I am banging my head for the last couple days in order to get this done but Im unable to. Someone please help me out!
Let me not tell u the whole thing and will try to explain it simply n clearly.
Im having 1 ArrayList. I am trying to replicate that into another one and trying to delete an item at a particular index. But this not only deletes the item in the replicated ArrayList but also the original ArrayList.
For ex:
var DuplicateList:ArrayList = new ArrayList();
DuplicateList = OriginalList;
DuplicateList.removeItemAt(2);
The above not only deletes the "Item 3" at Index-2 in the DuplicateList but also in the OriginalList.
I just need some workaround with this approach as this is the only way by which whatever I typed inside the controls present in an ItemRenderer of a FLEX List control that uses the OriginalList as a dataProvider is RETAINED, when I change the dataProvider of the List Control from OriginalList to DuplicateList. The following approach does not retain all the data.
var DuplicateList:ArrayList = new ArrayList();
DuplicateList.addAll(OriginalList);
DuplicateList.removeItemAt(2);
ListCntrl.dataProvider = DuplicateList;
Thanks for your help in advance...
A very, very important thing to understand:
ActionScript3 uses references to objects. Because of that, the two variables in this line of code refer to the exact same instance of an ArrayList:
DuplicateList = OriginalList;
So, when you remove an item from one reference, it is gone from the next. If you want two separate instances of ArrayList, then you need to clone it like you are suggesting later in your code.
So far, so good... but why is your ListCntrl retaining the data from the OriginalList? That doesn't make any sense at all. If you remove an item from DuplicateList and then use it as the data provider, then that item shouldn't be there. I think there is more to this story...
Related
Screen 1: GridView
Screen 2: Detail Page
Task Achieve:
1) Load all the videos in gridview from the server.
2) User clicks at any position of gridview item.
3) Open and play the particular video in detail screen.
4) On vertical scroll play next or previous videos.
Current Implementation:
GridFragment {
ArrayList<VideoPostModel> videoPostList;
RecyclerView gridView;
onnItemClick() {
Intent intent = new Intent(this, DetailActivity.class);
intent.putExtra("data", videoPostList);
intent.putExtra("click_index", clickedIndex);
intent.putExtra("pagination_index", paginationIndex);
startActivity(intent);
}
}
DetailActivity {
VerticlaViewPager vertiCalViewPager;
ArrayList<VideoPostModel> videoPostList;
onCreate() {
videoPostList = getIntent().getParcelableArrayListExtra("data");
clickedIndex = getIntent().getIntExtra("clickindex", 0);
paginationIndex = getIntent().getIntExtra("pagination_index", 0);
VideoFragmentStatePagerAdapter viewPagerAdapter = new VideoFragmentStatePagerAdapter(videoPostList);
vertiCalViewPager.setAdapter(viewPagerAdapter);
}
}
Problem:
If videoPostList has more data(approx 100+ objects of VideoPostModel) while passing data from fragment to activity then app crashes, as there is a limitation of sending data with intent(https://stackoverflow.com/a/37054839/3598052).
Hacky Alternatives:
1) Static arraylist
2) Arraylist in Application class
Looking for the OPTIMAL and EFFICIENT solution to achieve above functionality.
Any suggestion, reference link or code in the direction of achieving this would be highly appreciated, and thanks in advance.
Update 1:
Another solution I found is passing data with enum, but as per comments I'm not sure about it's performance. Refrence: https://stackoverflow.com/a/14706456/3598052
I think you can write in an activity or use Arraylist in the application as you mentioned. Or it could be a library that recently appeared in the Android Jetpack. It is similar in nature to the Arraylist in application.
ViewModel objects that make it easier to manage and store data.
It lets you access data at different activities or fragments in an application. You try it and hope it will be useful to you
You have several options. I'll put my opinion here.
Static list
Enum
Singleton class with list
LiveData
Most easy would be making static list at activity or application level. Just make sure you are freeing up List memory after use by making it NULL.
Another solution I found is passing data with enum, but as per
comments I'm not sure about it's performance
There would be sure some differences in each of above approaches. But that would not be measurable difference, because each approach put List in memory, use it and then free up.
Looking for the OPTIMAL and EFFICIENT solution to achieve above
functionality.
Make static List, and make it NULL after use. will be most efficient and easy way.
You can make List NULL in onDestroy() of your Fragment.
You can use LiveData but I think it would be not a good idea to add LiveData library just for one use in app. Also you need to understand it first. So you can go with static list.
in Activity
showFragment();
ApplicationClass.list = myList;
In Fragment
onViewCreated(){
...
setAdapter(ApplicationClass.list);
...
}
onDestroy(){
ApplicationClass.list = null;
}
Important
It is never a good idea to pull all data at once from server. Please do pagination, which you app needs most, because there can be thousands of users online at one time.
So by that approach you will pass only few items to Fragment. then you will do pagination in Fragment.
This approach needs time to change flow a bit. But is most robust way in your case.
Edit
If you are already using pagination and still getting large data at one time, that's again an issue. Because pagination is used to escape these memory issues.
You can do 2 things as solution.
1. Ask for limited data at once, say 50-60 items per request.
2. You can map and remove unnecessary fields from your list when passing in intent.
I would prefer the first one.
I know I'm late but this will help some future visitor.
Add Pagination & transfer data with arraylist & clicked position to detail activity using intent & after, set the current position of clicked position.
like viewpager.setCurrentPosition(clickedPosition);
I'm starting learning Android and I want to know if there is some option in Android that let you modify each item or view (I don't know how it's named exactly, I mean each of the items from an ArrayList that you show in a ListView).
Well, I made a ListView that is going to show some books that were located in an ArrayList named "books".
I made a custom adapter that I associate to the ListView to show each item with the corresponding layout in the application. I also have a class "book" for each item that is going to be shown in the ListView.
Further, I made an Intent that I call from MainActivity with startForActivityResult(), that I process in Book class and that I return to MainActivity with all data of a book with the method setResult and got the information with onActivityResult() and the requestCode.
So I don't have any problem to add items to the ListView, just I have the problems if I want to modify some of the items (or views) that are located in the ListView (for example if I have title and author of a book, if I put some wrong information, I want have the option to change it).
I have that, in the same moment that you click on some of the items of the ListView, a new layout will be show to modify the information that it's wrong so I use the method setOnItemClickListener with onItemClick event on the custom adapter that I created before. Here it's where I call the new Intent to modify the wrong information with the method startActivityForResult().
I made the same as before to add a new item but, instead of add a new item with custom_adapter.addBook(title,author) I want to know if there is some option to made something like this: custom_adapter.modify(title,author) or custom_adapter.update(title,author), I mean, when you have modify all the items that were wrong of a book (for example an EditText that were "title") and you have all the information in the MainActivity class (because you returned it with setResult), how to put it again in the same item updating it in the custom_adapter and also in the ArrayList.
I searched it on the Internet but I didn't find anything.
I'm sorry if I have a poor English, but I expect that it can be understand.
Thank you very much!
If I am understanding your problem correctly - you could simply modify the ArrayList of type Book that is backing your ArrayAdapter.
So if you know what Book object you want to modify then you can simply make your changes to the Book object itself. As long as this Book is a reference to the same object that you originally added to the ArrayList you instantiated your ArrayAdapter with then you can then call custom_adapter.notifyDataSetChanged() to tell the adapter to redraw its childviews with the new data.
There are some good code samples on the Internet but you have to understand the code for your purposes. So...here is a start, look at Using an ArrayAdapter with ListView. The code shows the use of ArrayAdapter with getView() method. And I hope it shows how to define the listeners, which you need.
How about that for a start? Have fun...
Thank you very much for all help you gave to me. I'm very pleased with you. :)
Finally, I just send the info with a Bundle when I started the Intent, also with the position. And after, I just used this position to set the new info to my items (in my case, books).
Again, thank you very much ;)
I have a class called people that has its own name, id etc...
I have a full list of people in an array list public ArrayList<people> pList;
When I click on some names I want to add the people in pList to public ArrayList<people> followList; Doing followList.add(pList.get(position)) doesn't work. What is the proper way to do this.
Also, on another click I would like to remove the particular object from the followList so I tried doing followList.remove(pList.get(position)) but obviously it doesn't work as well.
Im basically trying to have a list of people from the original list.
The followList seems to be not initialized. You should call initialize it with new ArrayList<people>() before adding to or removing from it.
Are you sure that you have instantiated the ArrayList followList, and that there is in fact a element at pList[position]?
I use a custom list adapter and ArrayList for my ListView. This solution was good enough but now I need to use Map of ArrayLists, something like this:
TreeMap<String, ArrayList<ItemsModel>>
where ItemsModel is a Java bean. Earlier I used to populate this ArrayList it that way:
itemsDataArrayList.add(itemModel)
Now I faced some difficulties with Map interface. First, I don't know how to populate my new Map structure: I suppose this
mapInstance.put(itemModel.getItemName.toString(), itemsDataArrayList)
won't work because itemsDataArrayList is the list of elements, not a certain element.
Second, I'm not sure how to properly declare this map instance in my ItemsAdapter class. When I was using just ArrayList it was very simple. Some examples would be very helpful.
What I recommend you look into / try is creating your own BaseAdapter. When you override this class it will give you all the functions you need to override to populate the list view.
This has the advantage of giving you complete control of what is put into the listview and how each view is created.
Then after you get it working I recommend looking into the ViewHolder design pattern along with recycling views which is a great way of improving efficiency when scrolling the listview.
What you are really looking for seem to be a MultiMap. To your first Question - your attemp was quite good, you can only put ArrayLists as values into your TreeMap.
The Problem with this might be, that if you want to add some ItemsModel to your Map, you first need to get the List of the key, and then add the ItemsModel to that list. Additionally you need to ensure, that this list for this particular key exist, and if not, create it.
Example:
String key = "hi";
ArrayList keyList = mapInstance.get(key);
if (keyList == null) {
keyList = new ArrayList();
mapInstance.put(key, keyList);
}
keyList.add(itemsModelInstance);
A get()/contains() and so on may be somehow equal. I'd suggest you build your own Multimap<?,?> Implementation or just take an existing one, like the one from Guava (link above).
Kind regards,
avi
I have implmented pagination and it display 5 records per page. Now suppose I am on page 3 and click 3'rd element then 3'rd element of page-1 is selected.
I am not able to figure out problem as I always create new list object while setting data.
I used below code
temp = new ArrayList();
this.someListAdapter = new SomeListAdapter(this, R.layout.row_facet,temp);
setListAdapter(this.someListAdapter );
Below is signature of SomeListAdapter class.
public class SomeListAdapter extends ArrayAdapter<VoNeighborhood> {
}
Please help....
There really aren't enough details here about how you do pagination with your ListView.
So I might guess you're overriding onListItemClick and using the position variable it sends you, but you then don't take into account the page you're on?
Alternatively, just don't use pagination as you have an infinite canvas to scroll your list within — I don't think I've recall seeing an Android app so far that uses pagination!