要在Android后台进行Wifi扫描并在前台服务中使用这些扫描结果，可以使用以下步骤和代码示例：

1. 在AndroidManifest.xml文件中添加必要的权限：

2. 创建一个WifiScanner类，用于在后台进行Wifi扫描：

import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.net.wifi.ScanResult;
import android.net.wifi.WifiManager;

import java.util.List;

public class WifiScanner {
    private WifiManager wifiManager;
    private Context context;
    private WifiScanReceiver wifiScanReceiver;

    public WifiScanner(Context context) {
        this.context = context;
        wifiManager = (WifiManager) context.getApplicationContext().getSystemService(Context.WIFI_SERVICE);
    }

    public void startScan() {
        wifiScanReceiver = new WifiScanReceiver();
        context.registerReceiver(wifiScanReceiver, new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));
        wifiManager.startScan();
    }

    public void stopScan() {
        context.unregisterReceiver(wifiScanReceiver);
    }

    public class WifiScanReceiver extends BroadcastReceiver {
        @Override
        public void onReceive(Context context, Intent intent) {
            List scanResults = wifiManager.getScanResults();
            // 在这里处理Wifi扫描结果，可以发送给前台服务
        }
    }
}

3. 创建一个前台服务，在其中调用WifiScanner类来进行Wifi扫描：

import android.app.Notification;
import android.app.NotificationChannel;
import android.app.NotificationManager;
import android.app.Service;
import android.content.Intent;
import android.os.Build;
import android.os.IBinder;

import androidx.annotation.Nullable;
import androidx.core.app.NotificationCompat;

public class MyForegroundService extends Service {
    private static final int NOTIFICATION_ID = 1;
    private static final String CHANNEL_ID = "ForegroundServiceChannel";

    private WifiScanner wifiScanner;

    @Override
    public void onCreate() {
        super.onCreate();
        wifiScanner = new WifiScanner(this);
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        createNotificationChannel();
        startForeground(NOTIFICATION_ID, createNotification());

        wifiScanner.startScan();

        return START_STICKY;
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        wifiScanner.stopScan();
    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    private void createNotificationChannel() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationChannel channel = new NotificationChannel(CHANNEL_ID, "Foreground Service Channel",
                    NotificationManager.IMPORTANCE_DEFAULT);
            NotificationManager manager = getSystemService(NotificationManager.class);
            manager.createNotificationChannel(channel);
        }
    }

    private Notification createNotification() {
        NotificationCompat.Builder builder = new NotificationCompat.Builder(this, CHANNEL_ID)
                .setContentTitle("Foreground Service")
                .setContentText("Scanning Wifi...")
                .setSmallIcon(R.drawable.ic_notification);

        return builder.build();
    }
}

4. 在MainActivity中启动前台服务：

import android.content.Intent;
import android.os.Bundle;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        startService(new Intent(this, MyForegroundService.class));
    }
}

这样，你就可以在Android后台进行Wifi扫描，并在前台服务中处理和使用这些扫描结果。记得在AndroidManifest.xml中声明相关权限和服务。