SupportMapFragment getMap为空

Question

我的XML中有一个MapFragment：

    <fragment
    android:id="@+id/mapFrag"
    android:name="com.google.android.gms.maps.MapFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_below="@+id/map_topbar"
    class="com.google.android.gms.maps.MapFragment" />

在我的MapViewFragment里

     GoogleMap gmap;

在onCreate中，我执行以下操作：

FragmentManager myFragmentManager = getFragmentManager();
SupportMapFragment mf =(SupportMapFragment)myFragmentManager.findFragmentById(R.id.mapFrag);
gmap = mf.getMap();

但我得到了一个NullPointerException.

我已经搜索并尝试了很多这样的解决方案，但到目前为止都没有起到任何作用。

我遵循了不同的教程：

http://android-er.blogspot.dk/2013/01/create-mapfragment-and-googlemap-using.html fragment

在那里他们使用同样的技术。

日志：

03-04 13:40:49.468: E/AndroidRuntime(32388): FATAL EXCEPTION: main
03-04 13:40:49.468: E/AndroidRuntime(32388): java.lang.NullPointerException
03-04 13:40:49.468: E/AndroidRuntime(32388):    at dk.adaptmobile.koegeapp.MapViewFragment.onCreate(MapViewFragment.java:56)
03-04 13:40:49.468: E/AndroidRuntime(32388):    at android.support.v4.app.Fragment.performCreate(Fragment.java:1477)
03-04 13:40:49.468: E/AndroidRuntime(32388):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:893)
03-04 13:40:49.468: E/AndroidRuntime(32388):    at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
03-04 13:40:49.468: E/AndroidRuntime(32388):    at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
03-04 13:40:49.468: E/AndroidRuntime(32388):    at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1467)
03-04 13:40:49.468: E/AndroidRuntime(32388):    at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:440)
03-04 13:40:49.468: E/AndroidRuntime(32388):    at android.os.Handler.handleCallback(Handler.java:615)
03-04 13:40:49.468: E/AndroidRuntime(32388):    at android.os.Handler.dispatchMessage(Handler.java:92)
03-04 13:40:49.468: E/AndroidRuntime(32388):    at android.os.Looper.loop(Looper.java:137)
03-04 13:40:49.468: E/AndroidRuntime(32388):    at android.app.ActivityThread.main(ActivityThread.java:4921)
03-04 13:40:49.468: E/AndroidRuntime(32388):    at java.lang.reflect.Method.invokeNative(Native Method)
03-04 13:40:49.468: E/AndroidRuntime(32388):    at java.lang.reflect.Method.invoke(Method.java:511)
03-04 13:40:49.468: E/AndroidRuntime(32388):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1027)
03-04 13:40:49.468: E/AndroidRuntime(32388):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:794)
03-04 13:40:49.468: E/AndroidRuntime(32388):    at dalvik.system.NativeStart.main(Native Method)

其中第56行为gmap = mf.getMap();

Answer 1

如果您想在片段中放置一个映射，那么我建议您在布局中使用MapView对象而不是MapFragment，下面是适合我的代码：

布局：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<com.google.android.gms.maps.MapView
    xmlns:map="http://schemas.android.com/apk/res-auto"
    android:id="@+id/mapview"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

</LinearLayout>

碎片本身：

public class MapFragment extends Fragment  {

private static final String TAG = MapFragment.class.getSimpleName();
private MapView mapView;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
    View view = inflater.inflate(R.layout.new_mapview, container, false);

    // Gets the MapView from the XML layout and creates it
    mapView = (MapView) view.findViewById(R.id.mapview);
    mapView.onCreate(savedInstanceState);

    return view;
}


@Override
public void onPause() {
    mapView.onPause();
    super.onPause();
}


@Override
public void onResume() {
    mapView.onResume();
    super.onResume();
}

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

@Override
public void onLowMemory() {
    super.onLowMemory();
    mapView.onLowMemory();
}
}

Answer 2

您的XML与您的片段代码不匹配，在XML中有SupportMapFragment时，您正在创建一个MapFragment对象。

代之以：

<fragment
android:id="@+id/mapFrag"
android:name="com.google.android.gms.maps.MapFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="@+id/map_topbar"
class="com.google.android.gms.maps.MapFragment" />

通过以下方式：

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

Answer 3

XML

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

JAVA文件

googleMap = ((MapFragment) getFragmentManager().findFragmentById(R.id.map)).getMap();

如果您的类扩展了Activity，这就适用于我了。