public class MainActivity extends FragmentActivity implements OnPageChangeListener{
    private ViewPager viewPager;
    private RadioGroup rgChannel=null;
    private HorizontalScrollView hvChannel;
    private PageFragmentAdapter adapter=null;
    private List<Fragment> fragmentList=new
 
 ArrayList<Fragment>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
    }
    private void initView(){
        rgChannel=(RadioGroup)super.findViewById(R.id.rgChannel);
        viewPager
 
=(ViewPager)super.findViewById(R.id.vpNewsList);
        hvChannel=(HorizontalScrollView)super.findViewById(R.id.hvChannel);
        rgChannel.setOnCheckedChangeListener(
                new RadioGroup.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(RadioGroup group, 
                    
 
int checkedId) {
                viewPager.setCurrentItem(checkedId);        
            }
        });
        viewPager.setOnPageChangeListener(this);
        initTab();//動態產生RadioButton
        initViewPager();
        rgChannel.check(0);
    }
    private void initTab(){
        List<Channel> channelList=ChannelDb.getSelectedChannel();
        for(int i=0;i<channelList.size();i++){
            RadioButton rb=(RadioButton)LayoutInflater.from(this).
                    inflate(R.layout.tab_rb, null);
            rb.setId(i);
            rb.setText(channelList.get(i).getName());
            RadioGroup.LayoutParams params=new 
            RadioGroup.LayoutParams(RadioGroup.LayoutParams.WRAP_CONTENT,
                            RadioGroup.LayoutParams.WRAP_CONTENT);
            rgChannel.addView(rb,params);
        }
        
    }
    private void initViewPager(){
        List<Channel> channelList=ChannelDb.getSelectedChannel();
        for(int i=0;i<channelList.size();i++){
            NewsFragment frag=new NewsFragment();
            Bundle bundle=new Bundle();
            bundle.putString("weburl", channelList.get(i).getWeburl());
            bundle.putString("name", channelList.get(i).getName());
            frag.setArguments(bundle);     //向Fragment傳入資料
            fragmentList.add(frag);
        }
        adapter=new PageFragmentAdapter(super.getSupportFragmentManager(),fragmentList);
        viewPager.setAdapter(adapter);
        //viewPager.setOffscreenPageLimit(0);
    }
    
    /**
     * 滑動ViewPager時調整ScroollView的位置以便顯示按鈕
     * @param idx
     */
    private void setTab(int idx){
        RadioButton rb=(RadioButton)rgChannel.getChildAt(idx);
        rb.setChecked(true);
        int left=rb.getLeft();
        int width=rb.getMeasuredWidth();
        DisplayMetrics metrics=new DisplayMetrics();
        super.getWindowManager().getDefaultDisplay().getMetrics(metrics);
        int screenWidth=metrics.widthPixels;
        int len=left+width/2-screenWidth/2;
        hvChannel.smoothScrollTo(len, 0);//滑動ScroollView
    }
    @Override
    public void onPageScrollStateChanged(int arg0) {
    
    }
    @Override
    public void onPageScrolled(int arg0, float arg1, int arg2) {

    }
    @Override
    public void onPageSelected(int position) {
        // TODO Auto-generated method stub
        setTab(position);
    }
}