java - 在范围内无法访问类型 MainActivity 的封闭实例

Question

我有这段代码，我想从 GPSTracker 类中获取 GPS 纬度和经度但是报错显示

            gps=new GPSTracker(MainActivity.this);
            gps.getLatitude();

在范围内无法访问类型 MainActivity 的封闭实例

完整代码BootComplete.java

public class BootComplete extends BroadcastReceiver{

//private static final String PREFS_NAME = null;
public static final String PREFS_NAME = "MyPrefs";
String storedSimSerial;
String currentSimSerial;
String email;       //email address input by user, generate email and sent to this address
String mobileno;    //mobile number input by user, generate SMS and send to this address
String sms;         //generate sms to user
public GPSTracker gps;


@Override
public void onReceive(final Context context, Intent intent) {

    SharedPreferences prefs = context.getSharedPreferences(PREFS_NAME, 0);
    storedSimSerial = prefs.getString("storedSimSerial", "");
    mobileno = prefs.getString("trustedNum", "");
    email = prefs.getString("Email", "");
    TelephonyManager tm = (TelephonyManager) context.getSystemService(Service.TELEPHONY_SERVICE);
    currentSimSerial = tm.getSimSerialNumber();

    if(currentSimSerial != null){
        if(currentSimSerial.compareToIgnoreCase(storedSimSerial) == 0){

        }else{

            prefs = context.getApplicationContext().getSharedPreferences(PREFS_NAME, 0);
            SharedPreferences.Editor editor = prefs.edit();

            gps=new GPSTracker(MainActivity.this);
            gps.getLatitude();

            sms = "Alert!!!\nSim card changed.\nSim Serial Number:\n"+tm.getSimSerialNumber()+
                    "\nNetwork : "+ tm.getNetworkOperatorName()+"\nLatitude:\n" + gps.getLatitude();

            editor.putBoolean("SimChangeMail", true);
            editor.putString("subjectSimChange", "Your Sim card has changed.");
            editor.putString("bodySimChange","Sim Serial Number is :\n"+tm.getSimSerialNumber()+"\n" +
                    "This Sim serial number is unique and used to identify the owner.\nNetwork Operator is : "+
                    tm.getNetworkOperatorName()+
                    "\nThanks for using Mobile Security Application");
            editor.putString("SimChangeSms", sms);
            editor.commit();

            SmsManager sm = SmsManager.getDefault();
            String num = mobileno;
            sm.sendTextMessage(num, null, sms, null, null);
        }
    }else{

    }
}
}

GPSTracker.java

public class GPSTracker extends Service implements LocationListener {

    private final Context mContext;

    // flag for GPS status
    boolean isGPSEnabled = false;

    // flag for network status
    boolean isNetworkEnabled = false;

    // flag for GPS status
    boolean canGetLocation = false;

    Location location; // location
    double latitude; // latitude
    double longitude; // longitude

    // The minimum distance to change Updates in meters
    private static final long MIN_DISTANCE_CHANGE_FOR_UPDATES = 10; // 10 meters

    // The minimum time between updates in milliseconds
    private static final long MIN_TIME_BW_UPDATES = 1000 * 60 * 1; // 1 minute

    // Declaring a Location Manager
    protected LocationManager locationManager;

    public GPSTracker(Context context) {
        this.mContext = context;
        getLocation();
    }

    public Location getLocation() {
        try {
            locationManager = (LocationManager) mContext
                    .getSystemService(LOCATION_SERVICE);

            // getting GPS status
            isGPSEnabled = locationManager
                    .isProviderEnabled(LocationManager.GPS_PROVIDER);

            // getting network status
            isNetworkEnabled = locationManager
                    .isProviderEnabled(LocationManager.NETWORK_PROVIDER);

            if (!isGPSEnabled && !isNetworkEnabled) {
                // no network provider is enabled
            } else {
                this.canGetLocation = true;
                // First get location from Network Provider
                if (isNetworkEnabled) {
                    locationManager.requestLocationUpdates(
                            LocationManager.NETWORK_PROVIDER,
                            MIN_TIME_BW_UPDATES,
                            MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                    Log.d("Network", "Network");
                    if (locationManager != null) {
                        location = locationManager
                                .getLastKnownLocation(LocationManager.NETWORK_PROVIDER);
                        if (location != null) {
                            latitude = location.getLatitude();
                            longitude = location.getLongitude();
                        }
                    }
                }
                // if GPS Enabled get lat/long using GPS Services
                if (isGPSEnabled) {
                    if (location == null) {
                        locationManager.requestLocationUpdates(
                                LocationManager.GPS_PROVIDER,
                                MIN_TIME_BW_UPDATES,
                                MIN_DISTANCE_CHANGE_FOR_UPDATES, this);
                        Log.d("GPS Enabled", "GPS Enabled");
                        if (locationManager != null) {
                            location = locationManager
                                    .getLastKnownLocation(LocationManager.GPS_PROVIDER);
                            if (location != null) {
                                latitude = location.getLatitude();
                                longitude = location.getLongitude();
                            }
                        }
                    }
                }
            }

        } catch (Exception e) {
            e.printStackTrace();
        }

        return location;
    }

    /**
     * Stop using GPS listener
     * Calling this function will stop using GPS in your app
     * */
    public void stopUsingGPS(){
        if(locationManager != null){
            locationManager.removeUpdates(GPSTracker.this);
        }
    }

    /**
     * Function to get latitude
     * */
    public double getLatitude(){
        if(location != null){
            latitude = location.getLatitude();
        }

        // return latitude
        return latitude;
    }

    /**
     * Function to get longitude
     * */
    public double getLongitude(){
        if(location != null){
            longitude = location.getLongitude();
        }

        // return longitude
        return longitude;
    }

    /**
     * Function to check GPS/wifi enabled
     * @return boolean
     * */
    public boolean canGetLocation() {
        return this.canGetLocation;
    }

    /**
     * Function to show settings alert dialog
     * On pressing Settings button will lauch Settings Options
     * */
    public void showSettingsAlert(){
        AlertDialog.Builder alertDialog = new AlertDialog.Builder(mContext);

        // Setting Dialog Title
        alertDialog.setTitle("GPS is settings");

        // Setting Dialog Message
        alertDialog.setMessage("GPS is not enabled. Do you want to go to settings menu?");

        // On pressing Settings button
        alertDialog.setPositiveButton("Settings", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog,int which) {
                Intent intent = new Intent(Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                mContext.startActivity(intent);
            }
        });

        // on pressing cancel button
        alertDialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
            dialog.cancel();
            }
        });

        // Showing Alert Message
        alertDialog.show();
    }

    @Override
    public void onLocationChanged(Location location) {
    }

    @Override
    public void onProviderDisabled(String provider) {
    }

    @Override
    public void onProviderEnabled(String provider) {
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
    }

    @Override
    public IBinder onBind(Intent arg0) {
        return null;
    }

}

Answer 1

如果 BootComplete 是 MainActivity 中的嵌套类，则只能使用 MainActivity.this。

因为您的 GPSTracker 只需要一个上下文，您可以这样做

gps = new GPSTracker(context);