ViewPager PageAdapter gets reset when orientation changes

Question

I am using ViewPager for a multiple-choice application that randomly selects thirty questions from a larger set. I do this in the PageAdapter that supplies the ViewPager pages.

The problem is that when the orientation changes, not only the pager but also the adapter is rebooted - I know how to save the current position of the pager, but when the adapter receives a reset, it also selects new questions from the set. What will be the right way to deal with this?

Also, the side question is, what would be the best way to register your choice with RadioGroups? Directly by click or in another way?

I am new to Android app development.

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Activity:

 public class MyActivity extends SherlockActivity { ActionBar actionBar; ViewPager pager; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); pager = new ViewPager(this); setContentView(pager); QuestionsAdapter adapter = new QuestionsAdapter(this); pager.setAdapter(adapter); int position = 0; if (savedInstanceState != null) { position = savedInstanceState.getInt("Q_NUMBER"); } pager.setCurrentItem(position); } @Override public void onSaveInstanceState(Bundle savedInstanceState) { int position = pager.getCurrentItem(); savedInstanceState.putInt("Q_NUMBER", position); } } 

Adapter:

 class QuestionsAdapter extends PagerAdapter { Context context; QuestionsHelper dbQuestions; boolean exam; List<HashMap<String,Object>> examQuestions; public QuestionsAdapter(Context context, boolean exam) { this.context = context; this.examQuestions = GetQuestionsFromDB(30); } public Object instantiateItem(View collection, int position) { LayoutInflater inflater = (LayoutInflater) collection.getContext() .getSystemService(Context.LAYOUT_INFLATER_SERVICE); View view; HashMap<String,Object> q; view = inflater.inflate(R.layout.exam_question_layout, null); q = getQuestion(position+1); ((TextView)view.findViewById(R.id.q_number)).setText(Integer.toString(position+1)+"."); ((TextView)view.findViewById(R.id.q_question)).setText(q.get("question").toString()); ((RadioButton)view.findViewById(R.id.q_answer_a)).setText(q.get("answer_a").toString()); ((RadioButton)view.findViewById(R.id.q_answer_b)).setText(q.get("answer_b").toString()); ((RadioButton)view.findViewById(R.id.q_answer_c)).setText(q.get("answer_c").toString()); ((ViewPager)collection).addView(view, 0); return view; } } 

Answer 1

I know how to save the current position of the pager, but when the adapter receives a reset, it also selects new questions from the set. What will be the right way to handle this?

Your questions must have an id to uniquely identify them. I'm not sure how you get them from the database, but when that happens, you will need to save your identifiers. Also:

• Your adapter should have a long array (or an integer) containing 30 values ​​representing the identifiers of the currently selected batch of questions.
• You will need to implement the following logic in the adapter: if the long array from the previous point is null , then suppose this is a clean start and get a new set of 30 questions. If the long array is not zero, we are faced with recovery from the configuration, and you will need to use these identifiers to get the right questions from the database instead of a random batch
• In Activity you save a long adapter array in the onSaveInstanceState() method ( savedInstanceState.putLongArray )
• In the onCreate Activity method, when creating the adapter, you check the savedInstanceState Bundle to see if it is unnecessary and has a long array, and install it on the adapter (so that it knows what questions you need to get)

What would be the best way to register your choice with RadioGroups? Directly by click or in another way?

You can use the above method or create your own class with Parcelable , as it was already recommended to you in the comments.

Answer 2

Rotating the screen will redraw the entire screen in a new orientation, we can prevent it from overriding configuration changes.

add android: configChanges = "orientation | screenSize" under the screen declaration in the Android manifest

  android:configChanges="orientation|screenSize" 

And override onConfigurationChanged in your activity like

  @Override public void onConfigurationChanged(Configuration newConfig) { super.onConfigurationChanged(newConfig); }