android - 未调用 Android onBackStackChanged()

Question

我有一个Activity像下面的代码：

public class AuthenticatedMainActivity extends Activity implements FragmentManager.OnBackStackChangedListener{

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        .............
        FragmentManager fragmentManager = getFragmentManager();           
        fragmentManager.beginTransaction().add(R.id.frame_container,fragment, "First").addToBackStack(null).commit();
    }

    private void switchFragment(Fragment fragment){            
      FragmentManager fragmentManager = getFragmentManager();
      fragmentManager.beginTransaction()
        .replace(R.id.frame_container, fragment).addToBackStack("Tag").commit();
    }

    @Override
public void onBackStackChanged() {
    System.out.println("====================================================changeeeeeeeeeeeeeeeeeeeeeeeeee");
}       
}

但是，onBackStackChanged()即使在成功用该方法替换片段后，也不会调用该switchFragment方法。

Answer 1

您需要将您的添加Activity为OnBackStackChangedListenerusing addOnBackStackChangedListener。

例子：

@Override
protected void onCreate(Bundle savedInstanceState) {
    .............
    FragmentManager fragmentManager = getFragmentManager();     
    fragmentManager.addOnBackStackChangedListener(this);      
    fragmentManager.beginTransaction().add(R.id.frame_container,fragment, "First").addToBackStack(null).commit();
}

Answer 2

唯一需要的就是在创建时执行此操作：

getFragmentManager().addOnBackStackChangedListener(this);