如何在两个特定日期之间获取 Firebase 记录？

Question

我想从 Firebase Realtime Firebase DB 中获取患者在“CurrentDate”到 2 个月“PreviousDate”之间的病历。我面临的问题是日期正在进入我将通过调试代码检查的查询。这是我将获得“CurrentDate”和“PreviousDate”的代码：

    date = Calendar.getInstance().time;
    val dateFormat = SimpleDateFormat("d-M-yyyy")
    currentDate = dateFormat.format(date)
    cDate.text = currentDate //this gives me **24-4-2021**


    val calendar = Calendar.getInstance()
    calendar.add(Calendar.MONTH, -2)
    val preDate = calendar.time
    previousDate = dateFormat.format(preDate)
    pDate.text = previousDate /// this gives me **24-2-2021**

这是我为获取记录而编写的以下函数的代码：

private fun browseAppointmentByDate() {
    mFirebaseInstance = FirebaseDatabase.getInstance()
    appointmentDBReference = mFirebaseInstance!!.reference
    completeAppointArrayList = ArrayList()

    val ref = FirebaseDatabase.getInstance()
    ref.getReference("PatientChecked").child(currentUserID).orderByChild("date").startAt(previousDate)
            .endAt(currentDate)
            .addListenerForSingleValueEvent(object : ValueEventListener {

                override fun onDataChange(doctorList: DataSnapshot) {
                    try {
                        completeAppointArrayList?.clear()
                        for (eachDoctor in doctorList.children) {
                            Log.e("TAG", "onDataChange: " + eachDoctor.value.toString())
                            var patientsListModel: CheckPatientModel = eachDoctor.getValue(CheckPatientModel::class.java)!!
                            completeAppointArrayList!!.add(patientsListModel)
                        }

                        if (completeAppointArrayList == null || completeAppointArrayList!!.size == 0) {
                            txtNoCompAppointFound!!.visibility = View.VISIBLE
                            txtNoCompAppointFound.text = "You have no recent appointment!!"
                            pbCompAppointment!!.visibility = View.GONE
                        } else {
                            txtNoCompAppointFound.visibility = View.GONE
                            pbCompAppointment!!.visibility = View.GONE
                        }

                        mCompleteAppointmentAdapter = CompleteAppointmentAdapter(activity, completeAppointArrayList)
                        rvCompletedAppoint!!.adapter = mCompleteAppointmentAdapter


                    } catch (e: Exception) {
                        Log.e("TAG", "onDataChange: $e")

                    } catch (e: Exception) {
                        Log.e("TAG", "onDataLoad: $e")
                        pbCompAppointment!!.visibility = View.GONE
                    }
                }

                override fun onCancelled(error: DatabaseError) {
                    Log.w(ContentValues.TAG, "loadPost:onCancelled", error.toException())
                }
            })
}

这是我的 Firebase 数据库的结构，在当前日期和上一个日期之间，至少我会得到 23-4-2021 的记录，但它没有显示。

Answer 1

您的“日期”属性作为字符串存储在数据库中。这意味着当您调用“orderByChild("date")”时，结果将按lexicographically 排序。这意味着字符串在排序时不考虑任何类型的数值，尤其是在涉及日期时，即使日期包含数字“23-4-2021”。所以查询数据库时不能使用字符串值：

.startAt(previousDate).endAt(currentDate)

而不是 Timestamp 对象，并期望像日期一样表现。为了解决这个问题，您应该将数据库中“日期”属性的类型更改为时间戳类型，并按照我在以下帖子中的回答中的说明将其相应地添加到数据库中：

• How to save the current date/time when I add new value to Firebase Realtime Database

一旦您进行了更改，您的代码可能会保持不变，您将获得所需的结果。