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adapter.notifyDataSetChanged() crashes for listview inside fragment

i have one arraylist inside onCreateView() of fragment which contains the data to be updated inside listview, i am using interface callback to update the data from another activity as follow:
listUpdatable.update(nameStr,otpStr,timeStr);
my update method inside the fragment is as follow:
#Override
public void update(String name, String time, String otp) {
SentMessageModel message = new SentMessageModel();
message.setOtp(otp);
message.setName(name);
message.setTime(time);
messages.add(0, message);
adapter.notifyDataSetChanged();
}
The app carashes on calling update method is showing the NPE on arraylist.
What should i do?
View view = inflater.inflate(R.layout.fragment_sent_message_history, container, false);
ListView listView = view.findViewById(R.id.sent_message_listView);
emptyText = view.findViewById(R.id.empty_text);
messages = new ArrayList<>();
databaseCodeForAll(); // fetches the content of messages arraylist from sqlite
adapter = new SentMessageAdapter(getContext(), messages);
listView.setAdapter(adapter);
The code is inside onCreateView().

How to reload listview on a activity?

I have 2 activity.
In activity 1, i have a listview show data from database and button Insert
Activity 2 use to add something to database.
When I click button ADD in activity 2, i call method finish() and return to activity 1.
So, somebody can show me how to reload listview in activity 1 please?

Recreating the adapter should help, because you need to get a new dataset as Kaaaarll said.
So for example you have something like this in your code:
MyData data = database.getData();
MyAdapter adapter = new MyAdapter(data);
ListView list = new ListView();
list.setAdapter(adapter);
and in the next run, in the onResume(), get fresh data and reapply the adapter:
MyData data = database.getData();
MyAdapter adapter = new MyAdapter(data);
list.setAdapter(adapter);

You can re-query the database to get the latest data and then repopulate your listview's adapter.

Notify the dataset in the onResume() method activity 1. It should be something like listViewAdapter.notifyDataSetChanged();. Don't forget to check whether they are null or not.
Let me know if it worked.
EDIT:
Something like this should do the work (in activity 1):
#Override
protected void onResume() {
super.onResume();
if (listViewAdapter != null) {
listViewAdapter.notifyDataSetChanged();
}
}

ListView items not getting populated when activity is launched

Here is my scenario:
I have a MainActivity and a CustomListViewActivity. In my MainActivity, I have 1 button and 1 spinner. On click of the button, I pass the selected spinner value to the CustomListViewActivity via Bundle and using Intents.
Now, in my CustomListViewActivity, I have a ListView that uses ArrayAdapter for populating it. I send a ArrayList from MainActivity, say for example
items = [abc]
In my CustomListViewActivity, I receive the same and use it to populate my ListView. The first time I do this, my value gets populated. The second time I do the same, the value existing is now replaced with the new one and the ListView shows one item instead of showing two.
So basically the problem is that the ListView is not updating and not showing both the items. Instead it shows me a single item always.
Here are snippets of my code
MainActivity.java
//code inside button click
..
{
items.add(spinner1.getSelectedItem().toString());
Bundle bundle =new Bundle();
bundle.putStringArrayList("data",items);
Intent i = new Intent(MainActivity.this,MyListViewActivity.class);
i.putExtras(bundle);
startActivity(i);
finish();
}
protected void onSaveInstanceState(Bundle icicle) {
super.onSaveInstanceState(icicle);
Log.i("App","onSave");
icicle.putStringArrayList("data",items);
}
#Override
protected void onRestoreInstanceState(Bundle icicle2) {
// TODO Auto-generated method stub
super.onRestoreInstanceState(icicle2);
Log.i("App","onRestore");
icicle2.putStringArrayList("data",items);
}
MyListViewActivity.java
private ArrayList<String> myItems;
private static String[] titles;
CustomListViewAdapter adapter;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.list_main);
listView = (ListView) findViewById(R.id.list1);
rowItems = new ArrayList<RowItem>();
adapter = new CustomListViewAdapter(this,R.layout.list_item, rowItems);
listView.setAdapter(adapter);
b=getIntent().getExtras();
if(b!=null)
{
myItems=b.getStringArrayList("data");
titles= new String[myItems.size()];
titles = myItems.toArray(myItems);
}
...
int i=0;
while(i<titles.length) {
item = new RowItem(titles[i]);
//rowItems.add(item);
Log.i("ROW", ""+rowItems.size());
i++;
adapter.add(item);
listView.setAdapter(adapter);
}
adapter.setNotifyOnChange(true);
adapter.notifyDataSetChanged();
}
}
How to make the ListView maintain the current data as well reflect the added data?
Thanks in advance
EDIT : Forgot to mention one more thing. In my MyListViewActivity class I have a button above the ListView that on clicked takes me to my MainActivity so that I can add a new Item again. So when I go back to MainActivity and try and add a new Item , it's the new Item that get displayed rather than showing both the previous and the new one

You need to persist and restore your items list in MainActivity's onSaveInstanceState and onRestoreInstanceState methods.
You also probably don't need to close the MainActivity by calling finish() every time you start the ListView activity but that depends on your application.
Basically, the problem you are having is that items is being recreated with each new instance of MainActivity. Since you finish MainActivity, a new instance is used every time you access that activity (and I assume you thought that items would just keep getting items added to it).

android refresh listview adapter within getview()

I have got a custom list view adapter and an image button in the adapter class. When i click on the image button, the listener should reload the list view. I need to reload the list view within getview() of adapter class. So I need to know other options than using notifyDataSetChanged() in my listActivity class.
Thanks

You want to refresh a cell inside the listview or do you want to refresh the whole listview, if a single row is loaded inside getView() ?
Check this out:
Android ListView Refresh Single Row

Create a static handler inside the activity which calls a method which reloads the listview and send a message to this handler from the adapter whenever required.
handler = new Handler() {
public void handleMessage(Message paramAnonymousMessage) {
switch (paramAnonymousMessage.what) {
case 1:
populateList();
break;
}
}
};
public void populateBill() {
MyBasketAdapter adapter = new MyBasketAdapter(this, basketList);
listView = (ListView) findViewById(android.R.id.list);
listView.setAdapter(adapter);
}
Inside the adapter class. for example,
button.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
Message msg = Message.obtain();
msg.what = 1;
MyActivity.handler.sendMessage(msg);
}
});

That is very Simple just write a method in your adapter class and call it get view when you deleting or adding anything in your list which you are binding to your adapter.and use notifyDataSetChanged after change in list
public void updateResults(ArrayList<CustomList> results) {
// assign the new result list to your existing list it will work
notifyDataSetChanged();
}

List view back on first position after updating from custom adapter

List view is refreshed every N minutes of interval using a web service call. After refresh my current position goes back to the first item in list view.
Here is my code.
private void updateListUI(String response){
arrList = new ArrayList<Object>(); // to store array list
Object obj;
obj = some data; // some parsing of data and store in obj instance
arrList.add(obj);
if(listview.getAdapter()==null){
adapter = new customAdapter(myActivity,layout,arrList);
listview.setAdapter(adapter);
}else{
HeaderViewListAdapter adapterwrap =
(HeaderViewListAdapter) listview.getAdapter();
BaseAdapter basadapter = (BaseAdapter) adapterwrap.getWrappedAdapter();
customAdapter ad = (customAdapter)basadapter;
ad.setData(arrList); // it is a func in custom adapter that add items
ad.notifyDataSetChanged();
// here i want to set the position of list view,as it goes back to first item
}
}
BroadcastReceiver serviceReceiver = new BroadcastReceiver() {
public void onReceive( final Context context, final Intent intent ) {
updateListUI(intent.getStringExtra(response_from_service));
}
}
// Intent service calls webservice and broadcast response to receiver as finishes call. My question is on every updateListUI call list view goes back to first position. Is any way to solve this..?

use listLead.setSelectionFromTop(index, top); to set the position in list view

You can restore the posistion of your ListView using:
int position = 12; // your position in listview
ListView listView = (ListView) findViewById(R.id.listView);
listView.setSelectionFromTop(position, 0);

Instead of loading setAdapter during refresh
use the below code ... it will work
yourAdapterName.notifyDataSetChanged();

Just use the method notifyDataSetChanged() at the point where you want to refresh your list view.