活动中的后退按钮正在删除片段

Question

我正在努力保持Fragment的状态。我有MotherActivity，其中有FragmentOne，FragmentTwo，FragmentThree，以及来自FragmentTwo的内部，我称之为另一个ActivityChildActivity。问题是，当我在ChildActivity中按回按钮时，它是在刷新MotherActivity，而不是保持MotherActivity的状态，而是向我展示了第一次出现的FragmentOne。

我只希望当我从ChildActivity按下ChildActivity时，容器FragmentTwo上应该有：

MainAcitivity：

public class MotherActivity extends FragmentActivity {

    AHBottomNavigation bottomNavigation;
    Fragment selectedFragment = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        bottomNavigation = (AHBottomNavigation) findViewById(R.id.navigation);
        bottomNavigation.addItem(item1);
        bottomNavigation.addItem(item2);
        bottomNavigation.addItem(item3);

        bottomNavigation.setOnTabSelectedListener(new AHBottomNavigation.OnTabSelectedListener() {
            @Override
            public boolean onTabSelected(int position, boolean wasSelected) {

                if (position == 0) {
                    selectedFragment = FragmentOne.newInstance(bottomNavigation);
                } else if (position == 1) {
                    selectedFragment = FragmentTwo.newInstance(bottomNavigation);
                } else if (position == 2) {
                    selectedFragment = FragmentThree.newInstance(bottomNavigation);
                } 

                android.app.FragmentManager fragmentManager = getFragmentManager();
                android.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
                fragmentTransaction.replace(R.id.frame_layout,selectedFragment);
                fragmentTransaction.commit();


                return true;

            }

        });
    }

    @Override
    protected void onStart() {
        super.onStart();
        android.app.FragmentManager fragmentManager = getFragmentManager();
        android.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.replace(R.id.frame_layout, FragmentOne.newInstance(bottomNavigation));
        fragmentTransaction.commit();

    }

    public void setNotification(){
        bottomNavigation.setNotification("1", 1);
    }
    @Override
    protected void onSaveInstanceState(Bundle outState) {
        //No call for super().
    }
    @Override
    public void onBackPressed() {
        Intent intent = new Intent();
        setResult(113, intent);
        finish();
        return;

    }
}

FragmentTwo，在我打电话给childActivity的地方

public class FragmentTwo extends Fragment {
    public static AHBottomNavigation bottomNavigation1;
    Card_detail_Adapter_Footer searchabledapter;
    public static boolean showAddress = false;
    Fragment selectedFragment;

    public static FragmentTwo newInstance(AHBottomNavigation bottomNavigation) {
        FragmentTwo fragment = new FragmentTwo();
        bottomNavigation1 = bottomNavigation;
        showNotificationCounter(3);

        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        View view   = inflater.inflate(R.layout.fragment_cart, container, false);
        if(showAddress == true){
            showAddress = false;

      // From here I am calling ChildActivity

            Intent intent = new Intent(getActivity(), ChildActivity.class);
            startActivity(intent);

        }
        return view;
    }

}

在ChildActivity中，只需调用onBackPressed()

Answer 1

问题在于您的onStart()方法是MotherActivity.java，因为当您从FragmentTwo打开另一个活动时，会调用您的MotherActivity onStop()。当您按下ChildActivity的后退按钮时，调用onStart() of MotherActivity，这将通过提交事务来取代FragmentOne中的FragmentTwo。请看一下https://developer.android.com/guide/components/activities/activity-lifecycle.html

Answer 2

将onStart()方法中的代码放入onCreate()方法，并检查配置是否已更改：

if (savedInstanceState == null) {
    android.app.FragmentManager fragmentManager = getFragmentManager();
    android.app.FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
    fragmentTransaction.add(R.id.frame_layout, FragmentOne.newInstance(bottomNavigation));
    fragmentTransaction.commit();
}