Paint textPaint = new Paint( Paint.ANTI_ALIAS_FLAG); 
textPaint.setTextSize( 35); 
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; 
// 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, 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, getWidth(), topY, topLinePaint); 
// AscentLine描画 
Paint ascentLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG); 
ascentLinePaint.setColor( Color.GREEN); 
canvas.drawLine(0, ascentY, getWidth(), ascentY, ascentLinePaint); 
// DescentLine描画 
Paint descentLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG); 
descentLinePaint.setColor( Color.YELLOW); 
canvas.drawLine(0, descentY, getWidth(), descentY, descentLinePaint); 
// ButtomLine描画 
Paint bottomLinePaint = new Paint( Paint.ANTI_ALIAS_FLAG); 
bottomLinePaint.setColor( Color.MAGENTA); 
canvas.drawLine(0, bottomY, getWidth(), bottomY, bottomLinePaint);