomeAsUpEnabled(true);
        getActionBar().setHomeButtonEnabled(true);
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
        for (String tab_name: tabs) {
            actionBar.addTab(actionBar.newTab().setText(tab_name)
                    .setTabListener(this));
        }

        viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {

            /**
             * on swipe select the respective tab
             * */
            @Override
            public void onPageSelected(int position) {
                actionBar.setSelectedNavigationItem(position);
            }


            @Override
            public void onPageScrolled(int arg0, float arg1, int arg2) {}


            @Override
            public void onPageScrollStateChanged(int arg0) {}
        });
    }


    @Override
    public void onTabReselected(Tab tab, FragmentTransaction ft) {}


    @Override
    public void onTabSelected(Tab tab, FragmentTransaction ft) {
        viewPager.setCurrentItem(tab.getPosition());
    }


    @Override
    public void onTabUnselected(Tab tab, FragmentTransaction ft) {}


    @Override
    public void onBackPressed() {
        // TODO Auto-generated method stub
        super.onBackPressed();
        overridePendingTransition(R.anim.open_main, R.anim.close_next);
    }


    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case android.R.id.home:
                // app icon in action bar clicked; go home
                this.finish();
                overridePendingTransition(R.anim.open_main, R.anim.close_next);
                return true;
            default:
                return super.onOptionsItemSelected(item);
        }
    }
}