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Question

我有一个有viewpager的活动，这个viewpager包含Fragment A和Fragment B. 片段B还有一个viewpager，它包含例如一个C片段。 Fragment C实现了Fragment B的内部接口OnNextButtonListener。

FragmentB.java：

public class FragmentB extends Fragment{
    private OnNextButtonListener mFragmentCListener;
    private Button mNextButton;
    //instance variables
    //other methods
    @Override
    View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState){
        View view = inflater.inflate(R.layout.fragment_b,      container, false);
        init(view);//initialize views
        mNextButton.setOnClickListener(new View.OnClickListener() {
          @Override
          public void onClick(View v) {
             //mFragmentCListener is instance of FragmentC casted to   OnNextButtonListener
             mFragmentCListener.onNextButtonClick();
        });
    return view;
    }

    public interface OnNextButtonListener{
       void onNextButtonClick();
    }
}

FragmentC.java：

public class FragmentC extends Fragment implements OnNextButtonListener{
  //...
  private EditText mEditText;
   @Override 
   View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    View view = inflater.inflate(R.layout.fragment_c, container, false);
    init(view);//initialized mEditText and it is not null on rotation 
    return view;
  }
  @Override
  void onNextButtonClick(){
     String text = (String)mEditText.getText();//mEditText gets null on rotation
     //...
  }
}

一切正常但是当旋转设备然后单击mNextButton（片段B）时，onNextButtonClick中的mEditText（片段C）变为null但在onCreateView中仍然不为null。 我在onNextButtonClick中调试了第一行，调试器显示了debugger.png