Rebase [email protected]

Fixed #37

Author: cesardeazevedo

android/src/main/java/com/rnnestedscrollview/ReactNestedScrollView.java

@@ -13,8 +13,8 @@
 import android.graphics.Rect;
 import android.graphics.drawable.ColorDrawable;
 import android.graphics.drawable.Drawable;
-import android.support.v4.widget.NestedScrollView;
-import android.support.v4.view.ViewCompat;
+import androidx.core.widget.NestedScrollView;
+import androidx.core.view.ViewCompat;
 import android.util.Log;
 import android.view.MotionEvent;
 import android.view.View;
@@ -61,9 +61,7 @@ public class ReactNestedScrollView extends NestedScrollView implements ReactClip
   private boolean mActivelyScrolling;
   private @Nullable Rect mClippingRect;
   private @Nullable String mOverflow = ViewProps.HIDDEN;
-  private boolean mDoneFlinging;
   private boolean mDragging;
-  private boolean mFlinging;
   private boolean mPagingEnabled = false;
   private @Nullable Runnable mPostTouchRunnable;
   private boolean mRemoveClippedSubviews;
@@ -76,6 +74,8 @@ public class ReactNestedScrollView extends NestedScrollView implements ReactClip
   private int mSnapInterval = 0;
   private float mDecelerationRate = 0.985f;
   private @Nullable List<Integer> mSnapOffsets;
+  private boolean mSnapToStart = true;
+  private boolean mSnapToEnd = true;
   private View mContentView;
   private ReactViewBackgroundManager mReactBackgroundManager;
 
@@ -164,6 +164,13 @@ public void setSnapOffsets(List<Integer> snapOffsets) {
     mSnapOffsets = snapOffsets;
   }
 
+  public void setSnapToStart(boolean snapToStart) {
+    mSnapToStart = snapToStart;
+  }
+  public void setSnapToEnd(boolean snapToEnd) {
+    mSnapToEnd = snapToEnd;
+  }
+
   public void flashScrollIndicators() {
     awakenScrollBars();
   }
@@ -307,8 +314,21 @@ public void getClippingRect(Rect outClippingRect) {
 
   @Override
   public void fling(int velocityY) {
+    // Workaround.
+    // On Android P if a ScrollView is inverted, we will get a wrong sign for
+    // velocityY (see https://issuetracker.google.com/issues/112385925). 
+    // At the same time, mOnScrollDispatchHelper tracks the correct velocity direction. 
+    //
+    // Hence, we can use the absolute value from whatever the OS gives
+    // us and use the sign of what mOnScrollDispatchHelper has tracked.
+    float signum = Math.signum(mOnScrollDispatchHelper.getYFlingVelocity());
+    if (signum == 0) {
+      signum = Math.signum(velocityY);
+    }
+    final int correctedVelocityY = (int)(Math.abs(velocityY) * signum);
+
     if (mPagingEnabled) {
-      flingAndSnap(velocityY);
+      flingAndSnap(correctedVelocityY);
     } else if (mScroller != null) {
       // FB SCROLLVIEW CHANGE
 
@@ -324,7 +344,7 @@ public void fling(int velocityY) {
         getScrollX(), // startX
         getScrollY(), // startY
         0, // velocityX
-        velocityY, // velocityY
+        correctedVelocityY, // velocityY
         0, // minX
         0, // maxX
         0, // minY
@@ -335,14 +355,14 @@ public void fling(int velocityY) {
 
       ViewCompat.postInvalidateOnAnimation(this);
 
-      // RNNestedScrollView CHANGE
+      // RNNestedScrollView CHANGE (Should we use correctedVelocityY here as well?)
       // Fixed fling issue on support library 26 (see issue https://github.com/cesardeazevedo/react-native-nested-scroll-view/issues/16)
       super.fling(velocityY);
       // END FB SCROLLVIEW CHANGE
     } else {
-      super.fling(velocityY);
+      super.fling(correctedVelocityY);
     }
-    handlePostTouchScrolling(0, velocityY);
+    handlePostTouchScrolling(0, correctedVelocityY);
   }
 
   private void enableFpsListener() {
@@ -575,10 +595,29 @@ private void flingAndSnap(int velocityY) {
       ? smallerOffset
       : largerOffset;
 
-    // Chose the correct snap offset based on velocity
-    if (velocityY > 0) {
+    // if scrolling after the last snap offset and snapping to the
+    // end of the list is disabled, then we allow free scrolling
+    if (!mSnapToEnd && targetOffset >= lastOffset) {
+      if (getScrollY() >= lastOffset) {
+        // free scrolling
+      } else {
+        // snap to end
+        targetOffset = lastOffset;
+      }
+    } else if (!mSnapToStart && targetOffset <= firstOffset) {
+      if (getScrollY() <= firstOffset) {
+        // free scrolling
+      } else {
+        // snap to beginning
+        targetOffset = firstOffset;
+      }
+    } else if (velocityY > 0) {
+      // when snapping velocity can feel sluggish for slow swipes
+      velocityY += (int) ((largerOffset - targetOffset) * 10.0);
       targetOffset = largerOffset;
     } else if (velocityY < 0) {
+      // when snapping velocity can feel sluggish for slow swipes
+      velocityY -= (int) ((targetOffset - smallerOffset) * 10.0);
       targetOffset = smallerOffset;
     } else {
       targetOffset = nearestOffset;
@@ -634,7 +673,7 @@ public void setEndFillColor(int color) {
 
   @Override
   protected void onOverScrolled(int scrollX, int scrollY, boolean clampedX, boolean clampedY) {
-    if (mScroller != null) {
+    if (mScroller != null && mContentView != null) {
       // FB SCROLLVIEW CHANGE
 
       // This is part two of the reimplementation of fling to fix the bounce-back bug. See #fling() for

android/src/main/java/com/rnnestedscrollview/ReactNestedScrollViewManager.java

@@ -9,14 +9,14 @@
 
 import android.annotation.TargetApi;
 import android.graphics.Color;
-import android.support.v4.view.ViewCompat;
+import androidx.core.view.ViewCompat;
 import android.util.DisplayMetrics;
 
 import com.facebook.react.bridge.ReadableArray;
 import com.facebook.react.common.MapBuilder;
 import com.facebook.react.module.annotations.ReactModule;
-import com.facebook.react.uimanager.PixelUtil;
 import com.facebook.react.uimanager.DisplayMetricsHolder;
+import com.facebook.react.uimanager.PixelUtil;
 import com.facebook.react.uimanager.ReactClippingViewGroupHelper;
 import com.facebook.react.uimanager.Spacing;
 import com.facebook.react.uimanager.ThemedReactContext;
@@ -43,7 +43,6 @@
  * <p>Note that {@link ReactNestedScrollView} and {@link ReactHorizontalScrollView} are exposed to JS
  * as a single ScrollView component, configured via the {@code horizontal} boolean property.
  */
-@TargetApi(11)
 @ReactModule(name = ReactNestedScrollViewManager.REACT_CLASS)
 public class ReactNestedScrollViewManager
     extends ViewGroupManager<ReactNestedScrollView>
@@ -105,6 +104,15 @@ public void setSnapToOffsets(ReactNestedScrollView view, @Nullable ReadableArray
     view.setSnapOffsets(offsets);
   }
 
+  @ReactProp(name = "snapToStart")
+  public void setSnapToStart(ReactNestedScrollView view, boolean snapToStart) {
+    view.setSnapToStart(snapToStart);
+  }
+  @ReactProp(name = "snapToEnd")
+  public void setSnapToEnd(ReactNestedScrollView view, boolean snapToEnd) {
+    view.setSnapToEnd(snapToEnd);
+  }
+
   @ReactProp(name = ReactClippingViewGroupHelper.PROP_REMOVE_CLIPPED_SUBVIEWS)
   public void setRemoveClippedSubviews(ReactNestedScrollView view, boolean removeClippedSubviews) {
     view.setRemoveClippedSubviews(removeClippedSubviews);
@@ -135,6 +143,11 @@ public void setScrollPerfTag(ReactNestedScrollView view, @Nullable String scroll
     view.setScrollPerfTag(scrollPerfTag);
   }
 
+  @ReactProp(name = "pagingEnabled")
+  public void setPagingEnabled(ReactNestedScrollView view, boolean pagingEnabled) {
+    view.setPagingEnabled(pagingEnabled);
+  }
+
   /**
    * When set, fills the rest of the scrollview with a color to avoid setting a background and
    * creating unnecessary overdraw.
@@ -253,6 +266,11 @@ public void scrollToEnd(
     }
   }
 
+  @ReactProp(name = "persistentScrollbar")
+  public void setPersistentScrollbar(ReactNestedScrollView view, boolean value) {
+    view.setScrollbarFadingEnabled(!value);
+  }
+
   @Override
   public @Nullable Map<String, Object> getExportedCustomDirectEventTypeConstants() {
     return createExportedCustomDirectEventTypeConstants();