Question

使用Retofit2和Rxjava2进行JSON数据解析。此数据成功获取ArrayList。它的ArrayList大小为9，但在表中仅显示两个记录。两点之后记录其Kotlin.NullPointerException。

JSON数据：

 {"success":1,"salesGst":[{"Cmp_Name":"ABC","GSTIN":"AAAA","FirmName":"SALES GJ","ChallanNo":"1","ChallanDate":"2019-03-15 00:00:00","ChallanAmount":"2778.75","TaxTotal":"2778.75","InvoiceType":"Retail Invoice","CGSTTotal":"0.0","PartyGST":"CDE","SGSTTotal":"0.0","IGSTTotal":"0.0"},{"Cmp_Name":"ABC","GSTIN":"AAAA","FirmName":"SALES GJ","ChallanNo":"1","ChallanDate":"2019-03-13 00:00:00","ChallanAmount":"2203.0","TaxTotal":"2118.5","InvoiceType":"Tax Invoice","CGSTTotal":"52.96","PartyGST":"CDE","SGSTTotal":"52.96","IGSTTotal":"0.0"},{"Cmp_Name":"ABC","GSTIN":"AAAA","FirmName":"VIKAS","ChallanNo":"2","ChallanDate":"2019-03-16 00:00:00","ChallanAmount":"6975.0","TaxTotal":"6975.0","InvoiceType":"Retail Invoice","CGSTTotal":"0.0","PartyGST":null,"SGSTTotal":"0.0","IGSTTotal":"0.0"},{"Cmp_Name":"ABC","GSTIN":"AAAA","FirmName":"SALES MH","ChallanNo":"2","ChallanDate":"2019-03-13 00:00:00","ChallanAmount":"420.0","TaxTotal":"403.75","InvoiceType":"Tax Invoice","CGSTTotal":"0.0","PartyGST":"ABC","SGSTTotal":"0.0","IGSTTotal":"20.19"},{"Cmp_Name":"ABC","GSTIN":"AAAA","FirmName":"SALES GJ","ChallanNo":"3","ChallanDate":"2019-03-14 00:00:00","ChallanAmount":"4788.0","TaxTotal":"4560.0","InvoiceType":"Tax Invoice","CGSTTotal":"114.0","PartyGST":"CDE","SGSTTotal":"114.0","IGSTTotal":"0.0"},{"Cmp_Name":"ABC","GSTIN":"AAAA","FirmName":"SALES GJ","ChallanNo":"4","ChallanDate":"2019-03-15 00:00:00","ChallanAmount":"241.9","TaxTotal":"230.38","InvoiceType":"Tax Invoice","CGSTTotal":"5.76","PartyGST":"CDE","SGSTTotal":"5.76","IGSTTotal":"0.0"},{"Cmp_Name":"ABC","GSTIN":"AAAA","FirmName":"SALES GJ","ChallanNo":"5","ChallanDate":"2019-03-15 00:00:00","ChallanAmount":"5563.68","TaxTotal":"5101.5","InvoiceType":"Tax Invoice","CGSTTotal":"231.28","PartyGST":"CDE","SGSTTotal":"231.28","IGSTTotal":"0.0"},{"Cmp_Name":"ABC","GSTIN":"AAAA","FirmName":"SALES GJ","ChallanNo":"6","ChallanDate":"2019-03-16 00:00:00","ChallanAmount":"13238.0","TaxTotal":"12459.25","InvoiceType":"Tax Invoice","CGSTTotal":"389.29","PartyGST":"CDE","SGSTTotal":"389.29","IGSTTotal":"0.0"},{"Cmp_Name":"ABC","GSTIN":"AAAA","FirmName":"SALES MH","ChallanNo":"7","ChallanDate":"2019-03-16 00:00:00","ChallanAmount":"2074.0","TaxTotal":"1975.0","InvoiceType":"Tax Invoice","CGSTTotal":"0.0","PartyGST":"ABC","SGSTTotal":"0.0","IGSTTotal":"98.75"}]}

获取如何在TableLayout中显示后，请引导我。

在ArrayList中有9条记录，但在表中仅显示2条记录，另外7条记录未显示。在第三条记录中，taxtotal给出kotlin.nullpointerException。缺少什么？

 private fun displaySalesGSTData(salesGSt : List<SalesGST>) {

        salesGST = SalesGST()
        tvSalesCompanyName.setText(salesGSt.get(1).Cmp_Name)
        tvGSTIN.setText(salesGSt.get(1).GSTIN)


        val rowHeader = TableRow(this@Sales)
        rowHeader.setBackgroundColor(Color.parseColor("#c0c0c0"))
        rowHeader.setLayoutParams(TableLayout.LayoutParams(TableLayout.LayoutParams.MATCH_PARENT,
                TableLayout.LayoutParams.WRAP_CONTENT))
        val headerText = arrayOf<String>("Sr.No.", "Invoice Type", "Bill No.", "Bill Date", "Firm Name", "GST NO","TAX Total","CGST","SGST","IGST","Net Amount")
        for (c in headerText)
        {
            val tv = TextView(this@Sales)
            tv.setLayoutParams(TableRow.LayoutParams(TableRow.LayoutParams.WRAP_CONTENT,
                    TableRow.LayoutParams.WRAP_CONTENT))
            tv.setGravity(Gravity.CENTER)
           // tv.setBackgroundResource(R.drawable.table_header)
            tv.setTextColor(Color.parseColor("#3F51B5"))
            tv.setTextSize(18F)
            tv.setPadding(5, 5, 5, 5)
            tv.setText(c)
            rowHeader.addView(tv)
        }
        tableMarks.addView(rowHeader)

        for (j in 0 until salesGSt.size)
        {
            /*val jsonObject1 = jsonArray.getJSONObject(j)
            val date = jsonObject1.getString("ExamDate")
            val inputFormatter1 = SimpleDateFormat("yyyy-MM-dd HH:mm:ss")
            val date1 = inputFormatter1.parse(date)
            val outputFormatter1 = SimpleDateFormat("dd-MMM-yyyy")
            ExamDate = outputFormatter1.format(date1)*/
            /* String replaceDate = date.replace("/Date(", "").replace(")/", "");
           Long getDate = Long.valueOf(replaceDate);
           ExamDate = dateFormat.format(getDate);*/
            /*Subject = jsonObject1.getString("subject")
            ExamName = jsonObject1.getString("ExamName")
            TotalMark = jsonObject1.getLong("TotalMarks")
            PassingMark = jsonObject1.getLong("PassingMarks")
            Mark = jsonObject1.getLong("Marks")*/

            var fName : String = salesGSt.get(j).FirmName!!
            var invoice : String = salesGSt.get(j).InvoiceType!!
            var bill_no : String = salesGSt.get(j).ChallanNo!!
            var bill_date : String = salesGSt.get(j).ChallanDate!!
            var gst_no : String = salesGSt.get(j).PartyGST!!
            var tax_total : Double = salesGSt.get(j).TaxTotal!!.toDouble()
            var cgst : String = salesGSt.get(j).CGSTTotal!!
            var igst : String = salesGSt.get(j).IGSTTotal!!
            var sgst : String = salesGSt.get(j).SGSTTotal!!
            var net_amount : String = salesGSt.get(j).ChallanAmount!!

            var sr : Int = j + 1
            // dara rows
            val row = TableRow(this@Sales)
            row.setLayoutParams(TableLayout.LayoutParams(TableLayout.LayoutParams.MATCH_PARENT,
                    TableLayout.LayoutParams.WRAP_CONTENT))
            val colText = arrayOf<String>(sr.toString(),(invoice), bill_no, bill_date, fName, gst_no, tax_total.toString(),cgst,sgst,igst,net_amount)
            for (text in colText)
            {
                val tv = TextView(this@Sales)
                tv.setLayoutParams(TableRow.LayoutParams(TableRow.LayoutParams.WRAP_CONTENT,
                        TableRow.LayoutParams.WRAP_CONTENT))
                tv.setGravity(Gravity.CENTER)
               // tv.setBackgroundResource(R.drawable.table_shape)
                tv.setTextSize(18F)
                tv.setTextColor(Color.parseColor("#3F51B5"))
                tv.setPadding(5, 5, 5, 5)
                tv.setText(text)
                row.addView(tv)
            }
            tableMarks.addView(row)
        }



    }

Answer 1

第三项salesGst[2]是"PartyGST": null。您的json解串器库将无法处理非null字段，因为它是用Java编写的。我假设您有一个数据类，其中PartGST被定义为非null，但反序列化器仍会将其解析为null。因此，当您访问PartyGST时，您会收到一个NullPointerException，因为Kotlin期望它为非空。这是一篇很好的文章，其中有更详细的解释：

I've trusted you! You promised no null pointer exceptions!

对此的一种解决方案是拥有两个模型。 DTO（用于JSON响应），其中所有字段都是可选的，而内部模型（由您的应用程序使用），您在其中定义希望哪些字段是可选的。然后，您可以有一个映射器来处理DTO中字段为空而内部模型中字段不为空的情况：

// Models for your API response
data class SalesGstsDTO(val gsts: List<GstDTO>)
data class GstDTO(val name: String?, val surname: String?)

// Internal models used by your app
data class SalesGsts(val gsts: List<Gst>)
data class Gst(val name: String, val surname: String?)

class SalesGstDTOMapper {

    fun mapToSalesGsts(salesGstsDTO: SalesGstsDTO): SalesGsts {
        val gsts = mutableListOf<Gst>()
        salesGstsDTO.gsts.map {
            val name = it.name ?: return@map // Skips this item. You could handle this how you wish
            val surname = it.surname
            val gst = Gst(name, surname)
            gsts.add(gst)
        }
        return SalesGsts(gsts)
    }

}

这还允许您将应用程序与JSON响应解耦。

使用改造和rxjava2数据显示在Textview和TableLayout中进行json数据解析

1 个答案: