LocationClient.getLastKnownLocation() is null

I gets the following error compilation:

AndroidRuntime: FATAL EXCEPTION: main java.lang.RuntimeException: Unable to start activity ComponentInfo{fsy.wydra/fsy.wydra.MainActivity}: java.lang.NullPointerException at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2295) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2349) at android.app.ActivityThread.access$700(ActivityThread.java:159) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1316) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:176) at android.app.ActivityThread.main(ActivityThread.java:5419) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:525) at com.android.inteal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1209) at com.android.inteal.os.ZygoteInit.main(ZygoteInit.java:1025) at dalvik.system.NativeStart.main(Native Method) Caused by: java.lang.NullPointerException at fsy.wydra.MainActivity.onCreate(MainActivity.java:57) at android.app.Activity.performCreate(Activity.java:5372) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2257) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2349) at android.app.ActivityThread.access$700(ActivityThread.java:159) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1316) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:176) at android.app.ActivityThread.main(ActivityThread.java:5419) at java.lang.reflect.Method.invokeNative(Native Method) at java.lang.reflect.Method.invoke(Method.java:525)

and this is my MainActivity:

public class MainActivity extends Activity {

private MapView mapView;

private BaiduMap mBaiduMap;

public LocationClient mLocationClient = null;
public BDLocationListener myListener = new MyLocationListener();





@Override
protected void onCreate(Bundle savedInstanceState) {

    super.onCreate(savedInstanceState);
    SDKInitializer.initialize(getApplicationContext());

    setContentView(R.layout.activity_main);
    mapView = (MapView) findViewById(R.id.bmapView);

    mBaiduMap = mapView.getMap();
    //普通地图
    mBaiduMap.setMapType(BaiduMap.MAP_TYPE_NORMAL);

    //开启交通图
    mBaiduMap.setTrafficEnabled(false);
    //开启热力图
    mBaiduMap.setBaiduHeatMapEnabled(false);

    mLocationClient = new LocationClient(getApplicationContext());     //声明LocationClient类
    mLocationClient.registerLocationListener(myListener);    //注册监听函数
    initLocation();
    mLocationClient.start();


    BDLocation location = mLocationClient.getLastKnownLocation();
    Double x = location.getLatitude();
    Double y = location.getLongitude();




    MapStatus.Builder builder = new MapStatus.Builder();
    builder.target(new LatLng(x,y));
    mBaiduMap.setMapStatus(MapStatusUpdateFactory.newMapStatus(builder.build()));
    mBaiduMap.setMapStatus(MapStatusUpdateFactory.zoomTo(15));














}



@Override
protected void onDestroy() {
    super.onDestroy();
    mapView.onDestroy();
}

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

}

@Override
protected void onPause() {
    super.onPause();
    mapView.onPause();
}
private void initLocation(){
    LocationClientOption option = new LocationClientOption();
    option.setLocationMode(LocationMode.Hight_Accuracy
    );//可选，默认高精度，设置定位模式，高精度，低功耗，仅设备
    option.setCoorType("bd09ll");//可选，默认gcj02，设置返回的定位结果坐标系
    int span=1000;
    option.setScanSpan(span);//可选，默认0，即仅定位一次，设置发起定位请求的间隔需要大于等于1000ms才是有效的
    option.setIsNeedAddress(false);//可选，设置是否需要地址信息，默认不需要
    option.setOpenGps(false);//可选，默认false,设置是否使用gps
    option.setLocationNotify(false);//可选，默认false，设置是否当gps有效时按照1S1次频率输出GPS结果
    option.setIsNeedLocationDescribe(false);//可选，默认false，设置是否需要位置语义化结果，可以在BDLocation.getLocationDescribe里得到，结果类似于“在北京天安门附近”
    option.setIsNeedLocationPoiList(false);//可选，默认false，设置是否需要POI结果，可以在BDLocation.getPoiList里得到
    option.setIgnoreKillProcess(false);//可选，默认true，定位SDK内部是一个SERVICE，并放到了独立进程，设置是否在stop的时候杀死这个进程，默认不杀死
    option.SetIgnoreCacheException(false);//可选，默认false，设置是否收集CRASH信息，默认收集
    option.setEnableSimulateGps(false);//可选，默认false，设置是否需要过滤gps仿真结果，默认需要
    mLocationClient.setLocOption(option);
}



}

in the error i find LocationClient.getLastKnownLocation() is null,but i don't know how to fix it.