调用 onBackPressed() 时崩溃

Question

我正在发送 API 请求来发送电子邮件，并且在成功响应后，我将在我的EmailActivity类中调用onBackPressed()。

我还有AbstractBaseActivity类，它由我的EmailActivity类扩展。

我经常遇到这种崩溃。

Fatal Exception: java.lang.NullPointerException: Attempt to invoke virtual method 'android.os.Handler android.app.FragmentHostCallback.getHandler()' on a null object reference
       at android.app.FragmentManagerImpl.ensureExecReady + 2003(FragmentManager.java:2003)
       at android.app.FragmentManagerImpl.execPendingActions + 2056(FragmentManager.java:2056)
       at android.app.FragmentManagerImpl.popBackStackImmediate + 870(FragmentManager.java:870)
       at android.app.FragmentManagerImpl.popBackStackImmediate + 831(FragmentManager.java:831)
       at android.app.Activity.onBackPressed + 3111(Activity.java:3111)
       at android.support.v4.app.FragmentActivity.onBackPressed + 187(FragmentActivity.java:187)
       at com.test.test.core.AbstractBaseActivity.onBackPressed + 71(AbstractBaseActivity.java:71)
       at com.test.test.emails.EmailActivity.displayEmailSent + 283(EmailActivity.java:283)
       at com.test.presentation.emails.EmailPresenter.lambda$sendEmail$2$EmailPresenter + 100(EmailPresenter.java:100)
       at com.test.presentation.emails.EmailPresenter$$Lambda$2.accept + 4(:4)
       at io.reactivex.internal.observers.ConsumerSingleObserver.onSuccess + 62(ConsumerSingleObserver.java:62)
       at io.reactivex.internal.operators.single.SingleObserveOn$ObserveOnSingleObserver.run + 81(SingleObserveOn.java:81)
       at io.reactivex.android.schedulers.HandlerScheduler$ScheduledRunnable.run + 124(HandlerScheduler.java:124)
       at android.os.Handler.handleCallback + 873(Handler.java:873)
       at android.os.Handler.dispatchMessage + 99(Handler.java:99)
       at android.os.Looper.loop + 193(Looper.java:193)
       at android.app.ActivityThread.main + 6718(ActivityThread.java:6718)
       at java.lang.reflect.Method.invoke(Method.java)
       at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run + 493(RuntimeInit.java:493)
       at com.android.internal.os.ZygoteInit.main + 858(ZygoteInit.java:858)

这是我的 EmailActivity 中的代码。

  @Override public void displayEmailSent() {
    Toast.makeText(this, R.string.email_sent, Toast.LENGTH_SHORT).show();
    onBackPressed();
  }

这是我在 AbstractBaseActivity 中的代码。

  @Override public void onBackPressed() {
    if(this instanceof AddTaskActivity ||
        this instanceof AddCustomerActivity ||
        this instanceof AddContactsActivity ||
        this instanceof NoteDetailsActivity ||
        this instanceof AddEstimateActivity ||
        this instanceof AddAgreementsActivity ||
        this instanceof AddAppointmentActivity ||
        this instanceof EditServiceLocationActivity) {
      showExitDialogForFormScreens();
    } else {
      super.onBackPressed();
    }
  }

这是来自 EmailPresenter 的代码。

 public void sendEmail(int entityId, EmailType emailType, String emailBody, String subject, List<String> recipients) {
    disposables = RxUtil.initDisposables(disposables);

    if(TextUtils.isEmpty(subject)) {
      view.displaySubjectInvalid();
      return;
    }

    if(TextUtils.isEmpty(emailBody)) {
      view.displayEmailBodyInvalid();
      return;
    }

    if(recipients == null || recipients.isEmpty()) {
      view.displayRecipientsEmpty();
      return;
    }

    if(!Utils.isValidEmailAddress(recipients.get(0))) {
      view.displayEmailToInvalid();
      return;
    }

    String modelType = getModelType(emailType);

    view.disableEmailButton();

    Disposable disposable = emailsRepository.sendEmail(entityId, modelType, emailBody, subject, recipients)
        .subscribeOn(Schedulers.io())
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe(response -> {
          view.enableEmailButton();
          if (response.isSuccessful()) {
            view.displayEmailSent();
          } else {
            view.displayEmailError();
          }
        }, throwable -> {
          view.enableEmailButton();
          view.handleError(throwable);});

    disposables.add(disposable);
  }

从 EmailActivity 我将返回到另一个活动，但如果我返回两个或三个屏幕，它将返回到 Fragment，

我该如何解决这个问题？

Answer 1

如果您只想终止当前活动并返回到上一个活动，则可以调用finish()而不是onBackPressed().