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

如图:

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

 测试

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); } 
}

 结果是这样的：