为什么我的纬度总是0？

Question

import android.app.Activity;
import android.app.AlertDialog;
import android.app.ProgressDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.location.Location;
import android.location.LocationManager;
import android.os.Bundle;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;

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


public class MainActivity extends Activity implements GoogleApiClient.ConnectionCallbacks, GoogleApiClient.OnConnectionFailedListener {

    private static final String TAG = MainActivity.class.getSimpleName();

    private final static int PLAY_SERVICES_RESOLUTION_REQUEST = 1000;

    private Location mLastLocation;

    // Google client to interact with Google API
    private GoogleApiClient mGoogleApiClient;

    // boolean flag to toggle periodic location updates
    private boolean mRequestingLocationUpdates = false;

    private LocationRequest mLocationRequest;

    // Location updates intervals in sec
    private static int UPDATE_INTERVAL = 10000; // 10 sec
    private static int FATEST_INTERVAL = 5000; // 5 sec
    private static int DISPLACEMENT = 10; // 10 meters

    // UI elements
    //private TextView lblLocation;
    //private Button btnShowLocation, btnStartLocationUpdates;
    public String stringLat;
    public double latitude;



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

            // Building the GoogleApi client
            buildGoogleApiClient();
            mLastLocation = LocationServices.FusedLocationApi
                    .getLastLocation(mGoogleApiClient);
        }

        if(mLastLocation != null){
            latitude = mLastLocation.getLatitude();
        }

        //Testing testing = new Testing();

        Log.d("ADebugTag", "Value: " + latitude);
        //Log.w("Longitude is: ", getCurrentLocation.lgt);
        //Log.d("TestingTestingTag", "Value: " + testing.getTestingNum());








    }

    protected void displayLocation() {

        mLastLocation = LocationServices.FusedLocationApi
                .getLastLocation(mGoogleApiClient);

        if (mLastLocation != null) {
            latitude = mLastLocation.getLatitude();
            double longitude = mLastLocation.getLongitude();

            //lblLocation.setText(latitude + ", " + longitude);
            stringLat = String.valueOf(latitude);

        } else {

            //lblLocation
            //.setText("(Couldn't get the location. Make sure location is enabled on the device)");
        }
    }

    /**
     * Creating google api client object
     * */
    protected synchronized void buildGoogleApiClient() {
        mGoogleApiClient = new GoogleApiClient.Builder(this)
                .addConnectionCallbacks(this)
                .addOnConnectionFailedListener(this)
                .addApi(LocationServices.API).build();
    }

    /**
     * Method to verify google play services on the device
     * */
    protected boolean checkPlayServices() {
        int resultCode = GooglePlayServicesUtil
                .isGooglePlayServicesAvailable(this);
        if (resultCode != ConnectionResult.SUCCESS) {
            if (GooglePlayServicesUtil.isUserRecoverableError(resultCode)) {
                GooglePlayServicesUtil.getErrorDialog(resultCode, this,
                        PLAY_SERVICES_RESOLUTION_REQUEST).show();
            } else {
                Toast.makeText(getApplicationContext(),
                        "This device is not supported.", Toast.LENGTH_LONG)
                        .show();
                finish();
            }
            return false;
        }
        return true;
    }

    @Override
    protected void onStart() {
        super.onStart();
        if (mGoogleApiClient != null) {
            mGoogleApiClient.connect();
        }
    }

    @Override
    protected void onResume() {
        super.onResume();

        checkPlayServices();
    }

    /**
     * Google api callback methods
     */
    @Override
    public void onConnectionFailed(ConnectionResult result) {
        Log.i(TAG, "Connection failed: ConnectionResult.getErrorCode() = "
                + result.getErrorCode());
    }

    @Override
    public void onConnected(Bundle arg0) {

        // Once connected with google api, get the location
        displayLocation();
    }

    @Override
    public void onConnectionSuspended(int arg0) {
        mGoogleApiClient.connect();
    }



}

我在真实设备上测试了它的位置服务。为什么我的纬度在logcat中总是显示为0？有什么问题？我想获得当前位置的纬度。

03-08 00：34：02.950 14159-14159 / com.example.user.stuff D / ADebugTag：Value：0.0

Answer 1

GPS会在 onConnected() 方法中获取您上一个已知位置的值，而您尝试在onCreate()方法中获取最后一个已知位置的值肯定会回归0。

在由Log.d("ADebugTag", "Value: " + latitude);方法调用的displayLocation()方法中写onConnected()。