解析JSON时的空指针异常(仅在某些情况下)

Question

我使用这段代码来解析json文件，并在我构建的de app中更改一些项：

 fun fetchJson() {

        if (isNetworkAvailable()) {

            val request = Request.Builder().url(stationAPPJsonURL).build()

            client.newCall(request).enqueue(object : Callback {

                override fun onResponse(call: Call, response: Response) {
    
                    val body = response.body?.string()

                    val gson = GsonBuilder().create()

                    try {

                        val stationAPP = gson.fromJson(body, StationAPP::class.java)

                        //ACTIE
                        actie_zichtbaar = stationAPP.actie_zichtbaar
                        actie_img = stationAPP.actie_img
                        actie_url = stationAPP.actie_url

... I left out some code

                    catch (error: JsonParseException) {

                        runOnUiThread {

                            val toast = Toast.makeText(applicationContext, "Problem loading JSON.\nFunctionality may be limited for a while.", Toast.LENGTH_SHORT)

                            val view = toast.view!!.findViewById<TextView>(android.R.id.message)
                            toast?.let { view.gravity = Gravity.CENTER }
                            toast.setGravity(Gravity.CENTER, 0, 0)
                            toast.show()

                        }

                    }

               }

                override fun onFailure(call: Call, e: IOException) {
                runOnUiThread {

                    val toast = Toast.makeText(applicationContext, "Problem loading JSON.\nFunctionality may be limited for a while.", Toast.LENGTH_SHORT)

                    val view = toast.view!!.findViewById<TextView>(android.R.id.message)
                    view?.let { view.gravity = Gravity.CENTER }
                    toast.setGravity(Gravity.CENTER, 0, 0)
                    toast.show() --> line 1390!!

                }

            }

         }

  }

我在Google控制台的日志中看到，有时这部分代码会崩溃(4%)。我不知道为什么？我在几个设备上测试了它，没有任何错误。

谁能帮我？

是否有可能: val stationAPP = gson.fromJson(body，StationAPP::class.java)也不会抛出异常，但是json文件不知何故装载了一些错误？所以有些项目是空的？

(谢谢你的帮助;)

更新:这是它产生的错误：

Exception java.lang.NullPointerException:
  at com.familiekoning.grolloo.MainActivity$fetchJson$1.onFailure$lambda-10 (MainActivity.kt:1390)
  at com.familiekoning.grolloo.MainActivity$fetchJson$1.$r8$lambda$lczurdfMtnZdFDn9iwHvPqw9_Pg
  at com.familiekoning.grolloo.MainActivity$fetchJson$1$$ExternalSyntheticLambda8.run
  at android.os.Handler.handleCallback (Handler.java:938)
  at android.os.Handler.dispatchMessage (Handler.java:99)
  at android.os.Looper.loop (Looper.java:250)
  at android.app.ActivityThread.main (ActivityThread.java:7806)
  at java.lang.reflect.Method.invoke
  at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run (RuntimeInit.java:592)
  at com.android.internal.os.ZygoteInit.main (ZygoteInit.java:958)

Answer 1

这将是一个猜测，但如果您在任何地方看到!!，并且您有NullPointerException。你很确定这就是罪魁祸首。如果你想要一个不同的烤面包外观，有NPE安全ways。

依赖的东西，即android.id.x是不安全的，因为它可能是非常依赖OEM。

Answer 2

我改变了：

val toast = Toast.makeText(applicationContext, "Problem loading JSON.\nFunctionality may be limited for a while.", Toast.LENGTH_SHORT)

            val view = toast.view!!.findViewById<TextView>(android.R.id.message)
            view?.let { view.gravity = Gravity.CENTER }
            toast.setGravity(Gravity.CENTER, 0, 0)
            toast.show()

至：

val toast = Toast.makeText(applicationContext, "Problem loading JSON.\nFunctionality may be limited for a while.", Toast.LENGTH_SHORT)

            toast.setGravity(Gravity.CENTER, 0, 0)
            toast.show()

解决了问题。