android - 如何在 Android 中使用单独的类获取当前位置

Question

我需要使用不在 Activity 中的单独类来获取当前位置。这是我的代码，它不起作用。任何人都有解决此问题的想法。当我尝试获取位置详细信息时，此应用程序总是崩溃。

  package com.example.ishanfx.departmentapp.network;

import android.content.Context;
import android.location.Criteria;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;

import com.google.android.gms.common.ConnectionResult;
import com.google.android.gms.common.api.GoogleApiClient;
import com.google.android.gms.location.LocationRequest;
import com.google.android.gms.location.LocationServices;


public class LocationHandler implements LocationListener,GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener {
    private LocationManager locationManager;
    Location mLastLocation;
    LocationRequest mLocationRequest;
    private String latitude;
    private String longitude;
    Context context;
    private static GoogleApiClient mGoogleApiClient;

    public LocationHandler(Context context) {
        this.context = context;
        locationManager = (LocationManager) context
                .getSystemService(Context.LOCATION_SERVICE);
        buildGoogleApiClient();


    }
    protected synchronized void buildGoogleApiClient() {
        mGoogleApiClient = new GoogleApiClient.Builder(context)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API)
                .build();
        mGoogleApiClient.connect();

    }
    private void setMostRecentLocation(Location lastKnownLocation) {

    }

    public String getLatitude() {
        return latitude;
    }

    public String getLongitude() {
        return longitude;
    }


    @Override
    public void onLocationChanged(Location location) {
        double lon = (double) (location.getLongitude());
        double lat = (double) (location.getLatitude());

        latitude = lat + "";
        longitude = lon + "";

    }

    /*
     * (non-Javadoc)
     *
     * @see
     * android.location.LocationListener#onProviderDisabled(java.lang.String)
     */
    @Override
    public void onProviderDisabled(String arg0) {
        // TODO Auto-generated method stub

    }

    /*
     * (non-Javadoc)
     *
     * @see
     * android.location.LocationListener#onProviderEnabled(java.lang.String)
     */
    @Override
    public void onProviderEnabled(String arg0) {
        // TODO Auto-generated method stub

    }


    @Override
    public void onStatusChanged(String arg0, int arg1, Bundle arg2) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onConnected(Bundle bundle) {
        mLastLocation = LocationServices.FusedLocationApi.getLastLocation(
                mGoogleApiClient);
        if (mLastLocation != null) {
            latitude =String.valueOf(mLastLocation.getLatitude());
            longitude = String.valueOf(mLastLocation.getLongitude());
        }

    }

    @Override
    public void onConnectionSuspended(int i) {

    }

    @Override
    public void onConnectionFailed(ConnectionResult connectionResult) {

    }
}

这是 mainActivity。当我调用这个应用程序时会崩溃。

LocationHandler appLocationManager = new LocationHandler(HomeActivity.this);

                Toast.makeText(getApplicationContext(), appLocationManager.getLatitude().toString(), Toast.LENGTH_SHORT).show();
                Toast.makeText(getApplicationContext(), appLocationManager.getLongitude().toString(), Toast.LENGTH_SHORT).show();

这是日志

FATAL EXCEPTION: main
                                                                               java.lang.NullPointerException
                                                                                   at com.example.ishanfx.departmentapp.HomeActivity.onOptionsItemSelected(HomeActivity.java:172)
                                                                                   at android.app.Activity.onMenuItemSelected(Activity.java:2502)
                                                                                   at android.support.v4.app.FragmentActivity.onMenuItemSelected(FragmentActivity.java:361)
                                                                                   at android.support.v7.app.AppCompatActivity.onMenuItemSelected(AppCompatActivity.java:147)
                                                                                   at android.support.v7.view.WindowCallbackWrapper.onMenuItemSelected(WindowCallbackWrapper.java:100)
                                                                                   at android.support.v7.view.WindowCallbackWrapper.onMenuItemSelected(WindowCallbackWrapper.java:100)
                                                                                   at android.support.v7.app.ToolbarActionBar$2.onMenuItemClick(ToolbarActionBar.java:68)
                                                                                   at android.support.v7.widget.Toolbar$1.onMenuItemClick(Toolbar.java:172)
                                                                                   at android.support.v7.widget.ActionMenuView$MenuBuilderCallback.onMenuItemSelected(ActionMenuView.java:760)
                                                                                   at android.support.v7.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:811)
                                                                                   at android.support.v7.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:152)
                                                                                   at android.support.v7.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:958)
                                                                                   at android.support.v7.view.menu.MenuBuilder.performItemAction(MenuBuilder.java:948)
                                                                                   at android.support.v7.view.menu.MenuPopupHelper.onItemClick(MenuPopupHelper.java:191)
                                                                                   at android.widget.AdapterView.performItemClick(AdapterView.java:292)
                                                                                   at android.widget.AbsListView.performItemClick(AbsListView.java:1065)
                                                                                   at android.widget.AbsListView$PerformClick.run(AbsListView.java:2522)
                                                                                   at android.widget.AbsListView$1.run(AbsListView.java:3183)
                                                                                   at android.os.Handler.handleCallback(Handler.java:605)
                                                                                   at android.os.Handler.dispatchMessage(Handler.java:92)
                                                                                   at android.os.Looper.loop(Looper.java:137)
                                                                                   at android.app.ActivityThread.main(ActivityThread.java:4441)
                                                                                   at java.lang.reflect.Method.invokeNative(Native Method)
                                                                                   at java.lang.reflect.Method.invoke(Method.java:511)
                                                                                   at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
                                                                                   at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
                                                                                   at dalvik.system.NativeStart.main(Native Method)

Answer 1

我已经以干净的方式更新了上面的类。

public class LocationHandler implements LocationListener,
        GoogleApiClient.ConnectionCallbacks,
        GoogleApiClient.OnConnectionFailedListener {
    private Context mContext;
    private GoogleApiClient mGoogleApiClient;
    private LocationRequest mLocationRequest;
    private OnLocationUpdateListener onLocationUpdateListener;

    public LocationHandler(Context mContext) {
        this.mContext = mContext;
        buildGoogleApiClient();
        createLocationRequest();
    }

    protected synchronized void buildGoogleApiClient() {
        mGoogleApiClient = new GoogleApiClient.Builder(mContext)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API)
                .build();
        mGoogleApiClient.connect();
    }

    public void startLocationUpdates(Context mContext) {
        if (ActivityCompat.checkSelfPermission(mContext,
                Manifest.permission.ACCESS_FINE_LOCATION) != PackageManager.PERMISSION_GRANTED
                && ActivityCompat.checkSelfPermission(mContext,
                Manifest.permission.ACCESS_COARSE_LOCATION) != PackageManager.PERMISSION_GRANTED) {
            return;
        }
        LocationServices.FusedLocationApi.requestLocationUpdates(
                mGoogleApiClient, mLocationRequest, this);
    }

    private void stopLocationUpdate(Context mContext) {
        LocationServices.FusedLocationApi.removeLocationUpdates(
                mGoogleApiClient, this);
    }

    //other new Methods but not using right now..
    protected void createLocationRequest() {
        mLocationRequest = new LocationRequest();
        mLocationRequest.setInterval(10000);//set the interval in which you want to get locations
        mLocationRequest.setFastestInterval(5000);//if a location is available sooner you can get it (i.e. another app is using the location services)
        mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
    }

    @Override
    public void onConnected(@Nullable Bundle bundle) {
        startLocationUpdates(mContext);
    }

    @Override
    public void onConnectionSuspended(int i) {
    }

    @Override
    public void onConnectionFailed(@NonNull ConnectionResult connectionResult) {
    }

    @Override
    public void onLocationChanged(Location location) {
        if(mGoogleApiClient.isConnected() && onLocationUpdateListener != null){
            onLocationUpdateListener.onLocationChange(location);
        }
    }

    public void setOnLocationUpdateListener(OnLocationUpdateListener onLocationUpdateListener) {
        this.onLocationUpdateListener = onLocationUpdateListener;
    }
}

where OnLocationUpdateListener is

public interface OnLocationUpdateListener {
    void onLocationChange(Location location);
    void onError(EnumUtil.ErrorType errorType);
}