小编use*_*350的帖子

我有两个活动A和B.活动A有一个mapFragment,我将它添加到backstack.当我从B回到Actvity A时,我希望片段显示的状态与我离开时相同.但getFragmentManager().getBackStackEntryCount()返回0.这是我的代码:

MapFragment mMapFragment = MapFragment.newInstance();
    FragmentTransaction fragmentTransaction = getFragmentManager().beginTransaction();
    mMapFragment.getMapAsync(this);
    fragmentTransaction.replace(R.id.container, mMapFragment);
    fragmentTransaction.addToBackStack(null);
    fragmentTransaction.commit();
    getFragmentManager().executePendingTransactions();

从活动B返回时,我知道getBackStackEntryCount()的数量:

System.out.println("Number of entries in backstack "+ getFragmentManager().getBackStackEntryCount());

这显示我0.

提前致谢.