我需要在Kotlin的Asynctask替代方案，我知道使用Caroutines，执行者，处理程序，但不确定如何在Google Maps Koltin App中实现

Question

我正在构建一个Google Maps路由应用程序，并且无法构建Asynctask的弃用，我知道使用caroutines/opecuter/handlers，但我不知道如何在我的代码中实现它们，因为我遵循了几个教程并且不确定。我正在使用地图和Directions API构建Google Maps应用程序，并且与ASynctask折旧有问题。

这是我的下载任务功能：

inner class DownloadTask :
        AsyncTask<String?, Void?, String>(){

        override fun onPostExecute(result: String) {
            super.onPostExecute(result)
            val parserTask = ParserTask()
            parserTask.execute(result)
        }

        override fun doInBackground(vararg url: String?): String {
            var data = ""
            try{
                data = downloadUrl(url[0].toString()).toString()
            } catch (e: java.lang.Exception) {
                Log.d("Background Task", e.toString())
            }
            return data
        }

        }

这是我的解析器任务，可以通过数据解析器类解析JSON，

//parsing into JSON format
    inner class ParserTask :
        AsyncTask<String?, Int?, List<List<HashMap<String, String>>>?> () {
        override fun doInBackground(vararg jsonData: String?): List<List<HashMap<String, String>>>? {
            val jObject: JSONObject
            var routes: List<List<HashMap<String, String>>>? =
                null
            try {
                jObject = JSONObject(jsonData[0])
                val parser = DataParser()
                routes = parser.parse(jObject)
            } catch (e: java.lang.Exception) {
                e.printStackTrace()
            }
            return routes
        }


        override fun onPostExecute(result: List<List<HashMap<String, String>>>?) {
            val points = ArrayList<LatLng?>()
            val lineOptions = PolylineOptions()
            for (i in result!!.indices) {
                val path =
                    result[i]
                for (j in path.indices) {
                    val point = path[j]
                    val lat = point["lat"]!!.toDouble()
                    val lng = point["lng"]!!.toDouble()
                    val position = LatLng(lat, lng)
                    points.add(position)
                }
                lineOptions.addAll(points)
                lineOptions.width(8f)
                lineOptions.color(Color.RED)
                lineOptions.geodesic(true)
            }

            if (points.size != 0) mMap!!.addPolyline(lineOptions)
        }

    }

如果有人可以帮助我使用该代码使用executor and Handler，这将非常感谢！

这是我的完整MainActivity文件供参考。

class MainActivity : AppCompatActivity(), OnMapReadyCallback
    //, LocationListener, GoogleMap.OnCameraMoveListener, GoogleMap.OnCameraMoveStartedListener, GoogleMap.OnCameraIdleListener
{

    private var mMap: GoogleMap? = null

    lateinit var mapView: MapView

    private val MAP_VIEW_BUNDLE_KEY = "MapViewBundleKey"

    private val DEFAULT_ZOOM = 15f

    lateinit var B_search: Button

    lateinit var tvCurrentAddress: TextView

    private var fusedLocationProviderClient : FusedLocationProviderClient? = null

    var end_latitude = 0.0

    var end_longitude = 0.0

    lateinit var origin: MarkerOptions

    lateinit var destination:MarkerOptions

    var latitude = 0.0

    var longitude = 0.0

    private val myExecutor = Executors.newSingleThreadExecutor()
    private val myHandler = Handler(Looper.getMainLooper())

    override fun onMapReady(googleMap: GoogleMap) {

        mapView.onResume()
        mMap = googleMap

        askPermissionLocation()

        if (ActivityCompat.checkSelfPermission(
                this,
                Manifest.permission.ACCESS_FINE_LOCATION
            ) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(
                this,
                Manifest.permission.ACCESS_COARSE_LOCATION
            ) != PackageManager.PERMISSION_GRANTED
        ) {
            return
        }
        mMap!!.setMyLocationEnabled(true)
//        mMap!!.setOnCameraMoveListener (this)
//        mMap!!.setOnCameraMoveStartedListener(this)
//        mMap!!.setOnCameraIdleListener(this)
    }


    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        mapView = findViewById<MapView>(R.id.map1)

        tvCurrentAddress = findViewById<TextView>(R.id.tvAdd)

        B_search = findViewById(R.id.B_search)

        askPermissionLocation()

        var mapViewBundle: Bundle? = null
        if(savedInstanceState != null) {
            mapViewBundle = savedInstanceState.getBundle(MAP_VIEW_BUNDLE_KEY)
        }

        mapView.onCreate(mapViewBundle)
        mapView.getMapAsync(this)


        B_search.setOnClickListener {

            searchArea()
        }

    }

    private fun searchArea() {
        val tf_location =
            findViewById<View>(R.id.TF_location) as EditText

        val location = tf_location.text.toString()

        var addressList: List<Address>? = null

        val markerOptions = MarkerOptions()

        if (location != "") {
            val geocoder = Geocoder (applicationContext)
            try {
                addressList = geocoder.getFromLocationName(location, 5)
            } catch (e: IOException) {
                e.printStackTrace()
            }
            if (addressList != null) {
                for (i in addressList.indices) {
                    val myAddress = addressList[i]
                    val latLng =
                        LatLng(myAddress.latitude, myAddress.longitude)
                    markerOptions.position(latLng)
                    mMap!!.addMarker(markerOptions)
                    end_latitude = myAddress.latitude
                    end_longitude = myAddress.longitude

                    mMap!!.animateCamera(CameraUpdateFactory.newLatLng(latLng))

                    val mo = MarkerOptions()
                    mo.title("Distance")

                    val results = FloatArray(10)
                    Location.distanceBetween(
                        latitude,
                        longitude,
                        end_latitude,
                        end_longitude,
                        results
                    )

                    val s =
                        String.format("%.1f", results[0] / 1000)


                    //Setting marker to draw route between these two points
                    origin = MarkerOptions().position(LatLng(latitude, longitude))
                        .title("HSR Layout").snippet("origin")
                    destination =
                        MarkerOptions().position(LatLng(end_latitude, end_longitude))
                            .title(tf_location.text.toString())
                            .snippet("Distance = $s KM")
                    mMap!!.addMarker(destination)
                    mMap!!.addMarker(origin)

                    Toast.makeText(
                        this@MainActivity,
                        "Distance = $s KM",
                        Toast.LENGTH_SHORT
                    ) .show()


                    tvCurrentAddress!!.setText("Distance = $s KM")

                    //getting URL to the google Directions API
                    val url: String=
                        getDirectionsUrl(origin!!.getPosition(), destination!!.getPosition())!!

                    val downloadTask: DownloadTask = DownloadTask()

                    //start downloading the json data from google directions API
                    downloadTask.execute(url)
                }
            }
        }
    }

    @Throws(IOException::class)
    private fun downloadUrl(strUrl: String) : String?{
        var data = ""
        var iStream: InputStream? = null
        var urlConnection: HttpURLConnection? = null
        try{
            val url = URL(strUrl)
            urlConnection = url.openConnection() as HttpURLConnection
            urlConnection.connect()
            iStream = urlConnection!!.inputStream
            val br =
                BufferedReader(InputStreamReader(iStream))
            val sb = StringBuffer()
            var line: String? = ""
            while (br.readLine().also { line = it } != null) {
                sb.append(line)
            }
            data = sb.toString()
            br.close()
        } catch (e: java.lang.Exception) {
            Log.d("Exception", e.toString())
        } finally {
            iStream!!.close()
            urlConnection!!.disconnect()
        }
        return data
    }

    inner class DownloadTask :
        AsyncTask<String?, Void?, String>(){

        override fun onPostExecute(result: String) {
            super.onPostExecute(result)
            val parserTask = ParserTask()
            parserTask.execute(result)
        }

        override fun doInBackground(vararg url: String?): String {
            var data = ""
            try{
                data = downloadUrl(url[0].toString()).toString()
            } catch (e: java.lang.Exception) {
                Log.d("Background Task", e.toString())
            }
            return data
        }

        }

    //parsing into JSON format
    inner class ParserTask :
        AsyncTask<String?, Int?, List<List<HashMap<String, String>>>?> () {
        override fun doInBackground(vararg jsonData: String?): List<List<HashMap<String, String>>>? {
            val jObject: JSONObject
            var routes: List<List<HashMap<String, String>>>? =
                null
            try {
                jObject = JSONObject(jsonData[0])
                val parser = DataParser()
                routes = parser.parse(jObject)
            } catch (e: java.lang.Exception) {
                e.printStackTrace()
            }
            return routes
        }


        override fun onPostExecute(result: List<List<HashMap<String, String>>>?) {
            val points = ArrayList<LatLng?>()
            val lineOptions = PolylineOptions()
            for (i in result!!.indices) {
                val path =
                    result[i]
                for (j in path.indices) {
                    val point = path[j]
                    val lat = point["lat"]!!.toDouble()
                    val lng = point["lng"]!!.toDouble()
                    val position = LatLng(lat, lng)
                    points.add(position)
                }
                lineOptions.addAll(points)
                lineOptions.width(8f)
                lineOptions.color(Color.RED)
                lineOptions.geodesic(true)
            }

            if (points.size != 0) mMap!!.addPolyline(lineOptions)
        }

    }

    private fun getDirectionsUrl(origin: LatLng, dest: LatLng): String?{
        //Origin of route
        val str_origin = "origin=" + origin.latitude + "," + origin.longitude

        //Destination of Route
        val str_destination = "destination" + dest.latitude + "," + dest.longitude

        //transportation mode
        val mode = "mode=walking"

        //building parameters of webservice
        val parameters = "$str_origin&$str_destination&$mode"

        //output format
        val output = "json"

        //building the url to the web service
        return "https://maps.googleapis.com/maps/api/directions/$output?$parameters&key=AIzaSyCgraKSwPfUIyZLOmEDh_ptAbfRRAj7y1g"
    }

    public override fun onSaveInstanceState(outState: Bundle) {
        super.onSaveInstanceState(outState)

        askPermissionLocation()
        var mapViewBundle = outState.getBundle(MAP_VIEW_BUNDLE_KEY)
        if (mapViewBundle == null){
            mapViewBundle = Bundle()
            outState.putBundle(MAP_VIEW_BUNDLE_KEY, mapViewBundle)
        }

        mapView.onSaveInstanceState(mapViewBundle)
    }

    private fun askPermissionLocation(){
        askPermission(
            Manifest.permission.ACCESS_FINE_LOCATION,
            Manifest.permission.ACCESS_COARSE_LOCATION
        ){

            getCurrentLocation()
//            mapView.getMapAsync(this@MyNavigationActivity)

        }
    }

    private fun askPermission(accessFineLocation: String, accessCoarseLocation: String, function: () -> Unit) {

    }

    private fun getCurrentLocation() {
        fusedLocationProviderClient =
            LocationServices.getFusedLocationProviderClient(this@MainActivity)

        try {
            @SuppressLint ("MissingPermission")
            val location =
                fusedLocationProviderClient!!.getLastLocation()

            location.addOnCompleteListener(object : OnCompleteListener<Location> {
                override fun onComplete(loc: Task<Location>) {
                    if (loc.isSuccessful) {

                        val currentLocation = loc.result as Location?
                        if (currentLocation != null) {
                            moveCamera(
                                LatLng(currentLocation.latitude, currentLocation.longitude),
                                DEFAULT_ZOOM
                            )

                            latitude = currentLocation.latitude
                            longitude = currentLocation.longitude

                        }
                    } else {
                        askPermissionLocation()
                    }
                }
            })
        } catch (se: Exception) {
            Log.e("TAG", "Security Exception")
        }
    }

    private fun moveCamera(latLng: LatLng, zoom: Float) {
       // mMap!!.moveCamera(CameraUpdateFactory.newLatLngZoom(latLng, zoom))
    }


//    override fun onLocationChanged(location: Location?) {
//       val geocoder = Geocoder (this, Locale.getDefault())
//       var addresses: List<Address>? = null
//       try {
//           addresses = geocoder.getFromLocation(location!!.latitude, location.longitude, 1)
//       } catch (e: IOException) {
//           e.printStackTrace()
//       }
//       setAddress(addresses!![0])
//    }
//
//    private fun setAddress(addresses: Address) {
//        if (addresses != null) {
//
//            if (addresses.getAddressLine(0) != null) {
//                tvCurrentAddress!!.setText(addresses.getAddressLine(0))
//            }
//            if (addresses.getAddressLine(1) != null) {
//                tvCurrentAddress!!.setText(
//                        tvCurrentAddress.getText().toString() + addresses.getAddressLine(1)
//                )
//            }
//        }
//    }
//
//
//
//    override fun onStatusChanged(p0: String?, p1: Int, p2: Bundle?) {
//
//    }
//
//    override fun onProviderEnabled(p0: String?) {
//
//    }
//
//    override fun onProviderDisabled(p0: String?) {
//
//    }
//
//    override fun onCameraMove() {
//
//    }
//
//    override fun onCameraMoveStarted(p0: Int) {
//
//    }
//
//    override fun onCameraIdle() {
//        var addresses: List<Address>? = null
//        val geocoder = Geocoder (this, Locale.getDefault())
//        try {
//            addresses = geocoder.getFromLocation( mMap!!.getCameraPosition().target.latitude, mMap!!.getCameraPosition().target.longitude, 1)
//
//            setAddress(addresses!![0])
//
//        } catch (e: IndexOutOfBoundsException) {
//            e.printStackTrace()
//        } catch (e: IOException) {
//            e.printStackTrace()
//        }
//    }


}

Answer 1

您可以轻松地使用Coroutines来做到这一点。我无法在我这边执行您的代码，但我试图将其转换为Coroutine。

请注意，我正在使用GlobalsCope，如果您将添加此代码，则必须使用其他相关范围。您可以创建自定义范围。

fun func () {

    GlobalScope.launch (Dispatchers.Main){
        val result = parseDataAndGetRoutes()
        
        val points = ArrayList<LatLng?>()
        val lineOptions = PolylineOptions()
        for (i in result!!.indices) {
            val path =
                result[i]
            for (j in path.indices) {
                val point = path[j]
                val lat = point["lat"]!!.toDouble()
                val lng = point["lng"]!!.toDouble()
                val position = LatLng(lat, lng)
                points.add(position)
            }
            lineOptions.addAll(points)
            lineOptions.width(8f)
            lineOptions.color(Color.RED)
            lineOptions.geodesic(true)
        }

        if (points.size != 0) mMap!!.addPolyline(lineOptions)
    }
}

suspend fun parseDataAndGetRoutes() : List<List<HashMap<String, String>>>? =
    withContext(Dispatchers.Default){
        val jObject: JSONObject
        var routes: List<List<HashMap<String, String>>>? = null
        try {
            jObject = JSONObject(jsonData[0])
            val parser = DataParser()
            routes = parser.parse(jObject)
        } catch (e: java.lang.Exception) {
            e.printStackTrace()
        }
        return@withContext routes
    }