ViewPager migrate to ViewPager2. Fixes #522.

Swiping between tabs work. Fixes #105.

src/main/java/de/dennisguse/opentracks/chart/ChartView.java

@@ -30,6 +30,7 @@ import android.view.GestureDetector;
 import android.view.MotionEvent;
 import android.view.ScaleGestureDetector;
 import android.view.View;
+import android.view.ViewParent;
 import android.widget.Scroller;
 
 import androidx.annotation.NonNull;
@@ -117,6 +118,14 @@ public class ChartView extends View {
     private boolean reportSpeed = true;
     private boolean showPointer = false;
 
+    // To handle disallow intercept touch event in parent.
+    private static final int SCROLL_X_NONE = 0;
+    private static final int SCROLL_X_LEFT = 1;
+    private static final int SCROLL_X_RIGHT = 2;
+    private boolean isOnLeftEdge = true;
+    private boolean isOnRightEdge = true;
+    private int scrollXDirection = SCROLL_X_NONE;
+
     private final GestureDetectorCompat detectorScrollFlingTab = new GestureDetectorCompat(getContext(), new GestureDetector.SimpleOnGestureListener() {
 
         @Override
@@ -129,6 +138,14 @@ public class ChartView extends View {
 
         @Override
         public boolean onScroll(MotionEvent e1, MotionEvent e2, float distanceX, float distanceY) {
+            if (distanceX < 0) {
+                scrollXDirection = SCROLL_X_LEFT;
+            } else if (distanceX > 0) {
+                scrollXDirection = SCROLL_X_RIGHT;
+            } else {
+                scrollXDirection = SCROLL_X_NONE;
+            }
+
             if (Math.abs(distanceX) > 0) {
                 int availableToScroll = effectiveWidth * (zoomLevel - 1) - getScrollX();
                 if (availableToScroll > 0) {
@@ -434,6 +451,9 @@ public class ChartView extends View {
             chartPoints.clear();
             xExtremityMonitor.reset();
             zoomLevel = 1;
+            isOnLeftEdge = true;
+            isOnRightEdge = true;
+            scrollXDirection = SCROLL_X_NONE;
             updateDimensions();
         }
     }
@@ -500,6 +520,18 @@ public class ChartView extends View {
         invalidate();
     }
 
+    /**
+     * Handle parent's view disallow touch event.
+     *
+     * @param disallow Does disallow parent touch event?
+     */
+    private void requestDisallowInterceptTouchEventInParent(boolean disallow) {
+        ViewParent parent = getParent();
+        if (parent != null) {
+            parent.requestDisallowInterceptTouchEvent(disallow);
+        }
+    }
+
     /**
      * Scrolls the view horizontally by a given amount.
      *
@@ -507,13 +539,21 @@ public class ChartView extends View {
      */
     private void scrollBy(int deltaX) {
         int scrollX = getScrollX() + deltaX;
-        if (scrollX < 0) {
+        if (scrollX <= 0) {
             scrollX = 0;
+            isOnLeftEdge = true;
+        } else {
+            isOnLeftEdge = false;
         }
+
         int maxWidth = effectiveWidth * (zoomLevel - 1);
-        if (scrollX > maxWidth) {
+        if (scrollX >= maxWidth) {
             scrollX = maxWidth;
+            isOnRightEdge = true;
+        } else {
+            isOnRightEdge = false;
         }
+
         scrollTo(scrollX, 0);
     }
 
@@ -538,6 +578,15 @@ public class ChartView extends View {
     public boolean onTouchEvent(MotionEvent event) {
         boolean isZoom = detectorZoom.onTouchEvent(event);
         boolean isScrollTab = detectorScrollFlingTab.onTouchEvent(event);
+
+        if (event.getPointerCount() == 1 && ((isOnLeftEdge && scrollXDirection == SCROLL_X_LEFT) || (isOnRightEdge && scrollXDirection == SCROLL_X_RIGHT))) {
+            // Focus on view's parent.
+            requestDisallowInterceptTouchEventInParent(false);
+        } else {
+            // Focus on ChartView.
+            requestDisallowInterceptTouchEventInParent(true);
+        }
+
         return isZoom || isScrollTab;
     }