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在片段和活动之间交换数据-NullPointerException

[英]Exchange data between fragments and activities - NullPointerException

 原文  2015-01-27 20:04:37  4   1    java/ android/ android-activity/ android-fragments

问题描述

我的应用程序具有登录功能。 登录成功后，您将导航到具有导航抽屉的应用程序的第一页，因此我的大部分屏幕都是片段而不是活动，并由BaseActivity.java 。

我有片段AddShopFragment ，用户可以在其中添加有关商店的信息并保存。 在此片段中，我有一个名为moreinfo的按钮。 按下时，导航到名为AddMoreInfoForShopActivity的活动。 此活动有一个名为lessinfo的按钮，可将您导航到BaseActivity ，然后此活动将您和数据发送到AddShopFragment片段。

到目前为止，我设法使用来自活动，活动和片段的数据来保存商店。 因此，我可以在Activity之间交换那些信息以获取更多数据-保存数据的BaseActivity-Fragment 。

现在剩下的唯一事情就是，当按下按钮获取更多数据，然后按下按钮获取更少的数据时，我不希望我的AddShopFragment片段中的所有数据都被删除。

因此，我尝试将数据从AddShopFragment片段发送到AddMoreInfoForShopActivity活动，然后再发送到BaseActivity ，然后再发送到AddShopFragment ，以便可以填充文本区域和微调AddShopFragment 。

请注意，我要在片段中显示的数据是：类别，子类别，商店名称，位置，电子邮件和电话。

在尝试显示这些数据之前，所有信息均已正确保存在Parse中，因此该错误仅与将这些特定数据发送到其他活动并返回到片段有关。

这是在用户成功登录后发生的异常，因此应用程序必须导航到我已经设置的第一个片段： 

01-27 21:25:32.911  10009-10009/guide_me_for_all.guide_me_for_all E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: guide_me_for_all.guide_me_for_all, PID: 10009
    java.lang.RuntimeException: Unable to start activity ComponentInfo{guide_me_for_all.guide_me_for_all/guide_me_for_all.guide_me_for_all.BaseActivity}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2212)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2271)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5146)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:732)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at guide_me_for_all.guide_me_for_all.AddShopFragment.onCreateView(AddShopFragment.java:271)
            at android.support.v4.app.Fragment.performCreateView(Fragment.java:1786)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:947)
            at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1126)
            at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:739)
            at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1489)
            at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:548)
            at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1171)
            at android.app.Activity.performStart(Activity.java:5241)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2178)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2271)
            at android.app.ActivityThread.access$800(ActivityThread.java:144)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1205)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:136)
            at android.app.ActivityThread.main(ActivityThread.java:5146)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:732)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:566)
            at dalvik.system.NativeStart.main(Native Method)

错误行是：

if(!getArguments().getString("category").equals("Select:")&&getArguments().getString("category")!=null&&!getArguments().getString("category").isEmpty()&&!getArguments().getString("category").equals("")) {

代码的AddShopFragment部分发送我们不想丢失的数据： 

moreinfo.setOnClickListener(new View.OnClickListener() {
                    public void onClick(View view) {
                        Intent intent;
                        intent = new Intent(AddShopFragment.this.getActivity().getApplicationContext(), AddMoreInfoForShopActivity.class);

                        if (category.getSelectedItem().toString().equals("Select:") || category.getSelectedItem().toString().isEmpty() || category.getSelectedItem().toString() == null)
                            intent.putExtra("category", "");
                        else
                            intent.putExtra("category", category.getSelectedItem().toString());

                        if (subcategory_bar.getSelectedItem().toString().equals("Select:") || subcategory_bar.getSelectedItem().toString().isEmpty() || subcategory_bar.getSelectedItem().toString() == null){
                            if (subcategory_restaurant.getSelectedItem().toString().equals("Select:") || subcategory_restaurant.getSelectedItem().toString().isEmpty() || subcategory_restaurant.getSelectedItem().toString() == null) {
                                intent.putExtra("subcategory", "");
                            }
                            else
                                intent.putExtra("subcategory", subcategory_restaurant.getSelectedItem().toString());
                        }
                        else{
                            intent.putExtra("subcategory", subcategory_bar.getSelectedItem().toString());
                        }

                        if (shopname.getText().toString() == null || shopname.getText().toString().isEmpty())
                            intent.putExtra("shopname", "");
                        else
                            intent.putExtra("shopname", shopname.getText().toString());

                        if (location.getText().toString() == null || location.getText().toString().isEmpty())
                            intent.putExtra("location", "");
                        else
                            intent.putExtra("location", location.getText().toString());

                        if (email.getText().toString() == null || email.getText().toString().isEmpty())
                            intent.putExtra("email", "");
                        else
                            intent.putExtra("email", email.getText().toString());

                        if (telephone.getText().toString() == null || telephone.getText().toString().isEmpty())
                            intent.putExtra("telephone", "");
                        else
                            intent.putExtra("telephone", telephone.getText().toString());

//                        if (flag_photo == true)
//                            intent.putExtra("photo", image);

                        startActivity(intent);

                        //finish();
                    }
                });

该代码的AddMoreInfoForShopActivity部分从片段中获取数据： 

if (getIntent() != null) {
            Intent intent = getIntent();

            category = intent.getStringExtra("category");
            subcategory = intent.getStringExtra("subcategory");
            shopname = intent.getStringExtra("shopname");
            location = intent.getStringExtra("location");
            email = intent.getStringExtra("email");
            telephone = intent.getStringExtra("telephone");
        }
        else{
            category = "";
            subcategory = "";
            shopname = "";
            location = "";
            email = "";
            telephone = "";
        }

将数据发送到BaseActivity的代码的AddMoreInfoForShopActivity部分： 

Intent i = new Intent(AddMoreInfoForShopActivity.this,
                        BaseActivity.class);

                //pass data to an intent to load a specific fragment of reader activity
                i.putExtra("opening", OpeningTime);
                i.putExtra("closing", ClosingTime);
                i.putExtra("dresscoding", dresscoding2);
                i.putExtra("music", music2);
                i.putExtra("otherinfo", otherinfo2);
                i.putExtra("facebook", fb2);
                i.putExtra("moneyperperson", moneyperperson2);
                i.putExtra("smokingarea", smokingarea2);
                i.putExtra("parking", parking2);
                i.putExtra("creditcards", creditcards2);
                i.putExtra("takeout", takeout2);
                i.putExtra("delivery", delivery2);
                i.putExtra("freewifi", freewifi2);
                i.putExtra("happyhour", happyhour2);
                i.putExtra("outdoorseating", outdoorseating2);
                i.putExtra("reservations", reservations2);
                i.putExtra("appropriategroups", appropriategroup2);
                i.putExtra("appropriatekids", appropratekids2);

                i.putExtra("category", category);
                i.putExtra("subcategory", subcategory);
                i.putExtra("shopname", shopname);
                i.putExtra("location", location);
                i.putExtra("email", email);
                i.putExtra("telephone", telephone);

                overridePendingTransition(R.anim.push_up_in, R.anim.push_up_out);

                startActivity(i);

我从活动获取数据并发送的BaseActivity部分返回到片段： 

 if (getIntent() != null) {
            Intent i = getIntent();

            String opening = i.getStringExtra("opening");
            String closing = i.getStringExtra("closing");
            String dresscoding = i.getStringExtra("dresscoding");
            String music = i.getStringExtra("music");
            String otherinfo = i.getStringExtra("otherinfo");
            String facebook = i.getStringExtra("facebook");
            String moneyperperson = i.getStringExtra("moneyperperson");
            String smokingarea = i.getStringExtra("smokingarea");
            String creditcards = i.getStringExtra("creditcards");
            String parking = i.getStringExtra("parking");
            String takeout = i.getStringExtra("takeout");
            String delivery = i.getStringExtra("delivery");
            String freewifi = i.getStringExtra("freewifi");
            String happyhour = i.getStringExtra("happyhour");
            String outdoorseating = i.getStringExtra("outdoorseating");
            String reservations = i.getStringExtra("reservations");
            String appropriategroup = i.getStringExtra("appropriategroups");
            String appropratekids = i.getStringExtra("appropriatekids");

            String category = i.getStringExtra("category");
            String subcategory = i.getStringExtra("subcategory");
            String shopname = i.getStringExtra("shopname");
            String location = i.getStringExtra("location");
            String email = i.getStringExtra("email");
            String telephone = i.getStringExtra("telephone");

            Fragment fragment = new AddShopFragment();

                Bundle bundle=new Bundle();
                bundle.putString("opening", opening);
                bundle.putString("closing", closing);
                bundle.putString("dresscoding", dresscoding);
                bundle.putString("music", music);
                bundle.putString("otherinfo", otherinfo);
                bundle.putString("facebook", facebook);
                bundle.putString("moneyperperson", moneyperperson);
                bundle.putString("smokingarea", smokingarea);
                bundle.putString("creditcards", creditcards);
                bundle.putString("parking", parking);
                bundle.putString("takeout", takeout);
                bundle.putString("delivery", delivery);
                bundle.putString("freewifi", freewifi);
                bundle.putString("happyhour", happyhour);
                bundle.putString("outdoorseating", outdoorseating);
                bundle.putString("reservations", reservations);
                bundle.putString("appropriategroups", appropriategroup);
                bundle.putString("appropriatekids", appropratekids);

                bundle.putString("category", category);
                bundle.putString("subcategory", subcategory);
                bundle.putString("shopname", shopname);
                bundle.putString("location", location);
                bundle.putString("email", email);
                bundle.putString("telephone", telephone);

            //set Fragmentclass Arguments
                fragment.setArguments(bundle);

                FragmentManager fm = getSupportFragmentManager();

                fm.beginTransaction().replace(R.id.content_frame, fragment).commit();
            //}
        }

最后，这是我从BaseActivity获取数据并尝试在屏幕上显示数据的方法AddShopFragment ： 

 if (getArguments() != null) {

                    if (!getArguments().getString("category").equals("Select:") && getArguments().getString("category") != null && !getArguments().getString("category").isEmpty() && !getArguments().getString("category").equals("")) {
                        ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this.getActivity().getApplicationContext(), R.array.category, android.R.layout.simple_spinner_item);
                        adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
                        category.setAdapter(adapter);

                        int spinnerPostion = adapter.getPosition(getArguments().getString("category"));
                        category.setSelection(spinnerPostion);
                        spinnerPostion = 0;

                        if (getArguments().getString("category").equals("Bar")) {
                            subcategory_bar.setVisibility(View.VISIBLE);
                            subcategory_label.setVisibility(View.VISIBLE);

                            ArrayAdapter<CharSequence> adapter2 = ArrayAdapter.createFromResource(this.getActivity().getApplicationContext(), R.array.subcategory_bar, android.R.layout.simple_spinner_item);
                            adapter2.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
                            subcategory_bar.setAdapter(adapter2);

                            if (!getArguments().getString("subcategory").equals("Select:") && getArguments().getString("subcategory") != null && !getArguments().getString("subcategory").isEmpty() && !getArguments().getString("subcategory").equals("")) {
                                int spinnerPostion2 = adapter2.getPosition(getArguments().getString("subcategory"));
                                subcategory_bar.setSelection(spinnerPostion2);
                                spinnerPostion2 = 0;
                            }
                        }
                        if (getArguments().getString("category").equals("Restaurant")) {
                            subcategory_restaurant.setVisibility(View.VISIBLE);
                            subcategory_label.setVisibility(View.VISIBLE);

                            ArrayAdapter<CharSequence> adapter3 = ArrayAdapter.createFromResource(this.getActivity().getApplicationContext(), R.array.subcategory_restaurant, android.R.layout.simple_spinner_item);
                            adapter3.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
                            subcategory_restaurant.setAdapter(adapter3);

                            if (!getArguments().getString("subcategory").equals("Select:") && getArguments().getString("subcategory") != null && !getArguments().getString("subcategory").isEmpty() && !getArguments().getString("subcategory").equals("")) {
                                int spinnerPostion3 = adapter3.getPosition(getArguments().getString("subcategory"));
                                subcategory_restaurant.setSelection(spinnerPostion3);
                                spinnerPostion3 = 0;
                            }
                        }
                    }

                    if (getArguments().getString("shopname") != null && !getArguments().getString("shopname").isEmpty() && !getArguments().getString("shopname").equals("")) {
                        shopname.setText(getArguments().getString("shopname"));
                    }

                    if (getArguments().getString("location") != null && !getArguments().getString("location").isEmpty()  && !getArguments().getString("location").equals("")) {
                        location.setText(getArguments().getString("location"));
                    }

                    if (getArguments().getString("email") != null && !getArguments().getString("email").isEmpty()  && !getArguments().getString("email").equals("")) {
                        email.setText(getArguments().getString("email"));
                    }

                    if (getArguments().getString("telephone") != null && !getArguments().getString("telephone").isEmpty()  && !getArguments().getString("telephone").equals("")) {
                        telephone.setText(getArguments().getString("telephone"));
                    }

                    finalOpening = getArguments().getString("opening");
                    finalClosing = getArguments().getString("closing");
                    finalDresscoding = getArguments().getString("dresscoding");
                    finalMusic = getArguments().getString("music");
                    finalOtherinfo = getArguments().getString("otherinfo");
                    finalFacebook = getArguments().getString("facebook");
                    finalMoneyperperson = getArguments().getString("moneyperperson");

                    if (getArguments().getString("smokingarea") != null && !getArguments().getString("smokingarea").isEmpty()) {
                        smokingarea = getArguments().getString("smokingarea");
                        if (smokingarea.equals("Y")) {
                            finalSmokingarea = 1;
                        } else if (smokingarea.equals("N")) {
                            finalSmokingarea = 0;
                        } else
                            finalSmokingarea = 2;
                    }
                    else{
                        finalSmokingarea = 2;
                    }

                    if (getArguments().getString("parking") != null && !getArguments().getString("parking").isEmpty()) {
                        parking = getArguments().getString("parking");
                        if (parking.equals("Y")) {
                            finalParkingarea = 1;
                        } else if (parking.equals("N")) {
                            finalParkingarea = 0;
                        }
                        else
                            finalParkingarea = 2;
                    }
                    else{
                        finalParkingarea = 2;
                    }

                    if (getArguments().getString("creditcards") != null && !getArguments().getString("creditcards").isEmpty()) {
                        creditcards = getArguments().getString("creditcards");
                        if (creditcards.equals("Y")) {
                            finalCreditcards = 1;
                        } else if (creditcards.equals("N")) {
                            finalCreditcards = 0;
                        }
                        else
                            finalCreditcards = 2;
                    }
                    else{
                        finalCreditcards = 2;
                    }

                    if (getArguments().getString("takeout") != null && !getArguments().getString("takeout").isEmpty()) {
                        takeout = getArguments().getString("takeout");
                        if (takeout.equals("Y")) {
                            finalTakeout = 1;
                        } else if (takeout.equals("N")) {
                            finalTakeout = 0;
                        }
                        else
                            finalTakeout = 2;
                    }
                    else{
                        finalTakeout = 2;
                    }

                    if (getArguments().getString("delivery") != null && !getArguments().getString("delivery").isEmpty()) {
                        delivery = getArguments().getString("delivery");
                        if (delivery.equals("Y")) {
                            finalDelivery = 1;
                        } else if (delivery.equals("N")) {
                            finalDelivery = 0;
                        }
                        else
                            finalDelivery = 2;
                    }
                    else{
                        finalDelivery = 2;
                    }

                    if (getArguments().getString("freewifi") != null && !getArguments().getString("freewifi").isEmpty()) {
                        freewifi = getArguments().getString("freewifi");
                        if (freewifi.equals("Y")) {
                            finalFreewifi = 1;
                        } else if (freewifi.equals("N")) {
                            finalFreewifi = 0;
                        }
                        else
                            finalFreewifi = 2;
                    }
                    else{
                        finalFreewifi = 2;
                    }

                    if (getArguments().getString("happyhour") != null && !getArguments().getString("happyhour").isEmpty()) {
                        happyhour = getArguments().getString("happyhour");
                        if (happyhour.equals("Y")) {
                            finalHappyhour = 1;
                        } else if (happyhour.equals("N")) {
                            finalHappyhour = 0;
                        }
                        else
                            finalHappyhour = 2;
                    }
                    else{
                        finalHappyhour = 2;
                    }

                    if (getArguments().getString("outdoorseating") != null && !getArguments().getString("outdoorseating").isEmpty()) {
                        outdoorseating = getArguments().getString("outdoorseating");
                        if (outdoorseating.equals("Y")) {
                            finalOutdoorseating = 1;
                        } else if (outdoorseating.equals("N")) {
                            finalOutdoorseating = 0;
                        }
                        else
                            finalOutdoorseating = 2;
                    }
                    else{
                        finalOutdoorseating = 2;
                    }

                    if (getArguments().getString("reservations") != null && !getArguments().getString("reservations").isEmpty()) {
                        reservations = getArguments().getString("reservations");
                        if (reservations.equals("Y")) {
                            finalReservations = 1;
                        } else if (reservations.equals("N")) {
                            finalReservations = 0;
                        }
                        else
                            finalReservations = 2;
                    }
                    else{
                        finalReservations = 2;
                    }

                    if (getArguments().getString("appropriategroups") != null && !getArguments().getString("appropriategroups").isEmpty()) {
                        appropriategroup = getArguments().getString("appropriategroups");
                        if (appropriategroup.equals("Y")) {
                            finalAppropriategroup = 1;
                        } else if (appropriategroup.equals("N")) {
                            finalAppropriategroup = 0;
                        }
                        else
                            finalAppropriategroup = 2;
                    }
                    else{
                        finalAppropriategroup = 2;
                    }

                    if (getArguments().getString("appropriatekids") != null && !getArguments().getString("appropriatekids").isEmpty()) {
                        appropriatekids = getArguments().getString("appropriatekids");
                        if (appropriatekids.equals("Y")) {
                            finalAppropriatekids = 1;
                        } else if (appropriatekids.equals("N")) {
                            finalAppropriatekids = 0;
                        }
                        else
                            finalAppropriatekids = 2;
                    }
                    else{
                        finalAppropriatekids = 2;
                    }
                }
                else{
                    finalOpening = "";
                    finalClosing = "";
                    finalMoneyperperson = "";
                    finalDresscoding = "";
                    finalMusic = "";
                    finalOtherinfo = "";
                    finalFacebook = "";
                    finalSmokingarea = 2;
                    finalParkingarea = 2;
                    finalCreditcards = 2;
                    finalTakeout = 2;
                    finalDelivery = 2;
                    finalFreewifi = 2;
                    finalHappyhour = 2;
                    finalOutdoorseating = 2;
                    finalReservations = 2;
                    finalAppropriategroup = 2;
                    finalAppropriatekids = 2;
                }

如您所见，我还将已经设法保存的数据发布到了Parse，因此这些数据不是问题的一部分。 有了这一点，您会注意到，我所做的工作与那些正常工作的数据没有什么不同。

1 个解决方案

解决方案1
 2 已采纳  2015-01-27 21:03:52

问题似乎是getArguments().getString("category")为null 。 检查您如何评估变量： 

 if (!getArguments().getString("category").equals("Select:")
    //up here, you assume the variable is not null
    && getArguments().getString("category") != null
    //here you check if the variable is null or not, very late...
    && !getArguments().getString("category").isEmpty()
    //here you evaluate if the value of getArguments().getString("category") is not empty
    && !getArguments().getString("category").equals("")
    //here you check one more time if the value of getArguments().getString("category") is not empty) {

这可以通过在之前移动null检查来解决： 

if (getArguments().getString("category") != null
    && !getArguments().getString("category").isEmpty()
    && !getArguments().getString("category").equals("")
    && !getArguments().getString("category").equals("Select:")) {

或针对这些情况的更好解决方案：将所需的文字（或编译常量） String与您的String参数进行比较： 

if ("Select:".equals(getArguments().getString("category")) {

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