Question

我正在尝试在customDialog中的文本视图中获取位置管理器，如下所示：

但是给了我java空指针异常

当我打开Dialog并让GPS正常工作时，它运行正常，但是当关闭Dialog和GPS时，它会获得NPE的位置。

注意：我已经为您编辑了代码

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_tjamo3_last_date);

        locationManager = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, this);

        addNewPoint.setOnClickListener(new OnClickListener() {

                    @Override
                    public void onClick(View v) {

                        final Dialog dialog = new Dialog(Tjamo3LastDate.this);

                        dialog.setContentView(R.layout.custom_dialog);
                        dialog.setTitle("اضافة نقطة فحص جديدة");

                        Button save =(Button)dialog.findViewById(R.id.save);
                        if (locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)){
                            txtLat = (TextView) dialog.findViewById(R.id.textView1);
                            txtLag = (TextView) dialog.findViewById(R.id.textView2);
                            txtLat.setText("0.0");
                            txtLag.setText("0.0");
                        }
                        dialog.show();
                        save.setOnClickListener(new OnClickListener() {

                            @Override
                            public void onClick(View v) {
                                EditText editText=(EditText)dialog.findViewById(R.id.editText);
                                txtLat = (TextView) dialog.findViewById(R.id.textView1);
                                txtLag = (TextView) dialog.findViewById(R.id.textView2);
                                txtLat.setText(String.valueOf(mm));
                                txtLag.setText(String.valueOf(hh));

    });

    }

    @Override
    public void onLocationChanged(Location location) {
        hh = location.getLatitude();
        mm = location.getLongitude();
    }

Answer 1

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;
}

}

使用此服务获取最新位置。在您的应用启动时启动此服务

static GPSTracker gps; // set as your class variable to access anywhere from app
gps = new GPSTracker(getApplicationContext());

之后你可以使用

txtLat.setText(MainActivity.gps.getLatitude().toString());

与Dialog中的经度相同。

如果对您有帮助，请在此答案上标记。

Answer 2

根据我们的聊天：

保留对txtLat和txtLang的引用，并在对话框中输入

if(location!=null){ 
   txtLat.setText("" + location.getLatitude()); 
   txtLag.setText("" + location.getLongitude()); 
}

然后用此

替换onLocationChanged

@Override 
public void onLocationChanged(Location loc) { 
   location = loc; 
   if(txtLat !=null && txtLag!=null){ 
   txtLat.setText("" + location.getLatitude()); 
   txtLag.setText("" + location.getLongitude()); 
}

在自定义对话框中获取GPS位置

2 个答案: