Android_FontMetrics

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;

}

它的各基准线可以参考下图：



上图其实是通过代码画出来的，具体代码如下：

/** 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);

相信通过以上程序，能够很好的理解topLine，buttomLine，baseLine，ascentLine，descentLine。

另外：Paint类有两个方法
/**

* 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();

ascent()：the distance above the baseline（baseline以上的height）

descent()：the distance below the baseline（baseline以下的height）

所以ascent() + descent() 可以看成文字的height。

到此为止，怎么获取文字的height和width都已经揭晓了：

获取height ： mPaint.ascent() + mPaint.descent()

获取width ： mPaint.measureText(text)