RecyclerView 实现 OnItemTouchListener with LinearLayoutManager 正常滚动

Question

我正在尝试实现一个用例，当用户以低速滚动时，我需要正常滚动 RecyclerView（Android LayoutManager 滚动），而当用户向上滚动时，我需要滚动一定的额外量一定的速度。

我实现了一个 LinearLayoutManager 如下：

public class ScrollLayoutManager extends LinearLayoutManager {
    // constructors

    @Override
    public void onAttachedToWindow(RecyclerView recyclerView) {
        Log.d(TAG, "onAttachedToWindow");
        super.onAttachedToWindow(recyclerView);
        mRecyclerView = recyclerView;
        mRecyclerView.addOnItemTouchListener(new ThresholdDetector());
    }

    private final class ThresholdDetector implements RecyclerView.OnItemTouchListener {
        @Override
        public boolean onInterceptTouchEvent(RecyclerView recyclerView, MotionEvent e) {
            // some calculations
            return true;
        }

        @Override
        public void onTouchEvent(final RecyclerView view, final MotionEvent e) {
            final int action = e.getActionMasked();
            mVelocityTracker.addMovement(e);
            if(action == MotionEvent.ACTION_MOVE) {
                if (thresholdMet) {
                    // Custom scroll
                    mRecyclerView.scrollBy(calculatedAmount)
                } else {
                    // Scroll normally as per Android LinearLayoutManager
                }
            }
        }
    }
}

如果不满足阈值，我需要Android来处理滚动，否则无法平滑滚动。我在 else 中尝试了以下方法（当未达到阈值时），但它并不完全有效。

                    mRecyclerView.post(new Runnable() {
                        @Override
                        public void run() {
                            mRecyclerView.smoothScrollBy(-(int)getDeltaX(motionEvent), 0);
                        }
                    });

Answer 1

如果不完整地查看 ThresholdDetector class，就无法确定最佳解决方案是什么。也就是说，我认为问题在于您总是从 onInterceptTouchEvent().

returning true

在 onInterceptTouchEvent() 的 return 值的文档中：

Returns: true if this OnItemTouchListener wishes to begin intercepting touch events, false to continue with the current behavior and continue observing future events in the gesture.

并且在 onTouchEvent() 的描述中：

Process a touch event as part of a gesture that was claimed by returning true from a previous call to onInterceptTouchEvent().

换句话说，只有当您 return true 来自 onInterceptTouchEvent() 的给定事件时，才会调用 onTouchEvent()。如果您希望 RecyclerView 执行其默认行为，只需 return false from onInterceptTouchEvent() 当滚动速度低于您的阈值时。

RecyclerView 实现 OnItemTouchListener with LinearLayoutManager 正常滚动

RecyclerView that implements OnItemTouchListener with LinearLayoutManager scrolling normally

android

ontouchlistener

ontouch

android-recyclerview