Android 了解GridView中的当前单元格

我正在进行GridView活动，我希望在到达特定单元格索引时从服务器获取更多项目。
比如当我已经从服务器上带来了20个项目，当我达到索引17时，我会得到另一个20项目，当我达到37时，我会得到更多20。等等
就像Facebook下面的新闻提要和图片一样，我使用的不是ListView而是GridView，我该怎么做呢

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如果您使用的是常规GridView，则可以创建一个实现

AbsListView.OnScrollListener

的类。然后跟踪可见阈值（变量在

onScroll

函数中给定），如果超过该阈值，则调用在活动中定义的抽象方法。该方法将调用您的网络函数或任何您喜欢的函数

@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);

@覆盖
public void onScroll（AbsListView视图、int firstVisibleItem、int visibleItemCount、int totalItemCount）
{
//如果项目总数为零，而前一个不是，则假定
//列表无效，应重置回初始状态
if（totalItemCountpreviousTotalItemCount））{
加载=假；
previousTotalItemCount=totalItemCount；
currentPage++；
}
//如果当前未加载，我们将检查是否已违反
//VisibleSThreshold已关闭，需要重新加载更多数据。
//如果确实需要重新加载一些数据，则执行onLoadMore来获取数据。
如果（！loading&&（firstVisibleItem+visibleItemCount+visibleThreshold）>=totalItemCount）{
加载=onLoadMore（currentPage+1，totalItemCount）；
}
}
//定义根据页面实际加载更多数据的过程
//如果正在加载更多数据，则返回true；如果没有更多数据要加载，则返回false。
公共抽象布尔onLoadMore（int page，int totalItemsCount）；

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这是有案可查的。还为RecyclerView提供了说明

当您使用回收器视图时，您可以从layoutManager调用方法getLastVisibleItem（）

经过一些搜索，我得到了这些信息，我使用了

EndlessRecycleNewsCrollListener

类并将其添加到我的项目中

import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.StaggeredGridLayoutManager;


public abstract class EndlessRecyclerViewScrollListener extends RecyclerView.OnScrollListener {
    // The minimum amount 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;

    RecyclerView.LayoutManager mLayoutManager;

    public EndlessRecyclerViewScrollListener(LinearLayoutManager layoutManager) {
        this.mLayoutManager = layoutManager;
    }

    public EndlessRecyclerViewScrollListener(GridLayoutManager layoutManager) {
        this.mLayoutManager = layoutManager;
        visibleThreshold = visibleThreshold * layoutManager.getSpanCount();
    }

    public EndlessRecyclerViewScrollListener(StaggeredGridLayoutManager layoutManager) {
        this.mLayoutManager = layoutManager;
        visibleThreshold = visibleThreshold * layoutManager.getSpanCount();
    }

    public int getLastVisibleItem(int[] lastVisibleItemPositions) {
        int maxSize = 0;
        for (int i = 0; i < lastVisibleItemPositions.length; i++) {
            if (i == 0) {
                maxSize = lastVisibleItemPositions[i];
            }
            else if (lastVisibleItemPositions[i] > maxSize) {
                maxSize = lastVisibleItemPositions[i];
            }
        }
        return maxSize;
    }

    // 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 onScrolled(RecyclerView view, int dx, int dy) {
        int lastVisibleItemPosition = 0;
        int totalItemCount = mLayoutManager.getItemCount();

        if (mLayoutManager instanceof StaggeredGridLayoutManager) {
            int[] lastVisibleItemPositions = ((StaggeredGridLayoutManager) mLayoutManager).findLastVisibleItemPositions(null);
            // get maximum element within the list
            lastVisibleItemPosition = getLastVisibleItem(lastVisibleItemPositions);
        } else if (mLayoutManager instanceof GridLayoutManager) {
            lastVisibleItemPosition = ((GridLayoutManager) mLayoutManager).findLastVisibleItemPosition();
        } else if (mLayoutManager instanceof LinearLayoutManager) {
            lastVisibleItemPosition = ((LinearLayoutManager) mLayoutManager).findLastVisibleItemPosition();
        }

        // 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;
        }

        // 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.
        // threshold should reflect how many total columns there are too
        if (!loading && (lastVisibleItemPosition + visibleThreshold) > totalItemCount) {
            currentPage++;
            onLoadMore(currentPage, totalItemCount, view);
            loading = true;
        }
    }

    // Call this method whenever performing new searches
    public void resetState() {
        this.currentPage = this.startingPageIndex;
        this.previousTotalItemCount = 0;
        this.loading = true;
    }

    // Defines the process for actually loading more data based on page
    public abstract void onLoadMore(int page, int totalItemsCount, RecyclerView view);

}

它工作得很好，希望它能帮助你：），不幸的是我记不起参考资料，我会尽快更新答案

EndlessRecyclerViewScrollListener scrollListener= new EndlessRecyclerViewScrollListener((LinearLayoutManager) layoutManager) {
        @Override
        public void onLoadMore(int page, int totalItemsCount, RecyclerView view) {
            //implement what should your code do on scrolling
        }
    };
    recyclerView.addOnScrollListener(scrollListener);