http://blog.csdn.net/hursing/article/details/18703599
@Override
public void onDraw (Canvas canvas) {
Rect targetRect = new Rect(50, 50, 1000, 200);
Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
paint.setStrokeWidth(3);
paint.setTextSize(80);
String testString = "测试：ijkJQKA:1234";
paint.setColor(Color.CYAN);
canvas.drawRect(targetRect, paint);
paint.setColor(Color.RED);
FontMetricsInt fontMetrics = paint.getFontMetricsInt();
int baseline = (targetRect.bottom + targetRect.top - fontMetrics.bottom - fontMetrics.top) / 2;
// 下面这行是实现水平居中，drawText对应改为传入targetRect.centerX()
paint.setTextAlign(Paint.Align.CENTER);
canvas.drawText(testString, targetRect.centerX(), baseline, paint);
}
