android - VIEW PAGER 如何更改视图堆栈中的页面顺序

Question

我对 ViewPager 类有疑问。正如您在屏幕截图中看到的，正常页面从上到下按从左到右的顺序排列：右页在底部，而不是中央，最上面是左页，我想把中央（中间) 位于此堆栈顶部的页面。你怎么想，这是可能的？

现在如何：

http://oi57.tinypic.com/2hdsehd.jpg

我想要达到的目标：

http://oi60.tinypic.com/jkyddl.jpg

  @Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    mContent = inflater.inflate(R.layout.fragment_main, container, false);
    mViewPager = (ViewPager) mContent.findViewById(R.id.view_pager);
    mViewPager.setAdapter(new ViewPagerAdapter(getChildFragmentManager()));
    mViewPager.setCurrentItem(1);
    mViewPager.setPageTransformer(true, new DepthPageTransformer());

    return mContent;
}


class ViewPagerAdapter extends FragmentPagerAdapter {

    public ViewPagerAdapter(FragmentManager fm) {
        super(fm);
    }

    @Override
    public android.support.v4.app.Fragment getItem(int position) {

        switch (position) {
            case 0:
                return new FriendsFragment();
            case 1:
                return new CenterFragment();
            case 2:
                return new MenuFragment();
        }
        return new FriendsFragment();
    }

    @Override
    public float getPageWidth(int page) {
        if (page != 1) {
            Display display = getActivity().getWindowManager().getDefaultDisplay();
            Point size = new Point();
            display.getSize(size);
            Log.e("", "x: " + size.x);
            return 0.8f;
        } else
            return super.getPageWidth(page);
    }

    @Override
    public int getCount() {
        return 3;
    }
}

public class DepthPageTransformer implements ViewPager.PageTransformer {
    private static final float MIN_SCALE = 0.75f;

    public void transformPage(View view, float position) {
        int pageWidth = view.getWidth();

        Log.e("", "position: " + position + " pageWidth: " + pageWidth);

        if (position < -1) { // [-Infinity,-1)
            // This page is way off-screen to the left.
            //view.setAlpha(0);

        } else if (position <= 0) { // [-1,0]
            // Use the default slide transition when moving to the left page
            //                view.setAlpha(1);
            //                view.setScaleX(1);
            //                view.setScaleY(1);
            view.setTranslationX(pageWidth * -position );

        } else if (position <= 1) { // (0,1]
            // Fade the page out.
            //view.setAlpha(1 - position);

            // Counteract the default slide transition
            view.setTranslationX(pageWidth * -position + pageWidth / 5);

            // Scale the page down (between MIN_SCALE and 1)
            //                float scaleFactor = MIN_SCALE
            //                        + (1 - MIN_SCALE) * (1 - Math.abs(position));
            //                view.setScaleX(scaleFactor);
            //                view.setScaleY(scaleFactor);

        } else { // (1,+Infinity]
            // This page is way off-screen to the right.
            //view.setTranslationX(pageWidth * -position + pageWidth/5);
        }
    }
}

Answer 1

just change your code like this

switch (position) {
        case 0:
            return new CenterFragment();
        case 1:
            return new FriendsFragment();
        case 2:
            return new MenuFragment();
    }