我们如何知道用户在RecyclerView 中是向下滚动还是向上滚动？
我尝试使用 RecyclerView#OnScrollListener ，它给出了垂直滚动量和滚动状态。滚动状态空闲时如何获取开始拖动和滚动位置时的最后滚动位置。
【问题讨论】：
标签： java android android-recyclerview onscrolllistener
这段代码对我有用
private var nearmeListScrollListener = object : RecyclerView.OnScrollListener() {
override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
super.onScrolled(recyclerView, dx, dy)
if (recyclerView.scrollState == RecyclerView.SCROLL_STATE_SETTLING)
if (dy > 0) {
layout_vendros_list_header.hide()
layout_vendros_list_header.animate().translationY(1f)
} else if (dy < 0) {
layout_vendros_list_header.show()
layout_vendros_list_header.animate().translationY(0f)
}
}
}
```
【讨论】：
我的CustomRecyclerView 实现了所有类型的滚动监听器
public class CustomRecyclerView extends RecyclerView
{
private boolean mIsScrolling;
private boolean mIsTouching;
private OnScrollListener mOnScrollListener;
private Runnable mScrollingRunnable;
private int y = 0;
public abstract static class OnScrollListener
{
void onScrollChanged(CustomRecyclerView RvView, int x, int y, int oldX, int oldY)
{
//if you need just override this method
}
void onEndScroll(CustomRecyclerView RvView)
{
//if you need just override this method
}
protected abstract void onGoUp();
protected abstract void onGoDown();
}
public CustomRecyclerView(final Context context)
{
super(context);
}
public CustomRecyclerView(final Context context, @Nullable final AttributeSet attrs)
{
super(context, attrs);
}
public CustomRecyclerView(final Context context, @Nullable final AttributeSet attrs, final int defStyle)
{
super(context, attrs, defStyle);
}
@Override
public boolean dispatchTouchEvent(MotionEvent iEv)
{
if (isEnabled())
{
processEvent(iEv);
super.dispatchTouchEvent(iEv);
return true; //to keep receive event that follow down event
}
return super.dispatchTouchEvent(iEv);
}
private void processEvent(final MotionEvent iEv)
{
switch (iEv.getAction())
{
case MotionEvent.ACTION_DOWN:
y = (int) iEv.getY();
break;
case MotionEvent.ACTION_UP:
y = (int) iEv.getY();
if (mIsTouching && !mIsScrolling && mOnScrollListener != null)
{
mOnScrollListener.onEndScroll(this);
}
mIsTouching = false;
break;
case MotionEvent.ACTION_MOVE:
mIsTouching = true;
mIsScrolling = true;
int newY = (int) iEv.getY();
int difY = y - newY;
int MAX_VALUE = 200;
int MIN_VALUE = -200;
if (difY > MAX_VALUE)
{
if (mOnScrollListener != null)
{
mOnScrollListener.onGoDown();
}
y = newY;
}
else if (difY < MIN_VALUE)
{
if (mOnScrollListener != null)
{
mOnScrollListener.onGoUp();
}
y = newY;
}
break;
}
}
@Override
protected void onScrollChanged(int iX, int iY, int iOldX, int iOldY)
{
super.onScrollChanged(iX, iY, iOldX, iOldY);
if (Math.abs(iOldX - iX) > 0)
{
if (mScrollingRunnable != null)
{
removeCallbacks(mScrollingRunnable);
}
mScrollingRunnable = () ->
{
if (mIsScrolling && !mIsTouching && mOnScrollListener != null)
{
mOnScrollListener.onEndScroll(CustomRecyclerView.this);
}
mIsScrolling = false;
mScrollingRunnable = null;
};
postDelayed(mScrollingRunnable, 200);
}
if (mOnScrollListener != null)
{
mOnScrollListener.onScrollChanged(this, iX, iY, iOldX, iOldY);
}
}
public void scrollToView(final View iV)
{
// Get deepChild Offset
Point childOffset = new Point();
getDeepChildOffset(CustomRecyclerView.this, iV.getParent(), iV, childOffset);
// Scroll to child.
CustomRecyclerView.this.scrollToY(childOffset.y);
}
private void getDeepChildOffset(final ViewGroup mainParent, final ViewParent parent, final View child, final Point accumulatedOffset)
{
ViewGroup parentGroup = (ViewGroup) parent;
accumulatedOffset.x += child.getLeft();
accumulatedOffset.y += child.getTop();
if (parentGroup.equals(mainParent))
{
return;
}
getDeepChildOffset(mainParent, parentGroup.getParent(), parentGroup, accumulatedOffset);
}
public void scrollToY(final int iY)
{
CustomRecyclerView.this.postDelayed(() ->
{
int x = 0;
int y = iY;
ObjectAnimator xTranslate = ObjectAnimator.ofInt(CustomRecyclerView.this, "scrollX", x);
ObjectAnimator yTranslate = ObjectAnimator.ofInt(CustomRecyclerView.this, "scrollY", y);
AnimatorSet animators = new AnimatorSet();
animators.setDuration(500L);
animators.playTogether(xTranslate, yTranslate);
animators.addListener(new Animator.AnimatorListener()
{
@Override
public void onAnimationStart(Animator arg0)
{
// noting
}
@Override
public void onAnimationRepeat(Animator arg0)
{
// noting
}
@Override
public void onAnimationEnd(Animator arg0)
{
// noting
}
@Override
public void onAnimationCancel(Animator arg0)
{
// noting
}
});
animators.start();
}, 300);
}
public void scrollToTop()
{
scrollToY(0);
}
public void setOnRvScrollListener(OnScrollListener mOnEndScrollListener)
{
this.mOnScrollListener = mOnEndScrollListener;
}
}
还有使用示例
private void setRecyclerViewSettings()
{
mRv.setLayoutManager(new LinearLayoutManager(getActivity()));
mRv.setOnRvScrollListener(mScrollListener);
}
private CustomRecyclerView.OnScrollListener mScrollListener = new CustomRecyclerView.OnScrollListener()
{
@Override
protected void onGoUp()
{
AppUtils.hideKeyboard(getContext(), mRvDynamicFormQuestions.getFocusedChild());
}
@Override
protected void onGoDown()
{
AppUtils.hideKeyboard(getContext(), mRvDynamicFormQuestions.getFocusedChild());
}
};
【讨论】：
另一个可以借助适配器检测滚动方向的简单解决方案：
class MyRecyclerViewAdapter extends RecyclerView.Adapter<MyViewHolder> {
int lastItemPosition = -1;
@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
if (position > lastItemPosition) {
// Scrolled Down
}
else {
// Scrolled Up
}
lastItemPosition = position;
}
}
^ 有助于在滚动时制作项目动画。
PS：这将不连续地告诉你方向，直到进一步调用 onBindViewHolder。
【讨论】：
接受的答案工作正常，但@MaciejPigulski 在下面的评论中给出了更清晰和简洁的解决方案。我只是把它作为一个答案在这里。这是我的工作代码。
mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
super.onScrolled(recyclerView, dx, dy);
if (dy > 0) {
// Scrolling up
} else {
// Scrolling down
}
}
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if (newState == AbsListView.OnScrollListener.SCROLL_STATE_FLING) {
// Do something
} else if (newState == AbsListView.OnScrollListener.SCROLL_STATE_TOUCH_SCROLL) {
// Do something
} else {
// Do something
}
}
});
【讨论】：
setOnScrollListener(...)而不是addOnScrollListener(...)
switch (newState) {...}构造
我想在 recyclerview 向下滚动时隐藏布局，然后在 recyclerview 向上滚动时使其可见。我想了想，想出了这个逻辑。
变量 y 是一个全局静态 int。不要忘记将 y 声明为 static int y;
我希望它可以帮助某人:)
mRecyclerView.addOnScrollListener(new EndlessRecyclerOnScrollListener(lLayout) {
@Override
public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
// super.onScrolled(recyclerView, dx, dy);
y=dy;
}
@Override
public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
super.onScrollStateChanged(recyclerView, newState);
if(mRecyclerView.SCROLL_STATE_DRAGGING==newState){
//fragProductLl.setVisibility(View.GONE);
}
if(mRecyclerView.SCROLL_STATE_IDLE==newState){
// fragProductLl.setVisibility(View.VISIBLE);
if(y<=0){
fragProductLl.setVisibility(View.VISIBLE);
}
else{
y=0;
fragProductLl.setVisibility(View.GONE);
}
}
}
});
【讨论】：
试试这个方法：
private static int firstVisibleInListview;
firstVisibleInListview = yourLayoutManager.findFirstVisibleItemPosition();
在您的滚动监听器中：
public void onScrolled(RecyclerView recyclerView, int dx, int dy)
{
super.onScrolled(recyclerView, dx, dy);
int currentFirstVisible = yourLayoutManager.findFirstVisibleItemPosition();
if(currentFirstVisible > firstVisibleInListview)
Log.i("RecyclerView scrolled: ", "scroll up!");
else
Log.i("RecyclerView scrolled: ", "scroll down!");
firstVisibleInListview = currentFirstVisible;
}
【讨论】：
onScrollStateChanged `RecyclerView.SCROLL_STATE_DRAGGING' 状态下处理这个逻辑。
if (dy > 0) { // scrolling up } else { // scrolling down } 还不够吗？