Wie kann man andere Bluetooth-Geräte in Android Studio zur Erkennung scannen

Hallo zusammen,

Ich bin nicht ganz neu in der Android-Entwicklung, aber seit einigen Tagen versuche ich, eine Bluetooth-App zu entwickeln, die mehr Geräte wie in meinem Handy scannen kann, aber über meine App. Alle Tutorials, die ich bisher gefunden habe, funktionieren überhaupt nicht.
Ich poste bereits meinen Code aus dem Android Studio. Ich kann gekoppelte Geräte auflisten, der Scan jedoch nicht.

Wenn jemand hier gute Erfahrungen mit Bluetooth gemacht hat, bitte ich ihn um Hilfe. Ich danke Ihnen im Voraus.

`package cm.rulan.distcovid.ui.home;
import android.app.AlertDialog;
import android.app.ProgressDialog;
import android.bluetooth.BluetoothAdapter;
import android.bluetooth.BluetoothDevice;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.IntentFilter;
import android.content.pm.PackageManager;
import android.os.Bundle;
import android.os.Handler;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.lifecycle.Observer;
import androidx.lifecycle.ViewModelProvider;

import java.util.ArrayList;
import java.util.Set;

import cm.rulan.distcovid.R;

public class HomeFragment extends Fragment {

private static final String TAG = "Home";
private static final int REQUEST_ENABLE_BT = 1;
private static final int REQUEST_DISCOVERABLE_BT = 0;
Set<BluetoothDevice> pairedDevices;
private HomeViewModel homeViewModel;
private BluetoothAdapter bluethoothadapter;
private Button btnpairedDev, btnscan;
private ListView pairedDev;
private ArrayList list;
private ArrayList btdevnew;
private TextView tview;
private ProgressDialog mProgressDlg;
IntentFilter filter ;
BroadcastReceiver mReceiver ;

// Stops scanning after 10 seconds.
private static final long SCAN_PERIOD = 10000;

public View onCreateView(@NonNull LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    homeViewModel = new ViewModelProvider(this).get(HomeViewModel.class);
    View root = inflater.inflate(R.layout.fragment_home, container, false);
    homeViewModel.getText().observe(getViewLifecycleOwner(), new Observer<String>() {
        @Override
        public void onChanged(@Nullable String s) {
            //textView.setText(s);
        }
    });

    pairedDev = root.findViewById(R.id.listView);
    list = new ArrayList<>();
    btdevnew = new ArrayList<>();
    tview = root.findViewById(R.id.textView);
    btnpairedDev = root.findViewById(R.id.list);
    btnscan = root.findViewById(R.id.scanBT);
    mProgressDlg = new ProgressDialog(getContext());

    mReceiver = new BroadcastReceiver() {
        @Override
        public void onReceive(Context context, Intent intent) {
            String action = intent.getAction();
            switch (action) {
                case BluetoothAdapter.ACTION_DISCOVERY_STARTED:
                    mProgressDlg = new ProgressDialog(getContext());
                    mProgressDlg.setTitle(getContext().getString(R.string.searchForNewBluetoothDevices_titel));
                    mProgressDlg.setMessage(getContext().getString(R.string.searchForNewBluetoothDevices_msg));
                    mProgressDlg.setIndeterminate(true);
                    mProgressDlg.show();
                    break;
                case BluetoothAdapter.ACTION_DISCOVERY_FINISHED:
                    mProgressDlg.cancel();
                    //activity.setFoundLabel();
                    break;
                case BluetoothDevice.ACTION_FOUND:
                    BluetoothDevice device = intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE);
                    final ArrayAdapter mNewDevicesArrayAdapter = new ArrayAdapter<String>(getContext(), R.layout.device_adapter_view);

                    mNewDevicesArrayAdapter.add(device);
                    pairedDev.setAdapter(mNewDevicesArrayAdapter);
                    Log.d(TAG, "device" +device);

                    break;
            }
        }
    };

    bluethoothadapter = BluetoothAdapter.getDefaultAdapter();
    if (bluethoothadapter == null) {
        // Device doesn't support Bluetooth
        AlertDialog.Builder dialbuild = new AlertDialog.Builder(getContext());
        dialbuild.setTitle("Nicht Kompatibel")
                .setMessage("Your phone does not support Bluetooth")
                .setPositiveButton("Exit", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int which) {
                        System.exit(0);
                    }
                })
                .setIcon(android.R.drawable.ic_dialog_alert)
                .show();
    }

    if (!bluethoothadapter.isEnabled()) {
        Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE);
        startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT);
    } else {
        Toast.makeText(this.getContext(), "Bluetooth is already On", Toast.LENGTH_SHORT).show();
    }
    if (!getContext().getPackageManager().hasSystemFeature(PackageManager.FEATURE_BLUETOOTH_LE)) {
        Toast.makeText(getContext(), R.string.ble_not_supported, Toast.LENGTH_SHORT).show();
        getActivity().finish();
    }

    return root;
}

@Override
public void onPause() {
    if (bluethoothadapter != null) {
        if (bluethoothadapter.isDiscovering()) {
            bluethoothadapter.cancelDiscovery();
        }
    }
    super.onPause();
}
@Override
public void onActivityResult(int requestCode, int resultCode, Intent data)
{
    super.onActivityResult(requestCode, resultCode, data);

    if (requestCode == REQUEST_ENABLE_BT)
    {
        if (resultCode == 0)
        {
            // If the resultCode is 0, the user selected "No" when prompt to
            // allow the app to enable bluetooth.
            // You may want to display a dialog explaining what would happen if
            // the user doesn't enable bluetooth.
            Toast.makeText(getContext(), "The user decided to deny bluetooth access", Toast.LENGTH_LONG).show();
        }
        else
            Log.i(TAG, "User allowed bluetooth access!");
    }
}


@Override
public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    super.onViewCreated(view, savedInstanceState);
    //listPairedDevices();
    btnpairedDev.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            listPairedDevices();
        }
    });
    btnscan.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            ScanBluetoothDevices();
            //scanLeDevice(true);
        }
    });
}

public void listPairedDevices() {
    pairedDevices = bluethoothadapter.getBondedDevices();
    if (pairedDevices.size() > 0) {
        // Es gibt gekoppelte Geräte. Gib den name und adresse
        // von jedem gekoppelten Gerät.
        for (BluetoothDevice device : pairedDevices) {
            String deviceName = device.getName();  // device Name
            String deviceHardwareAddress = device.getAddress(); // MAC address
            list.add(deviceName + "\t" + "\t" + deviceHardwareAddress);
            Log.d("Device Name: ", "deviceName " + deviceName);
            Log.d("Device Hardwareaddr: ", "deviceHardwareAdresse " + deviceHardwareAddress);
            Toast.makeText(this.getContext(), "Showing Paired Devices", Toast.LENGTH_SHORT).show();
            final ArrayAdapter adapter = new ArrayAdapter(this.getContext(), android.R.layout.simple_list_item_1, list);
            pairedDev.setAdapter(adapter);

        }
    }
}

private void ScanBluetoothDevices() {
    // If we're already discovering, stop it
    if (bluethoothadapter.isDiscovering()) {
        bluethoothadapter.cancelDiscovery();
    } else {

        // Request discover from BluetoothAdapter
        // Create a BroadcastReceiver for ACTION_FOUND.
        //discovery starts, we can show progress dialog or perform other tasks
        filter = new IntentFilter();
        filter.addAction(BluetoothDevice.ACTION_FOUND);
        filter.addAction(BluetoothAdapter.ACTION_DISCOVERY_STARTED);
        filter.addAction(BluetoothAdapter.ACTION_DISCOVERY_FINISHED);
        this.getActivity().registerReceiver(mReceiver, filter);
        bluethoothadapter.startDiscovery();
    }
}

}

Nach der Ausführung des Programms haben wir durch Drücken der Taste folgende Ausgabe:

D / ViewRootImpl @ ef507c7 [MainActivity]: ViewPostIme pointer 0
D / ViewRootImpl @ ef507c7 [MainActivity]: ViewPostIme pointer 1
D / BluetoothAdapter: startDiscovery
W / libEGL: EGLNativeWindowType 0x78f6244250 disconnect failed
D / ViewRootImpl @ eb5ee08 [Toast]: dispatchDetachedFromWindow
D / InputTransport: Input channel destroyed: 'b8fe85f', fd = 73s

Es sagt Startentdeckung, aber es passiert einfach nichts danach

Danke für jegliche Hilfe

`

— geändert am 21.06.2020, 12:37:49