Created
July 11, 2014 05:34
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Endless scroll listener for list view
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| import android.widget.AbsListView; | |
| /** | |
| * Created by JohnMars on 7/10/14. | |
| * Version 1.0 | |
| */ | |
| public abstract class EndlessScrollListener implements AbsListView.OnScrollListener { | |
| private int visibleThreshold = 5; | |
| // The current offset index of data you have loaded | |
| private int currentPage = 0; | |
| // The total number of items in the data set after the last load | |
| private int previousTotalItemCount = 0; | |
| // True if we are still waiting for the last set of data to load. | |
| private boolean loading = true; | |
| // Sets the starting page index | |
| private int startingPageIndex = 0; | |
| public EndlessScrollListener() { | |
| } | |
| public EndlessScrollListener(int visibleThreshold) { | |
| this.visibleThreshold = visibleThreshold; | |
| } | |
| public EndlessScrollListener(int visibleThreshold, int startPage) { | |
| this.visibleThreshold = visibleThreshold; | |
| this.startingPageIndex = startPage; | |
| this.currentPage = startPage; | |
| } | |
| // This happens many times a second during a scroll, so be wary of the code you place here. | |
| // We are given a few useful parameters to help us work out if we need to load some more data, | |
| // but first we check if we are waiting for the previous load to finish. | |
| @Override | |
| public void onScroll(AbsListView view,int firstVisibleItem,int visibleItemCount,int totalItemCount) | |
| { | |
| // If the total item count is zero and the previous isn't, assume the | |
| // list is invalidated and should be reset back to initial state | |
| if (totalItemCount < previousTotalItemCount) { | |
| this.currentPage = this.startingPageIndex; | |
| this.previousTotalItemCount = totalItemCount; | |
| if (totalItemCount == 0) { this.loading = true; } | |
| } | |
| // If it’s still loading, we check to see if the dataset count has | |
| // changed, if so we conclude it has finished loading and update the current page | |
| // number and total item count. | |
| if (loading && (totalItemCount > previousTotalItemCount)) { | |
| loading = false; | |
| previousTotalItemCount = totalItemCount; | |
| currentPage++; | |
| } | |
| // If it isn’t currently loading, we check to see if we have breached | |
| // the visibleThreshold and need to reload more data. | |
| // If we do need to reload some more data, we execute onLoadMore to fetch the data. | |
| if (!loading && (totalItemCount - visibleItemCount)<=(firstVisibleItem + visibleThreshold)) { | |
| onLoadMore(currentPage + 1, totalItemCount); | |
| loading = true; | |
| } | |
| } | |
| // Defines the process for actually loading more data based on page | |
| public abstract void onLoadMore(int page, int totalItemsCount); | |
| @Override | |
| public void onScrollStateChanged(AbsListView view, int scrollState) { | |
| // Don't take any action on changed | |
| } | |
| } |
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