Question

我正在寻找包含10个项目的Listview。如果在第10个项目之后发生向下滚动，它应该从头开始回绕。

所有10个项目都已修复，我没有动态添加它们。

Item1，Item2 ...... Item10下一页滚动Item1，Item2，Item3 ....

Answer 1

您可以使用EndlessScrollListener执行此任务。

import android.widget.AbsListView; 

public abstract class EndlessScrollListener implements AbsListView.OnScrollListener {
    // The minimum number of items to have below your current scroll position
    // before loading more.
    private int visibleThreshold = 5;
    // The current offset index of data you have loaded
    private int currentPage = 0;
    // The total number of items in the dataset 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;
    }


    @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 && (firstVisibleItem + visibleItemCount + visibleThreshold) >= totalItemCount ) {
            loading = onLoadMore(currentPage + 1, totalItemCount);
        }
    }

    // Defines the process for actually loading more data based on page
    // Returns true if more data is being loaded; returns false if there is no more data to load.
    public abstract boolean onLoadMore(int page, int totalItemsCount);

    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) {
        // Don't take any action on changed
    }
}

然后在您的活动中覆盖onLoadMore方法。

 public class MainActivity extends Activity {
        @Override
        protected void onCreate(Bundle savedInstanceState) {
            // ... the usual 
            ListView lvItems = (ListView) findViewById(R.id.lvItems);
            // Attach the listener to the AdapterView onCreate
            lvItems.setOnScrollListener(new EndlessScrollListener() {
              @Override
              public boolean onLoadMore(int page, int totalItemsCount) {
                  // Triggered only when new data needs to be appended to the list
                  // Add whatever code is needed to append new items to your AdapterView
                  reloadFirst10(); 
                  return true; // ONLY if more data is actually being loaded; false otherwise.
              }
            });
        }


       // Append the next page of data into the adapter 
       public void reloadFirst10() {
         for(int i = 0; i < 10; i++) {
             yourArrayList.add(mAdapter.getItem(i));
         }
          //  --> Notify the adapter of the new items made with `notifyDataSetChanged()`
         mAdapter.notifyDataSetChanged();
       }
    }

Answer 2

首先，覆盖getCount()以返回一个巨大的数字：

@Override
public int getCount() {
    return Integer.MAX_VALUE;
}

这不会无限滚动，但我非常怀疑任何用户都会滚动超过20亿个项目。

然后，在getView()内，您可以使用模运算符索引到列表中：

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    position = (position % 10); // change 10 to whatever fixed number of items you have 
    ...
}

您的适配器的其余部分应该像您创建的任何其他ListView适配器一样编写。

具有预定义项目的Listview，在到达最终项目后，它应该从android中的第一个项目开始

2 个答案: