Android: looking for a drawArc() method with inner & outer radius

You can do this:

    Paint paint = new Paint();
    final RectF rect = new RectF();
    //Example values
    rect.set(mWidth/2- mRadius, mHeight/2 - mRadius, mWidth/2 + mRadius, mHeight/2 + mRadius); 
    paint.setColor(Color.GREEN);
    paint.setStrokeWidth(20);
    paint.setAntiAlias(true);
    paint.setStrokeCap(Paint.Cap.ROUND);
    paint.setStyle(Paint.Style.STROKE);
    canvas.drawArc(rect, -90, 360, false, paint);

The key is in paint.setStyle(Paint.Style.STROKE);, it crops the arc's center with the stroke that you define in setStrokeWidth (in the example draws an arc with a radius of mRadius and 20px thick).

Hope it helps!

You can paint over the inner area using the PorterDuff xfermode called "Clear." This will erase pixels.

private static final float CIRCLE_LIMIT = 359.9999f;
/**
 * Draws a thick arc between the defined angles, see {@link Canvas#drawArc} for more.
 * This method is equivalent to
 * <pre><code>
 * float rMid = (rInn + rOut) / 2;
 * paint.setStyle(Style.STROKE); // there's nothing to fill
 * paint.setStrokeWidth(rOut - rInn); // thickness
 * canvas.drawArc(new RectF(cx - rMid, cy - rMid, cx + rMid, cy + rMid), startAngle, sweepAngle, false, paint);
 * </code></pre>
 * but supports different fill and stroke paints.
 * 
 * @param canvas
 * @param cx horizontal middle point of the oval
 * @param cy vertical middle point of the oval
 * @param rInn inner radius of the arc segment
 * @param rOut outer radius of the arc segment
 * @param startAngle see {@link Canvas#drawArc}
 * @param sweepAngle see {@link Canvas#drawArc}, capped at &plusmn;360
 * @param fill filling paint, can be <code>null</code>
 * @param stroke stroke paint, can be <code>null</code>
 * @see Canvas#drawArc
 */
public static void drawArcSegment(Canvas canvas, float cx, float cy, float rInn, float rOut, float startAngle,
        float sweepAngle, Paint fill, Paint stroke) {
    if (sweepAngle > CIRCLE_LIMIT) {
        sweepAngle = CIRCLE_LIMIT;
    }
    if (sweepAngle < -CIRCLE_LIMIT) {
        sweepAngle = -CIRCLE_LIMIT;
    }

    RectF outerRect = new RectF(cx - rOut, cy - rOut, cx + rOut, cy + rOut);
    RectF innerRect = new RectF(cx - rInn, cy - rInn, cx + rInn, cy + rInn);

    Path segmentPath = new Path();
    double start = toRadians(startAngle);
    segmentPath.moveTo((float)(cx + rInn * cos(start)), (float)(cy + rInn * sin(start)));
    segmentPath.lineTo((float)(cx + rOut * cos(start)), (float)(cy + rOut * sin(start)));
    segmentPath.arcTo(outerRect, startAngle, sweepAngle);
    double end = toRadians(startAngle + sweepAngle);
    segmentPath.lineTo((float)(cx + rInn * cos(end)), (float)(cy + rInn * sin(end)));
    segmentPath.arcTo(innerRect, startAngle + sweepAngle, -sweepAngle);
    if (fill != null) {
        canvas.drawPath(segmentPath, fill);
    }
    if (stroke != null) {
        canvas.drawPath(segmentPath, stroke);
    }
}

Can be extended to oval arc by duplicating rInn and rOut for x and y directions.

Also wasn't part of the question, but to draw a text in the middle of a segment:

textPaint.setTextAlign(Align.CENTER);
Path midway = new Path();
float r = (rIn + rOut) / 2;
RectF segment = new RectF(cx - r, cy - r, cx + r, cy + r);
midway.addArc(segment, startAngle, sweepAngle);
canvas.drawTextOnPath("label", midway, 0, 0, textPaint);