Added feature to allow sliding of multiple views on fling gesture. us…

…e 'picker.setSlideOnFling(true)' to use it. Custom threshold set to 2100 which can dynamically be set by user using 'picker.setSlideOnFlingThreshold(value)'.
yarolegovich · Jun 21, 2017 · 34b23fc · 34b23fc
1 parent 0075182
commit 34b23fc
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Showing 2 changed files with 38 additions and 3 deletions.
diff --git a/library/src/main/java/com/yarolegovich/discretescrollview/DiscreteScrollLayoutManager.java b/library/src/main/java/com/yarolegovich/discretescrollview/DiscreteScrollLayoutManager.java
@@ -27,7 +27,7 @@ class DiscreteScrollLayoutManager extends RecyclerView.LayoutManager {
     static final int NO_POSITION = -1;
 
     private static final String EXTRA_POSITION = "extra_position";
-    private static final int DEFAULT_TIME_FOR_ITEM_SETTLE = 150;
+    private static final int DEFAULT_TIME_FOR_ITEM_SETTLE = 300;
 
     //This field will take value of all visible view's center points during the fill phase
     private Point viewCenterIterator;
@@ -57,6 +57,9 @@ class DiscreteScrollLayoutManager extends RecyclerView.LayoutManager {
     private boolean dataSetChangeShiftedPosition;
     private boolean isFirstOrEmptyLayout;
 
+    private int flingThreshold = 2100; //Decrease to increase sensitivity.
+    private boolean shouldSlideOnFling = false;
+
     @NonNull
     private final ScrollStateListener scrollStateListener;
     private DiscreteScrollItemTransformer itemTransformer;
@@ -183,6 +186,7 @@ private void layoutViews(RecyclerView.Recycler recycler, Direction direction, in
     }
 
     private void layoutView(RecyclerView.Recycler recycler, int position, Point viewCenter) {
+        if (position < 0) return;
         View v = detachedCache.get(position);
         if (v == null) {
             v = recycler.getViewForPosition(position);
@@ -414,19 +418,32 @@ private void onDragStart() {
 
     public void onFling(int velocityX, int velocityY) {
         int velocity = orientationHelper.getFlingVelocity(velocityX, velocityY);
-        int newPosition = currentPosition + Direction.fromDelta(velocity).applyTo(1);
+        int throttleValue = shouldSlideOnFling ? Math.abs(velocityX/flingThreshold) : 1;
+        int newPosition = currentPosition + Direction.fromDelta(velocity).applyTo(throttleValue);
+        if (currentPosition != 0 && newPosition < 0)
+            newPosition = 0;
+        else if (currentPosition != getItemCount() -1 && newPosition >= getItemCount())
+            newPosition = getItemCount() - 1;
         boolean isInScrollDirection = velocity * scrolled >= 0;
         boolean canFling = isInScrollDirection && newPosition >= 0 && newPosition < getItemCount();
         if (canFling) {
             pendingScroll = getHowMuchIsLeftToScroll(velocity);
             if (pendingScroll != 0) {
-                startSmoothPendingScroll();
+                startSmoothPendingScroll(newPosition);
             }
         } else {
             returnToCurrentPosition();
         }
     }
 
+    public void setShouldSlideOnFling(Boolean result){
+        this.shouldSlideOnFling = result;
+    }
+
+    public void setSlideOnFlingThreshold(int threshold){
+        this.flingThreshold = threshold;
+    }
+
     public void returnToCurrentPosition() {
         pendingScroll = -scrolled;
         if (pendingScroll != 0) {
@@ -465,6 +482,16 @@ private void startSmoothPendingScroll() {
         startSmoothScroll(scroller);
     }
 
+    private void startSmoothPendingScroll(int position){
+        if (currentPosition == position) return;
+        pendingScroll = -scrolled;
+        Direction direction = Direction.fromDelta(position - currentPosition);
+        int distanceToScroll = Math.abs(position - currentPosition) * scrollToChangeCurrent;
+        pendingScroll += direction.applyTo(distanceToScroll);
+        pendingPosition = position;
+        startSmoothPendingScroll();
+    }
+
     @Override
     public void onAdapterChanged(RecyclerView.Adapter oldAdapter, RecyclerView.Adapter newAdapter) {
         if (newAdapter.getItemCount() > 0) {

diff --git a/library/src/main/java/com/yarolegovich/discretescrollview/DiscreteScrollView.java b/library/src/main/java/com/yarolegovich/discretescrollview/DiscreteScrollView.java
@@ -104,6 +104,14 @@ public void setItemTransitionTimeMillis(@IntRange(from = 10) int millis) {
         layoutManager.setTimeForItemSettle(millis);
     }
 
+    public void setSlideOnFling(Boolean result){
+        layoutManager.setShouldSlideOnFling(result);
+    }
+
+    public void setSlideOnFlingThreshold(int threshold){
+        layoutManager.setSlideOnFlingThreshold(threshold);
+    }
+
     public void setOrientation(Orientation orientation) {
         layoutManager.setOrientation(orientation);
     }