问带ActionBar的双片段旋转安卓系统

EN

package rb.rfrag.namespace;

import android.app.ActionBar;
import android.app.ActionBar.Tab;
import android.app.Activity;
import android.os.Bundle;

    public class RFragActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // Notice that setContentView() is not used, because we use the root
        // android.R.id.content as the container for each fragment

     // setup action bar for tabs
        final ActionBar actionBar = getActionBar();
        actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
        //actionBar.setDisplayShowTitleEnabled(false);

        Tab tab;
        tab = actionBar.newTab()
                .setText(R.string.VarsTab)
                .setTabListener(new TabListener<VarValues>(
                        this, "VarValues", VarValues.class));
        actionBar.addTab(tab);

        tab = actionBar.newTab()
                .setText(R.string.SecTab)
                .setTabListener(new TabListener<SecFrag>(
                        this, "SecFrag", SecFrag.class));
        actionBar.addTab(tab);
    }
}

package rb.rfrag.namespace;

import android.app.ActionBar;
import android.app.Activity;
import android.app.Fragment;
import android.app.FragmentManager;
import android.app.FragmentTransaction;
import android.app.ActionBar.Tab;

public class TabListener<T extends Fragment> implements ActionBar.TabListener {
    private Fragment mFragment;
    private final Activity mActivity;
    private final String mTag;
    private final Class<T> mClass;

    /** Constructor used each time a new tab is created.
      * @param activity  The host Activity, used to instantiate the fragment
      * @param tag  The identifier tag for the fragment
      * @param clz  The fragment's Class, used to instantiate the fragment
      */
    public TabListener(Activity activity, String tag, Class<T> clz) {
        mActivity = activity;
        mTag = tag;
        mClass = clz;
    }

    /* The following are each of the ActionBar.TabListener callbacks */

    public void onTabSelected(Tab tab, FragmentTransaction ft) {    
        // Check if the fragment is already initialized
        if (mFragment == null) {
            // If not, instantiate and add it to the activity
            mFragment = Fragment.instantiate(mActivity, mClass.getName());
            ft.add(android.R.id.content, mFragment, mTag);
        } else {
            // If it exists, simply attach it in order to show it
            ft.attach(mFragment);
        }
    }

    public void onTabUnselected(Tab tab, FragmentTransaction ft) {
        if (mFragment != null) {
            // Detach the fragment, because another one is being attached
            ft.detach(mFragment);
        }
    }
}