Android_FontMetrics

Canvas 绘制文本时，使用FontMetrics对象，计算位置的坐标。

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)

Android_FontMetrics相关推荐

Android中获取文本宽度和高度
本文罗列Android中字体宽度和高度的相关概念,及测量方法 . 原文请参考Android_FontMetrics.Android字符串进阶之三:字体属性及测量(FontMetrics). Andro ...

Android_FontMetrics

Android_FontMetrics相关推荐

最新文章

热门文章