I'm using an actionbar in navigation mode in the mainActivity. Different tabs has different layouts, and on one of these tabs, I embed a layout which has a MapFragment inside. With the following code, the app works well, the mapFragments works fine, the tabs works fine. However, once I want to get access the mapFragment embeded in myFragment use getFragmentManager().findFragmentById(R.id.map_add), I always get null.
I've tried using FragmentManager and FragmentTransaction to add myfragment and the MapFragment, but still get null from findFragmentById(R.id.map_add). Please help...
The MainActivity initialized like this:
protected void onCreate(Bundle bundle) {
super.onCreate(bundle);
setContentView(R.layout.main);
// ActionBar gets initiated
ActionBar actionbar = getActionBar();
// Tell the ActionBar we want to use Tabs.
actionbar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS);
// initiating the tabs and set text to it.
ActionBar.Tab myTab = actionbar.newTab().setText("hey");
// create the fragments we want to use for display content
Fragment myFragment = new myFragment();
// set the Tab listener. Now we can listen for clicks.
myTab.setTabListener(new MyTabsListener(myFragment));
// add the tabs to the actionbar
actionbar.addTab(myTab);
map=((MapFragment)getFragmentManager().findFragmentById(R.id.map_add)).getMap();//line 103
}
the layout of the MainActivity, main.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/fragment_container"
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=".MainActivity" >
</RelativeLayout>
the code of the tablistener:
class MyTabsListener implements ActionBar.TabListener {
public Fragment fragment;
public MyTabsListener(Fragment fragment) {
this.fragment = fragment;
}
@Override
public void onTabReselected(Tab tab, FragmentTransaction ft) {
}
@Override
public void onTabSelected(Tab tab, FragmentTransaction ft) {
ft.replace(R.id.fragment_container, fragment);
}
@Override
public void onTabUnselected(Tab tab, FragmentTransaction ft) {
ft.remove(fragment);
}
}
the code of myFragment:
public static class AddAliasFragment extends Fragment {
private static View view;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
if (view != null) {
ViewGroup parent = (ViewGroup) view.getParent();
if (parent != null)
parent.removeView(view);
}
try {
view = inflater.inflate(R.layout.myfragment_layout, container, false);
} catch (InflateException e) {
/* map is already there, just return view as it is */
}
return view;
}
public MapFragment getMapFragment(){
return (MapFragment)getFragmentManager().findFragmentById(R.id.map_add);
}
}
the layout of myFragment: myfragment_layout.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/map_add_layout"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<EditText
android:id="@+id/search"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:hint="@string/searchhint"
/>
<Button
android:id="@+id/searchbtn"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignBottom="@+id/search"
android:layout_toRightOf="@id/search"
android:text="@string/go" />
<fragment
android:id="@+id/map_add"
android:tag="add"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="@id/search"
android:name="com.google.android.gms.maps.MapFragment"/>
the Logcat output: the nullpointer exception refers to line 103, which is the getMap() line, I have comment after it in the aforementioned code
04-02 21:23:12.122: E/AndroidRuntime(3672): FATAL EXCEPTION: main
04-02 21:23:12.122: E/AndroidRuntime(3672): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.test.test/com.test.test.MainActivity}: java.lang.NullPointerException
04-02 21:23:12.122: E/AndroidRuntime(3672): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2307)
04-02 21:23:12.122: E/AndroidRuntime(3672): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2357)
04-02 21:23:12.122: E/AndroidRuntime(3672): at android.app.ActivityThread.access$600(ActivityThread.java:153)
04-02 21:23:12.122: E/AndroidRuntime(3672): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1247)
04-02 21:23:12.122: E/AndroidRuntime(3672): at android.os.Handler.dispatchMessage(Handler.java:99)
04-02 21:23:12.122: E/AndroidRuntime(3672): at android.os.Looper.loop(Looper.java:137)
04-02 21:23:12.122: E/AndroidRuntime(3672): at android.app.ActivityThread.main(ActivityThread.java:5226)
04-02 21:23:12.122: E/AndroidRuntime(3672): at java.lang.reflect.Method.invokeNative(Native Method)
04-02 21:23:12.122: E/AndroidRuntime(3672): at java.lang.reflect.Method.invoke(Method.java:511)
04-02 21:23:12.122: E/AndroidRuntime(3672): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:795)
04-02 21:23:12.122: E/AndroidRuntime(3672): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:562)
04-02 21:23:12.122: E/AndroidRuntime(3672): at dalvik.system.NativeStart.main(Native Method)
04-02 21:23:12.122: E/AndroidRuntime(3672): Caused by: java.lang.NullPointerException
04-02 21:23:12.122: E/AndroidRuntime(3672): at com.test.test.MainActivity.onCreate(MainActivity.java:103)
04-02 21:23:12.122: E/AndroidRuntime(3672): at android.app.Activity.performCreate(Activity.java:5104)
04-02 21:23:12.122: E/AndroidRuntime(3672): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
04-02 21:23:12.122: E/AndroidRuntime(3672): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2261)
04-02 21:23:12.122: E/AndroidRuntime(3672): ... 11 more