Android Google地图和菜单

Question

I Have this bit of code and what happens when i run the app is that i get the map and when i click on the menu and i select the map option this happens again. Is there any way so I could run the app and I would click on the map option then I would get the map ? At the moment the map is still displayed and when i click on the map option it just keeps happening. I need a way so that the map is not visible when the application starts and make it visible when i hit the map option on my menu. Anyone could give me some advice.Please help me out thank you.

public class MainActivity extends Activity {
GoogleMap gMap;
private final LatLng LOCATION_AMERICA=new LatLng(someNo , someNo);


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

    gMap=((MapFragment)getFragmentManager().findFragmentById(R.id.map)).getMap();
    gMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);
    gMap.addMarker(new MarkerOptions().position(LOCATION_AMERICA).title("AMERICA"));


}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch(item.getItemId())
    {
    case R.id.map:
        // write logic here for open map
        Intent intent = new Intent(getApplicationContext(), MainActivity.class);
        startActivity(intent);
        }
    return true;
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);

    return true;

}

Answer 1

remove this code from onCreate and put in onOptionsItemSelected

 gMap=((MapFragment)getFragmentManager().findFragmentById(R.id.map)).getMap();
    gMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);
    gMap.addMarker(new MarkerOptions().position(LOCATION_AMERICA).title("AMERICA"));

also, if the item is clicked again, check if the fragment is already loaded, then don't load it again.