????private?fun?switchFragment(selectIndex:?Int)?{
????????if?(tab1Fragment?==?null)?{
????????????tab1Fragment?=?StudyFragment()
????????????//???????????添加參數(shù)
????????????addBundleToFragment(tab1Fragment!!,?"tab1")
????????}
????????if?(tab2Fragment?==?null)?{
????????????tab2Fragment?=?StudyFragment()
????????????//????????????添加參數(shù)
????????????addBundleToFragment(tab2Fragment!!,?"tab2")
????????}
????????if?(tab3Fragment?==?null)?{
????????????tab3Fragment?=?StudyFragment()
????????????//????????????添加參數(shù)
????????????addBundleToFragment(tab3Fragment!!,?"tab3")
????????}
//獲取fragment對象
????????val?fragment:?Fragment??=?when?(selectIndex)?{
????????????0?->?{
????????????????tab1Fragment
????????????}
????????????1?->?{
????????????????tab2Fragment
????????????}
????????????2?->?{
????????????????tab3Fragment
????????????}
????????????else?->?{
????????????????throw?IllegalStateException("${selectIndex}下標(biāo)不符合預(yù)期")
????????????}
????????}??:?return????????//如果fragment為空，則返回
//????????切換fragment顯示

????????if?(fragment?!=?null)?{
????????????if?(!fragment.isAdded)?{
????????????????fragmentTransaction.add(R.id.fragment_container,?fragment)//添加fragment
????????????}
????????????fragmentTransaction.show(fragment)//顯示fragment
????????}
????????//???隱藏之前顯示的shownFragment,以多個Fragemnt重疊
????????if?(shownFragment?!=?null)?{
????????????fragmentTransaction.hide(shownFragment!!)
????????}
????????shownFragment?=?fragment//設(shè)置當(dāng)前顯示的為fragment
????????fragmentTransaction.commitAllowingStateLoss()//提交業(yè)務(wù)
????}

報錯指向這一行：

????fragmentTransaction.commitAllowingStateLoss()//提交業(yè)務(wù)

整個文件只有這一個提交業(yè)務(wù) ，為什么說已經(jīng)called