android 动态设置控件的前提条件

简单的举个栗子说明一下：最外层有ReLativeLayout A，里面有两个LinearLayout B、C，而B中又有一个一个FrameLayout D。如果要在代码里设置B的LayoutParams,B的LayoutParams要为RelativeLayout.LayoutParams。

RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);B.setLayoutParams(params);

而D要设置的话，需要：

LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(LayoutParams.MATCH_PARENT, 0);params.weight = 8;D.setLayoutParams(params);

如果设置不正确将会引起java.lang.ClassCastException: android.widget.RelativeLayoutLayoutParamscannotbecasttoandroid.widget.AbsListViewLayoutParams错误