Android GetSupportFragmentManager始终返回null

我正在开发一个小型android应用程序，每当我调用

GoogleMap=（（SupportMapFragment）getSupportFragmentManager（）.findFragmentById（R.id.map））.getMap（）

，它总是返回null。 我正试图在带有API 17和Google Play的设备上运行此应用程序

地图活动：

public class MapActivity extends FragmentActivity implements LocationSource, LocationListener {

    private static final String TAG = "MapActivity";
    private String device = android.os.Build.MODEL;

    private static final String UPDATE_LOC_URL = "http://lab.uzlabina.cz/~vongrad/Tracker/update_loc.php";
    private static final String LOAD_LOCATIONS = "http://lab.uzlabina.cz/~vongrad/Tracker/load_locations.php";
    private static final int ADD_MAP_PIN = 1;

    private Controller controller;

    private LocationManager locationManager;
    private OnLocationChangedListener locListener;


    private GoogleMap map;

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

        controller = Controller.getInstance(new User());
        controller.setUserName(device);

        locationManager = (LocationManager)getSystemService(LOCATION_SERVICE);

        if (locationManager != null){
            boolean isGPSEnabled = locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER);
            boolean isNetworkEnabled = locationManager.isProviderEnabled(LocationManager.NETWORK_PROVIDER);
            Log.d(TAG, "GPS " + isGPSEnabled + "Net " + isNetworkEnabled);

            if (isGPSEnabled){
                locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 50L, 1F, this);
            }
            else if (isNetworkEnabled){
                locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 500L, 10F, this);
            }
            else{
                Toast.makeText(this, "GPS is disabled", Toast.LENGTH_LONG);
            }
        }
        else
        {
            Toast.makeText(this, "Something went wrrong", Toast.LENGTH_LONG);
        }
        setUpMapIfNeeded(); 




    }
    public void onResume(){
        //updateLocation.start();
        super.onResume();
        //setUpMapIfNeeded();

        if (locationManager != null){
            map.setMyLocationEnabled(true);
        }
    }

    public void onPause(){
        //loadFriendsLocations.stop();
        if (locationManager != null){
            locationManager.removeUpdates(this);
        }
        super.onPause();
    }


    private void setUpMapIfNeeded() {
        if (map == null){

            map = ((SupportMapFragment)getSupportFragmentManager().findFragmentById(R.id.map)).getMap();
            map.setLocationSource(this);

            if (map != null){
                setUpMap();
            }
        }
    }


    private void setUpMap() {
        map.setMyLocationEnabled(true); 
        loadFriendsLocations.start();
    }

布局：

    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MapActivity" >

    <TextView
        android:id="@+id/header"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

    <fragment
        android:id="@+id/map"
        android:name="com.google.android.gms.maps.SupportMapFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        />


</RelativeLayout>

如果有任何建议，我将不胜感激。

---

提前谢谢

尝试提前几行调用此setupMapiFneedd（）。。在初始化locationmanager之前

setContentView(R.layout.activity_main);

        controller = Controller.getInstance(new User());
        controller.setUserName(device);

 setUpMapIfNeeded(); 

---

我使用了getChildFragmentManager（）而不是getSupportFragmentManager（），它起了作用

你能发布声明检查你的设备位置服务吗。。两个选项都应标记为勾号。1）使用无线网络和2）定位，Google做到了，一切都打开了…问题可能是Google Play服务过时了吗？Google Play服务可用吗？你在其他设备上检查了你的应用程序吗..你没有看到崩溃日志吗，崩溃发生在那里。显示导入文件。你做了。。公共类MapActivity扩展FragmentActivity实现LocationSource，LocationListener{我认为您可能导入了错误的库文件..请显示。

   10-05 19:40:13.284: E/AndroidRuntime(2697): FATAL EXCEPTION: main
10-05 19:40:13.284: E/AndroidRuntime(2697): java.lang.RuntimeException: Unable to start activity ComponentInfo{cz.vongrad.locator/cz.vongrad.locator.MapActivity}: java.lang.NullPointerException
10-05 19:40:13.284: E/AndroidRuntime(2697):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
10-05 19:40:13.284: E/AndroidRuntime(2697):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
10-05 19:40:13.284: E/AndroidRuntime(2697):     at android.app.ActivityThread.access$600(ActivityThread.java:141)
10-05 19:40:13.284: E/AndroidRuntime(2697):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
10-05 19:40:13.284: E/AndroidRuntime(2697):     at android.os.Handler.dispatchMessage(Handler.java:99)
10-05 19:40:13.284: E/AndroidRuntime(2697):     at android.os.Looper.loop(Looper.java:137)
10-05 19:40:13.284: E/AndroidRuntime(2697):     at android.app.ActivityThread.main(ActivityThread.java:5041)
10-05 19:40:13.284: E/AndroidRuntime(2697):     at java.lang.reflect.Method.invokeNative(Native Method)
10-05 19:40:13.284: E/AndroidRuntime(2697):     at java.lang.reflect.Method.invoke(Method.java:511)
10-05 19:40:13.284: E/AndroidRuntime(2697):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
10-05 19:40:13.284: E/AndroidRuntime(2697):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
10-05 19:40:13.284: E/AndroidRuntime(2697):     at dalvik.system.NativeStart.main(Native Method)
10-05 19:40:13.284: E/AndroidRuntime(2697): Caused by: java.lang.NullPointerException
10-05 19:40:13.284: E/AndroidRuntime(2697):     at cz.vongrad.locator.MapActivity.setUpMapIfNeeded(MapActivity.java:115)
10-05 19:40:13.284: E/AndroidRuntime(2697):     at cz.vongrad.locator.MapActivity.onCreate(MapActivity.java:86)
10-05 19:40:13.284: E/AndroidRuntime(2697):     at android.app.Activity.performCreate(Activity.java:5104)
10-05 19:40:13.284: E/AndroidRuntime(2697):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
10-05 19:40:13.284: E/AndroidRuntime(2697):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
10-05 19:40:13.284: E/AndroidRuntime(2697):     ... 11 more

setContentView(R.layout.activity_main);

        controller = Controller.getInstance(new User());
        controller.setUserName(device);

 setUpMapIfNeeded();