无法使用广播接收器(Kotlin)更新UI

Question

我想在蓝牙打开/关闭时更新我的MainActivity的UI

主要活动

private val broadcastReceiver = Broadcast()
open var bluetooth : ImageView? = null
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
setContentView(R.layout.activity_main)
val filter = IntentFilter(BluetoothAdapter.ACTION_STATE_CHANGED)
registerReceiver(broadcastReceiver, filter)
val bluetoothAdapter = BluetoothAdapter.getDefaultAdapter()
bluetooth = findViewById(R.id.image_bluetooth)
val bluetoothName = findViewById<TextView>(R.id.text_bluetooth_name)
bluetoothName.text = bluetoothAdapter.name
bluetooth?.setOnClickListener {
if (!bluetoothAdapter.isEnabled) {
val turnOn = Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE)
startActivityForResult(turnOn, 0)
} else {
bluetoothAdapter.disable()
}
}
}
override fun onDestroy() {
super.onDestroy()
unregisterReceiver(broadcastReceiver)
}
fun enableBluetooth()
{
bluetooth?.setImageDrawable(ContextCompat.getDrawable(this,R.drawable.ic_bluetooth_enable_48dp))
}
fun disableBluetooth()
{
bluetooth?.setImageDrawable(ContextCompat.getDrawable(this,R.drawable.ic_bluetooth_disable_48dp))
}

广播接收器

class Broadcast : BroadcastReceiver() {
override fun onReceive(context: Context?, intent: Intent?) {
val action = intent?.action
val mainActivity = MainActivity()
if (action.equals(BluetoothAdapter.ACTION_STATE_CHANGED)) {
when (intent?.getIntExtra(BluetoothAdapter.EXTRA_STATE, BluetoothAdapter.ERROR)) {
BluetoothAdapter.STATE_OFF -> {
Toast.makeText(context, "Bluetooth Turned OFF", Toast.LENGTH_LONG).show()
mainActivity.disableBluetooth()
}
BluetoothAdapter.STATE_ON -> {
Toast.makeText(context, "Bluetooth Turned ON", Toast.LENGTH_LONG).show()
mainActivity.enableBluetooth()
}
}
}
}
}

在BroadcastReceiver中的onReceive调用后，在enableBluetooth和disableBluetooth方法中bluetooth值返回null。有人能帮我把这个过程改写一下吗？提前感谢

Answer 1

对于这种情况，请使用On onActivityResult方法更新UI

override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
super.onActivityResult(requestCode, resultCode, data)
if (requestCode == 0 && bluetoothAdapter!!.isEnabled) {
Toast.makeText(this, "Bluetooth Turned ON", Toast.LENGTH_LONG).show()
image_bluetooth?.setImageDrawable(ContextCompat.getDrawable(this, R.drawable.ic_bluetooth_enable_48dp))
}
}