Kotlin und zugriff auf den Bluetoothsensor

Question

Hallo zusammen

Ich habe ein Beispiel welches den Bluetoothsensor scannt. Der Manager dazu wird wie folgt gestartet.

    private val adapter = BluetoothAdapter.getDefaultAdapter()

Doch die Methode "getDefaultAdapter" ist veraltet. Daher versuchte ich es auf eine neue Art.

    var bluetoothManager = (BluetoothManager)(this.getSystemService(Context.BLUETOOTH_SERVICE))
    private val adapter = bluetoothManager.getAdapter()

Aber irgend wie funktioniert der Cast nicht. Denn "BluetoothManager" ist rot unterstrichen und es kommt die Meldung, dass der Alias fehlt. Aber ich habe den Import gemacht ("import android.bluetooth.BluetoothManager")

Was muss ich ändern, dass es zum laufen kommt?

Gruss Renato

Jokel · Accepted Answer

Tipp schau doch nochmal in die Grundlagen Kotlin.
Wie wird da ein cast gemacht.
Welchen Operator gibt es da dafür?

Jokel · Answer

in Java etwa so 

BluetoothManager manager = (BluetoothManager)context.getSystemService(Context.BLUETOOTH_SERVICE);
  
       BluetoothAdapter mAdapter = manager.getAdapter();


Kotlin :

 var manager   = getSystemService(Context.BLUETOOTH_SERVICE) as BluetoothManager;
 var adapter = manager.getAdapter();

oder 
 var adapter = manager.adapter;

Robbiani Renato · Answer

Danke Jokel

Genau richtig. Ich habe den Cast falsch gemacht. Nun musste ich noch alles ins onCreate verschieben und schon geht es.
Nur so wenn es jemand wunder nimmt den Code zur App:

package ch.robbisoft.bluetoothscannerdemo

import android.Manifest.permission.ACCESS_FINE_LOCATION
import android.app.Activity
import android.content.pm.PackageManager.PERMISSION_GRANTED
import android.bluetooth.BluetoothAdapter
import android.bluetooth.BluetoothDevice
import android.content.BroadcastReceiver
import android.content.Context
import android.content.Intent
import android.content.IntentFilter
import android.os.Build
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.activity.result.ActivityResult
import androidx.activity.result.contract.ActivityResultContracts
import androidx.core.content.ContextCompat.getSystemService
import ch.robbisoft.bluetoothscannerdemo.databinding.ActivityMainBinding
import android.bluetooth.BluetoothManager
import android.widget.Adapter

private const val REQUEST_ENABLE_BLUETOOTH = 123
private const val REQUEST_FINE_LOCATION = 321

private enum class BluetoothState {
NotAvailable, Disabled, Enabled
}

class MainActivity : AppCompatActivity() {

private lateinit var binding: ActivityMainBinding
private var started = false

// private val adapter = BluetoothAdapter.getDefaultAdapter()
// var bluetoothManager = (this.getSystemService(Context.BLUETOOTH_SERVICE)) as BluetoothManager
// private val adapter = bluetoothManager.getAdapter()
private lateinit var adapter : BluetoothAdapter
private val receiver = object : BroadcastReceiver(){
override fun onReceive(context: Context?, intent: Intent?) {
if( intent != null ) {
if (BluetoothDevice.ACTION_FOUND == intent.action) {
val device =
intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE)
binding.tv.append(getString(R.string.template, device?.name, device?.address, device?.type))
}
}
}
}

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    binding = ActivityMainBinding.inflate(layoutInflater)
    val view = binding.root
    setContentView(view)

    var bluetoothManager = (this.getSystemService(Context.BLUETOOTH_SERVICE)) as BluetoothManager
    adapter = bluetoothManager.getAdapter()

    val fileter = IntentFilter(BluetoothDevice.ACTION_FOUND)
    registerReceiver(receiver, fileter)
}

override fun onDestroy() {
    super.onDestroy()
    unregisterReceiver(receiver)
}

override fun onStart() {
    super.onStart()
    started = false
    if( getBluetoothState() == BluetoothState.NotAvailable ){
        binding.tv.text = getString(R.string.not_available)
    }else{
        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (checkSelfPermission(ACCESS_FINE_LOCATION) != PERMISSION_GRANTED) {
                requestPermissions(arrayOf(ACCESS_FINE_LOCATION), REQUEST_FINE_LOCATION)
            } else {
                showDevices()
            }
        }
    }
}

override fun onPause() {
    super.onPause()
    if( started ){
        adapter?.cancelDiscovery()
        started = false
    }
}

override fun onRequestPermissionsResult( requestCode: Int, permissions: Array<out String>, grantResults: IntArray) {
    super.onRequestPermissionsResult(requestCode, permissions, grantResults)
    if(requestCode == REQUEST_FINE_LOCATION && grantResults.isNotEmpty() && grantResults[0] == PERMISSION_GRANTED){
        showDevices()
    }
}

private fun getBluetoothState() : BluetoothState {
    val state = if( adapter != null ){
        if(adapter.isEnabled){
            BluetoothState.Enabled
        }else{
            BluetoothState.Disabled
        }
    }else{
        BluetoothState.NotAvailable
    }
    if(state == BluetoothState.Disabled){
        val enableBtIntent = Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE)

// startActivityForResult(enableBtIntent, REQUEST_ENABLE_BLUETOOTH)
getactivityresult.launch(enableBtIntent)
}
return state
}

private fun showDevices(){
    val sb = StringBuilder()
    sb.append(getString(R.string.paired))
    adapter?.bondedDevices?.forEach{
        sb.append(getString(R.string.template, it.name, it.address, it.type))
    }
    sb.append("\n")
    if( started ){
        adapter?.cancelDiscovery()
    }
    started = adapter?.startDiscovery() ?: false
    if( started ){
        sb.append(getString(R.string.others))
    }
    binding.tv.text = sb.toString()
}

val getactivityresult = registerForActivityResult(ActivityResultContracts.StartActivityForResult()){ result : ActivityResult? ->
    if( result != null ) {
        if (result.resultCode == Activity.RESULT_OK) {

// result.data
}
}
}
}

Gruss Renato