A ShowcaseDrawer that draws showcase circle with the greater side of a view divided by 2 as its radius value.

ViewBasedRadiusShowcaseDrawer.java

import android.content.res.Resources;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.view.View;

import com.github.amlcurran.showcaseview.MaterialShowcaseDrawer;

/**
 * A {@link com.github.amlcurran.showcaseview.ShowcaseDrawer} that draws showcase circle with the
 * greater side of a view divided by 2 as its radius value.
 */
public class ViewBasedRadiusShowcaseDrawer extends MaterialShowcaseDrawer {
    private float mRadius;
    private Paint mEraserPaint;

    public ViewBasedRadiusShowcaseDrawer(Resources resources, View view) {
        super(resources);
        mRadius = Math.max(view.getHeight(), view.getWidth()) / 2;
        mEraserPaint = new Paint();
        mEraserPaint.setColor(0xFFFFFF);
        mEraserPaint.setAlpha(0);
        mEraserPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.MULTIPLY));
        mEraserPaint.setAntiAlias(true);
    }

    @Override
    public void drawShowcase(Bitmap buffer, float x, float y, float scaleMultiplier) {
        Canvas bufferCanvas = new Canvas(buffer);
        bufferCanvas.drawCircle(x, y, mRadius, mEraserPaint);
    }

    @Override
    public int getShowcaseWidth() {
        return (int) (mRadius * 2);
    }

    @Override
    public int getShowcaseHeight() {
        return (int) (mRadius * 2);
    }

    @Override
    public float getBlockedRadius() {
        return mRadius;
    }
}