fix(ios): emit correct progress values for overdrag (#396)

Author: mikeqcp

example/src/component/ProgressBar.tsx

@@ -13,12 +13,13 @@ export class ProgressBar extends React.Component<Props> {
   render() {
     const fractionalPosition =
       this.props.progress.position + this.props.progress.offset;
-
     const size = fractionalPosition / (this.props.numberOfPages - 1);
-    console.log(size);
+    const clampedSize = Math.max(0, Math.min(1, size));
     return (
       <View style={styles.progressBarContainer}>
-        <View style={[styles.progressBar, { width: `${size * 100}%` }]} />
+        <View
+          style={[styles.progressBar, { width: `${clampedSize * 100}%` }]}
+        />
       </View>
     );
   }

ios/ReactNativePageView.m

@@ -392,22 +392,25 @@ - (void)scrollViewDidScroll:(UIScrollView *)scrollView {
 
 
     BOOL isAnimatingBackwards = ([self isLtrLayout] && offset<0) || (![self isLtrLayout] && offset > 0.05f);
-    if(isAnimatingBackwards && position > 0){
+    if(isAnimatingBackwards){
         position =  self.currentIndex - 1;
         absoluteOffset =  fmax(0, 1 - absoluteOffset);
     }
 
     if (!_overdrag) {
         NSInteger maxIndex = _reactPageIndicatorView.numberOfPages - 1;
-        BOOL isFirstPage = [self isLtrLayout] ? _currentIndex == 0 : _currentIndex == maxIndex;
-        BOOL isLastPage = [self isLtrLayout] ? _currentIndex == maxIndex : _currentIndex == 0;
+        NSInteger firstPageIndex = [self isLtrLayout] ?  0 :  maxIndex;
+        NSInteger lastPageIndex = [self isLtrLayout] ?  maxIndex :  0;
+        BOOL isFirstPage = _currentIndex == firstPageIndex;
+        BOOL isLastPage = _currentIndex == lastPageIndex;
         CGFloat contentOffset =[self isHorizontal] ? scrollView.contentOffset.x : scrollView.contentOffset.y;
         CGFloat topBound = [self isHorizontal] ? scrollView.bounds.size.width : scrollView.bounds.size.height;
 
         if ((isFirstPage && contentOffset <= topBound) || (isLastPage && contentOffset >= topBound)) {
             CGPoint croppedOffset = [self isHorizontal] ? CGPointMake(topBound, 0) : CGPointMake(0, topBound);
             scrollView.contentOffset = croppedOffset;
             absoluteOffset=0;
+            position = isLastPage ? lastPageIndex : firstPageIndex;
         }
     }