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Custom BaseAdapter duplicates items in ListView

I have a custom adapter which inherits from BaseAdapter, and I have a ListView in a different .java file. Basically I click on a button and this calls the custom adapter. So when the app first loads the fist time I click the button, it's fine. On every subsequent click the items (retaining order) are duplicated both the number and the contents of the items. I am sure there is something wrong with the overridden getView method:
public View getView(int position, View convertView, ViewGroup parent) {}
However I am not sure whether the View convertView is set to anything on when the items are ready to be displayed in the ListView. So I put a check in there:
if (view == null) {}
I think this check is the root of the problem.
Any help will be appreciated.
Here is the gist to the SharedResourcesAdapter, the custom adapter class:
https://gist.github.com/serceberka/f34c8f3339ef9e4bc9dc23d3ac8f74c4
Here is the gist to the SharedResources AppCompatActivity where the adapter gets set:
https://gist.github.com/serceberka/ea9fc73b42a9d271e6fbac7d7793667f
(You'll find it in the PageLoad class which extends AsyncTask)

The issue has been resolved.
Basically there was no problem with the custom adapter itself, the issue was that I was reading the items from a List and updating the List every time a new query was sent. To fix the problem I cleared the List before a adding items to it to avoid getting duplicated items (i.e. from the same search query) or retaining items from previous queries.

ExpandableListView forgets child changed textView

I have an expandable list view with checkboxes. When i click a child, an alertdialog and i choose the quantity and then the textView of a child changes. BUT when i scroll down the list and this child disappers from view , the list forget changed textview and set the old one. What's the reason?

ListView (and its descendent ExpandableListView) does NOT create and store the views forever; instead it creates them on-the-fly as needed.
Imagine a scenario where you have a ListView with a list containing 1000 items; but the views for only any 5 items can be visible on the screen at a given time. Do you think that ListView would create and maintain 1000 different views on the screen? That would be a waste of memory, and might cause the UI to lag.
Instead, ListView internally calls getView() function to obtain the view for each item and shows it on the screen. It does this every time the item is brought into the screen display, and only for those many number of items which can fit into the screen at a given time (ListView handles these things internally so you do not have to worry about this)
All you need to do is set the text in the corresponding list item, and use this text to populate the textview in getView(). Maintain a text String and create some form of getText() and setText(String) methods in whatever Object type you are using as an Item.
#Override
public View getView(int position, View convertView, ViewGroup parent)
{
......//initialize text view for this position
Item item = getItem(position);
textView.setText(item.getText());
.......
}
Once you set the text in the list item via alertDialog, Call notifyDataSetChanged() on the adapter to indicate that getView needs to be called again for all the views currently in display.
In your Listener, pass a reference to the adapter of the ListView. When you set the quantity in the alertDialog, just use
{
......
adapter.getItem(position).setText(quantityText);
adapter.notifyDataSetChanged();
......
}
The first line sets the text in the item; the second line tells the adapter that the information in the items have changed and it needs to create the views again.

Get child view inside a Listview Adapter

Inside my getView method I want to get a specific child view. I know that my adapter holds several items, by doing calling getCount:
getCount();
According to the JavaDoc:
public abstract int getCount ()
Added in API level 1
How many items are in the data set represented by this Adapter.
Now in my getView method:
public View getView(final int position, View convertView, ViewGroup parent) {
View lastAddedItem = parent.getChildAt(getCount()-1);
if(lastAddedItem == null) {
Log.w("ListAdapter", "View is null");
}
}
This message always appears in the LogCat, which means that the View I try to grab is Null.
I've also tried this:
View lastAddedItem = parent.getChildAt(parent.getChildCount()-1);
So how can I grab a specific view from my ViewGroup object?

I know that my adapter holds several items, by doing calling
getCount:
Yes it does, but the getCount()(returning the items in the Adapter) method of an adapter has nothing to do with getting the children of a ListView with getChildAt()(where you should use getChildCount() as this will return the Views present in the ViewGroup).
lastAddedItem = parent.getChildAt(parent.getChildCount()-1);
This should return a non-null view, the last view returned by the getView() method.
I just want to animate a specific View in my ViewGroup
If you are going to animate a list row(or part of that row) when it becomes visible than register a scroll listener for the ListView and start the animation from there when the target view is appearing on the screen.

I don't how are you implemented the rest of the adapter, but if you are doing it in the right way, and I am right, the parent only contains the Views being displayed on the device's screen, and each time you pull down or pull up the list, it modifies the content of those views, that is why you get Null.
What you want to achieve (animate a view), should be done in runtime, checking if the view currently being displayed in the screen should be animated or not.
Hope it helps.

Extending BaseAdapter, when does the view become null?

public class CustomAdapter extends BaseAdapter
I found a code that extends BaseAdapter
public View getView(int index, View view, final ViewGroup parent) {
if (view == null) {
LayoutInflater inflater = LayoutInflater.from(parent.getContext());
view = inflater.inflate(R.layout.single_list_item, parent, false);
}
}
TextView textView = (TextView) view.findViewById(R.id.tv_string_data);
textView.setText(dataModel.getName());
my question is when view == null ?
why we need the code if (view == null) {}
thanks

A ListView typically contain more data then the number of displayed rows. If the user scrolls the list then rows and their associated Views will be scrolled out of the visible area. The Java objects which represents the rows can be reused for newly visible rows.
If Android determines that a View which represents a row is not visible anymore it allows the getView() method to reuse it via the convertView parameter.
A performance optimized adapter assigns the new data to the convertView. This avoids inflating an XML file and creating new Java objects.
In case no View is available for reuse, Android will pass null to the convertView parameter. Therefore the adapter implementation need to check for this.

For the first item in the listView the View will be null. It needs to be inflated for the first item.
Please be free to ask any further doubts.

Android re-cycles View objects to minimize object creation and memory usage. The View that is passed to you will either be null, in which case you are expected to create it, or the view will be non-null which means it has been re-cycled. Re-cycled views are ones that you may have created earlier, but can now be used for a different purpose.
A good example of this is a listview. A list may have many elements, say 100. The screen however may only display 10 items of the list. Thus when you scroll the screen, views that were for items no longer on the screen may be passed to you for re-use. This is re-cycling.

For list view we have to provide view for each and every item, and also we have to fill contents also. In most cases the same view will be repeated in every item with different content. So at the first time in getView method we will check, if view is null then we should inflate a view and fill the contents and return. At second time the view will not be null. So you can reuse or provide different view.

Android:Problems with listview when I scroll the list and is disordered

I have an adapter for a ListView which dynamically gets relative layouts to display images and text loaded into the Adapter.
The problem is that when I scroll in its entirety, the Listview is ordered incorrectly. I tried using ViewHolder but that has not solved the problem.
I wonder if there is any other way to do it. Or integer Listview load without execute code that once adapter has already been loaded list.
The main problem is that the images of the other RelativeLayout layouts appear in the wrong list.
Now The problem I have now is that when you scroll through the list slowly shows fine, but if the scroll in the list is fast elements are dislodged. As if not process fast enough position parameter. public View getView(int position, View convertView, ViewGroup parent)

Check your ListAdapter's getView(); make sure that if convertView is null that you are creating it. In both cases you want to update convertView with new data, otherwise you'll have these issues (as Android will recycle those views but not update them).