尝试调用虚拟方法'double android.location.Location.getLatitude（）'

Question

Been坚持使用了很长时间。不知道要输入哪一行代码，以免出现空指针异常。当我按下Get Uber按钮时，该应用程序不会崩溃，只是没有执行任何操作，黑屏，然后再次显示地图页面。如何做到这一点，以便在我按下按钮时能获得客户的取货地点并更改按钮的文字？

        //requesting a driver
        mRequest.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String userId = FirebaseAuth.getInstance().getCurrentUser().getUid();

                //send request and pinpoint exact location from where customer
                //will be picked up from
                DatabaseReference ref = FirebaseDatabase.getInstance().getReference("customerRequest");
                GeoFire geoFire = new GeoFire(ref);


                geoFire.setLocation(userId, new GeoLocation(mLastLocation.getLatitude(), mLastLocation.getLongitude()));





                //THIS STILL ISN'T BLOODY WORKING RETRIEVING DRIVERS LOCATION WHEN BUTTON IS CALLED



                //create marker for customers pickup spot
                mPickupLocationLatLng = new LatLng(mLastLocation.getLatitude(), mLastLocation.getLongitude());
                mMap.addMarker(new MarkerOptions().position(mPickupLocationLatLng).title("Pickup here"));

                //change text of request button when it is pressed to request driver
                mRequest.setText("Getting your driver...");
            }

        });
    }

线路原因

geoFire.setLocation（userId，new GeoLocation（mLastLocation.getLatitude（），mLastLocation.getLongitude（）））;

LOGCAT


E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.e.friendrides, PID: 19739
    java.lang.NullPointerException: Attempt to invoke virtual method 'double android.location.Location.getLatitude()' on a null object reference
        at com.e.friendrides.CoPilotMapActivity$2.onClick(CoPilotMapActivity.java:156)
        at android.view.View.performClick(View.java:6663)
        at android.view.View.performClickInternal(View.java:6635)
        at android.view.View.access$3100(View.java:794)
        at android.view.View$PerformClick.run(View.java:26199)
        at android.os.Handler.handleCallback(Handler.java:907)
        at android.os.Handler.dispatchMessage(Handler.java:105)
        at android.os.Looper.loop(Looper.java:216)
        at android.app.ActivityThread.main(ActivityThread.java:7625)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:524)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:987)