刪除片段問題

Question

我有三個片段：

A是我的主要片段，B是登錄片段，成功登錄後會進入C片段。

當我點擊後退按鈕，我需要從片段下移到片段A

我的問題是，當我點擊後退按鈕我仍然片段B-片段從A.

移動

我該如何解決我的問題？

這是我的開關片段功能：

public void switchFragment(Fragment fragment) { 
    FragmentManager manager = getActivity().getSupportFragmentManager(); 
    FragmentTransaction transaction = manager.beginTransaction(); 
    transaction.replace(R.id.mainFrame, fragment, null); 
    transaction.addToBackStack(null); 
    transaction.commit(); 
} 

片段（NewHomepage）到B（LoginFragment）片段：

switchFragment(LogInFragment.newInstance()); 

這是我的乙片段，它具有值logged來決定當它來自C片段時，是否切換片段。

我認爲這個問題一定是在這裏，當回到A片段並點擊返回按鈕想要退出APP時，我可以看到logcat show 1 =>和2 =>。

String logged = memberData.getUD_MBTYPENAME(); //get the value when login succeed 
     Log.d(TAG,"1=>"+logged); 
     //If UD_MBTYPENAME is not null，change to A fragment 
     if (!TextUtils.isEmpty(logged)) { 
      Log.d(TAG,"2=>"+logged); 
      ((MainActivity) getActivity()).switchFragment(NewHomepage.newInstance()); 
     } 

這裏是我的約onKeyDown和switchFragment MainActivity：

@Override 
public boolean onKeyDown(int keyCode, KeyEvent event) { 
    if (keyCode == KeyEvent.KEYCODE_BACK) { 

     if (getSupportFragmentManager().getBackStackEntryCount() == 1) { 
      quickDialog();//It's a alert dialog 
      return false; 
     } 
    } 
    return super.onKeyDown(keyCode, event); 
} 

public void switchFragment(Fragment fragment) { 
    FragmentManager manager = getSupportFragmentManager(); 
    FragmentTransaction transaction = manager.beginTransaction(); 
    transaction.replace(R.id.mainFrame, fragment, null); 
    transaction.addToBackStack(null); 
    transaction.commit(); 
} 

以參考改變這樣的代碼，如果我不使用transaction.addToBackStack(null);，這個問題仍然存在，即使刪除transaction.addToBackStack(null);

當我回到A時，我必須點擊兩次以顯示警報對話框，我不知道當我在A片段中第一次點擊時發生了什麼。

if (!TextUtils.isEmpty(logged)){ 
     Log.d(TAG,"2=>"+logged); 

     hideFragment(LogInFragment.newInstance()); 
     switchFragment(NewHomepage.newInstance()); 
    } 

public void switchFragment(Fragment fragment) { 
    FragmentManager manager = getActivity().getSupportFragmentManager(); 
    FragmentTransaction transaction = manager.beginTransaction(); 
    transaction.replace(R.id.mainFrame, fragment, null); 
    //remove it will fix my issue , but I have to click back twice to show alert dialog , I don't know what happened click it first time in A fragment. 
    //transaction.addToBackStack(null); 
    transaction.commit(); 
} 

public void hideFragment(Fragment fragment) { 
    FragmentManager manager = getActivity().getSupportFragmentManager(); 
    FragmentTransaction transaction = manager.beginTransaction(); 
    transaction.hide(fragment); 
    transaction.commit(); 
} 

刪除hideFragment和使用上switchFragment manager.popBackStack();，這個問題將是固定的。

Answer 1

嘗試

它會顯示片段，如果它已被添加。

使用fragmentTransaction.show方法來重新使用現有片段，即保存的實例。

public void switchFragment (Fragment oldFragment, Fragment newFragment, int frameId) { 

    boolean addFragment = true; 

    FragmentManager fragmentManager = getFragmentManager(); 
    String tag = newFragment.getArguments().getString ("TAG"); 
    Fragment fragment = fragmentManager.findFragmentByTag (tag); 

    // Check if fragment is already added 
    if (fragment != null && fragment.isAdded()) { 
     addFragment = false; 
    } 

    // Hide previous fragment 
    String oldFragmentTag = oldFragment.getArguments().getString (BaseFragment.TAG); 

    if (!tag.equals (oldFragmentTag)) { 
     FragmentTransaction hideTransaction = fragmentManager.beginTransaction(); 
     Fragment fragment1 = fragmentManager.findFragmentByTag (oldFragmentTag); 
     hideTransaction.hide (fragment1); 
     hideTransaction.commit(); 
    } 

    // Add new fragment and show it 
    FragmentTransaction addTransaction = fragmentManager.beginTransaction(); 

    if (addFragment) { 
     addTransaction.add (frameId, newFragment, tag); 
     addTransaction.addToBackStack (tag); 
    } 
    else { 
     newFragment = fragmentManager.findFragmentByTag (tag); 
    } 

    addTransaction.show (newFragment); 

    addTransaction.commit(); 
}