组件的显示与隐藏:
隐藏组件并不占任何空间:but1.setVisibility(View.GONE);
隐藏组件但占一定的空间:but2.setVisibility(View.INVISIBLE);
显示组件:but3.setVisibility(View.VISIBLE);
隐藏组件并不占任何空间:but1.setVisibility(View.GONE);
隐藏组件但占一定的空间:but2.setVisibility(View.INVISIBLE);
显示组件:but3.setVisibility(View.VISIBLE);