Question

基本上我试图在尝试使用它之前检查某个对象是否存在，如果没有，我会事先添加它然后尝试使用它。

如果它不存在，它会被正确添加，但之后应用程序仍然找不到它，除非我重新打开该应用程序

如果对象以

开头，那么一切都按预期工作

private class ExerciseViewPageAdapter extends FragmentPagerAdapter {

    Realm realm;

    ExerciseViewPageAdapter(FragmentManager fm) {
        super(fm);

    }

    @Override
    public Fragment getItem(int pos) {
        realm = Realm.getDefaultInstance();

        String exercise_name = getIntent().getExtras().getString("exercise_name");

        boolean found_exercise = realm.where(Exercise.class).equalTo("name", exercise_name).findAll().size() > 0;
        if (!found_exercise) {
            CompositeDisposable disposable = new CompositeDisposable();
            ExerciseClient client = new ExerciseClient(getApplicationContext());
            disposable.add(client.getExerciseByName(exercise_name)
                    .subscribeOn(Schedulers.io())
                    .subscribe(
                            this::getExercisesSuccess,
                            this::getExercisesError
                    )
            );


        }

        final ArrayList<Exercise> exercise = new ArrayList<>();
        exercise.add(realm.where(Exercise.class).equalTo("name", exercise_name).findFirst());
        if (exercise.get(0) != null) {
            switch (pos) {
//returning new fragments depending on position
            }
        }
//if exercise.get(0) doesn't exist at first, even tho I added it afterwards it's still null here unless I reopen the app or let it crash
        finish();
        realm.close();
        return null;
    }

    private void getExercisesError(Throwable throwable) {

    }


    private void getExercisesSuccess(Exercise exercise) {
        try (Realm r = Realm.getDefaultInstance()) {
            r.executeTransaction(realm -> {
                realm.insertOrUpdate(exercise);
            });
        }

    }

    @Override
    public int getCount() {
        return 3;
    }
}

编辑：TL; DR：问题是realm.where()...只有在重新打开应用程序后再插入对象后才会看到该对象

Answer 1

你打电话给api，它会在后台运行，所以在api调用上编写的代码将会执行。因此，您的活动将自动关闭。

请求您的api成功失败验证

private void getExercisesSuccess(Exercise exercise) {
    try (Realm r = Realm.getDefaultInstance()) {
        r.beginTransaction();
        realm.insertOrUpdate(exercise);
        r.commitTransaction();

        //checking records are in realm
        final ArrayList<Exercise> exercise = new ArrayList<>();
        exercise.add(realm.where(Exercise.class).equalTo("name", exercise_name).findFirst());
        if (exercise.get(0) != null) {
            switch (pos) {
                //returning new fragments depending on position
            }
        }
        //if exercise.get(0) doesn't exist at first, even tho I added it    afterwards it's still null here unless I reopen the app or let it crash
        finish();
        realm.close();
    }catch(Exception e){}
}

从getItem（）

中删除以下行

  final ArrayList<Exercise> exercise = new ArrayList<>();
    exercise.add(realm.where(Exercise.class).equalTo("name", exercise_name).findFirst());
    if (exercise.get(0) != null) {
        switch (pos) {
            //returning new fragments depending on position
        }
    }
    //if exercise.get(0) doesn't exist at first, even tho I added it afterwards it's still null here unless I reopen the app or let it crash
    finish();
    realm.close();

领域仅在重新打开应用程序后才创建插入的对象

1 个答案: