在標籤內切換片段

Question

我正在創建一個使用ActionBarSherlock的應用程序。該應用程序由三個選項卡組成，並且在每個選項卡中，根據用戶輸入連續顯示多個屏幕。我可以在選項卡之間切換片段，但在選項卡內切換片段會產生問題。我試着這樣說：

在主類：

SingleStationFragment singleStationFragment = new SingleStationFragment(); 
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction(); 
transaction.replace(android.R.id.content, singleStationFragment); 
transaction.addToBackStack(null); 
transaction.commit(); 

這不替換第一個片段第二，但是當我更改選項卡，第二個片段是仍然可見，顯示新選項卡的內容位於舊選項卡內容的頂部。我想不知怎麼我需要分開onTabUnselected中的第二個片段，但我不知道如何得到這個片段的參考。

任何人都可以幫助我嗎？

爲了清楚起見，一些顯著類：

我的主類：

public class TreinVerkeer extends SherlockFragmentActivity { 

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

    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     MenuInflater inflater = getSupportMenuInflater(); 
     inflater.inflate(R.menu.menu, menu); 
     return true; 
    } 

    private void setupTabs(Bundle savedInstanceState) { 
     ActionBar actionBar = getSupportActionBar(); 
     actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS); 

     Tab tab = actionBar.newTab().setText("STATIONS").setTabListener(new TabListener<StationsFragment>(this, "stations", StationsFragment.class)); 
     actionBar.addTab(tab); 

     tab = actionBar.newTab().setText("ROUTE").setTabListener(new TabListener<RouteFragment>(this, "route", RouteFragment.class)); 
     actionBar.addTab(tab); 

     tab = actionBar.newTab().setText("DELAYS").setTabListener(new TabListener<DelaysFragment>(this, "delays", DelaysFragment.class)); 
     actionBar.addTab(tab); 

     if (savedInstanceState != null) { 
      actionBar.setSelectedNavigationItem(savedInstanceState.getInt("tab", 0)); 
     } 
    } 

    @Override 
    protected void onSaveInstanceState(Bundle outState) { 
     super.onSaveInstanceState(outState); 
     outState.putInt("tab", getSupportActionBar().getSelectedNavigationIndex()); 
    } 
} 

的TabListener（從"Adding Navigations Tabs" on the Android developer site進行一些小改動）：

public class TabListener<T extends SherlockFragment> implements com.actionbarsherlock.app.ActionBar.TabListener { 
    private SherlockFragment mFragment; 
    private final Activity mActivity; 
    private final String mTag; 
    private final Class<T> mClass; 

    /** 
    * Constructor used each time a new tab is created. 
    * 
    * @param activity 
    *   The host Activity, used to instantiate the fragment 
    * @param tag 
    *   The identifier tag for the fragment 
    * @param clz 
    *   The fragment's Class, used to instantiate the fragment 
    */ 
    public TabListener(Activity activity, String tag, Class<T> clz) { 
     mActivity = activity; 
     mTag = tag; 
     mClass = clz; 
    } 

    /* The following are each of the ActionBar.TabListener callbacks */ 

    public void onTabSelected(Tab tab, FragmentTransaction ft) { 
    SherlockFragment preInitializedFragment = (SherlockFragment) mActivity.getSupportFragmentManager().findFragmentByTag(mTag); 

    // Check if the fragment is already initialized 
    if (mFragment == null && preInitializedFragment == null) { 
     // If not, instantiate and add it to the activity 
     mFragment = (SherlockFragment) SherlockFragment.instantiate(mActivity, mClass.getName()); 
     ft.add(android.R.id.content, mFragment, mTag); 
    } else if (mFragment != null) { 
     // If it exists, simply attach it in order to show it 
     ft.attach(mFragment); 
    } else if (preInitializedFragment != null) { 
     ft.attach(preInitializedFragment); 
     mFragment = preInitializedFragment; 
    } 
} 

    public void onTabUnselected(Tab tab, FragmentTransaction ft) { 
     if (mFragment != null) { 
      // Detach the fragment, because another one is being attached 
      ft.detach(mFragment); 
     } 
    } 

    public void onTabReselected(Tab tab, FragmentTransaction ft) { 
     // User selected the already selected tab. Usually do nothing. 
    } 
} 

而且StationsFragment（RouteFragment和DelaysFragment是一樣的，只有不同的文字）

public class StationsFragment extends SherlockFragment { 

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

    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
     return inflater.inflate(R.layout.stationsfragment, container, false); 
    } 
} 

Answer 1

那麼實際情況是，在TabListener，在onTabUnselected法，Fragment完全沒有剝離，使其仍然節目的同時，一個新的Fragment被證明。

原因是這樣的，被分離的Fragment是第一個片段，而不是我的第二個片段。我做了一些改變。

在Activity：

SingleStationFragment singleStationFragment = new SingleStationFragment(); 
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction(); 
transaction.replace(android.R.id.content, singleStationFragment, "STATIONS"); 
transaction.addToBackStack(null); 
transaction.commit(); 

在這裏，我已經添加在replace()方法，這是相同的標籤與第一片段的"STATIONS"標籤。
的TabListener現在如下：

public class TabListener<T extends SherlockFragment> implements com.actionbarsherlock.app.ActionBar.TabListener { 
    private final SherlockFragmentActivity mActivity; 
    private final String mTag; 
    private final Class<T> mClass; 

    private SherlockFragment mFragment; 

    public TabListener(SherlockFragmentActivity activity, String tag, Class<T> clz) { 
     mActivity = activity; 
     mTag = tag; 
     mClass = clz; 
    } 

    public void onTabSelected(Tab tab, FragmentTransaction ft) { 
     SherlockFragment preInitializedFragment = (SherlockFragment) mActivity.getSupportFragmentManager().findFragmentByTag(mTag); 
     if (preInitializedFragment == null) { 
      mFragment = (SherlockFragment) SherlockFragment.instantiate(mActivity, mClass.getName()); 
      ft.add(R.id.treinverkeer_fragmentcontent, mFragment, mTag); 
     } else { 
      ft.attach(preInitializedFragment); 
     } 
    } 

    public void onTabUnselected(Tab tab, FragmentTransaction ft) { 
     SherlockFragment preInitializedFragment = (SherlockFragment) mActivity.getSupportFragmentManager().findFragmentByTag(mTag); 

     if (preInitializedFragment != null) { 
      ft.detach(preInitializedFragment); 
     } else if (mFragment != null) { 
      ft.detach(mFragment); 
     } 
    } 

    public void onTabReselected(Tab tab, FragmentTransaction ft) { 
     // User selected the already selected tab. Usually do nothing. 
    } 
} 

在onTabUnselected方法我現在先檢索正確Fragment，然後卸下。

希望這可以幫助別人！