title: How to draw the contour of a union of Path
body: <p>Hello i have a pack of Hexagon Path and a want to draw the contour(border) of the union of those Path. I thought of using Region, to union the Path together then get the border resulting Path with getBoundaryPath(), but it draw nothing.
  So can someone tell me how can I have the contour(border) of the union of all my Path objects ?</p>
  
  <pre><code> @Override
  protected void onDraw(Canvas canvas) {
      super.onDraw(canvas);
      // if (pmBack != null) {
      // canvas.drawBitmap(pmBack, new Matrix(), paint);
      // }
  
      if (mCells != null) {
  
          for (int i = 0; i &lt; mCells.length; i++) {
              final HexCell cell = mCells[i];
              if (cell != null) {
                  final PointF p = cell.getDrawPoint();
                  paint.setColor(cell.mColor);
  
                  Path path = drawHexagon(cell.mSize, mCenterX + p.x, mCenterY + p.y);
                  canvas.drawPath(drawHexagon(cell.mSize, mCenterX + p.x, mCenterY + p.y), paint);
  
                  if (i == 0) {
                      region.setPath(path, mClip);
                  } else {
                      region2.setPath(path, mClip);
                      region.op(region2, Op.UNION);
                  }
              }
          }
          canvas.drawPath(region.getBoundaryPath(), paintContour);
      }
  
  }
  
  private Path drawHexagon(final float size, float centerX, float centerY) {
      Path path = new Path();
      for (int i = 0; i &lt;= 6; i++) {
          double angle = 2 * Math.PI / 6 * (i + 0.5);
          float x_i = (float) (centerX + size * Math.cos(angle));
          float y_i = (float) (centerY + size * Math.sin(angle));
          if (i == 0) {
              path.moveTo(x_i, y_i);
          } else {
              path.lineTo(x_i, y_i);
          }
      }
  
      return path;
  }
  </code></pre>