android

list

listview

How can I create a list where when you reach the end of the list I am notified so I can load more items?

Solution 1

One solution is to implement an OnScrollListener and make changes (like adding items, etc.) to the ListAdapter at a convenient state in its onScroll method.

The following ListActivity shows a list of integers, starting with 40, adding items when the user scrolls to the end of the list.

public class Test extends ListActivity implements OnScrollListener {

    Aleph0 adapter = new Aleph0();

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setListAdapter(adapter); 
        getListView().setOnScrollListener(this);
    }

    public void onScroll(AbsListView view,
        int firstVisible, int visibleCount, int totalCount) {

        boolean loadMore = /* maybe add a padding */
            firstVisible + visibleCount >= totalCount;

        if(loadMore) {
            adapter.count += visibleCount; // or any other amount
            adapter.notifyDataSetChanged();
        }
    }

    public void onScrollStateChanged(AbsListView v, int s) { }    

    class Aleph0 extends BaseAdapter {
        int count = 40; /* starting amount */

        public int getCount() { return count; }
        public Object getItem(int pos) { return pos; }
        public long getItemId(int pos) { return pos; }

        public View getView(int pos, View v, ViewGroup p) {
                TextView view = new TextView(Test.this);
                view.setText("entry " + pos);
                return view;
        }
    }
}

You should obviously use separate threads for long running actions (like loading web-data) and might want to indicate progress in the last list item (like the market or gmail apps do).

Solution 2

Just wanted to contribute a solution that I used for my app.

It is also based on the OnScrollListener interface, but I found it to have a much better scrolling performance on low-end devices, since none of the visible/total count calculations are carried out during the scroll operations.

  1. Let your ListFragment or ListActivity implement OnScrollListener
  2. Add the following methods to that class:

    @Override
    public void onScroll(AbsListView view, int firstVisibleItem,
            int visibleItemCount, int totalItemCount) {
        //leave this empty
    }
    
    @Override
    public void onScrollStateChanged(AbsListView listView, int scrollState) {
        if (scrollState == SCROLL_STATE_IDLE) {
            if (listView.getLastVisiblePosition() >= listView.getCount() - 1 - threshold) {
                currentPage++;
                //load more list items:
                loadElements(currentPage);
            }
        }
    }
    

    where currentPage is the page of your datasource that should be added to your list, and threshold is the number of list items (counted from the end) that should, if visible, trigger the loading process. If you set threshold to 0, for instance, the user has to scroll to the very end of the list in order to load more items.

  3. (optional) As you can see, the "load-more check" is only called when the user stops scrolling. To improve usability, you may inflate and add a loading indicator to the end of the list via listView.addFooterView(yourFooterView). One example for such a footer view:

    <?xml version="1.0" encoding="utf-8"?>
    
    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/footer_layout"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:padding="10dp" >
    
        <ProgressBar
            android:id="@+id/progressBar1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerVertical="true"
            android:layout_gravity="center_vertical" />
    
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_centerVertical="true"
            android:layout_toRightOf="@+id/progressBar1"
            android:padding="5dp"
            android:text="@string/loading_text" />
    
    </RelativeLayout>
    
  4. (optional) Finally, remove that loading indicator by calling listView.removeFooterView(yourFooterView) if there are no more items or pages.

Solution 3

You can detect end of the list with help of onScrollListener, working code is presented below:

@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
    if (view.getAdapter() != null && ((firstVisibleItem + visibleItemCount) >= totalItemCount) && totalItemCount != mPrevTotalItemCount) {
        Log.v(TAG, "onListEnd, extending list");
        mPrevTotalItemCount = totalItemCount;
        mAdapter.addMoreData();
    }
}

Another way to do that (inside adapter) is as following:

    public View getView(int pos, View v, ViewGroup p) {
            if(pos==getCount()-1){
                addMoreData(); //should be asynctask or thread
            }
            return view;
    }

Be aware that this method will be called many times, so you need to add another condition to block multiple calls of addMoreData().

When you add all elements to the list, please call notifyDataSetChanged() inside yours adapter to update the View (it should be run on UI thread - runOnUiThread)

Solution 4

At Ognyan Bankov GitHub i found a simple and working solution!

It makes use of the Volley HTTP library that makes networking for Android apps easier and most importantly, faster. Volley is available through the open AOSP repository.

The given code demonstrates:

  1. ListView which is populated by HTTP paginated requests.
  2. Usage of NetworkImageView.
  3. "Endless" ListView pagination with read-ahead.

For future consistence i forked Bankov's repo.

Solution 5

Here is a solution that also makes it easy to show a loading view in the end of the ListView while it's loading.

You can see the classes here:

https://github.com/CyberEagle/OpenProjects/blob/master/android-projects/widgets/src/main/java/br/com/cybereagle/androidwidgets/helper/ListViewWithLoadingIndicatorHelper.java - Helper to make it possible to use the features without extending from SimpleListViewWithLoadingIndicator.

https://github.com/CyberEagle/OpenProjects/blob/master/android-projects/widgets/src/main/java/br/com/cybereagle/androidwidgets/listener/EndlessScrollListener.java - Listener that starts loading data when the user is about to reach the bottom of the ListView.

https://github.com/CyberEagle/OpenProjects/blob/master/android-projects/widgets/src/main/java/br/com/cybereagle/androidwidgets/view/SimpleListViewWithLoadingIndicator.java - The EndlessListView. You can use this class directly or extend from it.

Solution 6

May be a little late but the following solution happened very useful in my case. In a way all you need to do is add to your ListView a Footer and create for it addOnLayoutChangeListener.

http://developer.android.com/reference/android/widget/ListView.html#addFooterView(android.view.View)

For example:

ListView listView1 = (ListView) v.findViewById(R.id.dialogsList); // Your listView
View loadMoreView = getActivity().getLayoutInflater().inflate(R.layout.list_load_more, null); // Getting your layout of FooterView, which will always be at the bottom of your listview. E.g. you may place on it the ProgressBar or leave it empty-layout.
listView1.addFooterView(loadMoreView); // Adding your View to your listview 

...

loadMoreView.addOnLayoutChangeListener(new View.OnLayoutChangeListener() {
    @Override
    public void onLayoutChange(View v, int left, int top, int right, int bottom, int oldLeft, int oldTop, int oldRight, int oldBottom) {
         Log.d("Hey!", "Your list has reached bottom");
    }
});

This event fires once when a footer becomes visible and works like a charm.

Solution 7

The key of this problem is to detect the load-more event, start an async request for data and then update the list. Also an adapter with loading indicator and other decorators is needed. In fact, the problem is very complicated in some corner cases. Just a OnScrollListener implementation is not enough, because sometimes the items do not fill the screen.

I have written a personal package which support endless list for RecyclerView, and also provide a async loader implementation AutoPagerFragment which makes it very easy to get data from a multi-page source. It can load any page you want into a RecyclerView on a custom event, not only the next page.

Here is the address: https://github.com/SphiaTower/AutoPagerRecyclerManager

Solution 8

Best solution so far that I have seen is in FastAdapter library for recycler views. It has a EndlessRecyclerOnScrollListener.

Here is an example usage: EndlessScrollListActivity

Once I used it for endless scrolling list I have realised that the setup is a very robust. I'd definitely recommend it.

Solution 9

I've been working in another solution very similar to that, but, I am using a footerView to give the possibility to the user download more elements clicking the footerView, I am using a "menu" which is shown above the ListView and in the bottom of the parent view, this "menu" hides the bottom of the ListView, so, when the listView is scrolling the menu disappear and when scroll state is idle, the menu appear again, but when the user scrolls to the end of the listView, I "ask" to know if the footerView is shown in that case, the menu doesn't appear and the user can see the footerView to load more content. Here the code:

Regards.

listView.setOnScrollListener(new OnScrollListener() {

    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) {
        // TODO Auto-generated method stub
        if(scrollState == SCROLL_STATE_IDLE) {
            if(footerView.isShown()) {
                bottomView.setVisibility(LinearLayout.INVISIBLE);
            } else {
                bottomView.setVisibility(LinearLayout.VISIBLE);
            } else {
                bottomView.setVisibility(LinearLayout.INVISIBLE);
            }
        }
    }

    @Override
    public void onScroll(AbsListView view, int firstVisibleItem,
            int visibleItemCount, int totalItemCount) {

    }
});

Solution 10

I know its an old question and the Android world has mostly moved on to RecyclerViews, but for anyone interested, you may find this library very interesting.

It uses the BaseAdapter used with the ListView to detect when the list has been scrolled to the last item or when it is being scrolled away from the last item.

It comes with an example project(barely 100 lines of Activity code) that can be used to quickly understand how it works.

Simple usage:

class Boy{

private String name;
private double height;
private int age;
//Other code

}

An adapter to hold Boy objects would look like:


public class BoysAdapter extends EndlessAdapter<Boy>{




        ViewHolder holder = null;


        if (convertView == null) {
            LayoutInflater inflater = LayoutInflater.from(parent
                    .getContext());

            holder = new ViewHolder();

            convertView = inflater.inflate(
                    R.layout.list_cell, parent, false);


            holder.nameView = convertView.findViewById(R.id.cell);

            // minimize the default image.
            convertView.setTag(holder);
        } else {
            holder = (ViewHolder) convertView.getTag();
        }

        Boy boy = getItem(position);

        try {
            holder.nameView.setText(boy.getName());

            ///Other data rendering codes.

        } catch (Exception e) {
            e.printStackTrace();
        }

        return super.getView(position,convertView,parent);

}

Notice how the BoysAdapter's getView method returns a call to the EndlessAdapter superclass's getView method. This is 100% essential.

Now to create the adapter, do:

   adapter = new ModelAdapter() {
            @Override
            public void onScrollToBottom(int bottomIndex, boolean moreItemsCouldBeAvailable) {

                if (moreItemsCouldBeAvailable) { 
                    makeYourServerCallForMoreItems();
                } else {
                    if (loadMore.getVisibility() != View.VISIBLE) {
                        loadMore.setVisibility(View.VISIBLE);
                    }
                }
            }

            @Override
            public void onScrollAwayFromBottom(int currentIndex) { 
                loadMore.setVisibility(View.GONE);
            }

            @Override
            public void onFinishedLoading(boolean moreItemsReceived) { 
                if (!moreItemsReceived) {
                    loadMore.setVisibility(View.VISIBLE);
                }
            }
        };

The loadMore item is a button or other ui element that may be clicked to fetch more data from the url. When placed as described in the code, the adapter knows exactly when to show that button and when to disable it. Just create the button in your xml and place it as shown in the adapter code above.

Enjoy.