AsyncTask没有泄漏

这个AsyncTask类应该是静态的，否则可能发生泄漏

为什么我的AsyncTask不起作用？

调用： PlacesTask(this).execute(...)

码：

 private class PlacesTask internal constructor(activity: MainActivity) : AsyncTask<String, Int, String>() { var data: String? = null private val mRef: WeakReference<MainActivity> = WeakReference(activity) override fun doInBackground(vararg url: String): String? { try { data = MainActivity().downloadUrl(url[0]) } catch (e: Exception) { Log.d("Background Task", e.toString()) } return data } override fun onPostExecute(result: String) { val asyncTaskLeak = mRef.get() if (asyncTaskLeak != null) SetPlaceTask().execute(result) } } private class SetPlaceTask : AsyncTask<String, Int, List<HashMap<String, String>>>() { var places: List<HashMap<String, String>>? = null override fun doInBackground(vararg jsonData: String): List<HashMap<String, String>>? { try { places = PlaceJSONParser().parse(JSONObject(jsonData[0])) } catch (e: Exception) { Log.d("Exception", e.toString()) } return places } override fun onPostExecute(list: List<HashMap<String, String>>) { ... } } @Throws(IOException::class) private fun downloadUrl(strUrl: String): String { var data = "" var iStream: InputStream? = null var urlConnection: HttpURLConnection? = null try { urlConnection = URL(strUrl).openConnection() as HttpURLConnection urlConnection.connect() iStream = urlConnection.inputStream val br = BufferedReader(InputStreamReader(iStream!!)) val sb = StringBuilder() var line: String? = null while ({line = br.readLine(); line }() != null) sb.append(line) data = sb.toString() br.close() } catch (e: Exception) { Log.d("downloading url", e.toString()) } finally { if (iStream != null) iStream.close() if (urlConnection != null) urlConnection.disconnect() } return data } 

错误：java.lang.IllegalArgumentException：指定为非null的参数为null：方法kotlin.jvm.internal.Intrinsics.checkParameterIsNotNull，参数result

请帮忙。 我错过了什么？

Answer 1

如例外所述，参数result为null而您将其定义为不可空。

由于该参数是由doInBackground返回的值，因为downloadUrl抛出一个异常， data变量为null 。

要修复它，请执行以下任一选项：

1. 当发生异常时定义一个非null的默认返回值，确保doInBackground永远不会返回null。
2. 将onPostExecute的参数类型更改为String? 并处理发生异常时可能为空的情况。

Answer 2

我明白了

1. AsyncTask应该是static
2. AsyncTask移动到 – > companion object {} 。
3. WeakReference – AsyncTask没有泄漏（好的exp。）

示例：没有泄漏的AsyncTask

 override fun onPause() { super.onPause() ... when { placesTask != null -> { placesTask!!.cancel(true) placesTask = null } setPlacesTask != null -> { setPlacesTask!!.cancel(true) setPlacesTask = null } } } ... @Throws(IOException::class) private fun downloadUrl(strUrl: String): String { var data = "" var iStream: InputStream? = null var urlConnection: HttpURLConnection? = null try { urlConnection = URL(strUrl).openConnection() as HttpURLConnection urlConnection.connect() iStream = urlConnection.inputStream val br = BufferedReader(InputStreamReader(iStream!!)) val sb = StringBuilder() var line: String? = null while ({line = br.readLine(); line }() != null) sb.append(line) data = sb.toString() br.close() } catch (e: Exception) { Log.d("downloading url", e.toString()) } finally { if (iStream != null) iStream.close() if (urlConnection != null) urlConnection.disconnect() } return data } companion object { ... var placesTask: PlacesTask? = null var setPlacesTask: SetPlaceTask? = null class PlacesTask(mainActivity: MainActivity) : AsyncTask<String, Int, String>() { private val mRef: WeakReference<MainActivity> = WeakReference(mainActivity) override fun doInBackground(vararg url: String): String? { var data: String? = null try { data = mRef.get()?.downloadUrl(url[0]) } catch (e: Exception) { Log.d("Background Task", e.toString()) } return data } override fun onPostExecute(result: String) { setPlacesTask = SetPlaceTask(mRef.get()!!).execute(result) as SetPlaceTask? } } class SetPlaceTask(mainActivity: MainActivity) : AsyncTask<String, Int, List<HashMap<String, String>>>() { private val mRef: WeakReference<MainActivity> = WeakReference(mainActivity) override fun doInBackground(vararg jsonData: String): List<HashMap<String, String>>? { var places: List<HashMap<String, String>>? = null try { places = PlaceJSONParser().parse(JSONObject(jsonData[0])) } catch (e: Exception) { Log.d("Exception", e.toString()) } return places } override fun onPostExecute(list: List<HashMap<String, String>>) { for (i in list.indices) { val hmPlace = list[i] mRef.get()?.parkingLatLng = LatLng(hmPlace["lat"]!!.toDouble(), hmPlace["lng"]!!.toDouble()) mRef.get()?.mMarkerPlaceLink!!.put(mRef.get()?.map!!.addMarker(MarkerOptions().icon(mRef.get()?.vectorToBitmap(R.drawable.ic_local_parking_black_12dp, ContextCompat.getColor(mRef.get()?.applicationContext, R.color.colorPrimaryDark))).position(mRef.get()?.parkingLatLng!!).title(hmPlace["place_name"] + "\n" + hmPlace["vicinity"])).id, hmPlace["reference"].toString()) mRef.get()?.map!!.addCircle(CircleOptions().center(mRef.get()?.parkingLatLng).radius(1.0).strokeColor(Color.BLACK).fillColor(Color.WHITE).strokeWidth(1f).zIndex(1f)) } } } } 

调用： placesTask = PlacesTask(this).execute("https://maps.googleapis.com/maps/api/place/nearbysearch/json?location="...) as PlacesTask?

祝你好运！