android - 循环 FragmentPagerAdapter

Question

我有一个可以正常工作的 FragmentPagerAdapter 但我想知道的是，如果 FragmentPagerAdapter 在最后一个 View 中，我如何让它循环回到首先查看并像往常一样继续

这是我正在使用的示例代码

public class FragmentPager extends FragmentActivity {
MyAdapter mAdapter;
ViewPager mPager;
static final int NUM_ITEMS = 5;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    mAdapter = new MyAdapter(getSupportFragmentManager());

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

public static class MyAdapter extends FragmentPagerAdapter {
    public MyAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public int getCount() {
        return NUM_ITEMS;
    }

    @Override
    public Fragment getItem(int position) {
        return MyFragment.newInstance(position);
    }
}

public static class MyFragment extends ListFragment{
    int mNum;

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

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

        return f;
    }

    /**
     * When creating, retrieve this instance's number from its arguments.
     */
    @Override
    public void 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
    public View 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
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        setListAdapter(new ArrayAdapter<String>(getActivity(),
                android.R.layout.simple_list_item_1, new String[] {"test1","test2","test3","test4","Test5"}));
    }

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

}

基本上，当它结束时，我如何让它显示第一个 fragment ，因为它会转到任何其他 fragment ？

即。 A->B, B->C、C->A 和向后的 A->C、C->B、B->A

Answer 1

这是我的解决方案，我有“n”个屏幕(在本例中为 5 个)，因为我想回到列表末尾的第一个屏幕，所以我“添加另一个屏幕”，这只是一个精确的副本最后一个屏幕的最后一个屏幕，也为相反的方向执行此操作。基本上我现在有“n”个屏幕+2(在这种情况下现在是 7 个)。屏幕设置如下 copy of C,A,B,C,copy of A 然后我设置了一个手势监听器来观察某些页面上的滑动。

如果在列表的末尾(“A 的副本”)并且我检测到向左滑动 > 一定数量的像素 我移动到页面 A并继续在正常的页面旋转中向后滑动。

向相反方向滑动也是如此。

问题

当从结束页面之一移动以模拟循环时，它确实会有点慢，因为 ViewPager 会加载您当前所在页面之前和之后的页面，但由于您在最后或页面列表的开头，它不会像通常那样加载下一页，因为从技术上讲没有下一页。只有当您对每个列表行都有复杂的自定义 View 时才会发生这种情况

你不能将它与动画一起用于页面滚动，因为它看起来不会无缝，并且当你从复制的页面移动到实际页面时会动画，即 A 的副本到 A。

而且有时它似乎确实卡在了页面的末尾，我不知道为什么

这是我基于 android 开发者网站上的 viewpager 示例的完整演示应用程序

public class FragmentPager extends FragmentActivity{
MyAdapter mAdapter;
public static ViewPager mPager;
static int currentPage = 1;
static final int NUM_ITEMS = 7;
public static View vContainer;
float dxInitial=0;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    mAdapter = new MyAdapter(getSupportFragmentManager());

    mPager = (ViewPager)findViewById(R.id.pager);
    mPager.setAdapter(mAdapter);
    mPager.setCurrentItem(1,false);

    mPager.setOnTouchListener(new OnTouchListener(){

        @Override
        public boolean onTouch(View v, MotionEvent event) {


            if(event.getAction() == MotionEvent.ACTION_DOWN){
                dxInitial=event.getX();
                Log.d("INITIAL X", String.valueOf(dxInitial));
            }else if(event.getAction() == MotionEvent.ACTION_MOVE){
                if(event.getX() - dxInitial > 100 && currentPage==1){
                    mPager.setCurrentItem(6,false);
                }else if(dxInitial - event.getX() > 100 && currentPage==5){
                    mPager.setCurrentItem(0,false);
                }else if(dxInitial - event.getX() > 50 && currentPage==6){
                    mPager.setCurrentItem(1,false);
                }else if(event.getX() - dxInitial > 50 && currentPage==0){
                    mPager.setCurrentItem(5,false);
                }
            }

            /*if(Math.abs(dx) > Math.abs(dy)) {
                if(dx>75){ directiion = "right";
                }else if{
                    direction = "left";
                }
            } else {
                if(dy>0) direction = "down";
                else direction = "up";
            }*/

            return false;
        }

    });
    mPager.setOnPageChangeListener(new OnPageChangeListener(){

        @Override
        public void onPageScrollStateChanged(int state) {
            // TODO Auto-generated method stub
            if(state == ViewPager.SCROLL_STATE_IDLE){

            }
        }

        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

        }

        @Override
        public void onPageSelected(int arg0) {
            currentPage=arg0;

        }

    });
}

public static class MyAdapter extends FragmentPagerAdapter{
    public MyAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public int getCount() {
        return NUM_ITEMS;
    }

    @Override
    public Fragment getItem(int position) {
        return MyFragment.newInstance(position);
    }

    @Override
    public Object instantiateItem(View container, int position) {
        vContainer=container;
        return super.instantiateItem(container, position);

    }
}

public static class MyFragment extends ListFragment{
    int mNum;

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

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

        return f;
    }

    /**
     * When creating, retrieve this instance's number from its arguments.
     */
    @Override
    public void 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
    public View 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);
        if(mNum == 6){
            mNum=1;
        }else if(mNum==7){
            mNum=5;
        }else if(mNum==0){
            mNum=5;
        }
        ((TextView)tv).setText("Fragment #" + mNum);
        return v;
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        setListAdapter(new ArrayAdapter<String>(getActivity(),
                android.R.layout.simple_list_item_1, new String[] {"test1","test2","test3","test4","Test5"}));
    }

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

}