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Android: Fragment manager becomes null

I get crashes for my application. Basically, I have a fragment in which the dialogue should be displayed in one scenario. I created a dialogue by expanding a portion of the dialogue. The problem is that some users throw a null pointer exception throw. This is a snippet of dialogue:

VerifyOTPDialog verifyOTPDialog = VerifyOTPDialog.newInstance("Kindly Enter the OTP sent to your Registered Mobile No. :", false, "Verify & Proceed", "home_screen"); verifyOTPDialog.show(getFragmentManager(), VerifyOTPDialog.class.getSimpleName());

The application crashes in the second line. From crashlytics, I got the following stack trace:

 Fatal Exception: java.lang.NullPointerException: Attempt to invoke virtual method 'android.app.FragmentTransaction android.app.FragmentManager.beginTransaction()' on a null object reference at android.app.DialogFragment.show(DialogFragment.java:228) at in.droom.fragments.HomeScreenFragment.updateUI(HomeScreenFragment.java:553) at in.droom.fragments.HomeScreenFragment.onResponse(HomeScreenFragment.java:626) at in.droom.fragments.HomeScreenFragment.onResponse(HomeScreenFragment.java:100) at in.droom.util.DroomApi$1.onPostExecute(DroomApi.java:1136) at in.droom.util.DroomApi$1.onPostExecute(DroomApi.java:1094) at android.os.AsyncTask.finish(AsyncTask.java:636) at android.os.AsyncTask.access$500(AsyncTask.java:177) at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:653) at android.os.Handler.dispatchMessage(Handler.java:111) at android.os.Looper.loop(Looper.java:194) at android.app.ActivityThread.main(ActivityThread.java:5637) at java.lang.reflect.Method.invoke(Method.java) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:959) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:754)

0. Crashed: main: 0 0 0x0000000000000000

  at android.app.DialogFragment.show(DialogFragment.java:228) at in.droom.fragments.HomeScreenFragment.updateUI(HomeScreenFragment.java:553) at in.droom.fragments.HomeScreenFragment.onResponse(HomeScreenFragment.java:626) at in.droom.fragments.HomeScreenFragment.onResponse(HomeScreenFragment.java:100) at in.droom.util.DroomApi$1.onPostExecute(DroomApi.java:1136) at in.droom.util.DroomApi$1.onPostExecute(DroomApi.java:1094) at android.os.AsyncTask.finish(AsyncTask.java:636) at android.os.AsyncTask.access$500(AsyncTask.java:177) at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:653) at android.os.Handler.dispatchMessage(Handler.java:111) at android.os.Looper.loop(Looper.java:194) at android.app.ActivityThread.main(ActivityThread.java:5637) at java.lang.reflect.Method.invoke(Method.java) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:959) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:754)

As I understand it, the fragment manager at some point in time became zero. But I can not reproduce the script. Failures happen with no. users almost every day.

Update: (VerifyOtpDialog)

 public class VerifyOTPDialog extends DialogFragment implements OnClickListener { private static final String TAG_NAME = VerifyOTPDialog.class.getSimpleName(); private Context ctx; private Dialog dialog; private boolean isLaterVisible; private String strTitle, strBtnTitle, strFragment = ""; private BroadcastReceiver broadcastReceiver; private ProfileAddressContactInfoModel userModel; private VerifyOTPDialogDismissed verifyOTPDialogDismissed; public static final String RECEIVE_OTP = "com.myapp.ACTION_RECEIVED"; private ImageView imgViewForClose; private RobotoRegularEditTextView editTextForOTP; private RobotoBoldTextView btnLater, btnVerifyAndProceed; private RobotoLightTextView txtViewForTitle, txtViewForResendOTP; public popFragmentListener mPopFragmentListener; public VerifyOTPDialog() { } public static VerifyOTPDialog newInstance(String strTitle, boolean isLaterVisible, String strBtnTitle, String strFragment) { VerifyOTPDialog dialog = new VerifyOTPDialog(); Bundle b = new Bundle(); b.putString("title", strTitle); b.putBoolean("isLaterVisible", isLaterVisible); b.putString("btnTitle", strBtnTitle); b.putString("strFrom", strFragment); dialog.setArguments(b); return dialog; } @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); ctx = getActivity(); registerReceiver(); } @Override public Dialog onCreateDialog(Bundle savedInstanceState) { dialog = super.onCreateDialog(savedInstanceState); dialog.setOnKeyListener(new OnKeyListener() { @Override public boolean onKey(android.content.DialogInterface dialog, int keyCode, android.view.KeyEvent event) { if ((keyCode == android.view.KeyEvent.KEYCODE_BACK)) { AppUtil.hideKeyboard(); return true; } else return false; } }); return dialog; } @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { View view = inflater.inflate(R.layout.verify_otp_popup, container, false); Bundle b = getArguments(); strTitle = b.getString("title"); isLaterVisible = b.getBoolean("isLaterVisible"); strBtnTitle = b.getString("btnTitle"); strFragment = b.getString("strFrom"); getDialog().setCanceledOnTouchOutside(false); getDialog().getWindow().requestFeature(Window.FEATURE_NO_TITLE); getDialog().getWindow().setBackgroundDrawable(new ColorDrawable(0)); userModel = AppUtil.getUserProfile(); imgViewForClose = (ImageView) view.findViewById(R.id.imgViewForClose); editTextForOTP = (RobotoRegularEditTextView) view.findViewById(R.id.editTextForOTP); btnLater = (RobotoBoldTextView) view.findViewById(R.id.btnLater); btnVerifyAndProceed = (RobotoBoldTextView) view.findViewById(R.id.btnVerifyAndProceed); txtViewForTitle = (RobotoLightTextView) view.findViewById(R.id.txtViewForTitle); txtViewForResendOTP = (RobotoLightTextView) view.findViewById(R.id.txtViewForResendOTP); if (userModel != null) txtViewForTitle.setText(strTitle + " +91 " + userModel.getContactInfo().getMobilePhone()); txtViewForResendOTP.setText(getUnderlinedContent()); if (!isLaterVisible) btnLater.setVisibility(View.GONE); btnVerifyAndProceed.setText(strBtnTitle); imgViewForClose.setOnClickListener(this); txtViewForResendOTP.setOnClickListener(this); btnLater.setOnClickListener(this); btnVerifyAndProceed.setOnClickListener(this); return view; } public interface VerifyOTPDialogDismissed { void dialogDismissing(String... s); } @Override public void onDismiss(DialogInterface dialog) { super.onDismiss(dialog); } public VerifyOTPDialogDismissed getDialogDismissListener() { return verifyOTPDialogDismissed; } public void setDialogDismissListener(VerifyOTPDialogDismissed VerifyOTPDialogDismissed) { this.verifyOTPDialogDismissed = VerifyOTPDialogDismissed; } private void registerReceiver() { IntentFilter intentFilter = new IntentFilter(); intentFilter.addAction(RECEIVE_OTP); broadcastReceiver = new BroadcastReceiver() { @Override public void onReceive(Context context, Intent intent) { String strOTP = intent.getExtras().getString("otp"); if (strOTP != null && editTextForOTP != null) editTextForOTP.setText(strOTP); } }; ctx.registerReceiver(broadcastReceiver, intentFilter); } private SpannableString getUnderlinedContent() { SpannableString content = new SpannableString(getResources().getString(R.string.resend_otp)); content.setSpan(new UnderlineSpan(), 0, content.length(), 0); content.setSpan(new ForegroundColorSpan(getResources().getColor(R.color.blue_button)), 0, content.length(), 0); return content; } private void sendOTP(HashMap<String, String> params) { Response.Listener<JSONObject> responseListener = new Response.Listener<JSONObject>() { @Override public void onResponse(JSONObject response) { try { Logger.debugMessage("Response Object", response.toString()); String responseCode = response.getString("code"); if (responseCode.equalsIgnoreCase("success")) { String message = response.getString("message"); Toast.makeText(ctx, message, Toast.LENGTH_SHORT).show(); } else if (responseCode.equalsIgnoreCase("failed")) { if (response.has("error")) { if (response.has("error_code")) { String error_code = response.optString("error_code"); displayMessageAlert(response.optString("error"), "", error_code); } else { displayMessageAlert(response.optString("error"), "", ""); } } else if (response.has("errors")) { JSONArray errorsArray; try { errorsArray = response.getJSONArray("errors"); Toast.makeText(ctx, errorsArray.getString(0), Toast.LENGTH_SHORT).show(); } catch (JSONException e) { e.printStackTrace(); } } } } catch (JSONException e) { e.printStackTrace(); } } }; Response.ErrorListener errorListener = new Response.ErrorListener() { @Override public void onErrorResponse(VolleyError error) { } }; Api.sendOTP(params, responseListener, errorListener); } private void verifyOTP(HashMap<String, String> params, final String strFragment) { Response.Listener<JSONObject> responseListener = new Response.Listener<JSONObject>() { @Override public void onResponse(JSONObject response) { try { Logger.debugMessage("Response Object", response.toString()); String responseCode = response.getString("code"); if (responseCode.equalsIgnoreCase("success")) { if (userModel != null) { userModel.setPhoneVerified(true); userModel.setOTPVerified(true); AppUtil.saveUserProfile(userModel); } VerifyOTPDialog.this.dismissAllowingStateLoss(); String event_name = ""; if (strFragment.equalsIgnoreCase("SellFragment")) { event_name = "otp_verified_on_sell"; MainActivity.getInstance().pushFragment(SellFragment.newInstance(), SellFragment.class.getSimpleName(), true); } else if (strFragment.equalsIgnoreCase("QuickSellFragment")) { event_name = "otp_verified_on_quick_sell"; MainActivity.getInstance().pushFragment(new QuickSellFragment(), QuickSellFragment.class.getSimpleName(), true); } else if (strFragment.equalsIgnoreCase("gotoPaymentFlow")) { event_name = "otp_verified_on_payment"; DraftSummaryFragment.getInstance().gotoPaymentFlow(); } else if (strFragment.equalsIgnoreCase("gotoPlaceBidPage")) { event_name = "otp_verified_on_place_bid"; verifyOTPDialogDismissed.dialogDismissing(strFragment); } else if (strFragment.equalsIgnoreCase("make_best_offer")) { event_name = "otp_verified_on_make_best_offer"; verifyOTPDialogDismissed.dialogDismissing(strFragment); } else if (strFragment.equalsIgnoreCase("checkAvailableFees")) { event_name = "otp_verified_on_quick_sell"; QuickSellDraftSummaryFragment.getInstance().checkAvailableFees(); } else if (strFragment.equalsIgnoreCase("home_screen")) { event_name = "otp_verified_for_casual_seller"; } else if (strFragment.equalsIgnoreCase("my_profile")) { event_name = "otp_verified_from_my_profile"; } else if (strFragment.equalsIgnoreCase("my_profile")) { event_name = "otp_verified_from_my_profile"; } else if (strFragment.equalsIgnoreCase("pro_seller_profile_settings")) { event_name = "otp_verified_from_pro_seller_profile_settings"; } else if (strFragment.equalsIgnoreCase("pro_seller_welcome")) { event_name = "otp_verified_from_pro_seller_welcome"; } else if (strFragment.equalsIgnoreCase("seller_badges")) { event_name = "otp_verified_from_seller_badges"; } else if (strFragment.equalsIgnoreCase("trust_factor")) { event_name = "otp_verified_from_trust_factor"; } else if (strFragment.equalsIgnoreCase("ProSellerDashboard")) MainActivity.getInstance().pushFragment(ProSellerDashboardFragment.newInstance(false), ProSellerDashboardFragment.class.getSimpleName(), true); else event_name = "otp_verified_from_my_account"; JSONObject post = BetaOutAPIs.getPostDataForUserAdd(userModel, "update"); JSONArray eventArray = new JSONArray(); JSONObject event = new JSONObject(); event.put("name", event_name); event.put("timestamp", String.valueOf(System.currentTimeMillis() / 1000)); eventArray.put(event); post.put("events", eventArray); BetaOutAPIs.sendEventToBetaOut(post, TAG_NAME); BaseApplication.getInstance().trackMoEngageEvents(event_name, new PayloadBuilder().build()); } else if (responseCode.equalsIgnoreCase("failed")) { btnVerifyAndProceed.setEnabled(true); if (response.has("error")) { if (response.has("error_code")) { String error_code = response.optString("error_code"); displayMessageAlert(response.optString("error"), "", error_code); } else { displayMessageAlert(response.optString("error"), "", ""); } } else if (response.has("errors")) { Toast.makeText(ctx, response.optString("errors"), Toast.LENGTH_SHORT).show(); } } } catch (JSONException e) { e.printStackTrace(); } } }; Response.ErrorListener errorListener = new Response.ErrorListener() { @Override public void onErrorResponse(VolleyError error) { error.printStackTrace(); } }; Api.verifyOTP(params, responseListener, errorListener); } private boolean validateOTP() { String validationMessage = ""; boolean isValid = true; String email = editTextForOTP.getText().toString(); if (email.length() == 0) { isValid = false; validationMessage = "Please Enter OTP"; Toast.makeText(getActivity(), validationMessage, Toast.LENGTH_SHORT).show(); } return isValid; } @Override public void onClick(View v) { switch (v.getId()) { case R.id.imgViewForClose: VerifyOTPDialog.this.dismissAllowingStateLoss(); break; case R.id.txtViewForResendOTP: if (userModel != null) { HashMap<String, String> params = new HashMap<String, String>(); params.put("user_id", AppSharedPref.getUserId()); params.put("phone", userModel.getContactInfo().getMobilePhone()); sendOTP(params); } break; case R.id.btnLater: VerifyOTPDialog.this.dismissAllowingStateLoss(); if (mPopFragmentListener != null) mPopFragmentListener.gotoRootFragment(); if (strFragment.equalsIgnoreCase("SellFragment")) { MainActivity.getInstance().pushFragment(SellFragment.newInstance(), SellFragment.class.getSimpleName(), true); } else if (strFragment.equalsIgnoreCase("QuickSellFragment")) { MainActivity.getInstance().pushFragment(new QuickSellFragment(), QuickSellFragment.class.getSimpleName(), true); } else if (strFragment.equalsIgnoreCase("gotoPlaceBidPage")) { //verifyOTPDialogDismissed.dialogDismissing(); } else if (strFragment.equalsIgnoreCase("ProSellerDashboard")) MainActivity.getInstance().pushFragment(ProSellerDashboardFragment.newInstance(false), ProSellerDashboardFragment.class.getSimpleName(), true); break; case R.id.btnVerifyAndProceed: if (validateOTP()) { btnVerifyAndProceed.setEnabled(false); HashMap<String, String> map = new HashMap<String, String>(); map.put("user_id", SharedPref.getUserId()); map.put("code", editTextForOTP.getText().toString()); verifyOTP(map, strFragment); } break; default: break; } } protected void displayMessageAlert(String message, String title, final String error_code) { String s = "Alert"; if (title != null && title.length() > 0) { s = title; } if (message != null) { new AlertDialog.Builder(ctx).setTitle(s).setMessage(message) .setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int which) { if (error_code.toLowerCase().equals("logout")) { AppUtil.logoutUser((MainActivity) ctx); MainActivity.getInstance().pushFragment(LoginFragment.newInstance(true, true), LoginFragment.class.getSimpleName(), true); } dialog.dismiss(); } }).show(); } } @Override public void onDestroy() { super.onDestroy(); if (broadcastReceiver != null) { ctx.unregisterReceiver(broadcastReceiver); } } public void setPopFragmentListener(popFragmentListener mPopFragmentListener) { this.mPopFragmentListener = mPopFragmentListener; } public interface popFragmentListener { void gotoRootFragment(); } }
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4 answers

You should get a fragment manager before:

FragmentManager fragMan = getSupportFragmentManager();

then check its nullity value

 if(fragMan != null){ // Do stuff }

And if you use, if in a DoInBackground from asinthe you should get Uithread:

 runOnUiThread(new Runnable() { public void run() { // do stuff on the ui like display fragments } });

EDIT:

You must use the v4 support library to support the fragment

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You said you use android.app.fragment to post your snippet. Since you are creating a dialog using android DialogFragment, the Fragment dialog itself is a fragment, which makes this case nested fragments in android. When we nest on fragments, we use getChildFragmentManager().

Support for nested fragments in android was not available in API 11. Support for nested fragments began with API 17 and beyond. If you want to use nested fragments in API 11-16, you need to use fragments of the support library.

So you have to make your DialogFragment of type android.support.v4.app.dialogFragment and your fragment of type android.support.v4.app.fragment

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If you are showing a snippet, use getChildFragmentManager() :

Like:

 verifyOTPDialog.show(getChildFragmentManager(),VerifyOTPDialog.class.getSimpleName());
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I would recommend calling DialogFragment from parent activity so that you don't encounter problems with the fragment life cycle. Since you are probably trying to share fragments with each other, this should be done through Activity.

Read more ... https://developer.android.com/training/basics/fragments/communicating.html

Following the instructions:

  • Define an interface
  • Implement interface
  • Provide a message to the fragment

In the last step, you can call DialogFragment, and then Dialog get the data back, and then pass it to the calling fragment.

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