在做自定義view事，看了這個方法，查找資料了解下，看到這篇文章不錯，記錄下！
http://blog.csdn.net/chuekup/article/details/7518239

String str = "Hello";  
    canvas.drawText( str , x , y , paint);  
      
    //1. 粗略計算文字寬度  
    Log.d(TAG, "measureText=" + paint.measureText(str));  
      
    //2. 計算文字所在矩形，可以得到寬高  
    Rect rect = new Rect();  
    paint.getTextBounds(str, 0, str.length(), rect);  
    int w = rect.width();  
    int h = rect.height();  
    Log.d(TAG, "w=" +w+"  h="+h);  
      
    //3. 精確計算文字寬度  
    int textWidth = getTextWidth(paint, str);  
    Log.d(TAG, "textWidth=" + textWidth);  
      
        public static int getTextWidth(Paint paint, String str) {  
            int iRet = 0;  
            if (str != null && str.length() > 0) {  
                int len = str.length();  
                float[] widths = new float[len];  
                paint.getTextWidths(str, widths);  
                for (int j = 0; j < len; j++) {  
                    iRet += (int) Math.ceil(widths[j]);  
                }  
            }  
            return iRet;  
        }