Android Api Demos登顶之路（四十二）Fragment-->Nesting Tabs

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这个demo演示了如何为Fragment添加tab导航标签，与Activity的用法基本相同，这里需要注意的就是当在不同的tab之间切换时注意fragment与activity的分离与关联。
TabFragment1

public class TabFragment1 extends Fragment {    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);    }    @Override    public View onCreateView(LayoutInflater inflater, ViewGroup container,            Bundle savedInstanceState) {        TextView tv=new TextView(getActivity());        tv.setText("第一个选项卡中的内容");        return tv;    }}

MainActivity

public class MainActivity extends Activity {    @SuppressWarnings("deprecation")    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        ActionBar bar = getActionBar();        // 显示actionbar的标题        bar.setDisplayOptions(0, ActionBar.DISPLAY_SHOW_TITLE);        bar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);        bar.addTab(bar                .newTab()                .setText("tab1")                .setTabListener(                        new TabFragmentListener<TabFragment1>(this, "tab1",                                TabFragment1.class)));        bar.addTab(bar                .newTab()                .setText("tab2")                .setTabListener(                        new TabFragmentListener<TabFragment2>(this, "tab2",                                TabFragment2.class)));        if(savedInstanceState!=null){            bar.setSelectedNavigationItem(savedInstanceState.getInt("tab", 0));        }    }    @SuppressWarnings("deprecation")    @Override    protected void onSaveInstanceState(Bundle outState) {        super.onSaveInstanceState(outState);        outState.putInt("tab", getActionBar().getNavigationItemCount());    }    // 设置tab的选择监听器    @SuppressWarnings("deprecation")    public class TabFragmentListener<T extends Fragment> implements TabListener {        private Class<T> clz;        private Fragment frg;        private String mTag;        private Activity mActivity;        public TabFragmentListener(Activity activity, String tag, Class<T> clz) {            this.clz = clz;            this.mTag = tag;            this.mActivity = activity;            // 检查当前的Tab中是否已经有了一个fragment，如果则将其与activity分离            // 因为我们在初始化的时候是不显示Tab的            frg = activity.getFragmentManager().findFragmentByTag(mTag);            if (frg != null && !frg.isDetached()) {                FragmentTransaction ft = activity.getFragmentManager()                        .beginTransaction();                ft.detach(frg);                ft.commit();            }        }        // 选中时向tab中添加fragment的视图        @Override        public void onTabSelected(Tab tab, FragmentTransaction ft) {            if (frg == null) {                frg = Fragment.instantiate(mActivity, clz.getName());                ft.add(android.R.id.content, frg, mTag);            } else {                ft.attach(frg);            }        }        @Override        public void onTabUnselected(Tab tab, FragmentTransaction ft) {            if (frg != null) {                ft.detach(frg);            }        }        @Override        public void onTabReselected(Tab tab, FragmentTransaction ft) {            Toast.makeText(mActivity, "Reselected", 0).show();        }    }}

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