Android实现上拉加载更多ListView(PulmListView)

public class PulmListView extends ListView {
  public PulmListView(Context context) {
    this(context, null);
  }

  public PulmListView(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
  }

  public PulmListView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    // 初始化
    init();
  }
}

private void init() {
  super.setOnScrollListener(new OnScrollListener() {
    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) {
      // 调用用户设置的OnScrollListener
      if (mUserOnScrollListener != null) {
        mUserOnScrollListener.onScrollStateChanged(view, scrollState);
      }
    }

    @Override
    public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
      // 调用用户设置的OnScrollListener
      if (mUserOnScrollListener != null) {
        mUserOnScrollListener.onScroll(view, firstVisibleItem, visibleItemCount, totalItemCount);
      }

      // firstVisibleItem是当前屏幕能显示的第一个元素的位置
      // visibleItemCount是当前屏幕能显示的元素的个数
      // totalItemCount是ListView包含的元素总数
      int lastVisibleItem = firstVisibleItem + visibleItemCount;
      if (!mIsLoading && !mIsPageFinished && lastVisibleItem == totalItemCount) {
        if (mOnPullUpLoadMoreListener != null) {
          mIsLoading = true;
          mOnPullUpLoadMoreListener.onPullUpLoadMore();
        }
      }
    }
  });
}

/**
 * 加载更多的View布局,可自定义.
 */
public class LoadMoreView extends LinearLayout {

  public LoadMoreView(Context context) {
    this(context, null);
  }

  public LoadMoreView(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
  }

  public LoadMoreView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    init();
  }

  private void init() {
    LayoutInflater.from(getContext()).inflate(R.layout.lv_load_more, this);
  }
}

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  android:id="@+id/id_load_more_layout"
  android:layout_width="match_parent"
  android:layout_height="wrap_content"
  android:orientation="horizontal"
  android:gravity="center"
  android:layout_margin="@dimen/loading_view_margin_layout">

  <ProgressBar
    android:id="@+id/id_loading_progressbar"
    android:layout_width="@dimen/loading_view_progress_size"
    android:layout_height="@dimen/loading_view_progress_size"
    android:indeterminate="true"
    style="?android:progressBarStyleSmall"/>

  <TextView
    android:id="@+id/id_loading_label"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/page_loading"/>
</LinearLayout>

private View mLoadMoreView;
private void init() {
  mLoadMoreView = new LoadMoreView(getContext());
}

private void init() {
  mIsLoading = false; // 初始化时没处于加载状态
  mIsPageFinished = false; // 初始化时默认还有更多数据需要加载
  mLoadMoreView = new LoadMoreView(getContext()); // 实例化FooterView
  super.setOnScrollListener(new OnScrollListener() {
    @Override
    public void onScrollStateChanged(AbsListView view, int scrollState) {
      // 调用用户设置的OnScrollListener
      if (mUserOnScrollListener != null) {
        mUserOnScrollListener.onScrollStateChanged(view, scrollState);
      }
    }

    @Override
    public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
      // 调用用户设置的OnScrollListener
      if (mUserOnScrollListener != null) {
        mUserOnScrollListener.onScroll(view, firstVisibleItem, visibleItemCount, totalItemCount);
      }

      int lastVisibleItem = firstVisibleItem + visibleItemCount;
      // 当处于ListView尾部且有更多数据需要加载且当前没有加载程序再进行中时, 执行加载更多操作
      if (!mIsLoading && !mIsPageFinished && lastVisibleItem == totalItemCount) {
        if (mOnPullUpLoadMoreListener != null) {
          mIsLoading = true; // 将加载更多进行时状态设置为true
          showLoadMoreView(); // 显示加载更多布局
          mOnPullUpLoadMoreListener.onPullUpLoadMore(); // 调用用户设置的加载更多回调接口
        }
      }
    }
  });
}

private void showLoadMoreView() {
  // 这里将加载更多的根布局id设置为id_load_more_layout, 便于用户自定制加载更多布局.
  if (findViewById(R.id.id_load_more_layout) == null) {
    addFooterView(mLoadMoreView);
  }
}

/**
 * 加载更多结束后ListView回调方法.
 *
 * @param isPageFinished 分页是否结束
 * @param newItems    分页加载的数据
 * @param isFirstLoad  是否第一次加载数据(用于配置下拉刷新框架使用, 避免出现页面闪现)
 */
public void onFinishLoading(boolean isPageFinished, List<?> newItems, boolean isFirstLoad) {
  mIsLoading = false; // 标记当前已经没有加载更多的程序在执行
  setIsPageFinished(isPageFinished); // 设置分页是否结束标志并移除FooterView
}

private void setIsPageFinished(boolean isPageFinished) {
  mIsPageFinished = isPageFinished;
  removeFooterView(mLoadMoreView);
}

/**
 * 上拉加载更多的回调接口
 */
public interface OnPullUpLoadMoreListener {
  void onPullUpLoadMore();
}

private OnPullUpLoadMoreListener mOnPullUpLoadMoreListener;
/**
 * 设置上拉加载更多的回调接口.
 * @param l 上拉加载更多的回调接口
 */
public void setOnPullUpLoadMoreListener(OnPullUpLoadMoreListener l) {
  this.mOnPullUpLoadMoreListener = l;
}

/**
 * 抽象的Adapter.
 */
public abstract class PulmBaseAdapter<T> extends BaseAdapter {
  protected List<T> items;

  public PulmBaseAdapter() {
    this.items = new ArrayList<>();
  }

  public PulmBaseAdapter(List<T> items) {
    this.items = items;
  }

  public void addMoreItems(List<T> newItems, boolean isFirstLoad) {
    if (isFirstLoad) {
      this.items.clear();
    }
    this.items.addAll(newItems);
    notifyDataSetChanged();
  }

  public void removeAllItems() {
    this.items.clear();
    notifyDataSetChanged();
  }
}

/**
 * 加载更多结束后ListView回调方法.
 *
 * @param isPageFinished 分页是否结束
 * @param newItems    分页加载的数据
 * @param isFirstLoad  是否第一次加载数据(用于配置下拉刷新框架使用, 避免出现页面闪现)
 */
public void onFinishLoading(boolean isPageFinished, List<?> newItems, boolean isFirstLoad) {
  mIsLoading = false;
  setIsPageFinished(isPageFinished);
  // 添加更新后的数据
  if (newItems != null && newItems.size() > 0) {
    PulmBaseAdapter adapter = (PulmBaseAdapter) ((HeaderViewListAdapter) getAdapter()).getWrappedAdapter();
    adapter.addMoreItems(newItems, isFirstLoad);
  }
}