android - 在 ViewPager 上，在 onPageSelected 上的 Fragment 上启动动画

Question

我有一个带有 FragmentPageAdapter 的 ViewPager。显示 fragment 时，我希望它启动动画(淡入 fragment 中的 View )。

但是，动画运行不一致，当我向左/向右滑动时，它每隔几页运行一次。我想我需要在 onPageSelected 事件上启动动画，但我不知道如何获取 fragment 并启动动画。

我的代码如下。 TourFragment 是我使用 FragmentPageAdapter 添加到 ViewPager 的 fragment ，而 TourActivty 包含 ViewPager。

旅游 fragment

public class TourFragment extends Fragment  {

    Tour tour;
    ImageView ivTitle;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {

    View v = inflater.inflate(R.layout.fragment_tour,
            container, false);

    RelativeLayout rlImageContainer = (RelativeLayout) v.findViewById(R.id.tour_image_container);

    Resources resources = getActivity().getResources();

    ivTitle = (ImageView) v.findViewById(R.id.tour_title);
    ivTitle.setImageDrawable(resources.getDrawable(tour.getDrawableTitleId()));

    Animation fadeInAnimation = AnimationUtils.loadAnimation(getActivity(), R.anim.fadein);
    ivTitle.startAnimation(fadeInAnimation );

    return v;
}

@Override
public void onResume() {
    super.onResume();
    Animation fadeInAnimation = AnimationUtils.loadAnimation(getActivity(), R.anim.fadein);
    ivTitle.startAnimation(fadeInAnimation );
}



public static Fragment newInstance(Tour tour) {

    TourFragment f = new TourFragment();
    f.tour = tour;
    return f;
}
}

旅游 Activity

public class TourActivity extends FragmentActivity {

MyPageAdapter pageAdapter;
String tourType;
Drawable drawableSelected;
Drawable drawableNotSelected;
LinearLayout llIndicators;
int prevPagePosition = 0;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_tour);

    List<Fragment> fragments = getFragments();
    pageAdapter = new MyPageAdapter(getSupportFragmentManager(), fragments);
    ViewPager pager = (ViewPager) findViewById(R.id.viewpager);
    pager.setAdapter(pageAdapter);

    pager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int i, float v, int i2) {

        }

        @Override
        public void onPageSelected(int position) {

        }

        @Override
        public void onPageScrollStateChanged(int i) {

        }
        });
    }

    private List<Fragment> getFragments(){
    List<Fragment> fList = new ArrayList<Fragment>();

    List<Tour> tours = new ArrayList<Tour>();

        messages = getResources().getStringArray(R.array.guess_tour_messages);
        Tour tour = new Tour();
        tour.setDrawableImageId(R.drawable.tu_guest_image_1);
        tour.setDrawableTitleId(R.drawable.tu_guest_text_1);
        tour.setMessage(messages[0]);
        tour.setPageIndex(0);
        tour.setTotalPages(messages.length);
        tours.add(tour);

        tour = new Tour();
        tour.setDrawableImageId(R.drawable.tu_guest_image_2);
        tour.setDrawableTitleId(R.drawable.tu_guest_text_2);
        tour.setMessage(messages[1]);
        tour.setPageIndex(1);
        tour.setTotalPages(messages.length);
        tours.add(tour);

        tour = new Tour();
        tour.setDrawableImageId(R.drawable.tu_guest_image_3);
        tour.setDrawableTitleId(R.drawable.tu_guest_text_3);
        tour.setMessage(messages[2]);
        tour.setPageIndex(2);
        tour.setTotalPages(messages.length);
        tours.add(tour);

        tour = new Tour();
        tour.setDrawableImageId(R.drawable.tu_guest_image_4);
        tour.setDrawableTitleId(R.drawable.tu_guest_text_4);
        tour.setMessage(messages[3]);
        tour.setPageIndex(3);
        tour.setTotalPages(messages.length);
        tours.add(tour);


    for (Tour tour : tours) {
        fList.add(TourFragment.newInstance(tour));
    }


    return fList;
}

}

class MyPageAdapter extends FragmentPagerAdapter {
private List<Fragment> fragments;

public MyPageAdapter(FragmentManager fm, List<Fragment> fragments) {
    super(fm);
    this.fragments = fragments;
}

@Override
public Fragment getItem(int position) {
    return this.fragments.get(position);
}

@Override
public int getCount() {
    return this.fragments.size();
}
}

Answer 1

你应该在你的 fragment 中使用

@Override
public void setUserVisibleHint(boolean isVisibleToUser) {
    super.setUserVisibleHint(isVisibleToUser);
    if (isVisibleToUser) { 
        Log.v(TAG, "run now");
            Animation animationFadeIn = AnimationUtils.loadAnimation(getActivity(), R.anim.fade_view);
            iv.startAnimation(animationFadeIn);
            animationFadeIn.setFillAfter(true);
    }
    else {  }
}