Fix tapping

src/main/java/com/jjoe64/graphview/GraphView.java

@@ -450,14 +450,27 @@ public boolean onTouchEvent(MotionEvent event) {
 
         // is it a click?
         if (mTapDetector.onTouchEvent(event)) {
+            Series nearestSeries = null;
+            float minDistance = Float.MAX_VALUE;
             for (Series s : mSeries) {
-                s.onTap(event.getX(), event.getY());
+                float distance = s.distanceToNearestPoint(event.getX(), event.getY());
+                if (distance < minDistance) {
+                    nearestSeries = s;
+                    minDistance = distance;
+                }
             }
             if (mSecondScale != null) {
                 for (Series s : mSecondScale.getSeries()) {
-                    s.onTap(event.getX(), event.getY());
+                    float distance = s.distanceToNearestPoint(event.getX(), event.getY());
+                    if (distance < minDistance) {
+                        nearestSeries = s;
+                        minDistance = distance;
+                    }
                 }
             }
+            if (minDistance != Float.MAX_VALUE) {
+                nearestSeries.onTap(event.getX(), event.getY());
+            }
         }
 
         return b || a;

src/main/java/com/jjoe64/graphview/series/BaseSeries.java

@@ -294,6 +294,34 @@ public void setOnDataPointTapListener(OnDataPointTapListener l) {
         this.mOnDataPointTapListener = l;
     }
 
+    /**
+     * @param x
+     * @param y
+     * @return the distance between the given x,y and the nearest point of the series
+     */
+    public float distanceToNearestPoint(float x, float y) {
+        float shortestDistance = Float.NaN;
+        E shortest = null;
+        for (Map.Entry<PointF, E> entry : mDataPoints.entrySet()) {
+            float x1 = entry.getKey().x;
+            float y1 = entry.getKey().y;
+            float x2 = x;
+            float y2 = y;
+
+            float distance = (float) Math.sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2));
+            if (shortest == null || distance < shortestDistance) {
+                shortestDistance = distance;
+                shortest = entry.getValue();
+            }
+        }
+        if (shortest != null) {
+            if (shortestDistance < 120) {
+                return shortestDistance;
+            }
+        }
+        return Float.MAX_VALUE;
+    }
+
     /**
      * called by the tap detector in order to trigger
      * the on tap on datapoint event.

src/main/java/com/jjoe64/graphview/series/Series.java

@@ -99,6 +99,14 @@ public interface Series<E extends DataPointInterface> {
      */
     public void setOnDataPointTapListener(OnDataPointTapListener l);
 
+
+    /**
+     * @param x
+     * @param y
+     * @return the distance between the given x,y and the nearest point of the series
+     */
+    float distanceToNearestPoint(float x, float y);
+
     /**
      * called by the tap detector in order to trigger
      * the on tap on datapoint event.