DialogFragment getActivity（）在分片處理其他數據後返回null

Question

我已經閱讀了很多getActivity()返回空問題，但我似乎無法找到與此方案匹配的問題。

我有一個DialogFragment認爲應該做到以下幾點：

• 採取由用戶輸入
• 驗證，如果輸入的是正確的，只有繼續/駁回對話框如果是
• 進行交易/寫數據Firebase數據庫（這需要一秒左右的時間）
• 移至新活動並完成致電活動

我可以讓所有這些部分獨立工作，但是如果我在FB事務處理完成後將代碼移動到新活動中，則在設置我的startActivity()意圖時，我會得到一個NPE。

從我所知道的情況來看，在Firebase交易發生的時候，AlertDialog和DialogFragment會自動解散，我無法再獲取上下文來設置我的意圖。

如何獲得正確的活動或上下文以致電startActivity()？ 謝謝！

public class FinishedDialog extends DialogFragment { 

private String pushId; 

private AlertDialog alertDialog; 

public static FinishedDialog newInstance(String PushId) { 
    FinishedDialog frag = new FinishedDialog(); 
    Bundle args = new Bundle(); 
    args.putString("pushId", pushId); 
    frag.setArguments(args); 
    return frag; 
} 

@Override 
public Dialog onCreateDialog(Bundle savedInstanceState) { 
    pushId = getArguments().getString("pushId"); 

    AlertDialog.Builder builder = new AlertDialog.Builder(getActivity()); 
    LayoutInflater inflater = getActivity().getLayoutInflater(); 

    builder.setView(inflater.inflate(R.layout.dialog_finished, null)) 
      .setPositiveButton(R.string.send_text_response, new DialogInterface.OnClickListener() { 
       @Override 
       public void onClick(DialogInterface dialog, int id) { 
        // This will be overridden for data validations 
       } 
      }) 
      .setNegativeButton(R.string.continue_without_response, new DialogInterface.OnClickListener() { 
       public void onClick(DialogInterface dialog, int id) { 
        finishListening(); 
       } 
      }) 
      .setNeutralButton(R.string.listen_again, new DialogInterface.OnClickListener() { 
       @Override 
       public void onClick(DialogInterface dialog, int id) { 
        //Dismisses Dialog 
       } 
      }); 
    return builder.create(); 
} 

//This is set up so that if user hasn't entered data, positiveButton won't dismiss dialog 
@Override 
public void onStart() { 
    super.onStart(); 

    alertDialog = (AlertDialog)getDialog(); 
    if(alertDialog != null) 
    { 
     Button positiveButton = alertDialog.getButton(Dialog.BUTTON_POSITIVE); 
     final EditText responseEditText = (EditText) alertDialog.findViewById(R.id.entered_response); 

     positiveButton.setOnClickListener(new View.OnClickListener() 
     { 
      @Override 
      public void onClick(View v) 
      { 
       Boolean wantToCloseDialog = false; 
       String enteredData = responseEditText.getText().toString(); 

       if (enteredData.length()>1) { 
        wantToCloseDialog = true; 
       } 

       if (wantToCloseDialog) { 
        alertDialog.dismiss(); //This line may be part of the problem, but I still get the NPE if I comment it out. 
        uploadResponseToFB(enteredData); 
       } else { 
        Toast.makeText(getContext(), "You didn't enter a response!", 
          Toast.LENGTH_SHORT).show(); 
       } 
      } 
     }); 
    } 
} 

private void uploadResponseToFB(String response) { 
    //Uploads some data to Firebase. 
    finishListening(); 
} 

private void finishListeningToStory() { 
    //This method does a number of firebase transactions and data writes 
    //The goBackToMainScreen() method is called onCompletion of the last data write. 
} 

private void goBackToMainScreen(){ 
    //Again, called onCompletion of last data write. 
    //This crashes on next line due to NPE from getActivity(), but when I test this exact code without the FB transactions (closer to onCreateDialog() or onStart()) it works fine. 
    Intent intent = new Intent(getActivity(), ConversationListActivity.class); 
    getActivity().startActivity(intent); 
    progressDialog.dismiss(); 
} 

} 

Answer 1

從我可以告訴，在火力地堡的交易發生時，AlertDialog和DialogFragment自動開除，我不能再獲得上下文設置我的意圖。

AFAIK這是確切的原因。

解決方案1 ​​

經過驗證的數據傳遞給主機Activity做火力點寫在那裏。通過這種方式，您將始終擁有啓動其他活動的環境。

解決方案2

不要放棄Dialog（顯示ProgressBar），直到你的火力寫操作完成，ConversationListActivity開始。