I have an issue with Auto-scroll in scroll view.
In my case, there are two Recyclerview. First Recyclerview, horizontally scrollable and second vertically. First RecyclerView only for drag and Second RecyclerView only for a drop. Both recyclerviews are inside ScrollView so, I disabled vertical scroll in second Recyclerview. I added DragListener on Second Recyclerview's item. Every item have drag listener so based on that I add/replace item while drop item.
So My main issue with scroll, so scroll not working properly while i drag item. currently i used below code for scroll while drag.
case DragEvent.ACTION_DRAG_LOCATION:
RecyclerView recyclerView = (RecyclerView) viewSource.getParent();
MyAdapter adapter = (MyAdapter) recyclerView.getAdapter();
int y = Math.round(dragEvent.getY());
Timber.d("onDrag(): " + y);
int translatedY = y - adapter.getScrollDistance();
Timber.d("onDrag(): translated : " + translatedY + " getScrollDistance : " + adapter.getScrollDistance());
int threshold = 50;
// make a scrolling up due the y has passed the threshold
if (translatedY < threshold) {
// make a scroll up by 30 px
mScrollView.smoothScrollBy(0, -30);
} else
// make a autoscrolling down due y has passed the 500 px border
if (translatedY + threshold > 500) {
// make a scroll down by 30 px
mScrollView.smoothScrollBy(0, 30);
}
break;
But above code not working properly for multiple items if recyclerview have only one item than its working fine. but when recyclerview having multiple items that time scrollview scroll above and below slitly while itemX in between two items.
Edited Question: Now, I put above code on Second Recycler view's OnDragListener. Now the problem with drag listener, so I want if user drag First Recyclerview's item below/above than second Recyclerview's drag listener needs to work else Second Recyclerview's item's drag listener needs to work.
I resolved this issue by returning false in Second RecyclerView's item's drag listener's ACTION_DRAG_LOCATION event. I disabled ACTION_DRAG_LOCATION event, so that event not tracked by Second RecyclerView's Item's DragListener. That time Its Parent(Second RecyclerView)'s Draglistener work. Below code, I put on Second RecyclerView's DragListener
case DragEvent.ACTION_DRAG_LOCATION:
RecyclerView recyclerView = (RecyclerView) viewSource.getParent();
MyAdapter adapter = (MyAdapter) recyclerView.getAdapter();
int y = Math.round(dragEvent.getY());
int translatedY = y - adapter.getScrollDistance();
int threshold = 50;
// make a scrolling up due the y has passed the threshold
if (translatedY < threshold) {
// make a scroll up by 30 px
mScrollView.smoothScrollBy(0, -30);
} else
// make a autoscrolling down due y has passed the 500 px border
if (translatedY + threshold > 500) {
// make a scroll down by 30 px
mScrollView.smoothScrollBy(0, 30);
}
break;
To disable Second RecyclerView's item's DragListener's ACTION_DRAG_LOCATION event use below code:
@Override
public boolean onDrag(View view, DragEvent dragEvent) {
int action = dragEvent.getAction();
View viewSource = (View) dragEvent.getLocalState();
switch (action) {
case DragEvent.ACTION_DRAG_STARTED:
break;
case DragEvent.ACTION_DRAG_ENTERED:
break;
case DragEvent.ACTION_DRAG_LOCATION:
return false;
case DragEvent.ACTION_DRAG_EXITED:
break;
case DragEvent.ACTION_DROP:
break;
default:
break;
}
return true;
}
So whatever Event from Draglistener you need to handle you just need to return true otherwise return false.
I have made a helper class to make it a bit easier to add scrolling in drag a drop in RecyclerViews.
It's written in C# for Xamarin, but it should be trivial to change it in to Java or Kotlin.
RecyclerViewDragScrollHelper On GitHub
using System;
using System.Threading.Tasks;
using Android.Graphics;
using Android.OS;
using Android.Support.V7.Widget;
using Android.Views;
namespace SharedLibrary.Droid.Helpers {
public class RecyclerViewDragScrollHelper {
DragEvent dragEvent = null; //For passing the drag event to newly bound views
Handler handler = new Handler(); //to pass the run things in the ui thread
ScrollDirection currentScrollDirection = ScrollDirection.None; //the current direction being scrolled
/// <summary>
/// If this is not set then it will try to find a recycler view
/// in the hovered over view's view tree
/// </summary>
public RecyclerView RecyclerViewToScroll { get; set; }
public RecyclerViewDragScrollHelper() {
}
public RecyclerViewDragScrollHelper(RecyclerView recyclerViewToScroll) {
RecyclerViewToScroll = recyclerViewToScroll;
}
public enum UnitType {
Pixels,
Percent
}
enum ScrollDirection {
None,
Foward,
Back
}
/// <summary>
/// Threshold value can be a percentage or pixels
/// </summary>
public UnitType ThresholdUnits { get; set; } = UnitType.Percent;
/// <summary>
/// Threshold of how many pixels or percentage from the edge it has to be before it
/// starts scrolling
/// </summary>
public float Threshold { get; set; } = 0.20f;
/// <summary>
/// Speed of the scroll
/// </summary>
public int ScrollInterval { get; set; } = 5;
/// <summary>
/// Place this method in the method for event handler for View.Drag
/// Or if useing View.SetOnDragListener(), in the implimentation of
/// View.IOnDragListener
/// </summary>
/// <param name="view"></param>
/// <param name="dragEvent"></param>
/// <returns></returns>
public void HandleDrag(View view, DragEvent dragEvent) {
var action = dragEvent.Action;
switch (action) {
case DragAction.Started:
DragStarted(dragEvent);
break;
case DragAction.Ended:
DragEnded();
break;
case DragAction.Location:
var dragpoint = new Point(Convert.ToInt32(dragEvent.GetX()), Convert.ToInt32(dragEvent.GetY()));
HandleLocation(view, dragpoint);
break;
case DragAction.Exited:
currentScrollDirection = ScrollDirection.None;
break;
}
}
/// <summary>
/// Run on DragAction.Location.
/// If it's within the threshold bounds it should scroll the recycler view.
/// Should work for both vertical and horizontal linear layouts.
/// Wont currently work for other layouts
/// </summary>
/// <param name="viewHoveredOver">This is the view that is being dragged over.
/// It can be a view in a recyclerview, or the recycler view it's self</param>
/// <param name="position"></param>
/// <returns></returns>
private void HandleLocation(View viewHoveredOver, Point position) {
var recyclerView = RecyclerViewToScroll;
var viewHoveredOverIsChildOfRecyclerView = false;
//if RecyclerViewToScroll has not been set then
//see if there is a recycler view in the viewHoveredOver view tree
if (recyclerView == null) {
recyclerView = FindRecyclerViewInTree(viewHoveredOver);
viewHoveredOverIsChildOfRecyclerView = true;
} else {
viewHoveredOverIsChildOfRecyclerView = IsViewChildOfView(viewHoveredOver, recyclerView);
}
if (recyclerView != null &&
viewHoveredOverIsChildOfRecyclerView
&& recyclerView.GetLayoutManager() is LinearLayoutManager layoutManager) {
//get the drag position in the view, and work out where it is
//relative to the recycler view. (Both viewHoveredOver and recyclerView
//might be the same view, this doesn't matter)
var pointInRecyclerView = GetPointRelativeTo(viewHoveredOver, recyclerView, position);
//work out the properties for the scrolling based on if it's
//verticle or horizontal
float offSet = 0; //the x or y coord for the drag depending on the orientaion
float upperThreshold = 0; //threshold postion at the end of the recyclerview
int scrollX = 0; //the absolute amount to scroll horizontally
int scrollY = 0; //the absolute amount to scroll vertically
var layoutDirection = layoutManager.Orientation;
//If the threshold units are pixels then just take the threshold value.
//If it's percentage times the threshold by the height to get the pixels
var thresholdPixels = ThresholdUnits == UnitType.Pixels ? Threshold : Threshold * recyclerView.Height;
//If the layout direction is vertical scroll Y coord and check Y offset
//If the layout direction is horizontal scroll X coord and check X offset
if (layoutDirection == LinearLayoutManager.Vertical) {
offSet = pointInRecyclerView.Y;
upperThreshold = recyclerView.Height - thresholdPixels;
scrollY = ScrollInterval;
} else if (layoutDirection == LinearLayoutManager.Horizontal) {
offSet = pointInRecyclerView.X;
upperThreshold = recyclerView.Width - thresholdPixels;
scrollX = ScrollInterval;
}
//if the drag position is less than the lower threshold then scroll backwards
//if it's greater than the uper threshold then scroll forward
//if it's in neither, the set the scroll direction to none
var newScrollDirection = offSet < thresholdPixels
? ScrollDirection.Back
: offSet > upperThreshold
? ScrollDirection.Foward
: ScrollDirection.None;
InScrollPostion(newScrollDirection, recyclerView, scrollX, scrollY);
}
}
Java.Util.Timer timer;
/// <summary>
/// Scroll continiously in the set direction while the position is in the bounds
/// </summary>
/// <param name="newDirection"></param>
/// <param name="recyclerView"></param>
/// <param name="scrollX"></param>
/// <param name="scrollY"></param>
/// <returns></returns>
private void InScrollPostion(
ScrollDirection newDirection,
RecyclerView recyclerView,
int scrollX,
int scrollY) {
//if it's not already scrolling
if (currentScrollDirection != newDirection && newDirection != ScrollDirection.None) {
currentScrollDirection = newDirection;
//1 for forward -1 for backwards
var scrollDirectionInt = newDirection == ScrollDirection.Foward ? 1 : -1;
var canScrollDown = recyclerView.CanScrollVertically(scrollDirectionInt);
var canScrollRight = recyclerView.CanScrollHorizontally(scrollDirectionInt);
scrollX *= scrollDirectionInt;
scrollY *= scrollDirectionInt;
timer?.Cancel(); //cancel the previous timer so they don't stack
timer?.Dispose();
timer = new Java.Util.Timer(); //make a new timer
//Action to be performed every timer tick
Action action = () => {
if (currentScrollDirection == newDirection
&& (recyclerView.CanScrollVertically(scrollDirectionInt)
|| recyclerView.CanScrollHorizontally(scrollDirectionInt))) {
handler.Post(() => recyclerView.ScrollBy(scrollX, scrollY));
} else {
currentScrollDirection = ScrollDirection.None;
timer?.Cancel();
timer?.Dispose();
timer = null;
}
};
//start the timer to do the action every 25ms
timer.ScheduleAtFixedRate(new TimerTask(action), 0, 25);
//the C# async way of doing it
//while (currentScrollDirection == newDirection
// && (recyclerView.CanScrollVertically(scrollDirectionInt)
// || recyclerView.CanScrollHorizontally(scrollDirectionInt))) {
// //Not sure how this would be done in a native android way
// recyclerView.ScrollBy(scrollX, scrollY);
// await Task.Delay(25); //Go back to the ui thread for 25ms before scrolling another increment
//}
//currentScrollDirection = ScrollDirection.None;
} else if (newDirection == ScrollDirection.None) {
currentScrollDirection = ScrollDirection.None;
timer?.Cancel();
timer?.Dispose();
timer = null;
}
}
private class TimerTask : Java.Util.TimerTask {
Action action;
public TimerTask(Action action) {
this.action = action;
}
public override void Run() {
action?.Invoke(); ;
}
}
/// <summary>
/// Run this on DragAction.Ended
/// </summary>
private void DragEnded() {
currentScrollDirection = ScrollDirection.None;
dragEvent = null;
}
/// <summary>
/// Run on DragAction.Started
/// </summary>
/// <param name="dragEvent"></param>
private void DragStarted(DragEvent dragEvent) {
this.dragEvent = dragEvent;
}
/// <summary>
/// This allows a newly bound cell that was previously off screen when
/// the drag started to trigger drag events.
/// Add this to OnBindViewHolder in override of RecyclerView.Adapter
/// </summary>
/// <param name="view"></param>
public void PrepareCellView(View view) {
handler.Post(() => {
if (dragEvent != null && view.Parent is ViewGroup parent) {
parent.DispatchDragEvent(dragEvent);
}
});
}
/// <summary>
/// This allows a newly bound cell that was previously off screen when
/// the drag started to trigger drag events.
/// Add this to OnBindViewHolder in override of RecyclerView.Adapter
/// </summary>
/// <param name="view"></param>
public void PrepareCellView(RecyclerView.ViewHolder holder) {
handler.Post(() => {
if (dragEvent != null && holder.ItemView.Parent is ViewGroup parent) {
parent.DispatchDragEvent(dragEvent);
}
});
}
/// <summary>
/// Find a recycler view in the views view tree
/// </summary>
/// <param name="view"></param>
/// <returns></returns>
private static RecyclerView FindRecyclerViewInTree(View view) {
if (view == null) {
return null;
} else if(view is RecyclerView recyclerView) {
return recyclerView;
} else {
return FindRecyclerViewInTree(view.Parent as View);
}
}
private static bool IsViewChildOfView(View child, View parent) {
if (child == null || parent == null) {
return false;
} else if(child.Parent is View childsParent && childsParent == parent) {
return true;
} else {
return IsViewChildOfView(child.Parent as View, parent);
}
}
/// <summary>
/// Get's a point in a view relative to another view
/// </summary>
/// <param name="fromView"></param>
/// <param name="toView"></param>
/// <param name="fromPoint"></param>
/// <returns></returns>
public static Point GetPointRelativeTo(View fromView, View toView, Point fromPoint) {
var toViewRect = GetRectOnScreen(toView);
var fromViewRect = GetRectOnScreen(fromView);
var pointInToView = new Point(fromViewRect.Left - toViewRect.Left + fromPoint.X,
fromViewRect.Top - toViewRect.Top + fromPoint.Y);
return pointInToView;
}
/// <summary>
/// Gets the views Rect relative to the screen
/// </summary>
/// <param name="view"></param>
/// <returns></returns>
public static Rect GetRectOnScreen(View view) {
int[] l = new int[2];
view.GetLocationOnScreen(l);
int x = l[0];
int y = l[1];
Rect rect = new Rect(x, y, view.Width + x, view.Height + y);
return rect;
}
}
}
Add an instance of RecyclerViewDragScrollHelper to your class, and add recyclerDragScroller.HandleDrag() to your override of onDrag().
@Override
public boolean onDrag(View view, DragEvent dragEvent) {
recyclerDragScroller.HandleDrag(view, dragEvent);
return true;
}
If a viewholder wasn't bound when the drag started it won't interact with drags so add recyclerDragScroller.PrepareCellView() to your OnBindViewHolder() override in your adaptor to pass the drag event on.
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
recyclerDragScroller.PrepareCellView(viewHolder);
}
来源：https://stackoverflow.com/questions/42486167/auto-scroll-scrollbar-while-drag-item-in-recyclerview