为什么这个错误代码

Question

public class MainActivity extends FragmentActivity implements
ActionBar.TabListener {

    private ViewPager viewPager;
    private TabsPagerAdapter mAdapter;
    private ActionBar actionBar;
    // Tab titles
    private String[] tabs = { "xxx","xx", "xxv" };

    @Override
        protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Initilization
        viewPager = (ViewPager) findViewById(R.id.pager);
        actionBar = getActionBar();
        mAdapter = new TabsPagerAdapter(getSupportFragmentManager());

        viewPager.setAdapter(mAdapter);
        actionBar.setHomeButtonEnabled(false);
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);

        // Adding Tabs
        for (String tab_name : tabs) {
            actionBar.addTab(actionBar.newTab().setText(tab_name)
                             .setTabListener(this));
        }

        /**
         * on swiping the viewpager make respective tab selected
         * */
        viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {

                @Override
                    public void onPageSelected(int position) {
                    // on changing the page
                    // make respected tab selected
                    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) {
        // on tab selected
        // show respected fragment view
        viewPager.setCurrentItem(tab.getPosition());
    }

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

}

这是我在哪里我的Activity片段被用于库项目如何为每个标签刷新ViewPager？ Android：无法在屏幕底部的viewpager put标签中替换片段，错误截图link