必须使用relativelayout
RelativeLayout.LayoutParams lp = new RelativeLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
lp.addRule(RelativeLayout.CENTER_IN_PARENT, RelativeLayout.TRUE);//居中显示。
layout.addView(button,lp);
同理 ，也可以设置其他对齐方式：
lp.addRule(RelativeLayout.ALIGN_WITH_PARENT_TOP);//父容器顶部对齐
lp.addRule(RelativeLayout.POSITION_BELOW,
view1);//与view1底部对齐
lp.addRule(RelativeLayout.ALIGN_LEFT, view2);//与view2左对齐