Issue
Updated to describe the requested code; the updates are at the end.
I'm trying to do something that seems like it should be simple but the Android Life Cycle doesn't seem to be working as described. I expect this is a misunderstanding on my part, not a bug in Android!
I am new to Android and am just getting familiar with the Android Life Cycle after developing Java apps for Windows so I'm still struggling with a lot of new ideas, especially the Life Cycle.
I have nearly finished my first app, which is based on a RecyclerView. It shows a bunch of sales records (each representing one sale) of a small company. Users can click on a FloatingActionButton to report a new sale or click on edit or remove icons on the individual records to change the details of a sale or delete it entirely. Each of these things has its own activity. Also, there is a SettingsActivity to show settings.
One of the settings lets the user select from amongst three different date formats for displaying the date of the sale. When I back out of Settings (by hitting the back button), I want to see the visible rows using the newly-changed date format immediately but this is NOT happening. Up until now, I would just click on the buttons to take me to one of the other activities, then click the cancel button when I get there; on returning to my main activity, I would see the new date format.
I don't feel my user should have to go to that other activity; simply returning from Settings should change the dates immediately. I started looking at the Android Life Cycle. As I read the documentation, I should be overriding the onResume() method and issuing a notifyDataChanged() to the Adapter that controls the RecyclerView to get it to rebind the visible rows, using the new date format.
Unfortunately, that has no effect whatever that I can see. Here's my onResume:
@Override
protected void onResume() {
super.onResume();
mAdapter.notifyDataSetChanged();
}
Am I doing the notifyDataSetChanged() in the wrong method? If not, why doesn't it work? If it is the wrong method, which method should I be overriding?
Is there any particularly good text or video tutorial explaining the Life Cycle that I should be reading or viewing?
Updates
The date format is set in my SettingsActivity, which is the default one provided in the SettingsActivity template, tailored to meet my needs. All I've touched is the General settings. I replaced all of the ones from the template with six of my own settings. One is called Date format and defaults to YYYY-MM-DD; there are two other choices.
My main activity, which is the one that invokes SettingsActivity via a menu option, gets the value of the date format from the default SharedPreferences. This is because I don't want to look up the value of the Date format once for every row in the ArrayList but just once for all the rows in the ArrayList. I pass the value of the Date format to the Adapter via its constructor. The format gets used in OnBindViewHolder() to control the appearance of the date on the various sales records.
Solution
Define a set method to your adapter,
public class MyAdapter extends RecyclerView.Adapter<AdapterContactList.ViewHolder> {
private String dateFormat;
.....
public void setDateFormat(String dateFormat) {
this.dateFormat = dateFormat;
}
}
After user change the dateformat; set it to your adapter, then notify datas for change. That means, you need set new dateformat before notifyDataSetChanged
method; because adapter doesn't know the new value.
@Override
protected void onResume() {
super.onResume();
String newDateFormat = getFromSharedPreferencesOrInstantly();
mAdapter.setDateFormat(newDateFormat);
mAdapter.notifyDataSetChanged();
}
Answered By - misman
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