Class Overview

它是PagerAdapter的一种实现，每一个页面都是一个Fragment，并且每一个页面都会保存到fragment manager中，当用户没有可能回到该页面时fragment manager才会将这个fragment销毁。

这种页面十分适用于有一些静态的fragment，例如一组tabs，用户访问的每一个页面都会保存在内存中，尽管当view不可见时可能会被销毁。这就会导致应用程序会占用太多的资源，所以，通常当页面数据量过大时使用FragmentStatePagerAdapter来代替FragmentPagerAdapter

当使用FragmentPageAdapter时ViewPager必须有一个ID。

子类只需要实现适配器的getItem(int)和getCount()方法

下面是官方给出的一个例子：

publicclassFragmentPagerSupportextendsFragmentActivity{
    staticfinalint NUM_ITEMS =10;

    MyAdapter mAdapter;

    ViewPager mPager;

    @Override
    protectedvoid onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.fragment_pager);

        mAdapter =newMyAdapter(getSupportFragmentManager());

        mPager =(ViewPager)findViewById(R.id.pager);
        mPager.setAdapter(mAdapter);

        // Watch for button clicks.
        Button button =(Button)findViewById(R.id.goto_first);
        button.setOnClickListener(newOnClickListener(){
            publicvoid onClick(View v){
                mPager.setCurrentItem(0);
            }
        });
        button =(Button)findViewById(R.id.goto_last);
        button.setOnClickListener(newOnClickListener(){
            publicvoid onClick(View v){
                mPager.setCurrentItem(NUM_ITEMS-1);
            }
        });
    }

    publicstaticclassMyAdapterextendsFragmentPagerAdapter{
        publicMyAdapter(FragmentManager fm){
            super(fm);
        }

        @Override
        publicint getCount(){
            return NUM_ITEMS;
        }

        @Override
        publicFragment getItem(int position){
            returnArrayListFragment.newInstance(position);
        }
    }

    publicstaticclassArrayListFragmentextendsListFragment{
        int mNum;

        /**
         * Create a new instance of CountingFragment, providing "num"
         * as an argument.
         */
        staticArrayListFragment newInstance(int num){
            ArrayListFragment f =newArrayListFragment();

            // Supply num input as an argument.
            Bundle args =newBundle();
            args.putInt("num", num);
            f.setArguments(args);

            return f;
        }

        /**
         * When creating, retrieve this instance‘s number from its arguments.
         */
        @Override
        publicvoid onCreate(Bundle savedInstanceState){
            super.onCreate(savedInstanceState);
            mNum = getArguments()!=null? getArguments().getInt("num"):1;
        }

        /**
         * The Fragment‘s UI is just a simple text view showing its
         * instance number.
         */
        @Override
        publicView onCreateView(LayoutInflater inflater,ViewGroup container,
                Bundle savedInstanceState){
            View v = inflater.inflate(R.layout.fragment_pager_list, container,false);
            View tv = v.findViewById(R.id.text);
            ((TextView)tv).setText("Fragment #"+ mNum);
            return v;
        }

        @Override
        publicvoid onActivityCreated(Bundle savedInstanceState){
            super.onActivityCreated(savedInstanceState);
            setListAdapter(newArrayAdapter<String>(getActivity(),
                    android.R.layout.simple_list_item_1,Cheeses.sCheeseStrings));
        }

        @Override
        publicvoid onListItemClick(ListView l,View v,int position,long id){
            Log.i("FragmentList","Item clicked: "+ id);
        }
    }
}

The R.layout.fragment_pager resource of the top-level fragment is:

<LinearLayoutxmlns:android="http://schemas.android.com/apk/res/android"
        android:orientation="vertical"android:padding="4dip"
        android:gravity="center_horizontal"
        android:layout_width="match_parent"android:layout_height="match_parent">

    <android.support.v4.view.ViewPager
            android:id="@+id/pager"
            android:layout_width="match_parent"
            android:layout_height="0px"
            android:layout_weight="1">
    </android.support.v4.view.ViewPager>

    <LinearLayoutandroid:orientation="horizontal"
            android:gravity="center"android:measureWithLargestChild="true"
            android:layout_width="match_parent"android:layout_height="wrap_content"
            android:layout_weight="0">
        <Buttonandroid:id="@+id/goto_first"
            android:layout_width="wrap_content"android:layout_height="wrap_content"
            android:text="@string/first">
        </Button>
        <Buttonandroid:id="@+id/goto_last"
            android:layout_width="wrap_content"android:layout_height="wrap_content"
            android:text="@string/last">
        </Button>
    </LinearLayout>
</LinearLayout>

The R.layout.fragment_pager_list resource containing each individual fragment‘s layout is:

<LinearLayoutxmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:drawable/gallery_thumb">

    <TextViewandroid:id="@+id/text"
        android:layout_width="match_parent"android:layout_height="wrap_content"
        android:gravity="center_vertical|center_horizontal"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:text="@string/hello_world"/>

    <!-- The frame layout is here since we will be showing either
    the empty view or the list view.  -->
    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="0dip"
        android:layout_weight="1">
        <!-- Here is the list. Since we are using a ListActivity, we
             have to call it "@android:id/list" so ListActivity will
             find it -->
        <ListViewandroid:id="@android:id/list"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:drawSelectorOnTop="false"/>

        <!-- Here is the view to show if the list is emtpy -->
        <TextViewandroid:id="@android:id/empty"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:textAppearance="?android:attr/textAppearanceMedium"
            android:text="No items."/>

    </FrameLayout>

</LinearLayout>

Summary

[Expand] Inherited Constants
From class android.support.v4.view.PagerAdapter