使用Maps API v2以编程方式初始化MapFragment
使用Maps API v2以编程方式初始化MapFragment
提问于 2012-12-06 06:03:56
我正在尝试将MapFragment添加到我当前的片段。嵌套片段的使用仅限于FragmentTransactions，您不能在布局中使用xml标记。此外，我希望在用户按下按钮时将其添加到主片段中。因此，当用户按下该按钮并将其添加到适当的位置时，我将使用getInstance()以编程方式创建MapFragment。它显示正确，到目前为止一切正常。
问题是在附加MapFragment之后，我需要获得一个对GoogleMap 的引用来放置一个标记，但是getMap()方法返回null (因为片段的onCreateView()还没有被调用)。
我看了演示示例代码，我发现他们使用的解决方案是在onCreate()中初始化MapFragment，并在onCreateView()被调用之后在onResume()中获取对onCreateView()的引用。
我需要在MapFragment初始化之后立即获得对GoogleMap的引用，因为我希望用户能够通过按钮显示或隐藏地图。我知道一个可能的解决方案是在开始时创建地图，如上所述，只需设置它的可见性消失，但我希望地图在默认情况下是关闭的，这样如果用户没有明确要求它就不会占用用户的带宽。
我试过使用MapsInitializer，但也不起作用。我有点卡住了。有什么想法吗？到目前为止，我的测试代码如下：
public class ParadaInfoFragment extends BaseDBFragment {
// BaseDBFragment is just a SherlockFragment with custom utility methods.
private static final String MAP_FRAGMENT_TAG = "map";
private GoogleMap mMap;
private SupportMapFragment mMapFragment;
private TextView mToggleMapa;
private boolean isMapVisible = false;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_parada_info, container, false);
mToggleMapa = (TextView) v.findViewById(R.id.parada_info_map_button);
return v;
}
@Override
public void onStart() {
super.onStart();
mToggleMapa.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (!isMapVisible) {
openMap();
} else {
closeMap();
}
isMapVisible = !isMapVisible;
}
});
}
private void openMap() {
// Creates initial configuration for the map
GoogleMapOptions options = new GoogleMapOptions().camera(CameraPosition.fromLatLngZoom(new LatLng(37.4005502611301, -5.98233461380005), 16))
.compassEnabled(false).mapType(GoogleMap.MAP_TYPE_NORMAL).rotateGesturesEnabled(false).scrollGesturesEnabled(false).tiltGesturesEnabled(false)
.zoomControlsEnabled(false).zoomGesturesEnabled(false);
// Modified from the sample code:
// It isn't possible to set a fragment's id programmatically so we set a
// tag instead and search for it using that.
mMapFragment = (SupportMapFragment) getChildFragmentManager().findFragmentByTag(MAP_FRAGMENT_TAG);
// We only create a fragment if it doesn't already exist.
if (mMapFragment == null) {
// To programmatically add the map, we first create a
// SupportMapFragment.
mMapFragment = SupportMapFragment.newInstance(options);
// Then we add it using a FragmentTransaction.
FragmentTransaction fragmentTransaction = getChildFragmentManager().beginTransaction();
fragmentTransaction.add(R.id.parada_info_map_container, mMapFragment, MAP_FRAGMENT_TAG);
fragmentTransaction.commit();
}
// We can't be guaranteed that the map is available because Google Play
// services might not be available.
setUpMapIfNeeded(); //XXX Here, getMap() returns null so the Marker can't be added
// The map is shown with the previous options.
}
private void closeMap() {
FragmentTransaction fragmentTransaction = getChildFragmentManager().beginTransaction();
fragmentTransaction.remove(mMapFragment);
fragmentTransaction.commit();
}
private void setUpMapIfNeeded() {
// Do a null check to confirm that we have not already instantiated the
// map.
if (mMap == null) {
// Try to obtain the map from the SupportMapFragment.
mMap = mMapFragment.getMap();
// Check if we were successful in obtaining the map.
if (mMap != null) {
mMap.addMarker(new MarkerOptions().position(new LatLng(37.4005502611301, -5.98233461380005)).title("Marker"));
}
}
}
}谢谢
回答 4
Stack Overflow用户
回答已采纳
发布于 2012-12-06 07:35:02
好心的AnderWebs用Google+给了我一个答案，但他太懒了……嗯，忙于在这里再次编写它，所以这里是简短的版本:扩展MapFragment类并覆盖onCreateView()方法。完成此方法后，我们可以获得对que GoogleMap对象的非空引用。
这是我的特殊解决方案：
public class MiniMapFragment extends SupportMapFragment {
private LatLng mPosFija;
public MiniMapFragment() {
super();
}
public static MiniMapFragment newInstance(LatLng posicion){
MiniMapFragment frag = new MiniMapFragment();
frag.mPosFija = posicion;
return frag;
}
@Override
public View onCreateView(LayoutInflater arg0, ViewGroup arg1, Bundle arg2) {
View v = super.onCreateView(arg0, arg1, arg2);
initMap();
return v;
}
private void initMap(){
UiSettings settings = getMap().getUiSettings();
settings.setAllGesturesEnabled(false);
settings.setMyLocationButtonEnabled(false);
getMap().moveCamera(CameraUpdateFactory.newLatLngZoom(mPosFija,16));
getMap().addMarker(new MarkerOptions().position(mPosFija).icon(BitmapDescriptorFactory.fromResource(R.drawable.marker)));
}
}现在在前面的片段类中，我这样做了
mMapFragment = MiniMapFragment.newInstance(new LatLng(37.4005502611301, -5.98233461380005));也许它还不完美，因为在显示地图时屏幕会闪烁。但不确定问题是因为这个原因还是其他原因。
Stack Overflow用户
发布于 2013-04-17 05:49:00
谢谢，我觉得这个很有帮助。我发布了我的略微修改的解决方案，因为当地图准备好时，告诉父片段对我来说更清晰。此方法也适用于saveInstanceState / restoreInstanceState周期。
public class CustomMapFragment extends SupportMapFragment {
private static final String LOG_TAG = "CustomMapFragment";
public CustomMapFragment() {
super();
}
public static CustomMapFragment newInstance() {
CustomMapFragment fragment = new CustomMapFragment();
return fragment;
}
@Override
public View onCreateView(LayoutInflater arg0, ViewGroup arg1, Bundle arg2) {
View v = super.onCreateView(arg0, arg1, arg2);
Fragment fragment = getParentFragment();
if (fragment != null && fragment instanceof OnMapReadyListener) {
((OnMapReadyListener) fragment).onMapReady();
}
return v;
}
/**
* Listener interface to tell when the map is ready
*/
public static interface OnMapReadyListener {
void onMapReady();
}
}要用作嵌套片段：-
public class ParentFragment extends Fragment implements OnMapReadyListener {
...
mMapFragment = CustomMapFragment.newInstance();
getChildFragmentManager().beginTransaction().replace(R.id.mapContainer, mMapFragment).commit();
@Override
public void onMapReady() {
mMap = mMapFragment.getMap();
}
...
}希望这能帮助到别人。
Stack Overflow用户
发布于 2013-05-02 10:40:27
这是我的解决方案，我从之前发布的代码中获得了灵感，并将其清理干净。我还添加了带有和不带有GoogleMapOptions参数的静态方法。
public class GoogleMapFragment extends SupportMapFragment {
private static final String SUPPORT_MAP_BUNDLE_KEY = "MapOptions";
public static interface OnGoogleMapFragmentListener {
void onMapReady(GoogleMap map);
}
public static GoogleMapFragment newInstance() {
return new GoogleMapFragment();
}
public static GoogleMapFragment newInstance(GoogleMapOptions options) {
Bundle arguments = new Bundle();
arguments.putParcelable(SUPPORT_MAP_BUNDLE_KEY, options);
GoogleMapFragment fragment = new GoogleMapFragment();
fragment.setArguments(arguments);
return fragment;
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
mCallback = (OnGoogleMapFragmentListener) getActivity();
} catch (ClassCastException e) {
throw new ClassCastException(getActivity().getClass().getName() + " must implement OnGoogleMapFragmentListener");
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View view = super.onCreateView(inflater, container, savedInstanceState);
if (mCallback != null) {
mCallback.onMapReady(getMap());
}
return view;
}
private OnGoogleMapFragmentListener mCallback;
}使用模式如下：
public class MyMapActivity implements OnGoogleMapFragmentListener {
...
@Override
public void onMapReady(GoogleMap map) {
mUIGoogleMap = map;
...
}
...
private GoogleMap mUIGoogleMap;
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/13733299
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