带有片段的actionbar向上导航

Question

我有一个带选项卡的ActionBar/ViewPager布局，有三个选项卡，比如a、B和C。在选项卡C选项卡（片段）中，我添加了另一个片段，比如片段D。

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

我修改了DFragment的onResume添加按钮中的actionbar：

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

现在在DFragment中，当我按下hardware（phone）Back按钮时，我返回到选中CFragment的原始选项卡(ABC)布局。如何使用actionbar up按钮实现此功能？

Answer 1

实现OnBackStackChangedListener并将此代码添加到碎片活动中。

@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 canGoBack = getSupportFragmentManager().getBackStackEntryCount()>0;
   getSupportActionBar().setDisplayHomeAsUpEnabled(canGoBack);
}

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