I'm willing to add a dynamic number of fragments to a ViewPager in my android app, so that I'm using the following way:
The FragmentActivity:
public class Lighting extends FragmentActivity {
private LightPageAdapter TabAdapter;
private VerticalViewPager Tab;
private List<Fragment> fragments = new Vector<Fragment>();
// to add a new Fragment
public void fragmenting() {
Bundle page = new Bundle();
page.putString("somedata", "somedata");
Fragment frag = Fragment.instantiate(this,MyFragment.class.getName(),page); // this is where I got the Exception
fragments.add(frag);
}
//to init the Page adapter
public void init_page_adapter(){
this.TabAdapter = new LightPageAdapter(super.getSupportFragmentManager(), fragments);
Tab = (ViewPager) findViewById(R.id.lighting_pager);
Tab.setAdapter(this.TabAdapter);
}
}
The PageAdapter:
public class LightPageAdapter extends FragmentStatePagerAdapter {
private List<Fragment> myFragments;
public LightPageAdapter (FragmentManager fragmentManager, List<Fragment> fragments) {
super(fragmentManager);
myFragments = fragments;
}
public Fragment getItem(int i) {
return myFragments.get(i);
}
@Override
public int getCount() {
return myFragments.size();
}
}
The Fragment:
public class MyFragment extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View lighting_fragment = inflater.inflate(R.layout.lighting_fragment, container, false);
return lighting_fragment;
}
}
The ErrorLog:
05-07 08:17:45.216: E/AndroidRuntime(1533): FATAL EXCEPTION: main
05-07 08:17:45.216: E/AndroidRuntime(1533): java.lang.NullPointerException
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.content.ContextWrapper.getClassLoader(ContextWrapper.java:122)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.support.v4.app.Fragment.instantiate(Fragment.java:399)
05-07 08:17:45.216: E/AndroidRuntime(1533): at com.automation.isolace.Lighting.fragmenting(Lighting.java:1301)
05-07 08:17:45.216: E/AndroidRuntime(1533): at com.automation.fragments.Light_Center.onViewCreated(Light_Center.java:46)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:941)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1104)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1467)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:472)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.support.v4.app.FragmentStatePagerAdapter.finishUpdate(FragmentStatePagerAdapter.java:163)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.support.v4.view.ViewPager.populate(ViewPager.java:1068)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.support.v4.view.ViewPager.populate(ViewPager.java:914)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1436)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.view.View.measure(View.java:15172)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.widget.LinearLayout.measureVertical(LinearLayout.java:833)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.widget.LinearLayout.onMeasure(LinearLayout.java:574)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.view.View.measure(View.java:15172)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:617)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:399)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.view.View.measure(View.java:15172)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4814)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.view.View.measure(View.java:15172)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4814)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1390)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.widget.LinearLayout.measureVertical(LinearLayout.java:681)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.widget.LinearLayout.onMeasure(LinearLayout.java:574)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.view.View.measure(View.java:15172)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4814)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
05-07 08:17:45.216: E/AndroidRuntime(1533): at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2148)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.view.View.measure(View.java:15172)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1848)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1100)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1273)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:998)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4212)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.view.Choreographer.doCallbacks(Choreographer.java:555)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.view.Choreographer.doFrame(Choreographer.java:525)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.os.Handler.handleCallback(Handler.java:615)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.os.Handler.dispatchMessage(Handler.java:92)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.os.Looper.loop(Looper.java:137)
05-07 08:17:45.216: E/AndroidRuntime(1533): at android.app.ActivityThread.main(ActivityThread.java:4745)
05-07 08:17:45.216: E/AndroidRuntime(1533): at java.lang.reflect.Method.invokeNative(Native Method)
05-07 08:17:45.216: E/AndroidRuntime(1533): at java.lang.reflect.Method.invoke(Method.java:511)
05-07 08:17:45.216: E/AndroidRuntime(1533): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
05-07 08:17:45.216: E/AndroidRuntime(1533): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
05-07 08:17:45.216: E/AndroidRuntime(1533): at dalvik.system.NativeStart.main(Native Method)
Fragment frag = new MyFragment();
frag.setArguments(page);
Will do the same as the Fragment.instantiate line.
Instantiate should only be used when you don't have a source code dependency to the fragment. i.e. you only have a String name of the class, not access to the class itself.
The cause is unclear, but it could be that MyFragment is a v11 fragment, and you try to create it with a v4 Fragment.instantiate.