动态设置一个view的margin，gravity的方式

代码如下：

imageView2=new ImageView(this);
LinearLayout.LayoutParams layoutParams=new LinearLayout.LayoutParams(new Double(width*0.8).intValue(),height/3);
layoutParams.gravity= Gravity.CENTER_HORIZONTAL;
layoutParams.setMargins(5,10,5,10);
imageView2.setLayoutParams(layoutParams);

当然还有SlidingPaneLayout.LayoutParams，ViewGroup.LayoutParams，DrawerLayout.LayoutParams等等，方式一样