我在Tab中有一个谷歌地图。当我更改标签并返回到我的谷歌地图标签时，地图再次加载。有没有办法只加载一次地图，只需在切换标签时获取实例???
这是我的代码：
管理2个标签的代码：
public class FragmentTabsPdv extends BaseActivity {
private ArrayList<Pdv> listaPdv;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
DatabaseHandlerTienda db = new DatabaseHandlerTienda(this);
listaPdv = (ArrayList<Pdv>) db.getAllTiendas();
ActionBar actionBar = getSupportActionBar();
actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
ActionBar.Tab tab1 = actionBar.newTab();
tab1.setText("Lista");
tab1.setIcon(R.drawable.ic_action_view_as_list);
ActionBar.Tab tab2 = getSupportActionBar().newTab();
tab2.setText("Mapa");
tab2.setIcon(R.drawable.ic_action_location_map);
actionBar.setDisplayHomeAsUpEnabled(true);
actionBar.setTitle("");
actionBar.setDisplayOptions(ActionBar.DISPLAY_SHOW_HOME
| ActionBar.DISPLAY_SHOW_TITLE | ActionBar.DISPLAY_SHOW_CUSTOM);
// create the two fragments we want to use for display content
tab1.setTabListener(new TabListener<ListPdvTabFragment>(this,
"lista", ListPdvTabFragment.class));
tab2.setTabListener(new TabListener<MapPdvTabFragment>(this,
"mapa", MapPdvTabFragment.class));
actionBar.addTab(tab1);
actionBar.addTab(tab2);
}
public ArrayList<Pdv> getListaPdv() {
return listaPdv;
}
public void setListaPdv(ArrayList<Pdv> listaPdv) {
this.listaPdv = listaPdv;
}
public static class TabListener<T extends Fragment> implements
ActionBar.TabListener {
private Fragment mFragment;
private final Activity mActivity;
private final String mTag;
private final Class<T> mClass;
/**
* Constructor used each time a new tab is created.
*
* @param activity
* The host Activity, used to instantiate the fragment
* @param tag
* The identifier tag for the fragment
* @param clz
* The fragment's Class, used to instantiate the fragment
*/
public TabListener(Activity activity, String tag, Class<T> clz) {
mActivity = activity;
mTag = tag;
mClass = clz;
}
/* The following are each of the ActionBar.TabListener callbacks */
public void onTabSelected(ActionBar.Tab tab, FragmentTransaction ft) {
// Check if the fragment is already initialized
if (mFragment == null) {
// If not, instantiate and add it to the activity
mFragment = Fragment.instantiate(mActivity, mClass.getName());
ft.add(android.R.id.content, mFragment, mTag);
} else {
// If it exists, simply attach it in order to show it
ft.attach(mFragment);
}
}
public void onTabUnselected(ActionBar.Tab tab, FragmentTransaction ft) {
if (mFragment != null) {
// Detach the fragment, because another one is being attached
ft.detach(mFragment);
}
}
public void onTabReselected(ActionBar.Tab tab, FragmentTransaction ft) {
// User selected the already selected tab. Usually do nothing.
}
}
}
我的Google地图标签代码：
public class MapPdvTabFragment extends SherlockFragment implements GoogleMap.OnMarkerClickListener {
private MapView mapView;
private GoogleMap map;
private ArrayList<Pdv> pdvs;
private ViewPager pager;
private PagerAdapter pagerAdapter;
private View fragmentView;
boolean showNoResults = false;
// private HashMap<String, Pdv> markerToRestaurantAvailabilityMap = new
// HashMap();
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setRetainInstance(true);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.tab_frag_map_pdv, container, false);
fragmentView = v;
Bundle localBundle = null;
if (savedInstanceState != null)
localBundle = (Bundle) savedInstanceState.getParcelable("mapViewBundle");
// Gets the MapView from the XML layout and creates it
mapView = (MapView) v.findViewById(R.id.map);
// Gets to GoogleMap from the MapView and does initialization stuff
mapView.onCreate(localBundle);
mapView.onResume();// needed to get the map to display immediately
map = mapView.getMap();
map.getUiSettings().setMyLocationButtonEnabled(false);
map.setOnMarkerClickListener(this);
// Needs to call MapsInitializer before doing any CameraUpdateFactory
// calls
try {
MapsInitializer.initialize(this.getActivity());
} catch (GooglePlayServicesNotAvailableException e) {
e.printStackTrace();
}
// Updates the location and zoom of the MapView
map.setMyLocationEnabled(true);
int zoom = 14;
CameraUpdate here = CameraUpdateFactory.newLatLngZoom(new LatLng(19.359180, -99.180901), zoom);
map.moveCamera(here);
FragmentTabsPdv parent = (FragmentTabsPdv) getActivity();
pdvs = parent.getListaPdv();
if (pdvs != null && pdvs.size() > 0)
showNoResults = false;
else
showNoResults = true;
displayPdvOnMap(pdvs); // Display marker ( work well)
initPager();
return v;
}
@Override
public void onResume() {
mapView.onResume();
super.onResume();
}
@Override
public void onPause() {
super.onPause();
if (mapView != null)
mapView.onPause();
}
@Override
public void onDestroy() {
super.onDestroy();
mapView.onDestroy();
}
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
if (mapView != null)
mapView.onSaveInstanceState(outState);
}
@Override
public void onLowMemory() {
super.onLowMemory();
mapView.onLowMemory();
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
}
public void displayPdvOnMap(ArrayList<Pdv> tiendas) {
for (Pdv pdv : tiendas) {
Marker marker = map.addMarker(new MarkerOptions()
.position(new LatLng(pdv.getLatitude(), pdv.getLongitude())).title(pdv.getTienda())
.snippet(pdv.getCalle()));
pdv.setMarker(marker);
}
}
public void initPager() {
pager = ((ViewPager) fragmentView.findViewById(R.id.pager));
pager.setOffscreenPageLimit(3);
pager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
public void onPageScrollStateChanged(int paramAnonymousInt) {
}
public void onPageScrolled(int paramAnonymousInt1, float paramAnonymousFloat, int paramAnonymousInt2) {
}
public void onPageSelected(int position) {
Pdv pdv = pdvs.get(position);
Marker m = pdv.getMarker();
m.showInfoWindow();
// Center map on current marker
CameraUpdate here = CameraUpdateFactory.newLatLngZoom(m.getPosition(), 14);
map.animateCamera(here);
}
});
pager.setSaveEnabled(false);
pagerAdapter = new PagerAdapter() {
public void destroyItem(ViewGroup paramAnonymousViewGroup, int paramAnonymousInt,
Object paramAnonymousObject) {
paramAnonymousViewGroup.removeView((View) paramAnonymousObject);
}
public int getCount() {
if (showNoResults)
return 1;
if (pdvs != null)
return pdvs.size();
return 0;
}
public Object instantiateItem(View container, int position) {
View view = null;
if (showNoResults) {
view = getLayoutInflater(null).inflate(R.layout.map_pager_empty, null);
} else {
view = getLayoutInflater(null).inflate(R.layout.row_lista_pdv, null);
Pdv pdv = pdvs.get(position);
TextView tienda_name = (TextView) view.findViewById(R.id.tienda_name);
TextView direccion = (TextView) view.findViewById(R.id.tienda_dir);
TextView contacto = (TextView) view.findViewById(R.id.tienda_contact);
TextView horIni = (TextView) view.findViewById(R.id.tienda_horarioIni);
TextView horFin = (TextView) view.findViewById(R.id.tienda_horarioFin);
tienda_name.setText(pdv.getTienda());
direccion.setText(pdv.getCalle());
contacto.setText(pdv.getContacto());
horIni.setText(pdv.getHorarioIni());
horFin.setText(pdv.getHorarioFin());
}
((ViewPager) container).addView(view, 0);
return view;
}
public boolean isViewFromObject(View paramAnonymousView, Object paramAnonymousObject) {
return paramAnonymousView == paramAnonymousObject;
}
};
this.pager.setAdapter(this.pagerAdapter);
return;
// this.pager.removeAllViews();
}
@Override
public boolean onMarkerClick(Marker marker) {
int i = 0;
i = getPdvPosition(marker);
if (i >= 0)
pager.setCurrentItem(i, true);
return false;
}
private int getPdvPosition(Marker marker) {
int position = 0;
for (Pdv pdv : pdvs) {
Marker m = pdv.getMarker();
String mId1 = m.getId();
String mId2 = marker.getId();
if (mId1.equals(mId2)) {
return position;
}
position++;
}
return 0;
}
}
答案 0 :(得分：0)
显示一个片段并隐藏另一个片段的最轻量级方式是show()和hide()。
attach()和detach()在用户看到的内容方面具有类似的效果，但也会在片段中触发onAttach()和onDetach()生命周期方法。有些片段在这里什么都不做其他片段可能在这里做更多工作。据推测，Maps V2片段在这里做了更多工作。
这可能会导致其他情况出现问题，例如使用FragmentStatePagerAdapter，其中（IIRC）使用attach()和detach()。