Android 绘制文字居中显示

FontMetrics对象 它以四个基本坐标为基准，分别为：
・FontMetrics.top
・FontMetrics.ascent
・FontMetrics.descent
・FontMetrics.bottom

//获取文字的宽高
            Rect rect = new Rect();
            wordsPaint.getTextBounds(string, 0, 1, rect);
            Paint.FontMetrics fontMetrics = wordsPaint.getFontMetrics();
            int wordWidth = rect.width();
            //绘制字母
            float wordX = itemWidth / 2 - wordWidth / 2;
//            float wordY = i * itemHeight+1/2 * itemHeight + 1/2 * (fontMetrics.descent- fontMetrics.ascent) - fontMetrics.bottom;
            float wordY = i * itemHeight + itemHeight / 2 +  
   ((fontMetrics.bottom - fontMetrics.top) / 2 - fontMetrics.bottom);