用代码设置 RelativeLayout.LayoutParams

1.注意

• 不能在RelativeLayout容器本身和他的子元素之间产生循环依赖，比如说，不能将RelativeLayout的高设置成为WRAP_CONTENT的时候将子元素的高设置成为 ALIGN_PARENT_BOTTOM。
• 如果parent是wrap_content的话，alignParentRight就意味着要求parent的layout_width="match_parent"； alignParentBottom就意味着要求parent的layout_height="match_parent"

　　等等。

2.用代码设置 RelativeLayout.LayoutParams

         RelativeLayout.LayoutParams params3 = (RelativeLayout.LayoutParams) holder.layout.getLayoutParams();

         //如果之前设置了rule，同时设置了多个rules可能冲突，下面代码清空rules
         if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1){// >= 17
             params3.removeRule(RelativeLayout.RIGHT_OF);
         }else{
             int rules[] = params3.getRules();
             rules[RelativeLayout.LEFT_OF] = ;
             rules[RelativeLayout.RIGHT_OF] = ;
         }
         //添加新的rules,一般刚创建RelativeLayout.LayoutParams时，不要添加任何rule
         if (mb.contact.isSelf()) {
             params3.addRule(RelativeLayout.LEFT_OF,R.id.msg_portrait);
         }else{
             params3.addRule(RelativeLayout.RIGHT_OF,R.id.msg_portrait);
         }
         holder.layout.setLayoutParams(params3);

3.常用的rule

     /**
      * Rule that aligns a child's right edge with another child's left edge.
      */
     public static final int LEFT_OF                  = ;
     /**
      * Rule that aligns a child's left edge with another child's right edge.
      */
     public static final int RIGHT_OF                 = ;
     /**
      * Rule that aligns a child's bottom edge with another child's top edge.
      */
     public static final int ABOVE                    = ;
     /**
      * Rule that aligns a child's top edge with another child's bottom edge.
      */
     public static final int BELOW                    = ;

     /**
      * Rule that aligns a child's baseline with another child's baseline.
      */
     public static final int ALIGN_BASELINE           = ;
     /**
      * Rule that aligns a child's left edge with another child's left edge.
      */
     public static final int ALIGN_LEFT               = ;
     /**
      * Rule that aligns a child's top edge with another child's top edge.
      */
     public static final int ALIGN_TOP                = ;
     /**
      * Rule that aligns a child's right edge with another child's right edge.
      */
     public static final int ALIGN_RIGHT              = ;
     /**
      * Rule that aligns a child's bottom edge with another child's bottom edge.
      */
     public static final int ALIGN_BOTTOM             = ;

     /**
      * Rule that aligns the child's left edge with its RelativeLayout
      * parent's left edge.
      */
     public static final int ALIGN_PARENT_LEFT        = ;
     /**
      * Rule that aligns the child's top edge with its RelativeLayout
      * parent's top edge.
      */
     public static final int ALIGN_PARENT_TOP         = ;
     /**
      * Rule that aligns the child's right edge with its RelativeLayout
      * parent's right edge.
      */
     public static final int ALIGN_PARENT_RIGHT       = ;
     /**
      * Rule that aligns the child's bottom edge with its RelativeLayout
      * parent's bottom edge.
      */
     public static final int ALIGN_PARENT_BOTTOM      = ;

     /**
      * Rule that centers the child with respect to the bounds of its
      * RelativeLayout parent.
      */
     public static final int CENTER_IN_PARENT         = ;
     /**
      * Rule that centers the child horizontally with respect to the
      * bounds of its RelativeLayout parent.
      */
     public static final int CENTER_HORIZONTAL        = ;
     /**
      * Rule that centers the child vertically with respect to the
      * bounds of its RelativeLayout parent.
      */
     public static final int CENTER_VERTICAL          = ;
     /**
      * Rule that aligns a child's end edge with another child's start edge.
      */
     public static final int START_OF                 = ;
     /**
      * Rule that aligns a child's start edge with another child's end edge.
      */
     public static final int END_OF                   = ;
     /**
      * Rule that aligns a child's start edge with another child's start edge.
      */
     public static final int ALIGN_START              = ;
     /**
      * Rule that aligns a child's end edge with another child's end edge.
      */
     public static final int ALIGN_END                = ;
     /**
      * Rule that aligns the child's start edge with its RelativeLayout
      * parent's start edge.
      */
     public static final int ALIGN_PARENT_START       = ;
     /**
      * Rule that aligns the child's end edge with its RelativeLayout
      * parent's end edge.
      */
     public static final int ALIGN_PARENT_END         = ;