这是MainAvctivity里的代码  运行之后APP打不开 马上闪退

package youban;


import java.nio.channels.ScatteringByteChannel;
import java.util.ArrayList;
import java.util.List;


import com.example.youban.R;


import android.app.Activity;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentActivity;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;







public class MainActivity extends FragmentActivity {
private ViewPager mViewPager;
private List<Fragment> mTabs = new ArrayList<Fragment>();
private String[] mTitles = new String[]
{ "First Fragment !", "Second Fragment !", "Third Fragment !",
"Fourth Fragment !" };
private FragmentPagerAdapter mAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
// TODO Auto-generated method stub
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
initView();
initDates();
mViewPager.setAdapter(mAdapter);
}
private void initDates() {
for(String tltle : mTitles)
{
Tabfragment tabfragment = new Tabfragment();
Bundle bundle = new Bundle();
bundle.putString(Tabfragment.TITLE, tltle);
tabfragment.setArguments(bundle);
mTabs.add(tabfragment);
}
mAdapter = new FragmentPagerAdapter(getSupportFragmentManager())
{


@Override
public int getCount()
{
return mTabs.size();
}


@Override
public Fragment getItem(int position)
{
return mTabs.get(position);
}
};

}
private void initView() {
mViewPager = (ViewPager)findViewById(R.id.viewpager);

}


}