How to notifydatasetchanged between two activities

Question

I have two activities that each contain fragments. Activity A has a fragment with a ListView. Rows of the ListView are obtained from a SQLiteDatabase.

Activity B contains a fragment that enables entries of the database to be edited. When a user edits a database entry, saves the data, then returns to Activity A via the backbutton or:

actionBar = getSupportActionBar();
actionBar.setDisplayHomeAsUpEnabled(true);
actionBar.setHomeButtonEnabled(true);

How do I notify the ListView in Activity A that there has been a change to the database? I understand how to communicate between an Activity and it's fragments, but how do I implement a notifydatasetchanged when the fragments are in two different activities?

I suspect that going back to Activity A via the back button is simply recalling the view from the stack, but that view has changed when there is a database change.

Possible duplicate of [Android ListView not refreshing after notifyDataSetChanged](http://stackoverflow.com/questions/14503006/android-listview-not-refreshing-after-notifydatasetchanged) — gevorg, Jul 06 '16 at 12:53
Please consider accepting an answer as it may be helpful for other having the same question. Thanks. — kodartcha, Aug 17 '17 at 09:14

score 0 · Answer 1 · answered Jul 06 '16 at 12:52

You could simply call the notifyDataSetChanged in onResume in your Activity A. So when you close or go back from Activity B to A, it will update the data. Don't forget to check if the adapter is different than null, otherwise it could crash the first time you open the App.

You could also make a public function in your Activity A which updates the list and call it from your Activity B.

class ActivityA

public static void updateList() {
    if(adapter != null){
      adapter.notifyDataSetChanged;
    }
}


class ActivityB

ActivityA.updateList();

Hope it helps :)

Marat · Answer 2 · 2016-07-06T13:11:55.437

You will need to read the updated dataset from your SQLite database and pass it adapter again. After you need to notify adapter. For example, like in the code below:

In your Activity A

@Override
protected void onResume() {
    super.onResume();

    // method to read new dataset
    Database ourDB = new Database(this);
    ourDB.openDB();
    data = ourDB.getData();
    ourDB.closeDB();

    if(adapter == null) {
        // initializes adapter when first launched
        adapter = new RecyclerViewAdapter(data, this);
        yourListView.setAdapter(adapter);
    }
    else {
        // in subsequent returns to activity we are replacing 
        // old data with new and reusing existing adapter
        adapter.updateData(data);
    }

}

In your adapter class include similar method:

public void updateData(ArrayList<String> newData) {
    data = newData;
    this.notifyDataSetChanged();
}

@user2254532 Did you solve your problem? If not have you tried my solution? — Marat, Jul 21 '16 at 15:24

score 0 · Answer 3 · answered Jul 06 '16 at 13:06

0

you could start activity with startActivityForResult(start activityB) and override method onActivityResult in activityA and notifyDataSetChanged when needed.

answered Jul 06 '16 at 13:06

user3593033

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How to notifydatasetchanged between two activities

3 Answers3