Android 字体高度的研究

2019-11-09 15:49:43

字体：大中小

来源：转载

供稿：网友

Android自定义View绘制的时候，会有很多情况下要与字体打交道，涉及到字体宽度、高度的时候要特别注意一下几个概念，见图：

baseLine：一行文字的底线。

Ascent：字符顶部到baseLine的距离。

Descent：字符底部到baseLine的距离。

Leading：字符行间距。

java代码

public class TestOnDraw extends Activity { @Override PRotected void onCreate(Bundle savedInstanceState) { // TODO Auto-generated method stub super.onCreate(savedInstanceState); MyView v = new MyView(this); this.setContentView(v); } } class MyView extends View { public MyView(Context context) { super(context); } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); Paint p = new Paint(); p.setColor(Color.WHITE); p.setTextSize(50); p.setAntiAlias(true); FontMetrics fm = p.getFontMetrics(); System.out.println("top = "+ fm.top); System.out.println("ascent = "+ fm.ascent); System.out.println("descent = "+ fm.descent); System.out.println("bottom = "+ fm.bottom); System.out.println("leading = "+ fm.leading); int textHeight = (int) (Math.ceil(fm.descent - fm.ascent) + 2); System.out.println("textHeight = " + textHeight); float width =500; float baseline = 100f; float offsetAscent = baseline + fm.ascent; float offsetDescent = baseline +fm.descent; float offsetTop = baseline + fm.top; float offsetBottom = baseline + fm.bottom; canvas.drawText("中国 bp Android", 0, baseline, p); canvas.drawLine(0, baseline, width, baseline, p);//baseline canvas.drawLine(0, offsetAscent, width, offsetAscent, p);//ascent canvas.drawLine(0, offsetDescent, width, offsetDescent, p);//descent canvas.drawLine(0, offsetTop, width, offsetTop, p);//top canvas.drawLine(0, offsetBotton, width, offsetBottom, p);//bottom } } [java] view plain copypublic class TestOnDraw extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { // TODO Auto-generated method stub super.onCreate(savedInstanceState); MyView v = new MyView(this); this.setContentView(v); } } class MyView extends View { public MyView(Context context) { super(context); } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); Paint p = new Paint(); p.setColor(Color.WHITE); p.setTextSize(50); p.setAntiAlias(true); FontMetrics fm = p.getFontMetrics(); System.out.println("top = "+ fm.top); System.out.println("ascent = "+ fm.ascent); System.out.println("descent = "+ fm.descent); System.out.println("bottom = "+ fm.bottom); System.out.println("leading = "+ fm.leading); int textHeight = (int) (Math.ceil(fm.descent - fm.ascent) + 2); System.out.println("textHeight = " + textHeight); float width =500; float baseline = 100f; float offsetAscent = baseline + fm.ascent; float offsetDescent = baseline +fm.descent; float offsetTop = baseline + fm.top; float offsetBottom = baseline + fm.bottom; canvas.drawText("中国 bp Android", 0, baseline, p); canvas.drawLine(0, baseline, width, baseline, p);//baseline canvas.drawLine(0, offsetAscent, width, offsetAscent, p);//ascent canvas.drawLine(0, offsetDescent, width, offsetDescent, p);//descent canvas.drawLine(0, offsetTop, width, offsetTop, p);//top canvas.drawLine(0, offsetBotton, width, offsetBottom, p);//bottom } }

运行效果：