问：canvas.drawText("3", x, y, paint); x和y是指画得时候数字3中心的坐标吗？还是左上角的坐标？
答：x默认是‘3’这个字符的左边在屏幕的位置，如果设置了paint.setTextAlign(Paint.Align.CENTER);那就是字符的中心，y是指定这个字符baseline在屏幕上的位置。
public
void drawText (String text, float x, float y, Paint paint)
Since: API Level 1
Draw the text, with origin at (x,y), using the specified
paint.
The origin is interpreted based on the Align setting in
the paint.
Parameters
text The text to be drawn
x The
x-coordinate of the origin of the text being drawn
y The y-coordinate
of the origin of the text being drawn
paint The paint used for the text
(e.g. color, size, style)
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
- 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);
drawText画字符串是baseline对齐的。所以要特别注意这点，不然画文字可能画到其它地方而误以为没有画出来。
如果baseline对齐的话：底端的Y坐标是：(行高-字体高度)/2+字体高度 ，但是字符串并不居中，经过测试如果：(行高-字体高度)/2+字体高度-6 ，就稍微居中了一点。
以上的方法只是一个取巧的做法，网上也没有找到设置文字居中的方法。
按上面办法会有误差。加上那段距离应该就行了:
- FontMetrics fontMetrics = mPaint.getFontMetrics();
- float fontTotalHeight = fontMetrics.bottom - fontMetrics.top;
- float offY = fontTotalHeight / 2 - fontMetrics.bottom;
- float newY = baseY + offY;
- canvas.drawText(text, baseX, newY, paint);
原文：http://blog.csdn.net/lvxiangan/article/details/8540774
FontMetricsInt fontMetrics = mTextPaint.getFontMetricsInt();
int centerX = width / 2;
int baseline = (height - fontMetrics.bottom + fontMetrics.top) / 2 - fontMetrics.top;
mTextPaint.setTextAlign(Paint.Align.CENTER);
canvas.drawText(("text", centerX, baseline, mTextPaint);
关于Canvas.drawText中xy位置问题,布布扣,bubuko.com
关于Canvas.drawText中xy位置问题
原文：http://www.cnblogs.com/veins/p/3725909.html
