android - How can I tell if a closed path contains a given point?

Question

In Android, I have a Path object which I happen to know defines a closed path, and I need to figure out if a given point is contained within the path. What I was hoping for was something along the lines of

path.contains(int x, int y)

but that doesn't seem to exist.

The specific reason I'm looking for this is because I have a collection of shapes on screen defined as paths, and I want to figure out which one the user clicked on. If there is a better way to be approaching this such as using different UI elements rather than doing it "the hard way" myself, I'm open to suggestions.

I'm open to writing an algorithm myself if I have to, but that means different research I guess.

Answer 1

Here is what I did and it seems to work:

RectF rectF = new RectF();
path.computeBounds(rectF, true);
region = new Region();
region.setPath(path, new Region((int) rectF.left, (int) rectF.top, (int) rectF.right, (int) rectF.bottom));

Now you can use the region.contains(x,y) method.

Point point = new Point();
mapView.getProjection().toPixels(geoPoint, point);

if (region.contains(point.x, point.y)) {
  // Within the path.
}

** Update on 6/7/2010 ** The region.setPath method will cause my app to crash (no warning message) if the rectF is too large. Here is my solution:

// Get the screen rect.  If this intersects with the path's rect
// then lets display this zone.  The rectF will become the 
// intersection of the two rects.  This will decrease the size therefor no more crashes.
Rect drawableRect = new Rect();
mapView.getDrawingRect(drawableRect);

if (rectF.intersects(drawableRect.left, drawableRect.top, drawableRect.right, drawableRect.bottom)) {
   // ... Display Zone.
}