如果onCreateView語句第一種觀點

Question

我試着去上onViewCreated

@Override 
public void onViewCreated(View view, Bundle savedInstanceState) { 
    super.onViewCreated(view, savedInstanceState); 


    date = (TextView) view.findViewById(R.id.textDate); 
    date.setText(DateFormat.getDateTimeInstance().format(Calendar.getInstance().getTime())); 
} 

創建if語句，其中如果視圖是第一次，設置此兩個線路：

date = (TextView) view.findViewById(R.id.textDate); 
     date.setText(DateFormat.getDateTimeInstance().format(Calendar.getInstance().getTime())); 

是否有任何其他我可能沒有想到和錯過的方法，或者if語句在這裏是更可行的方法。

下面的代碼的其餘部分：

public class Notifications extends Fragment { 
TextView servingqueue; 
TextView date; 


DatabaseReference mRootRef = FirebaseDatabase.getInstance().getReference(); 
DatabaseReference mServingQueue = mRootRef.child("ServingQueue"); 


public Notifications() { 
    // Required empty public constructor 
} 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 



    mServingQueue.addValueEventListener(new ValueEventListener() { 
     @Override 
     public void onDataChange(DataSnapshot dataSnapshot) { 
      Double number = dataSnapshot.getValue(Double.class); 
      servingqueue.setText(String.valueOf(number)); 

     } 

     @Override 
     public void onCancelled(DatabaseError databaseError) { 

     } 
    }); 
} 

@Override 
public void onAttach(Context context) { 
    super.onAttach(context); 

} 

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

} 

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, 
         Bundle savedInstanceState) { 
    View rootView = inflater.inflate(R.layout.fragment_notifications, container, false); 
    // Inflate the layout for this fragmentid.queueServing); 
    servingqueue = (TextView) rootView.findViewById(R.id.queueServing); 
    return rootView; 
} 
@Override 
public void onViewCreated(View view, Bundle savedInstanceState) { 
    super.onViewCreated(view, savedInstanceState); 


    date = (TextView) view.findViewById(R.id.textDate); 
    date.setText(DateFormat.getDateTimeInstance().format(Calendar.getInstance().getTime())); 
} 

} 

Answer 1

如果你只想來設置它第一時間，那麼你可以檢查是否savedInstanceState爲null。如果它爲空，那麼整個Fragment就是嶄新的品牌。如果它不爲空，那麼你從屏幕旋轉或其他東西回來。

但是，您的TextView會突然變空，因爲它會被創建，所以這裏有另一個選項。

在onSaveInstanceState，保存TextView的狀態，

@Override 
public void onSaveInstanceState(Bundle b) { 
    super.onSaveInstanceState(b); 
    b.putString("DATE_TEXT", date.getText().toString()); 
} 

然後，在你onViewCreated()，檢索像這樣的文字：

@Override 
public void onViewCreated(View view, Bundle savedInstanceState) { 
    super.onViewCreated(view, savedInstanceState); 

    String dateText = (savedInstanceState != null) ? 
      savedInstanceState.getString("DATE_TEXT") : 
      DateFormat.getDateTimeInstance().format(Calendar.getInstance().getTime()); 

    date = (TextView) view.findViewById(R.id.textDate); 
    date.setText(DateFormat.getDateTimeInstance().format(Calendar.getInstance().getTime())); 
}