自定義view實現：畫一個矩形 然後畫一個圓 再在圓中心顯示文字，效果如下

 RectF rect = new RectF(100,100,500,500);//畫一個矩形
        Paint mPaint = new Paint();
        mPaint.setColor(Color.GRAY);
        mPaint.setStyle(Paint.Style.FILL);
        canvas.drawRect(rect, mPaint);

        //設定畫筆的樣式，空心STROKE
        mPaint.setStyle(Paint.Style.FILL);
        //設定抗鋸齒
        mPaint.setAntiAlias(true);
        mPaint.setColor(Color.RED);
        canvas.drawCircle(rect.centerX(),rect.centerY(),150,mPaint);

        mPaint.setColor(Color.WHITE);
        mPaint.setTextSize(50);
        mPaint.setStyle(Paint.Style.FILL);
        //該方法即為設定基線上那個點究竟是left,center,還是right  這裡我設定為center
        mPaint.setTextAlign(Paint.Align.CENTER);

        Paint.FontMetrics fontMetrics = mPaint.getFontMetrics();
        float top = fontMetrics.top;//為基線到字型上邊框的距離,即上圖中的top
        float bottom = fontMetrics.bottom;//為基線到字型下邊框的距離,即上圖中的bottom

        int baseLineY = (int) (rect.centerY() - top/2 - bottom/2);//基線中間點的y軸計算公式

        canvas.drawText("小學",rect.centerX(),baseLineY,mPaint);