Button btn1;

btn1.setId(1001);

int width;   // layout width;

int btnWidth; // btn width;

int btnHeight; // btn height;

…….

RelativeLayout.LayoutParams p = new RelativeLayout.LayoutParams(btnWidth, btnHeight);

p.addRule(RelativeLayout.ALIGN_PARENT_TOP);

p.addRule(RelativeLayout.CENTER_HORIZONTAL, RelativeLayout.TRUE);

p.topMargin = config.topMargin;

// 这里必须设置，否则依赖这个左右对齐的控件无法对齐。

//   如果不设置，只使用水平居中的属性，则1001这个控件的leftmargin为0. 导致左右对齐失败

p.leftMargin = (width-btnWidth)/2;

//

Button btn2;

RelativeLayout.LayoutParams p = new RelativeLayout.LayoutParams(btnWidth, btnHeight);

p.addRule(RelativeLayout.ALIGN_PARENT_TOP);

p.addRule(RelativeLayout.ALIGN_LEFT, 1001); // 这里要想生效必须，1001这个控件必须添加leftmargin.

p.topMargin = config.topMargin;

//

Button btn3;

RelativeLayout.LayoutParams p = new RelativeLayout.LayoutParams(btnWidth, btnHeight);

p.addRule(RelativeLayout.ALIGN_PARENT_TOP);

// 这里要想生效必须，1001这个控件必须添加leftmargin/right margin.

p.addRule(RelativeLayout.ALIGN_RIGHT, 1001);

p.topMargin = config.topMargin;

原文：http://www.cnblogs.com/feitianlee/p/3944800.html