好记性不如烂笔杆Android开发android绘制文本

Canvas 作为绘制文本时，使用FontMetrics对象，计算位置的坐标。

它的思路和java.awt.FontMetrics的基本相同。

FontMetrics对象

它以四个基本坐标为基准，分别为：

・FontMetrics.top
・FontMetrics.ascent
・FontMetrics.descent
・FontMetrics.bottom

该图片将如下

绘制文字的代码

 1 Paint textPaint = new Paint( Paint.ANTI_ALIAS_FLAG);
 2 textPaint.setTextSize( 35);
 3 textPaint.setColor( Color.WHITE);
 4 
 5 // FontMetrics对象
 6 FontMetrics fontMetrics = textPaint.getFontMetrics();
 7 
 8 String text = "abcdefghijklmnopqrstu";
 9 
10 // 计算每一个坐标
11 float baseX = 0;
12 float baseY = 100;
13 float topY = baseY + fontMetrics.top;
14 float ascentY = baseY + fontMetrics.ascent;
15 float descentY = baseY + fontMetrics.descent;
16 float bottomY = baseY + fontMetrics.bottom;
17 
18 // 绘制文本
19 canvas.drawText( text, baseX, baseY, textPaint);
20 
21 // BaseLine描画
22 Paint baseLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG);>
23 baseLinePaint.setColor( Color.RED);
24 canvas.drawLine(0, baseY, getWidth(), baseY, baseLinePaint);
25 
26 // Base描画
27 canvas.drawCircle( baseX, baseY, 5, baseLinePaint);
28 
29 // TopLine描画
30 Paint topLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG);
31 topLinePaint.setColor( Color.LTGRAY);
32 canvas.drawLine(0, topY, getWidth(), topY, topLinePaint);
33 
34 // AscentLine描画
35 Paint ascentLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG);
36 ascentLinePaint.setColor( Color.GREEN);
37 canvas.drawLine(0, ascentY, getWidth(), ascentY, ascentLinePaint);
38 
39 // DescentLine描画
40 Paint descentLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG);
41 descentLinePaint.setColor( Color.YELLOW);
42 canvas.drawLine(0, descentY, getWidth(), descentY, descentLinePaint);
43 
44 // ButtomLine描画
45 Paint bottomLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG);
46 bottomLinePaint.setColor( Color.MAGENTA);
47 canvas.drawLine(0, bottomY, getWidth(), bottomY, bottomLinePaint);

这个是从别处转载的，图片是精华，谢谢原作者！