Ich habe das FragmentBasics-Beispiel vonHier. Gibt es eine Möglichkeit, die ViewPager-Animation einfach ein- und auszublenden, wenn ich wische, anstatt nach links und rechts zu schieben? Ich habe einige Dinge mit PageTransformer ausprobiert, aber kein Erfolg. Ich kann immer noch sehen, wie sie abrutschen. Ich schätze, ich muss irgendwie seine Position erzwingen, um in Position zu bleiben, während das Gleiten meines Fingers nur das Alpha beeinflusst.

public class SecondActivity extends Activity {

SectionsPagerAdapter mSectionsPagerAdapter;

ViewPager mViewPager;

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

    // Create the adapter that will return a fragment for each of the three
    // primary sections of the activity.
    mSectionsPagerAdapter = new SectionsPagerAdapter(getFragmentManager());

    // Set up the ViewPager with the sections adapter.
    mViewPager = (ViewPager) findViewById(R.id.pager);
    mViewPager.setPageTransformer(false, new FadePageTransformer());
    mViewPager.setAdapter(mSectionsPagerAdapter);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {

    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.second, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

public class SectionsPagerAdapter extends FragmentPagerAdapter {

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

    @Override
    public Fragment getItem(int position) {
        // getItem is called to instantiate the fragment for the given page.
        // Return a PlaceholderFragment (defined as a static inner class below).
        return PlaceholderFragment.newInstance(position + 1);
    }

    @Override
    public int getCount() {
        // Show 3 total pages.
        return 3;
    }

    @Override
    public CharSequence getPageTitle(int position) {
        Locale l = Locale.getDefault();
        switch (position) {
        case 0:
            return getString(R.string.title_section1).toUpperCase(l);
        case 1:
            return getString(R.string.title_section2).toUpperCase(l);
        case 2:
            return getString(R.string.title_section3).toUpperCase(l);
        }
        return null;
    }
}

public static class PlaceholderFragment extends Fragment {
    /**
     * The fragment argument representing the section number for this fragment.
     */
    private static final String ARG_SECTION_NUMBER = "section_number";

    /**
     * Returns a new instance of this fragment for the given section number.
     */
    public static PlaceholderFragment newInstance(int sectionNumber) {
        PlaceholderFragment fragment = new PlaceholderFragment();
        Bundle args = new Bundle();
        args.putInt(ARG_SECTION_NUMBER, sectionNumber);
        fragment.setArguments(args);
        return fragment;
    }

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_second, container, false);
        TextView textView = (TextView) rootView.findViewById(R.id.section_label);
        textView.setText(Integer.toString(getArguments().getInt(ARG_SECTION_NUMBER)));
        return rootView;
    }
}

public class FadePageTransformer implements ViewPager.PageTransformer {
        public void transformPage(View view, float position) {

            if (position < -1 || position > 1) {
                view.setAlpha(0);
            }
            else if (position <= 0 || position <= 1) {
                // Calculate alpha. Position is decimal in [-1,0] or [0,1]
                float alpha = (position <= 0) ? position + 1 : 1 - position;
                view.setAlpha(alpha);
            }
            else if (position == 0) {
                view.setAlpha(1);
            }
        }
    }