Android字符串进阶之三:字体属性及测量(FontMetrics)
2015-12-21 18:32
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(转载)http://mikewang.blog.51cto.com/3826268/871765/
最近的一个模块正好用到字体的相关内容,整理出来。
(一) 字体的几个参数 ,以Android API文档定义为准,见下图
![](https://oscdn.geek-share.com/Uploads/Images/Content/202011/28/93960a4a994d580f6a11c566c90f66b7.png)
要点如下:
1. 基准点是baseline
2. Ascent是baseline之上至字符最高处的距离
3. Descent是baseline之下至字符最低处的距离
4. Leading文档说的很含糊,其实是上一行字符的descent到下一行的ascent之间的距离
5. Top指的是指的是最高字符到baseline的值,即ascent的最大值
6. 同上,bottom指的是最下字符到baseline的值,即descent的最大值
Note:网上有很多错误的图,如果有疑问,就参看文档,区分对错。
为了帮助理解,我特此搜索了不同的示意图。对照示意图,会很容易理解FontMetrics的参数。
pic-1
![](https://oscdn.geek-share.com/Uploads/Images/Content/202011/22/cc1a618b27485264805d7684910bdd8a.png)
pic-2
![](https://oscdn.geek-share.com/Uploads/Images/Content/202006/07/d6b0a1a5dded182dd5144be20ffe4fa3.png)
pic-3
![](https://oscdn.geek-share.com/Uploads/Images/Content/202006/07/f6f8281eda1799845e5d7b38374a4c63.png)
pic-4
![](https://oscdn.geek-share.com/Uploads/Images/Content/202006/07/7e11bc62ba7fed74bf71c01c0d2832d4.png)
pic-5
![](https://oscdn.geek-share.com/Uploads/Images/Content/202006/07/1a8d0bbf37fe72bb6f671d24c0206cb4.png)
pic-6
![](https://oscdn.geek-share.com/Uploads/Images/Content/202006/07/7e12569e1fa4b3d4297f865e614a1357.png)
(二) 测试
1,测试的代码直接使用网上的代码,因为重复着众多,无所给出原始出处,故不注出。
我增加了Bitmap作为输出显示,完整代码如下:
log显示如下:
![](https://oscdn.geek-share.com/Uploads/Images/Content/202006/07/cf1d7dd43b77dc58455d6759a32c70e6.png)
Note1:注意到各个数值都是整数,这是建立在baseY=100的情况下,去掉baseY,重新运行代码,log如下:
![](https://oscdn.geek-share.com/Uploads/Images/Content/202006/07/cb49a78ae5ab99a31d1d8811584d5e14.png)
Note2: 参照线为baseline,即baseline=0的情况下,其他各线的数值。leading = 0,即行间距=0
2,以上是根据paint设置,获取相关的FontMetrics属性,并且只绘制了一行字符串,我们猜想,如果是多行,是否可以获得行间距leanding,代码如下:
log如下:
![](https://oscdn.geek-share.com/Uploads/Images/Content/202006/07/c78bb71ea0e329010c0e0a4cce496b3a.png)
Note:显然,即使是多行的情况下,仍不能获得leading。
3,如果text是单行,获得各个属性将会怎样,代码如下:
log如下图所示:
![](https://oscdn.geek-share.com/Uploads/Images/Content/202006/07/b4381cdb1f39bb5b60f4b45254c6b3a6.png)
Note:与多行获得的属性都相同。
结论:
A:虽然paint和textView所设置的textSize均为55,且为相同的字符串,但是两个获得的FontMetrics属性值并不相同。但是,我们发现,做除法之后,均为1.5倍关系。做出猜测,即Paint下,为mdpi对应的size,而TextView的size已经关联到了显示屏幕本身的320dip。所以获得属性值均为整1.5倍数
B:各种情况下,均未获得leading值。
本文出自 “小新专栏” 博客,转载请与作者联系!
最近的一个模块正好用到字体的相关内容,整理出来。
(一) 字体的几个参数 ,以Android API文档定义为准,见下图
![](https://oscdn.geek-share.com/Uploads/Images/Content/202011/28/93960a4a994d580f6a11c566c90f66b7.png)
要点如下:
1. 基准点是baseline
2. Ascent是baseline之上至字符最高处的距离
3. Descent是baseline之下至字符最低处的距离
4. Leading文档说的很含糊,其实是上一行字符的descent到下一行的ascent之间的距离
5. Top指的是指的是最高字符到baseline的值,即ascent的最大值
6. 同上,bottom指的是最下字符到baseline的值,即descent的最大值
Note:网上有很多错误的图,如果有疑问,就参看文档,区分对错。
为了帮助理解,我特此搜索了不同的示意图。对照示意图,会很容易理解FontMetrics的参数。
pic-1
![](https://oscdn.geek-share.com/Uploads/Images/Content/202011/22/cc1a618b27485264805d7684910bdd8a.png)
pic-2
![](https://oscdn.geek-share.com/Uploads/Images/Content/202006/07/d6b0a1a5dded182dd5144be20ffe4fa3.png)
pic-3
![](https://oscdn.geek-share.com/Uploads/Images/Content/202006/07/f6f8281eda1799845e5d7b38374a4c63.png)
pic-4
![](https://oscdn.geek-share.com/Uploads/Images/Content/202006/07/7e11bc62ba7fed74bf71c01c0d2832d4.png)
pic-5
![](https://oscdn.geek-share.com/Uploads/Images/Content/202006/07/1a8d0bbf37fe72bb6f671d24c0206cb4.png)
pic-6
![](https://oscdn.geek-share.com/Uploads/Images/Content/202006/07/7e12569e1fa4b3d4297f865e614a1357.png)
(二) 测试
1,测试的代码直接使用网上的代码,因为重复着众多,无所给出原始出处,故不注出。
我增加了Bitmap作为输出显示,完整代码如下:
public class FontMetricsDemoActivity extends Activity { private Canvas canvas; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); Paint textPaint = new Paint( Paint.ANTI_ALIAS_FLAG); textPaint.setTextSize( 55); textPaint.setColor( Color.WHITE); // FontMetrics对象 FontMetrics fontMetrics = textPaint.getFontMetrics(); String text = "abcdefghijklmnopqrstu"; // 计算每一个坐标 float baseX = 0; float baseY = 100; float topY = baseY + fontMetrics.top; float ascentY = baseY + fontMetrics.ascent; float descentY = baseY + fontMetrics.descent; float bottomY = baseY + fontMetrics.bottom; float leading = baseY + fontMetrics.leading; Log.d("fontMetrics", "baseX is:" + 0); Log.d("fontMetrics", "baseY is:" + 100); Log.d("fontMetrics", "topY is:" + topY); Log.d("fontMetrics", "ascentY is:" + ascentY); Log.d("fontMetrics", "descentY is:" + descentY); Log.d("fontMetrics", "bottomY is:" + bottomY); Log.d("fontMetrics", "leading is:" + leading); Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.fontmetrics); Bitmap mutableBitmap = bitmap.copy(Bitmap.Config.ARGB_8888, true); canvas = new Canvas(mutableBitmap); // 绘制文本 canvas.drawText(text, baseX, baseY, textPaint); // BaseLine描画 Paint baseLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG); baseLinePaint.setColor( Color.RED); canvas.drawLine(0, baseY, canvas.getWidth(), baseY, baseLinePaint); // Base描画 canvas.drawCircle( baseX, baseY, 5, baseLinePaint); // TopLine描画 Paint topLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG); topLinePaint.setColor( Color.LTGRAY); canvas.drawLine(0, topY, canvas.getWidth(), topY, topLinePaint); // AscentLine描画 Paint ascentLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG); ascentLinePaint.setColor( Color.GREEN); canvas.drawLine(0, ascentY, canvas.getWidth(), ascentY, ascentLinePaint); // DescentLine描画 Paint descentLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG); descentLinePaint.setColor( Color.YELLOW); canvas.drawLine(0, descentY, canvas.getWidth(), descentY, descentLinePaint); // ButtomLine描画 Paint bottomLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG); bottomLinePaint.setColor( Color.MAGENTA); canvas.drawLine(0, bottomY, canvas.getWidth(), bottomY, bottomLinePaint); ImageView imageView = (ImageView) findViewById(R.id.imageView1); imageView.setImageBitmap(mutableBitmap); } }
log显示如下:
![](https://oscdn.geek-share.com/Uploads/Images/Content/202006/07/cf1d7dd43b77dc58455d6759a32c70e6.png)
Note1:注意到各个数值都是整数,这是建立在baseY=100的情况下,去掉baseY,重新运行代码,log如下:
![](https://oscdn.geek-share.com/Uploads/Images/Content/202006/07/cb49a78ae5ab99a31d1d8811584d5e14.png)
Note2: 参照线为baseline,即baseline=0的情况下,其他各线的数值。leading = 0,即行间距=0
2,以上是根据paint设置,获取相关的FontMetrics属性,并且只绘制了一行字符串,我们猜想,如果是多行,是否可以获得行间距leanding,代码如下:
//test_multiply_lines TextView textView = (TextView) findViewById(R.id.textView1); String textMultiLines = "abcdefghijklmnopqrstuabcdefghijklmnopqrstuabcdefghijklmnopqrstuabcdefghijklmnopqrstuabcdefghijklmnopqrstu"; textView.setTextSize(55); textView.setText(textMultiLines); FontMetrics fontMetrics2 = textView.getPaint().getFontMetrics(); // 计算每一个坐标 float topY = fontMetrics2.top; float ascentY = fontMetrics2.ascent; float descentY = fontMetrics2.descent; float bottomY = fontMetrics2.bottom; float leading = fontMetrics2.leading; Log.d("fontMetrics", "topY is:" + topY); Log.d("fontMetrics", "ascentY is:" + ascentY); Log.d("fontMetrics", "descentY is:" + descentY); Log.d("fontMetrics", "bottomY is:" + bottomY); Log.d("fontMetrics", "leading is:" + leading);
log如下:
![](https://oscdn.geek-share.com/Uploads/Images/Content/202006/07/c78bb71ea0e329010c0e0a4cce496b3a.png)
Note:显然,即使是多行的情况下,仍不能获得leading。
3,如果text是单行,获得各个属性将会怎样,代码如下:
String text = "abcdefghijklmnopqrstu"; TextView textView = (TextView) findViewById(R.id.textView1); textView.setTextSize(55); textView.setText(text); FontMetrics fontMetrics = textView.getPaint().getFontMetrics(); // 计算每一个坐标 float baseX = 0; float baseY = 100; float topY = baseY + fontMetrics.top; float ascentY = baseY + fontMetrics.ascent; float descentY = baseY + fontMetrics.descent; float bottomY = baseY + fontMetrics.bottom; float leading = fontMetrics.leading; Log.d("fontMetrics", "topY is:" + fontMetrics.top); Log.d("fontMetrics", "ascentY is:" + fontMetrics.ascent); Log.d("fontMetrics", "descentY is:" + fontMetrics.descent); Log.d("fontMetrics", "bottomY is:" + fontMetrics.bottom); Log.d("fontMetrics", "leading is:" + fontMetrics.leading);
log如下图所示:
![](https://oscdn.geek-share.com/Uploads/Images/Content/202006/07/b4381cdb1f39bb5b60f4b45254c6b3a6.png)
Note:与多行获得的属性都相同。
结论:
A:虽然paint和textView所设置的textSize均为55,且为相同的字符串,但是两个获得的FontMetrics属性值并不相同。但是,我们发现,做除法之后,均为1.5倍关系。做出猜测,即Paint下,为mdpi对应的size,而TextView的size已经关联到了显示屏幕本身的320dip。所以获得属性值均为整1.5倍数
B:各种情况下,均未获得leading值。
本文出自 “小新专栏” 博客,转载请与作者联系!
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