val popupMenu: PopupMenu = PopupMenu(requireContext(), it)
popupMenu.menu.add("测试Menu1")
popupMenu.menu.add("测试Menu1")
//反射获取Popup
val mPopupMenu: Field = popupMenu.javaClass.getDeclaredField("mPopup")
mPopupMenu.isAccessible = true
val mHelper: MenuPopupHelper = mPopupMenu.get(popupMenu) as MenuPopupHelper
val standardMenuClass: Class<*> = Class.forName("androidx.appcompat.view.menu.StandardMenuPopup")
//设置不测量Item宽度
val mHasContentWidth: Field = standardMenuClass.getDeclaredField("mHasContentWidth")
mHasContentWidth.isAccessible = true
mHasContentWidth.setBoolean(mHelper.popup, true)
//设置弹出宽度
val mContentWidth: Field = standardMenuClass.getDeclaredField("mContentWidth")
mContentWidth.setAccessible(true)
//这里第二个参数填自己想要的宽度即可，获取屏幕宽度也行或者父控件
mContentWidth.setInt(mHelper.popup, it.width)
mHelper.show()
效果图
参考了以下文章写出来的，感谢作者
