ViewPager API
Layout 管理器允许用户可以在页面上，左右滑动来翻动页面。这个时候，你可以考虑实现PagerAdapter接口。
需要注意的是，这个类在不断更新中，所以在以后的版本中，API会有所改变。
ViewPager很多时候会结合Fragment一块使用，这种方法使得管理每个页面的生命周期变得很方便。其中，有一些adapter的具体实现，可以适合于这种ViewPager结合Fagment使用的情况。这些adapter包括： FragmentPagerAdapter,FragmentStatePagerAdapter, FragmentPagerAdapter, 和 FragmentStatePagerAdapter。
下面的代码实例，演示了ViewPager如何结合ActionTabs来使用：
publicclassActionBarTabsPagerextendsActivity{
ViewPager mViewPager;
TabsAdapter mTabsAdapter;
@Override
protectedvoid onCreate(Bundle savedInstanceState){
super.onCreate(savedInstanceState);
mViewPager =newViewPager(this);
mViewPager.setId(R.id.pager);
setContentView(mViewPager);
finalActionBar bar = getActionBar();
bar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
bar.setDisplayOptions(0,ActionBar.DISPLAY_SHOW_TITLE);
mTabsAdapter =newTabsAdapter(this, mViewPager);
mTabsAdapter.addTab(bar.newTab().setText("Simple"),
CountingFragment.class,null);
mTabsAdapter.addTab(bar.newTab().setText("List"),
FragmentPagerSupport.ArrayListFragment.class,null);
mTabsAdapter.addTab(bar.newTab().setText("Cursor"),
CursorFragment.class,null);
if(savedInstanceState !=null){
bar.setSelectedNavigationItem(savedInstanceState.getInt("tab",0));
}
}
@Override
protectedvoid onSaveInstanceState(Bundle outState){
super.onSaveInstanceState(outState);
outState.putInt("tab", getActionBar().getSelectedNavigationIndex());
}
/**
* This is a helperclass that implements the management of tabs and all
* details ofconnecting a ViewPager with associated TabHost. It relies on a
* trick. Normally a tab host has a simple API forsupplying a View or
* Intent that eachtab will show. This is not sufficientfor switching
* betweenpages. So instead we make the contentpart of the tab host
* 0dp high (it isnot shown) and the TabsAdapter supplies its own dummy
* view to show asthe tab content. It listens to changesin tabs, and takes
* care of switchto the correct paged in the ViewPager whenever the selected
* tab changes.
*/
publicstaticclassTabsAdapterextendsFragmentPagerAdapter
implementsActionBar.TabListener,ViewPager.OnPageChangeListener{
privatefinalContext mContext;
privatefinalActionBar mActionBar;
privatefinalViewPager mViewPager;
privatefinalArrayList<TabInfo> mTabs =newArrayList<TabInfo>();
staticfinalclassTabInfo{
privatefinalClass<?> clss;
privatefinalBundle args;
TabInfo(Class<?> _class,Bundle _args){
clss = _class;
args = _args;
}
}
publicTabsAdapter(Activity activity,ViewPager pager){
super(activity.getFragmentManager());
mContext = activity;
mActionBar = activity.getActionBar();
mViewPager = pager;
mViewPager.setAdapter(this);
mViewPager.setOnPageChangeListener(this);
}
publicvoid addTab(ActionBar.Tab tab,Class<?> clss,Bundle args){
TabInfo info =newTabInfo(clss, args);
tab.setTag(info);
tab.setTabListener(this);
mTabs.add(info);
mActionBar.addTab(tab);
notifyDataSetChanged();
}
@Override
publicint getCount(){
return mTabs.size();
}
@Override
publicFragment getItem(int position){
TabInfo info = mTabs.get(position);
returnFragment.instantiate(mContext, info.clss.getName(), info.args);
}
@Override
publicvoid onPageScrolled(int position,float positionOffset,int positionOffsetPixels){
}
@Override
publicvoid onPageSelected(int position){
mActionBar.setSelectedNavigationItem(position);
}
@Override
publicvoid onPageScrollStateChanged(int state){
}
@Override
publicvoid onTabSelected(Tab tab,FragmentTransaction ft){
Object tag = tab.getTag();
for(int i=0; i<mTabs.size(); i++){
if(mTabs.get(i)== tag){
mViewPager.setCurrentItem(i);
}
}
}
@Override
publicvoid onTabUnselected(Tab tab,FragmentTransaction ft){
}
@Override
publicvoid onTabReselected(Tab tab,FragmentTransaction ft){
}
}
}