有时候需要在在代码中设置LayoutParams，自己为一个FrameLayout设置LayoutParams的时候，遇上如题问题，

java.lang.ClassCastException: android.widget.FrameLayout$LayoutParams cannot be cast to android.widget.LinearLayout$LayoutParams

          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);

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