HorizontalLineSpan.java

public class HorizontalLineSpan extends ReplacementSpan {

    private Context context;

    public HorizontalLineSpan(Context context) {
        this.context = context;
    }
    
    @Override
    public int getSize(Paint paint, CharSequence text,
                         int start, int end,
                         Paint.FontMetricsInt fm) {
        
        return 0;
    }

    @Override
    public void draw(Canvas canvas, CharSequence text,
                     int start, int end, float x,
                     int top, int y, int bottom, Paint paint) {

        Paint.FontMetricsInt fmi = paint.getFontMetricsInt();

        int height = fmi.descent - fmi.ascent; // set the drawable height to the height of the current font
        Drawable b = getDrawable(canvas.getWidth(), height);

        canvas.save();

        int transY = bottom - b.getBounds().bottom;
        
        canvas.translate(x, transY);
        b.draw(canvas);

        canvas.restore();
    }

    private Drawable getDrawable(int width, int height) {

        // We copy the implementation of getCachedDrawable in DynamicDrawableSpan
        Drawable d = getCachedDrawable();
        d.setBounds(0, 0, width, height);
        return d;
    }
    
    public Drawable getDrawable() {
        return new LineDrawable(context);
    }
    
    // ...
}