Android: Implementing progressbar and “loading…” for Endless List like Android Market

问题

Taking inspiration from Android Market, i have implemented a Endless List which loads more data from the server when we reach the end of the List.

Now, i need to implement the progressbar & "Loading.." text as shown

Sample code to take inspiration from would be great.

回答1:

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.

回答2:

Add an onScrollListener to the ListView. When the user scrolls, check if the ListView is nearing its end. If yes, then fetch more data. As an example :

public abstract class LazyLoader implements AbsListView.OnScrollListener {

    private static final int DEFAULT_THRESHOLD = 10 ;

    private boolean loading = true  ;
    private int previousTotal = 0 ;
    private int threshold = DEFAULT_THRESHOLD ;

    public LazyLoader() {}

    public LazyLoader(int threshold) {
        this.threshold = threshold;
    }

    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) {
    }

    @Override
    public void onScroll(AbsListView view, int firstVisibleItem,
                         int visibleItemCount, int totalItemCount) {
        if(loading) {
            if(totalItemCount > previousTotal) {
                // the loading has finished
                loading = false ;
                previousTotal = totalItemCount ;
            }
        }

        // check if the List needs more data
        if(!loading && ((firstVisibleItem + visibleItemCount ) >= (totalItemCount - threshold))) {
            loading = true ;

            // List needs more data. Go fetch !!
            loadMore(view, firstVisibleItem,
                    visibleItemCount, totalItemCount);
        }
    }

    // Called when the user is nearing the end of the ListView
    // and the ListView is ready to add more items.
    public abstract void loadMore(AbsListView view, int firstVisibleItem,
                                  int visibleItemCount, int totalItemCount);
}

Activity :

public class MainActivity extends AppCompatActivity {

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);

            setContentView(R.layout.main_layout);
            ListView listView = (ListView) findViewById(R.id.listView);

            listView.setOnScrollListener(new LazyLoader() {
                @Override
                public void loadMore(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
                    // Fetch your data here !!!
                }
            });
        }
    }

You can find the complete implementation at this link

来源：https://stackoverflow.com/questions/4667064/android-implementing-progressbar-and-loading-for-endless-list-like-android

标签

android

android-listview