android - 重新加载 fragment 留下空白屏幕

Question

我通过以下方式在 framelayout 中添加了 fragment

    mUserListFragment = new UserListFragment();
    mMessageFragment = new MessageFragment();
    mAccountFragment = new AccountFragment();

    fragmentManager.beginTransaction().add(R.id.frame_layout, mAccountFragment, mAccountFragment.getClass().getSimpleName()).addToBackStack(mAccountFragment.getClass().getSimpleName()).commit();
    fragmentManager.beginTransaction().add(R.id.frame_layout, mMessageFragment, mMessageFragment.getClass().getSimpleName()).addToBackStack(mMessageFragment.getClass().getSimpleName()).commit();
    fragmentManager.beginTransaction().add(R.id.frame_layout, mUserListFragment, mUserListFragment.getClass().getSimpleName()).addToBackStack(mUserListFragment.getClass().getSimpleName()).commit();

后面我会按照下面的方式显示或者隐藏fragment

//for showing
fragmentManager.beginTransaction().show(fragment).commit();

//for hiding 
fragmentManager.beginTransaction().hide(fragment).commit();

我从一个 fragment 转到另一个 Activity，通过一些 onClick 方法，该 Activity 重定向到保存 fragment 的同一个 Activity。当回到 fragment 持有者 Activity 时，我在 onResume 中重新加载 fragment ，但它使该 fragment 空白，但是通过调试我开始知道， fragment 是可见的并且 onCreateView 方法被调用，我尝试以下列方式重新加载 fragment

FragmentManager fm = getSupportFragmentManager();
FragmentTransaction ft = fm.beginTransaction();

ft.setReorderingAllowed(false);

ft.detach(activeFragment).commitNow();
ft.attach(activeFragment).commitNow(); 

我也试过了

fragmentManager.beginTransaction().detach(activeFragment).attach(activeFragment).commitAllowingStateLoss();

所有这些只会留下空白屏幕。

Answer 1

您可以通过以下代码跟踪 fragment 的堆栈和 fragment 数。

getSupportFragmentManager().addOnBackStackChangedListener(new OnBackStackChangedListener() {
            public void onBackStackChanged() {
                Log.i(TAG, "back stack changed ");
                int backCount = getSupportFragmentManager().getBackStackEntryCount();

                // you can also track which are current fragments are in stack by
                getSupportFragmentManager().getFragments();

                if(backCount ==0){

                    //then you have to check whats going wrong in your case
                    // suppose to kill current activity also by finish();
                    // I means its depending on your requirements.


                }

            }
        });

它将帮助您找到自己的出路。