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如何使用 CoordinatorLayout.Behavior 检测嵌套投掷是否完全停止？当回收站视图完全停止时，没有这样的 api 可以给我回调。

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2 回答 2

6

当RecyclerView正在滚动时，我试图隐藏浮动操作按钮(FAB) 时，我从这个兔子洞开始。根据多个来源执行此操作的正确方法是扩展FloatingActionButton.Behavior，覆盖and方法，并将您的行为与 FAB 挂钩，例如. 这适用于正常（慢速）滚动事件，但不会在投掷结束时调用。 onStartNestedScrollonStopNestedScrollapp:layout_behavior="com.justingarrick.ui.ScrollAwareFabBehavior"onStopNestedScroll

目前，似乎有一些关于投掷和滚动行为的未解决问题；我的解决方法是为我的 RecyclerView 实现一个OnScrollListener并以编程方式更改 FAB 的状态，例如

public class MyFragment extends Fragment {

    @Bind(R.id.account_list) RecyclerView recyclerView;
    @Bind(R.id.button_fab) FloatingActionButton fab;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_accounts, container, false);
        ButterKnife.bind(this, view);

        recyclerView.setLayoutManager(layoutManager);
        recyclerView.setAdapter(adapter);
        recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                super.onScrollStateChanged(recyclerView, newState);
                if (newState == RecyclerView.SCROLL_STATE_DRAGGING)
                    fab.hide(); // or hideFab(), see below
                else if (newState == RecyclerView.SCROLL_STATE_IDLE)
                    fab.show(); // or showFab(), see below
            }
        });

        return view;
    }
}

更新：这在 99% 的情况下都可以正常工作，但是如果您使用设计库版本 22.2.1 中的show()和hide()方法，当您尝试在 RecyclerView 顶部向上滚动或在RecyclerView 的底部，因为回收器视图正在快速切换状态，RecyclerView.SCROLL_STATE_DRAGGING以至于RecyclerView.SCROLL_STATE_IDLE它在FloatingActionButtonHoneycombMr1#show(). setVisibility()所以，要解决这个问题（叹气），如果你不关心动画，你要么需要切换到调用，要么在没有竞争条件的情况下重新实现动画，例如

private void hideFab() {
     fab.animate().scaleX(0.0F).scaleY(0.0F).alpha(0.0F).setDuration(200L).setInterpolator(new FastOutSlowInInterpolator()).setListener(new AnimatorListenerAdapter() {
         @Override
         public void onAnimationEnd(Animator animation) {
             fab.setVisibility(View.GONE);
         }
     });
 }

 private void showFab() {
     fab.animate().scaleX(1.0F).scaleY(1.0F).alpha(1.0F).setDuration(200L).setInterpolator(new FastOutSlowInInterpolator()).setListener(new AnimatorListenerAdapter() {
         @Override
         public void onAnimationStart(Animator animation) {
            fab.setVisibility(View.VISIBLE);
         }
     });
 }
于 2015-08-10T15:49:26.080 回答
0

我使用 ScrollerCompat 和方法 ScrollerCompat.fling(..) 来处理滚动的中间状态。所以我知道滚动何时结束。

@Override
public boolean onNestedFling(final CoordinatorLayout coordinatorLayout, final AppBarLayout child, final View target, final float velocityX, final float velocityY, final boolean consumed) {
    final int scrollY = target.getScrollY();
    final double distance = mFlingHelper.getSplineFlingDistance(velocityY);

    fling(
            child,
            (int) distance + scrollY,
            velocityY,
            scrollY);

    return super.onNestedFling(coordinatorLayout, child, target, velocityX, velocityY, consumed);
}

private void fling(final View pChild, final int pMaxOffset, final float pVelocityY, final int pStartY) {
    stopFling(pChild);
    mIsFlingRunning = true;

    if (mScroller == null) {
        mScroller = ScrollerCompat.create(mContext);
    }

    mScroller.fling(
        0, pStartY, // current
        0, Math.round(pVelocityY), // velocity.
        0, 0, // x
        0, pMaxOffset); // y

    if (mScroller.computeScrollOffset()) {
        mFlingRunnable = new FlingRunnable(pChild);
        ViewCompat.postOnAnimation(pChild, mFlingRunnable);
    }

}

private void stopFling(final View pChild) {
    if (mFlingRunnable != null) {
        pChild.removeCallbacks(mFlingRunnable);
        mFlingRunnable = null;
    }
}




private class FlingRunnable implements Runnable {

     private final View mView;

     FlingRunnable(final View pView) {
         mView = pView;
     }

     @Override
     public void run() {
         if (mView != null && mScroller != null) {
             if (mScroller.computeScrollOffset()) {
                 mIsFlingRunning = true;
                 // Post ourselves so that we run on the next animation
                 ViewCompat.postOnAnimation(mAppBarLayout, this);
             }
         } else {
             mIsFlingRunning = false;
         }
     }
 }
于 2017-05-25T08:30:33.913 回答