title: where are the numbers ' baseline?
body: <p>i study the app like this ,<img src="https://i.stack.imgur.com/HzP4L.png" alt="the clock UI"> .</p>
  
  <pre><code>    /**
       * draw the hour text (12、3、6、9)
       * draw the arc
       */
      private void drawTimeText() {
          //draw the hour text 
          String timeText = "12";
          mTextPaint.getTextBounds(timeText, 0, timeText.length(), mTextRect);
          int textLargeWidth = mTextRect.width();//两位数字的宽
          mCanvas.drawText("12", getWidth() / 2 - textLargeWidth / 2, mPaddingTop + mTextRect.height(), mTextPaint);
          timeText = "3";
  
          mTextPaint.getTextBounds(timeText, 0, timeText.length(), mTextRect);
          int textSmallWidth = mTextRect.width();//一位数字的宽
          mCanvas.drawText("3", getWidth() - mPaddingRight - mTextRect.height() / 2 - textSmallWidth / 2,
                  getHeight() / 2 + mTextRect.height() / 2, mTextPaint);
  
          mCanvas.drawText("6", getWidth() / 2 - textSmallWidth / 2, getHeight() - mPaddingBottom, mTextPaint);
          mCanvas.drawText("9", mPaddingLeft + mTextRect.height() / 2 - textSmallWidth / 2,
                  getHeight() / 2 + mTextRect.height() / 2, mTextPaint);
  
  
        //draw the arc
          mCircleRectF.set(mPaddingLeft + mTextRect.height() / 2 + mCircleStrokeWidth / 2,
                  mPaddingTop + mTextRect.height() / 2 + mCircleStrokeWidth / 2,
                  getWidth() - mPaddingRight - mTextRect.height() / 2 + mCircleStrokeWidth / 2,
                  getHeight() - mPaddingBottom - mTextRect.height() / 2 + mCircleStrokeWidth / 2);
          for (int i = 0; i &lt; 4; i++) {
              mCanvas.drawArc(mCircleRectF, 5 + 90 * i, 80, false, mCirclePaint);
          }
  </code></pre>
  
  <p>i don't know  when draw the hour text "3",</p>
  
  <pre><code>mCanvas.drawText("3", getWidth() - mPaddingRight - mTextRect.height() / 2 - textSmallWidth / 2,
                      getHeight() / 2 + mTextRect.height() / 2, mTextPaint);
  </code></pre>
  
  <p>use canvas.drawText(),</p>
  
  <pre><code>void drawText (String text, 
                  int start, 
                  int end, 
                  float x, 
                  float y, 
                  Paint paint)
  </code></pre>
  
  <p>"y" means the baseline of number ,i don't know the rules of number's baseline ,like "3",where is the baseline of number ? i search google the "baseline",but it just about English alphabet baseline , nothing about the number baseline.</p>