View Order of Framelayout

Question

Here is the sample code:

FrameLayout Root = new FrameLayout(this);
this.addContentView(Root, LayoutParam0);
setContentView(this);

GLSurfaceView gls = new GLSurfaceView(this);
Root.addView(gls,0, LayoutParam1);

View view = new UnityPlayer(this);
Root.addView(view,1, LayoutParam2);

I want to let view on top and gls on the bottom, but some android device will let gls on top. How can I fix it?

p.s. bringToFront() some android device will let it go to bottom.