替换两个不同的片段后，按下后​​退按钮时会重新创建第一个片段

Posted 2023-02-26

【中文标题】替换两个不同的片段后，按下后​​退按钮时会重新创建第一个片段

【英文标题】：After two different fragments have been replaced, first fragment is recreated when on pressed back button

【发布时间】：2016-12-01 08:20:29

【问题描述】：

我有三个片段和一个活动。它是这样工作的：

[activity]-> [MainFragment]->[MenuFragment]->[SignUpFragment]

当[SignUpFragment] 被回按时，[MainFragment] 会被创建两次。

我尝试了setRetaInInstance(true) 并检查了savedInstanceState，但我无法阻止[MainFragment] 重新创建。

这是我的 MainActivity：

public class MainActivity extends AppCompatActivity 

public Bundle mSavedInstanceState;

@Override
protected void onCreate(Bundle savedInstanceState) 

    super.onCreate(savedInstanceState);

    mSavedInstanceState = savedInstanceState;

    setContentView(R.layout.activity_main);

    

    @Override
    protected void onResume() 

    super.onResume();

    callMainFragment();

    

    private void callMainFragment() 

    if (mSavedInstanceState == null) 

        FragmentManager manager = getSupportFragmentManager();

        FragmentTransaction transaction = manager.beginTransaction();

        transaction.replace(R.id.container_category, new MainFragment(), MainFragment.class.getSimpleName());

        transaction.addToBackStack(null);

        transaction.commit();

    



 public ActionBar getMainActionBar()

    ActionBar actionBar = getSupportActionBar();

    if (actionBar != null) 

        // Action Bar Display settings

        actionBar.setDisplayShowCustomEnabled(true);

        actionBar.setDisplayShowTitleEnabled(false);

        // Custom view inflater

        LayoutInflater inflater = (LayoutInflater) this.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        // Custom layout view

        View viewActionBar = inflater.inflate(R.layout.action_bar, null);

        // Set custom view

        actionBar.setCustomView(viewActionBar);

        actionBar.setDisplayOptions(ActionBar.DISPLAY_SHOW_CUSTOM);

    

    return actionBar;

这是我的 MainFragment：

    public class MainFragment extends BaseFragment implements AdapterView.OnItemClickListener, BuyersGuideCategoriesDelegate, View.OnClickListener 

private Bundle mSavedInstanceState;

private BuyersGuideCategoriesFragment mCategoriesFragment;

@Override
public void onCreate(@Nullable Bundle savedInstanceState) 

    super.onCreate(savedInstanceState);

    this.setRetainInstance(true);



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

    mSavedInstanceState = savedInstanceState;

        if (mSavedInstanceState == null) 

            mView = inflater.inflate(R.layout.fragment_main, container, false);

            // Call Grid View Buyers Guide Fragment

            mCategoriesFragment = new BuyersGuideCategoriesFragment();

            mCategoriesFragment.mGridViewDelegate = this;

            setIcons();

            setTitles();

            setTexts();

            initListView();

        

    return mView;



@Override
public void onResume() 

    super.onResume();

    ImageView menu = (ImageView) ((MainActivity) getActivity()).getMainActionBar().getCustomView().findViewById(R.id.action_bar_menu_icon);

    menu.setOnClickListener(this);



@Override
public void onClick(View v) 

    if (mSavedInstanceState == null) 

        MainActivity activity = (MainActivity) getActivity();

        FragmentManager manager = activity.getSupportFragmentManager();

        FragmentTransaction transaction = manager.beginTransaction();

        transaction.replace(R.id.container_category, new MenuFragment(),MenuFragment.class.getSimpleName());

        transaction.addToBackStack(null);

        transaction.commit();

    

这是我的 MenuFragment：

public class MenuFragment extends BaseFragment implements AdapterView.OnItemClickListener, View.OnClickListener 

private Bundle mSavedInstanceState;

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

    mSavedInstanceState = savedInstanceState;

    if (savedInstanceState == null) 

        mView = inflater.inflate(R.layout.fragment_menu, container, false);

        setMenuItemsListViewAdapter();

    

    return mView;



  private void setMenuItemsListViewAdapter() 

    ListView menuItems = (ListView) mView.findViewById(R.id.list_menu_items);

    ListMenuItemsListViewAdapter adapter = new ListMenuItemsListViewAdapter(getContext(),getMenuItemNames());

    menuItems.setAdapter(adapter);

    menuItems.setOnItemClickListener(this);


 @Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) 

    switch ((String) parent.getAdapter().getItem(position))

      case SIGN_UP:

            replaceFragment(R.id.container_category,new SignUpFragment(),SignUpFragment.class.getSimpleName());

            break;

    



private void replaceFragment(int containerId,Fragment fragment, String fragmentTag)

    if (mSavedInstanceState == null)

        MainActivity activity = (MainActivity) getActivity();

        FragmentManager manager = activity.getSupportFragmentManager();

        FragmentTransaction transaction = manager.beginTransaction();

        transaction.replace(containerId,fragment,fragmentTag);

        transaction.addToBackStack(null);

        transaction.commit();

    



@Override
public void onClick(View v) 

    switch (v.getId())

        case R.id.menu_back_icon:

                replaceFragment(R.id.container_category, new MainFragment(),MainFragment.class.getSimpleName());

            break;

    

这是我的 SignUpFragment：

public class SignUpFragment extends BaseFragment implements View.OnClickListener

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

    if (savedInstanceState == null) 

        mView = inflater.inflate(R.layout.fragment_sign_up, container, false);
    

    return mView;

编辑 1：仅当我从 SignUpFragment 返回到 MenuFragment 时，才重新创建 MainFragment。使用这么多片段我做错了吗？我应该使用活动吗？

【问题讨论】：

请给我们一些代码。没有任何实际信息就无法为您提供帮助！

您是否有一个活动托管三个不同的片段？

是的，我正在使用单个活动。

【参考方案1】：

当你在 Fragments 之间移动时，调用 addToBackStack() ：

FragmentTransaction ft = fragmentManager.beginTransation();
ft.replace( R.id.fragment, new MyFragment() ).addToBackStack( "ftransaction" ).commit();

【参考方案2】：

创建第一个片段：

FragmentTransaction ft = fragmentManager.beginTransation();
ft.add(R.id.container, new FirstFragment()).addToBackStack(null).commit();

第二：

FragmentTransaction ft = fragmentManager.beginTransation();
ft.replace(R.id.container, new SecondFragment()).addToBackStack(null).commit();

第三个：

FragmentTransaction ft = fragmentManager.beginTransation();
ft.replace(R.id.container, new ThirdFragment()).commit();