Android Kotlin：在 recyclerview 上显示蓝牙设备但为空

Question

I want to scan a list of bluetooth devices and display it on a recyclerview but it's still empty . It displays nothing on Recyclerview but It works only on Logcat.

In onCreate , binding.recyclerBluetooth.adapter = RecyclerBluetoothAdapter(devices_list, this)

devices_list is null here and yet I used devices_list.add(device) on onReceive , I don't know why...

Here is my Activity

class BluetoothActivity() : AppCompatActivity(), BluetoothOnItemClickListener {

    private lateinit var binding: FragmentBluetoothBinding
    private lateinit var manager: RecyclerView.LayoutManager
    private val devices_list: ArrayList<BluetoothDevice> = ArrayList()
    private var m_bluetoothAdapter: BluetoothAdapter? = null
    val REQUEST_ENABLE_BLUETOOTH = 1
    private var bluetoothViewModel: BluetoothViewModel = BluetoothViewModel()
    private lateinit var bluetoothOnItemClickListener: BluetoothOnItemClickListener


    private val mReceiver = object : BroadcastReceiver() {
        override fun onReceive(context: Context, intent: Intent) {
            val action = intent.action
            if (BluetoothDevice.ACTION_FOUND == action) {
                // A Bluetooth device was found
                // Getting device information from the intent
                val device =
                    intent.getParcelableExtra<BluetoothDevice>(BluetoothDevice.EXTRA_DEVICE)
                if (device != null) {
                    devices_list.add(device)
                    Log.e("DEVICE", "${device.name}")

                }
            }
        }
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        BluetoothUtils.grantPermissions(this)
        binding = FragmentBluetoothBinding.inflate(layoutInflater)
        setContentView(binding.root)


        m_bluetoothAdapter = BluetoothAdapter.getDefaultAdapter()
        supportActionBar?.setDisplayHomeAsUpEnabled(true)
        supportActionBar?.title = "Bluetooth"

        if (!m_bluetoothAdapter!!.isEnabled) {
            val enableBluetoothIntent = Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE)
            startActivityForResult(enableBluetoothIntent, REQUEST_ENABLE_BLUETOOTH)
            val discoverableIntent: Intent =
                Intent(BluetoothAdapter.ACTION_REQUEST_DISCOVERABLE).apply {
                    putExtra(BluetoothAdapter.EXTRA_DISCOVERABLE_DURATION, 300)
                }
            startActivity(discoverableIntent)
        } else {
            discoverDevices()
        }

        binding.toggleBluetooth.setOnCheckedChangeListener { _, state ->
            bluetoothViewModel.changeBluetoothState(true)

        }


        manager = LinearLayoutManager(this)
        binding.recyclerBluetooth.adapter = RecyclerBluetoothAdapter(devices_list, this)
        binding.recyclerBluetooth.layoutManager = manager


    }


    private fun discoverDevices() {
        if (m_bluetoothAdapter!!.isDiscovering) {
            // Bluetooth is already in mode discovery mode, we cancel to restart it again
            m_bluetoothAdapter!!.cancelDiscovery()
        }
        val bool = m_bluetoothAdapter?.startDiscovery()
        Log.i("", bool.toString())
        val filter = IntentFilter(BluetoothDevice.ACTION_FOUND)
        registerReceiver(mReceiver, filter)

    }


    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        if (requestCode == REQUEST_ENABLE_BLUETOOTH) {
            if (resultCode == Activity.RESULT_OK) {

                if (m_bluetoothAdapter!!.isEnabled) {
                    Toast.makeText(this, "Bluetooth enabled", Toast.LENGTH_SHORT).show()
                } else {
                    Toast.makeText(this, "Bluetooth disabled", Toast.LENGTH_SHORT).show()
                }
            } else if (resultCode == Activity.RESULT_CANCELED) {
                Toast.makeText(this, "Bluetooth enabling has been canceled", Toast.LENGTH_SHORT)
                    .show()
            }
        }
    }

My item: class BluetoothDeviceItem(val address: String?, var name: String?, val device: BluetoothDevice?, var selected: Boolean)

my adapter:

class RecyclerBluetoothAdapter(private val devices : ArrayList<BluetoothDevice>, var clickListener: BluetoothOnItemClickListener): RecyclerView.Adapter<RecyclerBluetoothAdapter.ItemViewHolder>(){

    inner class ItemViewHolder(val binding: ItemDeviceBinding) : RecyclerView.ViewHolder(binding.root){
        fun bind(device : BluetoothDevice,action: BluetoothOnItemClickListener){
            binding.tvName.text = device.name
            Log.e("RecyclerView", device.name.toString())
            itemView.setOnClickListener {
                binding.item?.selected= true
                notifyItemChanged(adapterPosition)

            }
        }
    }


    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ItemViewHolder {
        val inflater = LayoutInflater.from(parent.context)
        val adapterlayout = ItemDeviceBinding.inflate(inflater,parent,false)
        return ItemViewHolder(adapterlayout)
    }

    override fun onBindViewHolder(holder: ItemViewHolder, position: Int) {
        holder.bind(devices[position],clickListener)
        holder.binding.executePendingBindings()
    }

    override fun getItemCount(): Int {
        return devices.size
    }
}
interface BluetoothOnItemClickListener{
    //    fun OnClickListener(item : DataBluetooth, position: Int

then my layouts

<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools">
    <data>

        <variable name="item" type="com.example.bbuhf_lecture.ui.adapters.BluetoothDeviceItem"/>

    </data>
    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:foreground="?attr/selectableItemBackgroundBorderless"
        android:clickable="true"
        android:focusable="true">

        <TextView
            android:id="@+id/tv_name"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:foreground="?attr/selectableItemBackgroundBorderless"
            android:clickable="true"
            android:focusable="true"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintBottom_toBottomOf="parent"
            android:padding="10dp"
            android:textSize="@dimen/text_size_medium"
            android:background="@{item.selected ? @color/color_secondary : @android:color/transparent}"
            android:textColor="@{item.selected ? @android:color/white : @android:color/black}"
            android:text="@{item.name}"
            tools:text="TP200X-TP203079"
            />

        <View
            android:id="@+id/separator"
            android:layout_width="match_parent"
            android:layout_height="1dp"
            android:layout_marginBottom="@dimen/dimen_size_small"
            android:alpha="0.15"
            android:background="@color/gray"
            app:layout_constraintTop_toBottomOf="@+id/tv_name"
            />

    </androidx.constraintlayout.widget.ConstraintLayout>

</layout>```



Thank you 

Answer 1

Inside the BroadcastReceiver() try this:

After updating your list:

if (device != null) {
    devices_list.add(device)
    Log.e("DEVICE", "${device.name}")

    if (binding != null) {
        binding.recyclerBluetooth.adapter?.notifyDataSetChanged()
    }
}