public static class FontMetrics {

     /**

      * The maximum distance above the baseline for the tallest glyph in

      * the font at a given text size.

      */

     public float   top;

     /**

      * The recommended distance above the baseline for singled spaced text.

      */

     public float   ascent;

     /**

      * The recommended distance below the baseline for singled spaced text.

      */

     public float   descent;

     /**

      * The maximum distance below the baseline for the lowest glyph in

      * the font at a given text size.

      */

     public float   bottom;

     /**

      * The recommended additional space to add between lines of text.

      */

     public float   leading;

 }

 /** 绘制FontMetrics对象的各种线 */

 mPaint.reset();

 mPaint.setColor(Color.WHITE);

 mPaint.setTextSize(80);

 // FontMetrics对象

 FontMetrics fontMetrics = mPaint.getFontMetrics();

 String text = "abcdefg";

 // 计算每一个坐标

 float textWidth = mPaint.measureText(text);

 float baseX = 30;

 float baseY = 700;

 float topY = baseY + fontMetrics.top;

 float ascentY = baseY + fontMetrics.ascent;

 float descentY = baseY + fontMetrics.descent;

 float bottomY = baseY + fontMetrics.bottom;

 // 绘制文本

 canvas.drawText(text, baseX, baseY, mPaint);

 // BaseLine描画

 mPaint.setColor(Color.RED);

 canvas.drawLine(baseX, baseY, baseX + textWidth, baseY, mPaint);

 mPaint.setTextSize(20);

 canvas.drawText("base", baseX + textWidth, baseY, mPaint);

 // Base描画

 canvas.drawCircle(baseX, baseY, 5, mPaint);

 // TopLine描画

 mPaint.setColor(Color.LTGRAY);

 canvas.drawLine(baseX, topY, baseX + textWidth, topY, mPaint);

 canvas.drawText("top", baseX + textWidth, topY, mPaint);

 // AscentLine描画

 mPaint.setColor(Color.GREEN);

 canvas.drawLine(baseX, ascentY, baseX + textWidth, ascentY, mPaint);

 canvas.drawText("ascent", baseX + textWidth, ascentY + 10, mPaint);

 // DescentLine描画

 mPaint.setColor(Color.YELLOW);

 canvas.drawLine(baseX, descentY, baseX + textWidth, descentY, mPaint);

 canvas.drawText("descent", baseX + textWidth, descentY, mPaint);

 // ButtomLine描画

 mPaint.setColor(Color.MAGENTA);

 canvas.drawLine(baseX, bottomY, baseX + textWidth, bottomY, mPaint);

 canvas.drawText("buttom", baseX + textWidth, bottomY + 10, mPaint);

 /**

  * Return the distance above (negative) the baseline (ascent) based on the

  * current typeface and text size.

  *

  * @return the distance above (negative) the baseline (ascent) based on the

  *         current typeface and text size.

  */

 public native float ascent();

 /**

  * Return the distance below (positive) the baseline (descent) based on the

  * current typeface and text size.

  *

  * @return the distance below (positive) the baseline (descent) based on

  *         the current typeface and text size.

  */

 public native float descent();