locationservices . fusedlocationap . getlastlocation (mGoogleApiClient)不是第二次工作。

Now I have a strange problem. I have FusedLocationApi code.check it.I'm mentioning only related codes :

现在我有一个奇怪的问题。我有FusedLocationApi代码。检查它。我只提到相关的代码:

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

        GoogleApiClient mGoogleApiClient;
        Location mLastLocation;



        @Override
        protected void onStart() {
            mGoogleApiClient.connect();
            super.onStart();
        }


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


            if (mGoogleApiClient == null) {
                mGoogleApiClient = new GoogleApiClient.Builder(this)
                        .addConnectionCallbacks(this)
                        .addOnConnectionFailedListener(this)
                        .addApi(LocationServices.API)
                        .build();
            }




     mLastLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
                    double latitude = mLastLocation.getLatitude();
                    double longitude = mLastLocation.getLongitude();

}    
        @Override
        protected void onStop() {
            mGoogleApiClient.disconnect();
            super.onStop();

        }

            }

Now the problem is,this code is working perfectly for this activity.But when I'm writing the same code for other activity of the same project,mLastLocation is returning null and I am getting a java.lang.NullPointerException.

现在的问题是，这个代码非常适合这个活动。但是，当我为同一个项目的其他活动编写相同的代码时，mLastLocation返回null，我得到了一个java.lang.NullPointerException。

only difference for that class is that there I'm implementing OnMapReadyCallback also.Does it make any difference?

唯一不同的是，我在这里也实现了OnMapReadyCallback。这有什么区别吗?

I've read all the Q&A on this topic but not getting any help. What's the mistake from my side?

我已经阅读了关于这个主题的所有问答，但没有得到任何帮助。我身边的错误是什么?

1 个解决方案

#1

onCreate method called first then followed by onStart. So in your case if mGoogleApiClient is not connected on create it will return null.move this code from onCreate to onStart

onCreate方法首先调用，然后是onStart。在你的例子中如果mGoogleApiClient没有连接在create上它将返回null。将此代码从onCreate移动到onStart。

mLastLocation = LocationServices.FusedLocationApi.getLastLocation(mGoogleApiClient);
                double latitude = mLastLocation.getLatitude();
                double longitude = mLastLocation.getLongitude();

i will do something like this onStart

我会在开始的时候做一些类似的事情。

if(mGoogleApiClient.isConnected()){
        // check for last location
    }else{
        mGoogleApiClient.connect();
        //check for last location
    }

#1