動作條了片段

Question

我有三個標籤選項卡式動作條/ viewpager佈局導航說甲，乙，和Ç。在標籤C tab（片段）中，我添加了另一個片段說片段D。與

DFragment f= new DFragment(); 
ft.add(android.R.id.content, f, ""); 
ft.remove(CFragment.this); 
ft.addToBackStack(null); 
ft.commit(); 

我修改DFragment的的onResume動作條加起來按鈕：

ActionBar ab = getActivity().getActionBar(); 
ab.setNavigationMode(ActionBar.NAVIGATION_MODE_STANDARD); 
ab.setDisplayHomeAsUpEnabled(true); 
ab.setDisplayShowHomeEnabled(true); 

現在DFragment，當我按下硬件（手機）後退按鈕，我回到原來的選項卡式（ABC）佈局選擇了CFragment。如何通過操作欄向上按鈕來實現此功能？

Answer 1

實施OnBackStackChangedListener並將此代碼添加到您的Fragment活動中。

@Override 
public void onCreate(Bundle savedInstanceState) { 
    //Listen for changes in the back stack 
    getSupportFragmentManager().addOnBackStackChangedListener(this); 
    //Handle when activity is recreated like on orientation Change 
    shouldDisplayHomeUp(); 
} 

@Override 
public void onBackStackChanged() { 
    shouldDisplayHomeUp(); 
} 

public void shouldDisplayHomeUp(){ 
    //Enable Up button only if there are entries in the back stack 
    boolean canback = getSupportFragmentManager().getBackStackEntryCount()>0; 
    getSupportActionBar().setDisplayHomeAsUpEnabled(canback); 
} 

@Override 
public boolean onSupportNavigateUp() { 
    //This method is called when the up button is pressed. Just the pop back stack. 
    getSupportFragmentManager().popBackStack(); 
    return true; 
} 

Answer 2

我明白了。只是在託管活動中覆蓋onOptionsItemSelected並彈出後臺，例如，

public boolean onOptionsItemSelected(MenuItem item) { 

    switch (item.getItemId()) { 
    case android.R.id.home: 
    FragmentManager fm = getSupportFragmentManager(); 
    if (fm.getBackStackEntryCount() > 0) { 
      fm.popBackStack(); 
     } 
     return true; 
    default: 
     return super.onOptionsItemSelected(item);; 
    } 
} 

呼叫getActionBar().setDisplayHomeAsUpEnabled(boolean);和getActionBar().setHomeButtonEnabled(boolean);在onBackStackChanged()在下面的答案解釋。

Answer 3

如果你有一個父活動，並希望這件事按鈕的後退按鈕時，您可以使用此代碼：

這在主活動類添加到的onCreate

getSupportFragmentManager().addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() { 
     @Override 
     public void onBackStackChanged() { 
      int stackHeight = getSupportFragmentManager().getBackStackEntryCount(); 
      if (stackHeight > 0) { // if we have something on the stack (doesn't include the current shown fragment) 
       getSupportActionBar().setHomeButtonEnabled(true); 
       getSupportActionBar().setDisplayHomeAsUpEnabled(true); 
      } else { 
       getSupportActionBar().setDisplayHomeAsUpEnabled(false); 
       getSupportActionBar().setHomeButtonEnabled(false); 
      } 
     } 

    }); 

然後添加onOptionsItemSelected像這樣：

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    switch (item.getItemId()) { 
     case android.R.id.home: 
      getSupportFragmentManager().popBackStack(); 
      return true; 
    .... 
} 

我一般用這一切的時間似乎很合法

Answer 4

這是一個很好的和可靠的解決方案：http://vinsol.com/blog/2014/10/01/handling-back-button-press-inside-fragments/

的傢伙已經作出處理backPress行爲和使用戰略格局的活性片段之間切換的抽象的片段。

對於一些你有可能在抽象類有點缺點......

不久，從鏈路的解決方案是這樣的：

// Abstract Fragment handling the back presses 

public abstract class BackHandledFragment extends Fragment { 
    protected BackHandlerInterface backHandlerInterface; 
    public abstract String getTagText(); 
    public abstract boolean onBackPressed(); 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     if(!(getActivity() instanceof BackHandlerInterface)) { 
      throw new ClassCastException("Hosting activity must implement BackHandlerInterface"); 
     } else { 
      backHandlerInterface = (BackHandlerInterface) getActivity(); 
     } 
    } 

    @Override 
    public void onStart() { 
     super.onStart(); 

     // Mark this fragment as the selected Fragment. 
     backHandlerInterface.setSelectedFragment(this); 
    } 

    public interface BackHandlerInterface { 
     public void setSelectedFragment(BackHandledFragment backHandledFragment); 
    } 
} 

而且在活動中使用：

// BASIC ACTIVITY CODE THAT LETS ITS FRAGMENT UTILIZE onBackPress EVENTS 
// IN AN ADAPTIVE AND ORGANIZED PATTERN USING BackHandledFragment 

public class TheActivity extends FragmentActivity implements BackHandlerInterface { 
    private BackHandledFragment selectedFragment; 

    @Override 
    public void onBackPressed() { 
     if(selectedFragment == null || !selectedFragment.onBackPressed()) { 
      // Selected fragment did not consume the back press event. 
      super.onBackPressed(); 
     } 
    } 

    @Override 
    public void setSelectedFragment(BackHandledFragment selectedFragment) { 
     this.selectedFragment = selectedFragment; 
    } 
} 

Answer 5

你可以用向上按鈕返回按鈕;

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    switch (item.getItemId()) { 
     case android.R.id.home: 
      super.onBackPressed(); 
      return true; 
    } 
    return super.onOptionsItemSelected(item); 
} 

Answer 6

我用的Roger Garzon Nieto's和sohailaziz's答案的組合。我的應用程序有一個單一的MainActivity，並加載了A，B，C片段。我的「主頁」片段（A）實現了OnBackStackChangedListener，並檢查了backStack的大小;如果小於1，則隱藏UP按鈕。碎片B和C總是加載後退按鈕（在我的設計中，B從A啓動，C從B啓動）。在MainActivity本身只是對持久性有機污染物UP按鈕自來水返回堆棧，並且有方法來顯示/隱藏按鈕，該片段致電：

MainActivity：

public boolean onOptionsItemSelected(MenuItem item) { 
    switch (item.getItemId()) { 
     // Respond to the action bar's Up/Home button 
     case android.R.id.home: 
      getSupportFragmentManager().popBackStack(); 
      return true; 
    } 
    return super.onOptionsItemSelected(item); 
} 

public void showUpButton() { getSupportActionBar().setDisplayHomeAsUpEnabled(true); } 
public void hideUpButton() { getSupportActionBar().setDisplayHomeAsUpEnabled(false); } 

fragmentA（實現FragmentManager.OnBackStackChangedListener） ：

public void onCreate(Bundle savedinstanceSate) { 
    // listen to backstack changes 
    getActivity().getSupportFragmentManager().addOnBackStackChangedListener(this); 

    // other fragment init stuff 
    ... 
} 

public void onBackStackChanged() { 
    // enable Up button only if there are entries on the backstack 
    if(getActivity().getSupportFragmentManager().getBackStackEntryCount() < 1) { 
     ((MainActivity)getActivity()).hideUpButton(); 
    } 
} 

fragmentB，fragmentC：

public void onCreate(Bundle savedinstanceSate) { 
    // show the UP button 
    ((MainActivity)getActivity()).showUpButton(); 

    // other fragment init stuff 
    ... 
} 

Answer 7

我知道這個問題已經老了，但也許是某個人（像我一樣）也需要它。

如果你的活動延伸AppCompatActivity，你可以使用一個簡單（兩步）解決方案：

1 - 只要添加非家庭片段只顯示了按鈕，commiting片段交易之後。像這樣：

// ... add a fragment 
    // Commit the transaction 
    transaction.commit(); 

    getSupportActionBar().setDisplayHomeAsUpEnabled(true); 

2 - 然後當按下UP按鈕時，您將其隱藏。

@Override 
public boolean onSupportNavigateUp() { 
    getSupportActionBar().setDisplayHomeAsUpEnabled(false);   
    return true; 
} 

就是這樣。

Answer 8

這對我有效。例如，覆蓋onSupportNavigateUp和onBackPressed（Kotlin中的代碼）;

override fun onBackPressed() { 
    val count = supportFragmentManager.backStackEntryCount 
    if (count == 0) { 
     super.onBackPressed() 
    } else { 
     supportFragmentManager.popBackStack() 
    } 
} 

override fun onSupportNavigateUp(): Boolean { 
    super.onSupportNavigateUp() 
    onBackPressed() 
    return true 
} 

在片段

現在，如果你顯示向上箭頭

activity.supportActionBar?.setDisplayHomeAsUpEnabled(true) 

點擊它會回到以前的活動。

Answer 9

科特林：

class MyActivity : AppCompatActivity() { 

    override fun onCreate(savedInstanceState: Bundle?) { 
     ... 
     supportFragmentManager.addOnBackStackChangedListener { setupHomeAsUp() } 
     setupHomeAsUp() 
    } 

    private fun setupHomeAsUp() { 
     val shouldShow = 0 < supportFragmentManager.backStackEntryCount 
     supportActionBar?.setDisplayHomeAsUpEnabled(shouldShow) 
    } 

    override fun onSupportNavigateUp(): Boolean = 
     supportFragmentManager.popBackStack().run { true } 

    ... 
}