Fool-proof way to handle Fragment on orientation change

public class MainActivity extends Activity implements MainMenuFragment.OnMainMenuItemSelectedListener {


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


FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager
.beginTransaction();


// add menu fragment
MainMenuFragment myFragment = new MainMenuFragment();
fragmentTransaction.add(R.id.menu_fragment, myFragment);


//add content
DetailPart1 content1= new DetailPart1 ();
fragmentTransaction.add(R.id.content_fragment, content1);
fragmentTransaction.commit();


}
public void onMainMenuSelected(String tag) {
//next menu is selected replace existing fragment
}

I have a need to display two list views side by side, menu on left and its content on right side. By default, the first menu is selected and its content is displayed on right side. The Fragment that displays content is as below:

public class DetailPart1 extends Fragment {
ArrayList<HashMap<String, String>> myList = new ArrayList<HashMap<String, String>>();
ListAdapter adap;
ListView listview;


@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);


if(savedInstanceState!=null){
myList = (ArrayList)savedInstanceState.getSerializable("MYLIST_obj");
adap = new LoadImageFromArrayListAdapter(getActivity(),myList );
listview.setAdapter(adap);
}else{
//get list and load in list view
getlistTask = new GetALLListTasks().execute();
}




@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.skyview_fragment, container,false);
return v;
}




@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putSerializable("MYLIST_obj", myList );
}
}

The onActivityCreated and onCreateView are called twice. There are many examples out there using fragments. Since I am beginner in this subject, I am unable relate the example with my problem. I need a fool proof way to handle orientation change. I have NOT declared android:configChanges in manifest file. I need the activity destroy and recreate so that I can use different layout in landscape mode.

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最佳答案

You are creating a new fragment every time you turn the screen in your activity onCreate(); But you are also maintaining the old ones with super.onCreate(savedInstanceState);. So maybe set tag and find the fragment if it exists, or pass null bundle to super.

This took me a while to learn and it can really be a pain when you are working with stuff like viewpager.

I'd recommend you to read about fragments an extra time as this exact topic is covered.

Here is an example of how to handle fragments on a regular orientation change:

Activity:

public class MainActivity extends FragmentActivity {


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

if (savedInstanceState == null) {
TestFragment test = new TestFragment();
test.setArguments(getIntent().getExtras());
getSupportFragmentManager().beginTransaction().replace(android.R.id.content, test, "your_fragment_tag").commit();
} else {
TestFragment test = (TestFragment) getSupportFragmentManager().findFragmentByTag("your_fragment_tag");
}
}
}

Fragment:

public class TestFragment extends Fragment {


public static final String KEY_ITEM = "unique_key";
public static final String KEY_INDEX = "index_key";
private String mTime;
    

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_layout, container, false);
        

if (savedInstanceState != null) {
// Restore last state
mTime = savedInstanceState.getString("time_key");
} else {
mTime = "" + Calendar.getInstance().getTimeInMillis();
}
        

TextView title = (TextView) view.findViewById(R.id.fragment_test);
title.setText(mTime);
        

return view;
}
    

@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putString("time_key", mTime);
}
}