android - LocationClient getLastLocation()返回null

就像以前有人遇到的问题
我测试了nexus s(使用Google Play服务的4.0.4)和avd(使用Google API的4.2.2)，在两种情况下locationclient的getLastLocation()始终返回null。

public class MainActivity extends Activity implements LocationListener,
        GooglePlayServicesClient.ConnectionCallbacks,
        GooglePlayServicesClient.OnConnectionFailedListener {

    private LocationClient mLocationClient;
    private LocationRequest mLocationRequest;
    boolean mUpdatesRequested = false;
    boolean mConnected = false;
    SharedPreferences mPrefs;
    SharedPreferences.Editor mEditor;
    private TextView mText;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mText = (TextView) findViewById(R.id.text);
        mLocationRequest = LocationRequest.create();
        mLocationRequest
                .setInterval(LocationUtils.UPDATE_INTERVAL_IN_MILLISECONDS);
    mLocationRequest.setPriority(LocationRequest.PRIORITY_HIGH_ACCURACY);
        mLocationRequest
.setFastestInterval(LocationUtils.FAST_INTERVAL_CEILING_IN_MILLISECONDS);
        mUpdatesRequested = false;
        mPrefs = getSharedPreferences(LocationUtils.SHARED_PREFERENCES,
                Context.MODE_PRIVATE);
        mEditor = mPrefs.edit();
        mLocationClient = new LocationClient(this, this, this);
    }
    @Override
    public void onStart() {
        super.onStart();
        /*
         * Connect the client. Don't re-start any requests here; instead, wait
         * for onResume()
         */
        mLocationClient.connect();
    }

    @Override
    protected void onResume() {
        super.onResume();
        // If the app already has a setting for getting location updates, get it
        if (mPrefs.contains(LocationUtils.KEY_UPDATES_REQUESTED)) {
            mUpdatesRequested = mPrefs.getBoolean(
                    LocationUtils.KEY_UPDATES_REQUESTED, false);
            // Otherwise, turn off location updates until requested
        } else {
            mEditor.putBoolean(LocationUtils.KEY_UPDATES_REQUESTED, false);
            mEditor.commit();
        }
    }
    @Override
    public void onStop() {
        // If the client is connected
        if (mLocationClient.isConnected()) {
            stopPeriodicUpdates();
        }
        // After disconnect() is called, the client is considered "dead".
        mLocationClient.disconnect();
        super.onStop();
    }

    @Override
    public void onPause() {
        // Save the current setting for updates
        mEditor.putBoolean(LocationUtils.KEY_UPDATES_REQUESTED,
                mUpdatesRequested);
        mEditor.commit();
        super.onPause();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }
    public void getLocation(View v) {
        // If Google Play Services is available
        if (isGooglePlayServicesAvailable()) {
            if (!mConnected)
                mText.setText("location client is not connected to service yet");
            else {
                // Get the current location
                Location currentLocation = mLocationClient.getLastLocation();
                // Display the current location in the UI
                mText.setText(LocationUtils.getLocationString(currentLocation));
            }
        }
    }

    private boolean isGooglePlayServicesAvailable() {

        // Check that Google Play services is available
        int resultCode = GooglePlayServicesUtil
                .isGooglePlayServicesAvailable(this);

        // If Google Play services is available
        if (ConnectionResult.SUCCESS == resultCode) {
            // In debug mode, log the status
            Log.d(LocationUtils.APPTAG, "google play service is available");

            // Continue
            return true;
            // Google Play services was not available for some reason
        } else {
            // Display an error dialog
            Dialog dialog = GooglePlayServicesUtil.getErrorDialog(resultCode,
                    this, 0);
            if (dialog != null) {
                Log.e(LocationUtils.APPTAG,
                        "google play service is unavailable");
            }
            return false;
        }
    }

    private void stopPeriodicUpdates() {
        mLocationClient.removeLocationUpdates(this);
        // mConnectionState.setText(R.string.location_updates_stopped);
    }

    @Override
    public void onConnectionFailed(ConnectionResult arg0) {
        mConnected = false;
        Log.d(LocationUtils.APPTAG, "connection failed");
    }

    @Override
    public void onConnected(Bundle arg0) {
        mConnected = true;
        Log.d(LocationUtils.APPTAG,
                "location client connected to the location server");
        LocationManager lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);
        lm.requestLocationUpdates(LocationManager.PASSIVE_PROVIDER, 0, 0,
                new android.location.LocationListener() {
                    @Override
                    public void onStatusChanged(String provider, int status,
                            Bundle extras) {}

                    @Override
                    public void onProviderEnabled(String provider) {}

                    @Override
                    public void onProviderDisabled(String provider) {}

                    @Override
                    public void onLocationChanged(final Location location) {
                    }
                });
        Log.d(LocationUtils.APPTAG, "done trying to get location");
    }

    @Override
    public void onDisconnected() {
        // TODO Auto-generated method stub
        mConnected = false;
        Log.d(LocationUtils.APPTAG,
                "location client disconnected from the location server");
    }

    @Override
    public void onLocationChanged(Location arg0) {}

}

其中大多数来自谷歌给出的例子。在上面的代码中，hava尝试了如下方法:

LocationRequest request = LocationRequest.create();
request.setNumUpdates(1);
mLocationClient.requestLocationUpdates(request, this);

和

LocationManager lm = (LocationManager) getSystemService(Context.LOCATION_SERVICE);

        lm.requestLocationUpdates(LocationManager.PASSIVE_PROVIDER, 0, 0,
                new android.location.LocationListener() {
                    @Override
                    public void onStatusChanged(String provider, int status,Bundle extras) {}

                    @Override
                    public void onProviderEnabled(String provider) {}

                    @Override
                    public void onProviderDisabled(String provider) {}

                    @Override
                    public void onLocationChanged(final Location location) {}
                });

在onConnected()之前调用getLastLocation()，但仍然没有运气。
错误在哪里，请先谢谢。

最佳答案

当前，Fused Location Provider仅在至少有一个客户端连接到后台时才保持后台位置。一旦第一个客户端连接，它将立即尝试获取位置。如果您的 Activity 是第一个连接的客户端，并且您立即在getLastLocation()中调用onConnected()，则可能没有足够的时间进入第一个位置。

关于android - LocationClient getLastLocation()返回null，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/16830047/