Question

我正在使用castorflex / VerticalViewPager库，里面包含ListView的片段。问题是，当我开始滑动ListView元素时，我无法更改ViewPager的页面。当ListView到达ViewPager列表的顶部/底部时，有没有办法传递触摸事件？我不想达到平滑的效果（当列表不能再滚动时，ViewPager开始滚动，所有在一个触摸事件中）

Answer 1

这是我实施的垂直寻呼机类的解决方案here

而不是RecyclerView实现扩展它的自定义类，并在我们的自定义RecyclerView类覆盖中 public boolean onTouchEvent(MotionEvent event)

在这里，我们可以将MotionEvent event传递给类似下面的类，以确定是否应该拦截事件：

/**
 * Tests the MotionEvent for valid behavior to care about overriding the touch event with
 */
private boolean shouldDisableScrollableParent(final MotionEvent event) {
    boolean intercept = false;
    float x = event.getX();
    float y = event.getY();

    switch (event.getAction()) {
        case MotionEvent.ACTION_MOVE:

            float dx = x - mPreviousX;
            float dy = y - mPreviousY;

            // Here you can try to detect the swipe. It will be necessary to
            // store more than the previous value to check that the user move constantly in the same direction
            intercept = detectSwipe(dx, dy);
            break;

        case MotionEvent.ACTION_UP:
        case MotionEvent.ACTION_CANCEL:
        default:
            break;
    }

    mPreviousX = x;
    mPreviousY = y;

    return intercept;
}

/**
 * Tests if we want to disable the parent touch interception
 */
private boolean detectSwipe(final float dx, final float dy) {
    // True if we're scrolling in Y direction
    if (Math.abs(dx) < Math.abs(dy)) {
        FoundationLog.d(TAG, "Direction Y is yielding: " + dy);

        if (dy < 0) {
            // Touch from lower to higher
            return true;
        }

        // Top view isn't shown, can always scroll up
        final View view = getChildAt(0);
        if (view == null) {
            return true;
        }

        // Top view baseline doesn't equal to top of the RecyclerView
        if (view.getTop() < 0) {
            return true;
        }
    }

    return false;
}

然后在自定义RecyclerView类的public boolean onTouchEvent(MotionEvent event)方法中，检查getParent()（并且可能迭代地向根父级）解析是否解析为ViewParent的类。查看您要覆盖的触摸。如果是，请在requestDisallowInterceptTouchEvent()

上将true设置为ViewParent

Answer 2

这是一个迟到的回复，但我最近被要求将我们的应用程序ViewPager更改为垂直，我的列表内部存在完全相同的问题。我希望这可以帮助其他可能遇到同样问题的人。

首先，我的Fragment是ListFragment的扩展，但它对于任何包含列表的Fragment（显然有轻微修改）的工作方式相同。首先，我在我的列表上设置了OnScrollListener，在onScrollStateChanged中我有一个方法updateListVisibility，如果列表的顶部或底部的顶部在列表中可见（updateListPositionVisibility），则返回我的Activity更新。

public class MyListFragment extends ListFragment {

   .....
   private OnScrollStateChangedListener mListener;
   .....

    @Override
    public void onViewCreated(View view, Bundle savedInstanceState) {

        super.onViewCreated(view, savedInstanceState);
        ......
        getListView().setOnScrollListener(new AbsListView.OnScrollListener() {

            @Override
            public void onScrollStateChanged(AbsListView view, int scrollState) {
                updateListVisibility();
            }

            @Override
            public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {

            }
        });
    }

    public void updateListVisibility() {

        if (getListView() != null && getListView().getChildCount() > 0) {

            boolean firstItemVisible = getListView().getFirstVisiblePosition() == 0;
            boolean topOfFirstItemVisible = getListView().getChildAt(0).getTop() == 0;

            boolean lastItemVisible = getListView().getLastVisiblePosition() == getListView().getAdapter().getCount() - 1;
            boolean bottomOfLastItemVisible = getListView().getChildAt(getListView().getChildCount() - 1).getBottom() <= getListView().getHeight();

            mListener.updateListPositionVisibility(firstItemVisible && topOfFirstItemVisible, lastItemVisible && bottomOfLastItemVisible);
        }
    }

    @Override   
    public void onAttach(Activity activity) {

        super.onAttach(activity);
        try {
            mListener = (OnScrollStateChangedListener) activity;
        } catch (ClassCastException e) {
            throw new ClassCastException(activity.toString() + " must implement OnScrollStateChangedListener");
        }
    }


    /**
     * Container Activity must implement this interface....
     */
    public interface OnScrollStateChangedListener {

        public void updateListPositionVisibility(boolean topIsVisible, boolean bottomIsVisible);
    }

    .....
}

在我的活动中，我在ViewPager上设置了OnPageChangeListener，在onPageSelected中我使用我的适配器来获取Fragment，以便我可以在其上调用updateListVisibility，然后调用回我的活动。我的回调实现使用列表顶部和底部的可见性状态更新了ViewPager（请参阅setListViewPositionsInViewPager）。

public class VerticallyPagedActivity extends BaseFragmentActivity implements
    MyListFragment.OnScrollStateChangedListener {

    @Override
    protected void onCreate(Bundle savedInstanceState) {

        ......

        mPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
        @Override
        public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {

        }

        @Override
        public void onPageSelected(int position) {
            Object fragment = mAdapter.mItems.get(position);
            if (fragment instanceof MyListFragment) {
                ((MyListFragment) fragment).updateListVisibility();
            } else {
                setListViewPositionsInViewPager(false, false);
            }
        }

        @Override
        public void onPageScrollStateChanged(int state) {

        }
    });
}

public void setListViewPositionsInViewPager(boolean handleEventTop, boolean handleEventBottom) {
    mPager.setListVisibility(handleEventTop, handleEventBottom);
}

// Callback.
@Override
public void updateListPositionVisibility(boolean topIsVisible, boolean bottomIsVisible) {
    setListViewPositionsInViewPager(topIsVisible, bottomIsVisible);
}

我的适配器只是在mItems中维护一个片段的实例。

public class MyAdapter extends FragmentStatePagerAdapter {

    .....
    public Map<Integer, Fragment> mItems;

    public MyAdapter(FragmentManager fm, List<Content> content) {
    super(fm);
    mItems = new HashMap<>();
    .....

    @Override
    public Fragment getItem(int position) {

        .....   
        MyListFragment fragment = new MyListFragment();
        .....
        mItems.put(position, fragment);
        return fragment;
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        mItems.remove(position);
        super.destroyItem(container, position, object);
    }
}

然后在我的Castorflex垂直视图分页器中，我使用名为setListVisibility的方法设置列表可见性值。每次滚动列表或查看ViewPager时都会更新这些内容，这意味着它们始终是最新的。然后，当顶部可见并且用户试图上升或底部可见并且用户试图关闭时，寻呼机最重要的部分是拦截事件。使用在MotionEvent.ACTION_MOVE下的switch语句内计算的dy值可以轻松实现这一点。

public class VerticalPager extends ViewGroup {

    .....
    private boolean topOfListIsVisible;
    private boolean bottomOfListIsVisible;

    public void setListVisibility(boolean pTop, boolean pBottom) {
        topOfListIsVisible = pTop;
        bottomOfListIsVisible = pBottom;
    }

    .....

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {

        ......

        switch (action) {
            case MotionEvent.ACTION_MOVE: {

            ......
            final float y = MotionEventCompat.getY(ev, pointerIndex);
            final float dy = y - mLastMotionY;
            final float yDiff = Math.abs(dy);
            ......

            // Pager needs to handle the event.
            if (topOfListIsVisible && bottomOfListIsVisible || bottomOfListIsVisible && dy < 0 || topOfListIsVisible && dy > 0) {
                return true;
            }

        }
        .....
    }

    .....
}

使用ListView滚动垂直ViewPager

2 个答案: