没有得到当前的纬度

Question

我正在开发应用程序，我想在单击按钮时获取纬度和经度。但它总是显示 0。我的代码如下。 AndroidGPSTrackingActivity.java

package com.example.gpstracking;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class AndroidGPSTrackingActivity extends Activity {

Button btnShowLocation;

// GPSTracker class
GPSTracker gps;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    btnShowLocation = (Button) findViewById(R.id.btnShowLocation);

    // show location button click event
    btnShowLocation.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {        
            // create class object
            gps = new GPSTracker(AndroidGPSTrackingActivity.this);

            // check if GPS enabled     
            if(gps.canGetLocation()){

                double latitude = gps.getLatitude();
                double longitude = gps.getLongitude();

                // \n is for new line
                Toast.makeText(getApplicationContext(), "Your Location    is    - \nLat: " + latitude + "\nLong: " + longitude, Toast.LENGTH_SHORT).show(); 
            }else{
                // can't get location
                // GPS or Network is not enabled
                // Ask user to enable GPS/network in settings
                gps.showSettingsAlert();
            }

        }
    });
}

 }

第二类如下。

GPSTracker.java

      package com.example.gpstracking;

      import android.app.AlertDialog;
      import android.app.Service;
      import android.content.Context;
      import android.content.DialogInterface;
      import android.content.Intent;
      import android.location.Location;
      import android.location.LocationListener;
      import android.location.LocationManager;
      import android.os.Bundle;
      import android.os.IBinder;
      import android.provider.Settings;
      import android.util.Log;
      import android.widget.Toast;

     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 = 37.422006; // latitude
double longitude = -122.084095; // 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) {
    Log.i("*******", "Inside constructor");
    this.mContext = context;
    getLocation();
}

public Location getLocation() {
    try {
        Log.i("*******", "Inside get Location");
        locationManager = (LocationManager) mContext
                .getSystemService(LOCATION_SERVICE);

        // getting GPS status
        isGPSEnabled = locationManager
                .isProviderEnabled(LocationManager.GPS_PROVIDER);
        Log.i("*******", ""+isGPSEnabled);
        // getting network status
        isNetworkEnabled = locationManager
                .isProviderEnabled(LocationManager.NETWORK_PROVIDER);
        Log.i("*******", ""+isNetworkEnabled);
        if (!isGPSEnabled && !isNetworkEnabled) {
            // no network provider is enabled
            Toast.makeText(getApplicationContext(), "GPS:"+isGPSEnabled+"NEtwork:"+isNetworkEnabled, Toast.LENGTH_LONG).show();
        } else {
            this.canGetLocation = true;
            if (isGPSEnabled) {
                Log.i("*********", "Inside isGPSEnabled");
                if (location == null) {
                    locationManager.requestLocationUpdates(
                            LocationManager.GPS_PROVIDER,
                            0,
                            0, this);
                    Log.d("GPS Enabled", "GPS Enabled");
                    if (locationManager != null) {
                        Log.i("*********", locationManager.toString());
                        location = locationManager
                                .getLastKnownLocation(LocationManager.GPS_PROVIDER);
                        if (location != null) {
                            Log.i("*********", location.toString());
                            latitude = location.getLatitude();
                            longitude = location.getLongitude();
                            Log.i("*********", "Lat:"+latitude+"Long:"+longitude);
                        }Log.i("*********", location.toString());
                    }
                }
            }
            if (isNetworkEnabled) {
                Log.i("*********", "Inside isNetworkEnabled");
                locationManager.requestLocationUpdates(
                        LocationManager.NETWORK_PROVIDER,
                        0,
                        0, 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

        }

    } 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) {
    Toast.makeText(getApplicationContext(), "Location Changed called", Toast.LENGTH_SHORT).show();
    latitude =location.getLatitude();
    longitude = location.getLongitude();
}

public void onProviderDisabled(String provider) {
}

public void onProviderEnabled(String provider) {
}


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

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

}

我还在清单中添加了以下权限。

<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/>

谁能告诉我哪里出错了。我试图通过网络提供商获得很长的时间，但它们差异很大。即使对于相同的位置，距离网络的纬度也不同。

提前谢谢你..

Answer 1

试试这个方法...

LocationManager locManager = (LocationManager)getSystemService(Context.LOCATION_SERVICE); 
                locManager.requestLocationUpdates(LocationManager.GPS_PROVIDER,1000L,500.0f, locationListener);
                Location location = locManager.getLastKnownLocation(LocationManager.GPS_PROVIDER);
                if(location != null)                                
                {
                    double latitude = location.getLatitude();
                    double longitude = location.getLongitude();



                }  

Answer 2

当您创建位置侦听器时，实际获取位置需要一段时间，您可能希望从 onClick 更改 gpsTracker 类的创建，或者至少保存您在第一次单击时创建的实例，直到您销毁它，也许获得位置后，因此您不会每次都创建它，从而导致创建另一个位置侦听器。

获取位置后，您可以使用处理程序将消息传递给您的活动。

您的 Handler 可能是这样的： 为您的活动创建一个公共处理程序

public Handler handler;

然后将其添加到您的 onCreate 方法中

handler = new Handler(new Handler.Callback() {

        @Override
        public boolean handleMessage(Message msg) {
            // TODO Auto-generated method stub
            if(msg.what == 0){
                //do the methods that require knowing your location you location
                return true;
            }
            return false;
        }
    });

还有你的GPSTracker 类，你把它添加到你的 onLocationChanged：

Message msg = new Message();
msg.what = 0;
((AndroidGPSTrackingActivity)mContext).handler.sendMessage(msg);

您可以阅读有关处理程序的信息here。

Answer 3

当您拨打LocationListener 时，大多数设备都无法快速获取 GPS。所以我所做的是我试图在 AsyncTask 中以latitude and longitude !=0 的条件获取它。如果这个条件成功执行，那么我们就得到了纬度和经度。之后你就可以随心所欲了。

这是异步任务中的代码

public class GPSLocation extends AsyncTask<Void, Void, Void>
    {  
        boolean running =true;
                @Override
                protected void onPreExecute()
                {  
                    super.onPreExecute(); 
                    progressDialog = new ProgressDialog(RoadMaintenanceActivity.this);
                    progressDialog.setOnCancelListener(new DialogInterface.OnCancelListener(){
                          public void onCancel(DialogInterface dialog) {
                              getgps.cancel(true);  
                          }
                    });
                    LocationManager mlocManager = (LocationManager)getSystemService(Context.LOCATION_SERVICE); 
                    LocationListener mlocListener = new MyLocationListener();  
                    mlocManager.requestLocationUpdates( LocationManager.GPS_PROVIDER, 0, 0, mlocListener);    
                    progressDialog.setCancelable(true);
                    progressDialog.setMessage("Getting GPS Location...");
                    progressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
                    progressDialog.setProgress(1);
                    progressDialog.show();

                } 

                @Override 
                protected void onProgressUpdate(Void... values) {
                    super.onProgressUpdate(values);
                    // Things to be done while execution of long running operation is in progress. For example updating ProgessDialog
                 }

                @Override 
                protected void onPostExecute(Void result)
                {  
                        progressDialog.cancel(); 
                }

                @Override
                protected Void doInBackground(Void... params) {  
                    boolean isDataSubmitted = false; 
                 while(!isDataSubmitted)
                        {   
                            if(longitude !=0 && latitude!=0) 
                            {
                                    //Do your operation here 
                                isDataSubmitted = true;
                            } 
                    }

                    return null;    
                } 
     } 

它应该可以工作。