Question

我正在开发一个应用获取用户的当前位置并在地图上显示它，以及屏幕上的纬度和经度，到目前为止一切正常，地图显示我当前的位置以及显示纬度和经度在屏幕上使用此代码

@Override
public void onLocationChanged(Location location) {

    TextView tvLocation = (TextView) findViewById(R.id.tv_location);

    // Getting latitude of the current location
    double latitude = location.getLatitude();

    // Getting longitude of the current location
    double longitude = location.getLongitude();

    // Creating a LatLng object for the current location
    LatLng latLng = new LatLng(latitude, longitude);

    // Showing the current location in Google Map
    googleMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));

    // Zoom in the Google Map
    googleMap.animateCamera(CameraUpdateFactory.zoomTo(15));

    // Setting latitude and longitude in the TextView tv_location
    tvLocation.setText("Latitude:" +  latitude  + ", Longitude:"+ longitude );

}

当我想在服务器上发送此纬度和经度时出现问题，它会抛出NUll指针异常

 01-04 23:27:38.759 29286-29286/io.xgear.geotag E/AndroidRuntime: FATAL
 EXCEPTION: main
  Process: io.xgear.geotag, PID: 29286
  java.lang.NullPointerException
      at io.xgear.geotag.MainActivity$GeoTagTask.<init>(MainActivity.java:234)
      at io.xgear.geotag.MainActivity$1.onClick(MainActivity.java:181)
      at android.view.View.performClick(View.java:4633)
      at android.view.View$PerformClick.run(View.java:19270)
      at android.os.Handler.handleCallback(Handler.java:733)
      at android.os.Handler.dispatchMessage(Handler.java:95)
      at android.os.Looper.loop(Looper.java:146)
      at android.app.ActivityThread.main(ActivityThread.java:5602)
      at java.lang.reflect.Method.invokeNative(Native Method)
      at java.lang.reflect.Method.invoke(Method.java:515)
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1283)
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1099)
      at dalvik.system.NativeStart.main(Native Method)

这是获取发送纬度和经度的代码

 public class GeoTagTask extends AsyncTask<Void, Void, Boolean> {
        private final String shopCode;
       Location location;
        private String lat = Double.toString(location.getLatitude());
        private String lng = Double.toString(location.getLongitude());


        private boolean isConnect;
        GeoTagTask(String shopId) {
            shopCode = shopId;
            isConnect = false;

        }

        @Override
        protected Boolean doInBackground(Void... params) {
            boolean res = false;
     try {
                ContentValues nameValuePairs = new ContentValues();
                nameValuePairs.put("Id", shopCode);
                nameValuePairs.put("lat", lat);
                nameValuePairs.put("lng", lng);
         //Toast.makeText(getApplicationContext(), "Your Location is - \nLat: " + lat + "\nLong: " + lng, Toast.LENGTH_LONG).show();
               Log.i("Latitude", lat+"");

                Post post = new Post(getApplicationContext());
                String result = "";
//                isConnect = post.isConnected();
  //              if(isConnect) {
                    result = post.doPost(nameValuePairs);
                    jsonObj = new JSONObject(result);
                    Log.i("Result", result+"");
                    if(jsonObj.getInt("success") == 1)
                        res = true;
    //            }

            } catch (JSONException e) {
                e.printStackTrace();
            }
            return res;
        }

这是完整的代码

package io.xgear.geotag;


import android.Manifest;
import android.app.Dialog;
import android.app.FragmentTransaction;
import android.content.pm.PackageManager;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.support.v4.app.ActivityCompat;
import android.support.v4.app.FragmentActivity;
import android.view.Menu;
import android.widget.TextView;
import android.support.v4.app.Fragment;

import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.GooglePlayServicesUtil;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.GoogleMapOptions;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.MarkerOptions;

import android.animation.Animator;
import android.animation.AnimatorListenerAdapter;
import android.annotation.TargetApi;
import android.content.ContentValues;
import android.os.AsyncTask;
import android.os.Build;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.InputType;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import org.json.JSONException;
import org.json.JSONObject;



import io.xgear.geotag.helper.Post;

public class MainActivity extends FragmentActivity implements LocationListener {
    GoogleMap googleMap;
    private GeoTagTask mAuthTask = null;
    GPSTracker gps;
    private JSONObject jsonObj;

    // UI references.
    private EditText txtShopCode;
    private EditText lblAddress;
    private View mProgressView;
    private View mGeoTagForm;
    private Button btnGeoTag;

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

        txtShopCode = (EditText) findViewById(R.id.txtShopCode);
        btnGeoTag = (Button) findViewById(R.id.btnGeoTag);
        mGeoTagForm = (View) findViewById(R.id.geoTagForm);
        mProgressView = findViewById(R.id.geoTagProgress);

        // Getting Google Play availability status
        int status = GooglePlayServicesUtil.isGooglePlayServicesAvailable(getBaseContext());

        // Showing status
        if (status != ConnectionResult.SUCCESS) { // Google Play Services are not available

            int requestCode = 10;
            Dialog dialog = GooglePlayServicesUtil.getErrorDialog(status, this, requestCode);
            dialog.show();

        } else { // Google Play Services are available

            // Getting reference to the SupportMapFragment of activity_main.xml
            SupportMapFragment fm = (SupportMapFragment) getSupportFragmentManager().findFragmentById(R.id.map);

            // Getting GoogleMap object from the fragment
            googleMap = fm.getMap();

            // Enabling MyLocation Layer of Google Map
            googleMap.setMyLocationEnabled(true);

            // Getting LocationManager object from System Service LOCATION_SERVICE
            LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);

            // Creating a criteria object to retrieve provider
            Criteria criteria = new Criteria();

            // Getting the name of the best provider
            String provider = locationManager.getBestProvider(criteria, true);

            // Getting Current Location
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED && ActivityCompat.checkSelfPermission(this, Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
                // TODO: Consider calling
                //    ActivityCompat#requestPermissions
                // here to request the missing permissions, and then overriding
                //   public void onRequestPermissionsResult(int requestCode, String[] permissions,
                //                                          int[] grantResults)
                // to handle the case where the user grants the permission. See the documentation
                // for ActivityCompat#requestPermissions for more details.
                return;
            }
            Location location = locationManager.getLastKnownLocation(provider);

            if(location!=null){
                onLocationChanged(location);
            }
            locationManager.requestLocationUpdates(provider, 20000, 0, this);
        }

        btnGeoTag.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View arg0) {
                String shopid = txtShopCode.getText().toString();
                boolean cancel = false;
                View focusView = null;

               //txtShopCode.setInputType(InputType.TYPE_CLASS_NUMBER);

                if (TextUtils.isEmpty(shopid)) {
                    txtShopCode.setError(getString(R.string.error_field_required));
                    focusView = txtShopCode;
                    cancel = true;

                }
                else {


                    showProgress(true);
                    mAuthTask = new GeoTagTask(shopid);
                    mAuthTask.execute((Void) null);
                }
            }

        });

    }

//


//    public void btnGeoTag_Click(View v){
//
//    }
    @TargetApi(Build.VERSION_CODES.HONEYCOMB_MR2)
    public void showProgress(final boolean show) {
        // On Honeycomb MR2 we have the ViewPropertyAnimator APIs, which allow
        // for very easy animations. If available, use these APIs to fade-in
        // the progress spinner.
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB_MR2) {
            int shortAnimTime = getResources().getInteger(android.R.integer.config_shortAnimTime);

            mGeoTagForm.setVisibility(show ? View.GONE : View.VISIBLE);
            mGeoTagForm.animate().setDuration(shortAnimTime).alpha(
                    show ? 0 : 1).setListener(new AnimatorListenerAdapter() {
                @Override
                public void onAnimationEnd(Animator animation) {
                    mGeoTagForm.setVisibility(show ? View.GONE : View.VISIBLE);
                }
            });

            mProgressView.setVisibility(show ? View.VISIBLE : View.GONE);
            mProgressView.animate().setDuration(shortAnimTime).alpha(
                    show ? 1 : 0).setListener(new AnimatorListenerAdapter() {
                @Override
                public void onAnimationEnd(Animator animation) {
                    mProgressView.setVisibility(show ? View.VISIBLE : View.GONE);
                }
            });
        } else {
            // The ViewPropertyAnimator APIs are not available, so simply show
            // and hide the relevant UI components.
            mProgressView.setVisibility(show ? View.VISIBLE : View.GONE);
            mGeoTagForm.setVisibility(show ? View.GONE : View.VISIBLE);
        }
    }

    public class GeoTagTask extends AsyncTask<Void, Void, Boolean> {
        private final String shopCode;
       Location location;
        private String lat = Double.toString(location.getLatitude());
        private String lng = Double.toString(location.getLongitude());


        private boolean isConnect;
        GeoTagTask(String shopId) {
            shopCode = shopId;
            isConnect = false;

        }

        @Override
        protected Boolean doInBackground(Void... params) {
            boolean res = false;
     try {
                ContentValues nameValuePairs = new ContentValues();
                nameValuePairs.put("Id", shopCode);
                nameValuePairs.put("lat", lat);
                nameValuePairs.put("lng", lng);
         //Toast.makeText(getApplicationContext(), "Your Location is - \nLat: " + lat + "\nLong: " + lng, Toast.LENGTH_LONG).show();
               Log.i("Latitude", lat+"");

                Post post = new Post(getApplicationContext());
                String result = "";
//                isConnect = post.isConnected();
  //              if(isConnect) {
                    result = post.doPost(nameValuePairs);
                    jsonObj = new JSONObject(result);
                    Log.i("Result", result+"");
                    if(jsonObj.getInt("success") == 1)
                        res = true;
    //            }

            } catch (JSONException e) {
                e.printStackTrace();
            }
            return res;
        }

        @Override
        protected void onPostExecute(final Boolean success) {
            mAuthTask = null;
            showProgress(false);

            if (success) {
//                Intent intent = new Intent(LoginActivity.this, MainActivity.class);
//                intent.putExtra("jsonObj", jsonObj.toString());
//                startActivity(intent);
                txtShopCode.getText().clear();
                txtShopCode.requestFocus();
                Toast.makeText(getBaseContext(), "Your shop is geo tagged ", Toast.LENGTH_LONG).show();

            } else {
//                if(isConnect){
//                    mPasswordView.setError(getString(R.string.error_incorrect_password));
//                    mPasswordView.requestFocus();

//                }
//                else
                    Toast.makeText(getBaseContext(), R.string.geoTagError, Toast.LENGTH_LONG).show();
            }
        }

        @Override
        protected void onCancelled() {
            mAuthTask = null;
            showProgress(false);
        }
    }


    @Override
    public void onLocationChanged(Location location) {

        TextView tvLocation = (TextView) findViewById(R.id.tv_location);

        // Getting latitude of the current location
        double latitude = location.getLatitude();

        // Getting longitude of the current location
        double longitude = location.getLongitude();

        // Creating a LatLng object for the current location
        LatLng latLng = new LatLng(latitude, longitude);

        // Showing the current location in Google Map
        googleMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));

        // Zoom in the Google Map
        googleMap.animateCamera(CameraUpdateFactory.zoomTo(15));

        // Setting latitude and longitude in the TextView tv_location
        tvLocation.setText("Latitude:" +  latitude  + ", Longitude:"+ longitude );

    }

    @Override
    public void onProviderDisabled(String provider) {
        // TODO Auto-generated method stub
    }

    @Override
    public void onProviderEnabled(String provider) {
        // TODO Auto-generated method stub
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
        // TODO Auto-generated method stub
    }

//    @Override
//    public boolean onCreateOptionsMenu(Menu menu) {
//        // Inflate the menu; this adds items to the action bar if it is present.
//        getMenuInflater().inflate(R.menu.activity_main, menu);
//        return true;
//    }
}

更新我在GeoTagTask中添加了这些行按钮正在运行应用程序没有崩溃但是我不确定它是否会在位置发生变化时起作用，因为

 if( location != null){
            onLocationChanged(location);
       }
     locationManager.requestLocationUpdates(provider, 20000, 0, this);

给了我错误。

我添加的行

LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);
        Criteria criteria = new Criteria();
        String provider = locationManager.getBestProvider(criteria, true);

        Location location = locationManager.getLastKnownLocation(provider);

Answer 1

内GeoTagTask位置对象是不同的，也没有被启动。

    Location location;
    private String lat = Double.toString(location.getLatitude());
    private String lng = Double.toString(location.getLongitude());

Answer 2

问题

问题出在GeoTagTask，

中

Location location;
private String lat = Double.toString(location.getLatitude());
private String lng = Double.toString(location.getLongitude());

您正在访问未初始化的变量。

解决方案

将onCreate位置设为全局变量，

public class MainActivity extends FragmentActivity implements LocationListener {
    Location location;
    void onCreate() {
        ....
        location = locationManager.getLastKnownLocation(provider);
        ....
    }
}

在GeoTagTask，

中使用全局变量

public class GeoTagTask extends AsyncTask<Void, Void, Boolean> {
        private String lat = Double.toString(location.getLatitude());
        private String lng = Double.toString(location.getLongitude());
        ...
}

纬度和经度为空

2 个答案:

问题

解决方案