IllegalStateException: The application's PagerAdapter changed the adapter's content without calling PagerAdapter#notifyDataSetChanged
Solution 1
I had a hard time making my ViewPager
working. At the end, it seems that the example in the documentation is wrong.
The addTab
method should be as follows:
public void addTab(Tab tab, Class<?> clss, Bundle args) {
TabInfo info = new TabInfo(clss, args);
tab.setTag(info);
tab.setTabListener(this);
mTabs.add(info);
notifyDataSetChanged();
mActionBar.addTab(tab);
}
Notice the order of the last three operations. In the original example, notifyDataSetChanged
was called after the mActionBar.addTab
function.
Unfortunately, as soon as you call the addTab
on the ActionBar
, the first tab you add is automatically selected. Because of this, the onTabSelected
event is fired and while trying to retrieve the page, it throws the IllegalStateException
because it notices a discrepancy between the expected item count and the actual one.
Solution 2
I fixed it by callinig notifyDataSetChanged() once and just before next call of getCount():
private boolean doNotifyDataSetChangedOnce = false;
@Override
public int getCount() {
if (doNotifyDataSetChangedOnce) {
doNotifyDataSetChangedOnce = false;
notifyDataSetChanged();
}
return actionBar.getTabCount();
}
private void addTab(String text) {
doNotifyDataSetChangedOnce = true;
Tab tab = actionBar.newTab();
tab.setText(text);
tab.setTabListener(this);
actionBar.addTab(tab);
}
private void removeTab(int position) {
doNotifyDataSetChangedOnce = true;
actionBar.removeTabAt(position);
}
Solution 3
I was getting this error like you by referencing the tabs within getCount():
@Override
public int getCount() {
return mTabs.size();
}
When instantiated this should either be passed in as a separate variable, or the pager should be set up after the collection has been populated / mutated.
Solution 4
try this. I worked
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
System.out.println("Asyncrona onPostExecute");
/*::::::::::::::::::: Guardo los cambios ::::::::::::::*/
//menuTabs = menuTabs2;
viewPager = (ViewPager) rootView.findViewById(R.id.viewPager_menu);
costumAdapter = new CostumAdapter2(getActivity().getSupportFragmentManager());
costumAdapter.notifyDataSetChanged();
viewPager.setAdapter(costumAdapter);
tabLayout = (TabLayout) rootView.findViewById(R.id.tablayout_menu);
tabLayout.setOnTabSelectedListener(new TabLayout.OnTabSelectedListener() {
@Override
public void onTabSelected(TabLayout.Tab tab) {
System.out.println(" La Seleccionado: " + tab.getText()+", POSICION: "+tab.getPosition());
viewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabUnselected(TabLayout.Tab tab) {
viewPager.setCurrentItem(tab.getPosition());
}
@Override
public void onTabReselected(TabLayout.Tab tab) {
viewPager.setCurrentItem(tab.getPosition());
}
});
viewPager.setAdapter(costumAdapter);
tabLayout.setupWithViewPager(viewPager);
loading.closeMessage();
}
Zagorax
Updated on October 27, 2020Comments
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Zagorax over 3 years
I'm using the
ViewPager
example withActionBar
tabs taken from the Android documentation here.Unfortunately, as soon as I call the
addTab
method, the application crashes with the following exception:IllegalStateException: The application's PagerAdapter changed the adapter's content without calling PagerAdapter#notifyDataSetChanged! Expected adapter item count 0, found 1.
This is the
FragmentPagerAdapter
code:public static class TabsAdapter extends FragmentPagerAdapter implements ActionBar.TabListener, ViewPager.OnPageChangeListener { private final Context mContext; private final ActionBar mActionBar; private final ViewPager mViewPager; private final ArrayList<TabInfo> mTabs = new ArrayList<TabInfo>(); static final class TabInfo { private final Class<?> clss; private final Bundle args; TabInfo(Class<?> _class, Bundle _args) { clss = _class; args = _args; } } public TabsAdapter(Activity activity, ViewPager pager) { super(activity.getFragmentManager()); mContext = activity; mActionBar = activity.getActionBar(); mViewPager = pager; mViewPager.setAdapter(this); mViewPager.setOnPageChangeListener(this); } public void addTab(ActionBar.Tab tab, Class<?> clss, Bundle args) { TabInfo info = new TabInfo(clss, args); tab.setTag(info); tab.setTabListener(this); mTabs.add(info); mActionBar.addTab(tab); notifyDataSetChanged(); } @Override public int getCount() { return mTabs.size(); } @Override public Fragment getItem(int position) { TabInfo info = mTabs.get(position); return Fragment.instantiate(mContext, info.clss.getName(), info.args); } @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { } @Override public void onPageSelected(int position) { mActionBar.setSelectedNavigationItem(position); } @Override public void onPageScrollStateChanged(int state) { } @Override public void onTabSelected(Tab tab, FragmentTransaction ft) { Object tag = tab.getTag(); for (int i=0; i<mTabs.size(); i++) { if (mTabs.get(i) == tag) { mViewPager.setCurrentItem(i); } } } @Override public void onTabUnselected(Tab tab, FragmentTransaction ft) { } @Override public void onTabReselected(Tab tab, FragmentTransaction ft) { } } }
I'm not modifying my adapter in any other part of my code and I'm calling the
addTab
method from the main thread, theaddTab
method ends with a call tonotifyDataSetChanged
. As the documentation recommends to do:PagerAdapter supports data set changes. Data set changes must occur on the main thread and must end with a call to notifyDataSetChanged() similar to AdapterView adapters derived from BaseAdapter.
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wizurd almost 10 yearsI've been looking for this for a while. Am I the only one who finds it odd that the error reads as if I am not calling notifyDataSetChanged(), when really I need to just perform the action(setCurrentItem in my case) After notifyDataSetChanged()?