addView hierarchy

1. addview(view, 0); // Add to the bottom layer
2. Add addview(view1, 0);
   addview(view2, 2); // An error will be reported at this time. When adding this view, the parent window has only one view , so parameter 2 will be out of bounds
   addview(view3, 1);
3. Add addview(view1, 0);
   addview(view2, 1);
   addview(view3, 1);
   // At this time, view2 will be displayed last,
   // The sequence number of view3 is not greater than that of view2, and it is placed after view2