ViewPager.OnPageChangeListener在ViewPager完成初始化之前运行

Question

I add a OnPageChangeListener in my ViewPager in activity.

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    ...
    mPageAdapter = new PageAdapter(fragmentManager);
    mPager = (ViewPager) findViewById(R.id.pager);
    mPager.setAdapter(mPageAdapter);
    mPager.setOffscreenPageLimit(CACHE_SIZE);
    mPager.addOnPageChangeListener(mOnPageChangeListener);
    ...


private ViewPager.SimpleOnPageChangeListener mOnPageChangeListener = new ViewPager.SimpleOnPageChangeListener() {
    @Override
    public void onPageSelected(int i) {
        Log.d(TAG, "this: " + this);
        ChartFragment chartFragment = mFragmentList.get(i).second; // crash when activity recreate............
        ...

And I store all fragments in a List.

private List<Pair<String, ChartFragment>> mFragmentList = new ArrayList<Pair<String, ChartFragment>>();

private class PageAdapter extends FragmentPagerAdapter {
    public Object instantiateItem(ViewGroup container, int position) {
        mFragmentList.add(new Pair<String, ChartFragment>(...));

Now I stop my app process with DDMS and reopen it, this page crashes in function onPageSelected.
I don't know why the function onPageSelected exec before ViewPager "init".
How can I fix this? Help!

log:

Caused by: java.lang.IndexOutOfBoundsException: Invalid index 1, size is 0
MyActivity$1.onPageSelected(MyActivity.java:101)
...

the onPageSelected function call in ViewPager.onRestoreInstanceState.

10-15 13:22:57.745 D/MyAccountActivity( 8998):  at ...MyActivity$1.onPageSelected(MyActivity.java:103)
10-15 13:22:57.745 D/MyAccountActivity( 8998):  at android.support.v4.view.ViewPager.dispatchOnPageSelected(ViewPager.java:1792)
10-15 13:22:57.745 D/MyAccountActivity( 8998):  at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:547)
10-15 13:22:57.745 D/MyAccountActivity( 8998):  at android.support.v4.view.ViewPager.setCurrentItemInternal(ViewPager.java:513)
10-15 13:22:57.745 D/MyAccountActivity( 8998):  at android.support.v4.view.ViewPager.onRestoreInstanceState(ViewPager.java:1319)

Answer 1

Make sure data is available in "mFragmentList" before adding PageChangeListener for ViewPager.

Get data load in " mFragmentList " before the following line

mPager.addOnPageChangeListener(mOnPageChangeListener);