Android 我可以为 ScrollView 设置 onScrollListener 吗？
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Can I have onScrollListener for a ScrollView?
提问by arnp
I am using a HorizontalScrollViewin a layout and I need to identify the user have reached the start and end point of the scroll.
我HorizontalScrollView在布局中使用 a ，我需要确定用户已到达滚动的起点和终点。
For ListViewI have tried a the onScrollListenerand it is possible to find the start and end point of scroll.
因为ListView我已经尝试过，onScrollListener并且可以找到滚动的起点和终点。
I tried to do the same in my Scrollviewbut it seems not possible. Is there any other possible ways to achieve what I need.
我试图在我的身上做同样的事情，Scrollview但似乎不可能。有没有其他可能的方法来实现我所需要的。
回答by Zbun
Every instance of View calls getViewTreeObserver(). Now when holding an instance of ViewTreeObserver, you can add an OnScrollChangedListener()to it using the method addOnScrollChangedListener().
View 的每个实例都调用getViewTreeObserver(). 现在，当持有 的实例时ViewTreeObserver，您可以OnScrollChangedListener()使用 方法向其添加addOnScrollChangedListener()。
You can see more information about this class here.
您可以在此处查看有关此类的更多信息。
It lets you be aware of every scrolling event - but without the coordinates. You can get them by using getScrollY()or getScrollX()from within the listener though.
它让您知道每个滚动事件 - 但没有坐标。不过，您可以通过使用getScrollY()或getScrollX()从侦听器中获取它们。
scrollView.getViewTreeObserver().addOnScrollChangedListener(new OnScrollChangedListener() {
@Override
public void onScrollChanged() {
int scrollY = rootScrollView.getScrollY(); // For ScrollView
int scrollX = rootScrollView.getScrollX(); // For HorizontalScrollView
// DO SOMETHING WITH THE SCROLL COORDINATES
}
});
回答by Midhun Vijayakumar
This might be very useful.
Use NestedScrollViewinstead of ScrollView. Support Library 23.1 introduced an OnScrollChangeListenerto NestedScrollView.
So you can do something like this.
这可能非常有用。使用NestedScrollView代替ScrollView。支持库23.1引入了一个OnScrollChangeListener到NestedScrollView。所以你可以做这样的事情。
myScrollView.setOnScrollChangeListener(new NestedScrollView.OnScrollChangeListener() {
@Override
public void onScrollChange(NestedScrollView v, int scrollX, int scrollY, int oldScrollX, int oldScrollY) {
Log.d("ScrollView","scrollX_"+scrollX+"_scrollY_"+scrollY+"_oldScrollX_"+oldScrollX+"_oldScrollY_"+oldScrollY);
//Do something
}
});
回答by ZaBlanc
Here's a derived HorizontalScrollView I wrote to handle notifications about scrolling and scroll ending. It properly handles when a user has stopped actively scrolling andwhen it fully decelerates after a user lets go:
这是我编写的派生 HorizontalScrollView 来处理有关滚动和滚动结束的通知。当用户停止主动滚动以及在用户放手后完全减速时，它会正确处理：
public class ObservableHorizontalScrollView extends HorizontalScrollView {
public interface OnScrollListener {
public void onScrollChanged(ObservableHorizontalScrollView scrollView, int x, int y, int oldX, int oldY);
public void onEndScroll(ObservableHorizontalScrollView scrollView);
}
private boolean mIsScrolling;
private boolean mIsTouching;
private Runnable mScrollingRunnable;
private OnScrollListener mOnScrollListener;
public ObservableHorizontalScrollView(Context context) {
this(context, null, 0);
}
public ObservableHorizontalScrollView(Context context, AttributeSet attrs) {
this(context, attrs, 0);
}
public ObservableHorizontalScrollView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
int action = ev.getAction();
if (action == MotionEvent.ACTION_MOVE) {
mIsTouching = true;
mIsScrolling = true;
} else if (action == MotionEvent.ACTION_UP) {
if (mIsTouching && !mIsScrolling) {
if (mOnScrollListener != null) {
mOnScrollListener.onEndScroll(this);
}
}
mIsTouching = false;
}
return super.onTouchEvent(ev);
}
@Override
protected void onScrollChanged(int x, int y, int oldX, int oldY) {
super.onScrollChanged(x, y, oldX, oldY);
if (Math.abs(oldX - x) > 0) {
if (mScrollingRunnable != null) {
removeCallbacks(mScrollingRunnable);
}
mScrollingRunnable = new Runnable() {
public void run() {
if (mIsScrolling && !mIsTouching) {
if (mOnScrollListener != null) {
mOnScrollListener.onEndScroll(ObservableHorizontalScrollView.this);
}
}
mIsScrolling = false;
mScrollingRunnable = null;
}
};
postDelayed(mScrollingRunnable, 200);
}
if (mOnScrollListener != null) {
mOnScrollListener.onScrollChanged(this, x, y, oldX, oldY);
}
}
public OnScrollListener getOnScrollListener() {
return mOnScrollListener;
}
public void setOnScrollListener(OnScrollListener mOnEndScrollListener) {
this.mOnScrollListener = mOnEndScrollListener;
}
}
回答by mcspayne
If you want to know the scroll position of a view, then you can use the following extension function on View class:
如果你想知道一个视图的滚动位置，那么你可以在 View 类上使用以下扩展函数：
fun View?.onScroll(callback: (x: Int, y: Int) -> Unit) {
var oldX = 0
var oldY = 0
this?.viewTreeObserver?.addOnScrollChangedListener {
if (oldX != scrollX || oldY != scrollY) {
callback(scrollX, scrollY)
oldX = scrollX
oldY = scrollY
}
}
}
回答by Cristan
You can use NestedScrollViewinstead of ScrollView. However, when using a Kotlin Lambda, it won't know you want NestedScrollView's setOnScrollChangeListenerinstead of the one at View (which is API level 23). You can fix this by specifying the first parameter as a NestedScrollView.
您可以使用NestedScrollView代替ScrollView. 但是，当使用 Kotlin Lambda 时，它不会知道您想要 NestedScrollViewsetOnScrollChangeListener而不是 View（这是 API 级别 23）。您可以通过将第一个参数指定为 NestedScrollView 来解决此问题。
nestedScrollView.setOnScrollChangeListener { _: NestedScrollView, scrollX: Int, scrollY: Int, _: Int, _: Int ->
Log.d("ScrollView", "Scrolled to $scrollX, $scrollY")
}
回答by Chuanxing Zhao
you can define a custom ScrollView class, & add an interface be called when scrolling like this:
您可以定义一个自定义的 ScrollView 类，并添加一个在滚动时调用的界面，如下所示：
public class ScrollChangeListenerScrollView extends HorizontalScrollView {
private MyScrollListener mMyScrollListener;
public ScrollChangeListenerScrollView(Context context) {
super(context);
}
public ScrollChangeListenerScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public ScrollChangeListenerScrollView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
public void setOnMyScrollListener(MyScrollListener myScrollListener){
this.mMyScrollListener = myScrollListener;
}
@Override
protected void onScrollChanged(int l, int t, int oldl, int oldt) {
super.onScrollChanged(l, t, oldl, oldt);
if(mMyScrollListener!=null){
mMyScrollListener.onScrollChange(this,l,t,oldl,oldt);
}
}
public interface MyScrollListener {
void onScrollChange(View view,int scrollX,int scrollY,int oldScrollX, int oldScrollY);
}
}
回答by Wirote W.
// --------Start Scroll Bar Slide--------
final HorizontalScrollView xHorizontalScrollViewHeader = (HorizontalScrollView) findViewById(R.id.HorizontalScrollViewHeader);
final HorizontalScrollView xHorizontalScrollViewData = (HorizontalScrollView) findViewById(R.id.HorizontalScrollViewData);
xHorizontalScrollViewData.getViewTreeObserver().addOnScrollChangedListener(new ViewTreeObserver.OnScrollChangedListener() {
@Override
public void onScrollChanged() {
int scrollX; int scrollY;
scrollX=xHorizontalScrollViewData.getScrollX();
scrollY=xHorizontalScrollViewData.getScrollY();
xHorizontalScrollViewHeader.scrollTo(scrollX, scrollY);
}
});
// ---------End Scroll Bar Slide---------
