Android, ListView IllegalStateException: "The content of the adapter has changed but ListView did not receive a notification"
What I want to do: run a background thread which calculates ListView contents and update ListView partially, while results are calculated.
What I know I have to avoid: I cannot mess with ListAdapter contents from background thread, so I inherited AsyncTask and publish result (add entries to adapter) from onProgressUpdate. My Adapter uses ArrayList of result objects, all operations on those arraylists are synchronized.
Research of other people: there is very valuable data here. I also suffered from almost daily crashes for group of ~500 users, and when I added list.setVisibility(GONE)/trackList.setVisibility(VISIBLE) block in onProgressUpdate, crashes lowered by a factor of 10 but not disappeared. (it was suggested in answer )
What I got sometimes: please notice, it happens really rarely (once a week for one of 3.5k users). But I'd like to get rid of this bug completely. Here is partial stacktrace:
`java.lang.IllegalStateException:` The content of the adapter has changed but ListView did not receive a notification. Make sure the content of your adapter is not modified from a background thread, but only from the UI thread. [in ListView(2131296334, class android.widget.ListView) with Adapter(class com.transportoid.Tracks.TrackListAdapter)]
at android.widget.ListView.layoutChildren(ListView.java:1432)
at android.widget.AbsListView.onTouchEvent(AbsListView.java:2062)
at android.widget.ListView.onTouchEvent(ListView.java:3234)
at android.view.View.dispatchTouchEvent(View.java:3709)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:852)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:884)
[...]
Help? Not needed anymore, see below
FINAL ANSWER: As it turned out, I was calling notifyDataSetChanged every 5 insertions to avoid flickering and sudden list changes. It cannot be done such way, always notify adapter when base list changes. This bug it long gone for me now.
Solution 1:
I had the same issue.
I was adding items to my ArrayList outside the UI thread.
Solution: I have done both, adding the items and called notifyDataSetChanged() in the UI thread.
Solution 2:
I had the same problem, but I fixed it using the method
requestLayout();
from the class ListView
Solution 3:
This is a MultiThreading Issue and Using Properly Synchronized Blocks This can be prevented. Without putting extra things on UI Thread and causing loss of responsiveness of app.
I also faced the same. And as the most accepted answer suggests making change to adapter data from UI Thread can solve the issue. That will work but is a quick and easy solution but not the best one.
As you can see for a normal case. Updating data adapter from background thread and calling notifyDataSetChanged in UI thread works.
This illegalStateException arises when a ui thread is updating the view and another background thread changes the data again. That moment causes this issue.
So if you will synchronize all the code which is changing the adapter data and making notifydatasetchange call. This issue should be gone. As gone for me and i am still updating the data from background thread.
Here is my case specific code for others to refer.
My loader on the main screen loads the phone book contacts into my data sources in the background.
@Override
public Void loadInBackground() {
Log.v(TAG, "Init loadings contacts");
synchronized (SingleTonProvider.getInstance()) {
PhoneBookManager.preparePhoneBookContacts(getContext());
}
}
This PhoneBookManager.getPhoneBookContacts reads contact from phonebook and fills them in the hashmaps. Which is directly usable for List Adapters to draw list.
There is a button on my screen. That opens a activity where these phone numbers are listed. If i directly setAdapter over the list before the previous thread finishes its work which is fast naviagtion case happens less often. It pops up the exception .Which is title of this SO question. So i have to do something like this in the second activity.
My loader in the second activity waits for first thread to complete. Till it shows a progress bar. Check the loadInBackground of both the loaders.
Then it creates the adapter and deliver it to the activity where on ui thread i call setAdapter.
That solved my issue.
This code is a snippet only. You need to change it to compile well for you.
@Override
public Loader<PhoneBookContactAdapter> onCreateLoader(int arg0, Bundle arg1) {
return new PhoneBookContactLoader(this);
}
@Override
public void onLoadFinished(Loader<PhoneBookContactAdapter> arg0, PhoneBookContactAdapter arg1) {
contactList.setAdapter(adapter = arg1);
}
/*
* AsyncLoader to load phonebook and notify the list once done.
*/
private static class PhoneBookContactLoader extends AsyncTaskLoader<PhoneBookContactAdapter> {
private PhoneBookContactAdapter adapter;
public PhoneBookContactLoader(Context context) {
super(context);
}
@Override
public PhoneBookContactAdapter loadInBackground() {
synchronized (SingleTonProvider.getInstance()) {
return adapter = new PhoneBookContactAdapter(getContext());
}
}
}
Hope this helps
Solution 4:
I solved this by have 2 Lists. One list I use for only the adapter, and I do all data changes/updates on the other list. This allows me to do updates on one list in a background thread, and then update the "adapter" list in the main/UI thread:
List<> data = new ArrayList<>();
List<> adapterData = new ArrayList();
...
adapter = new Adapter(adapterData);
listView.setAdapter(adapter);
// Whenever data needs to be updated, it can be done in a separate thread
void updateDataAsync()
{
new Thread(new Runnable()
{
@Override
public void run()
{
// Make updates the "data" list.
...
// Update your adapter.
refreshList();
}
}).start();
}
void refreshList()
{
runOnUiThread(new Runnable()
{
@Override
public void run()
{
adapterData.clear();
adapterData.addAll(data);
adapter.notifyDataSetChanged();
listView.invalidateViews();
}
});
}
Solution 5:
I wrote this code and had it run in a 2.1 emulator image for ~12 hours and did not get the IllegalStateException. I'm going to give the android framework the benefit of the doubt on this one and say that it is most likely an error in your code. I hope this helps. Maybe you can adapt it to your list and data.
public class ListViewStressTest extends ListActivity {
ArrayAdapter<String> adapter;
ListView list;
AsyncTask<Void, String, Void> task;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1);
this.list = this.getListView();
this.list.setAdapter(this.adapter);
this.task = new AsyncTask<Void, String, Void>() {
Random r = new Random();
int[] delete;
volatile boolean scroll = false;
@Override
protected void onProgressUpdate(String... values) {
if(scroll) {
scroll = false;
doScroll();
return;
}
if(values == null) {
doDelete();
return;
}
doUpdate(values);
if(ListViewStressTest.this.adapter.getCount() > 5000) {
ListViewStressTest.this.adapter.clear();
}
}
private void doScroll() {
if(ListViewStressTest.this.adapter.getCount() == 0) {
return;
}
int n = r.nextInt(ListViewStressTest.this.adapter.getCount());
ListViewStressTest.this.list.setSelection(n);
}
private void doDelete() {
int[] d;
synchronized(this) {
d = this.delete;
}
if(d == null) {
return;
}
for(int i = 0 ; i < d.length ; i++) {
int index = d[i];
if(index >= 0 && index < ListViewStressTest.this.adapter.getCount()) {
ListViewStressTest.this.adapter.remove(ListViewStressTest.this.adapter.getItem(index));
}
}
}
private void doUpdate(String... values) {
for(int i = 0 ; i < values.length ; i++) {
ListViewStressTest.this.adapter.add(values[i]);
}
}
private void updateList() {
int number = r.nextInt(30) + 1;
String[] strings = new String[number];
for(int i = 0 ; i < number ; i++) {
strings[i] = Long.toString(r.nextLong());
}
this.publishProgress(strings);
}
private void deleteFromList() {
int number = r.nextInt(20) + 1;
int[] toDelete = new int[number];
for(int i = 0 ; i < number ; i++) {
int num = ListViewStressTest.this.adapter.getCount();
if(num < 2) {
break;
}
toDelete[i] = r.nextInt(num);
}
synchronized(this) {
this.delete = toDelete;
}
this.publishProgress(null);
}
private void scrollSomewhere() {
this.scroll = true;
this.publishProgress(null);
}
@Override
protected Void doInBackground(Void... params) {
while(true) {
int what = r.nextInt(3);
switch(what) {
case 0:
updateList();
break;
case 1:
deleteFromList();
break;
case 2:
scrollSomewhere();
break;
}
try {
Thread.sleep(0);
} catch(InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
};
this.task.execute(null);
}
}