RecyclerView上拉加載更多功能回彈實現

部分代碼參考http://blog.csdn.net/dalancon/article/details/46125667

實現原理是使用RecyclerView的OnTouchListener方法監聽滑動 在adapter裏面增加兩項footview 其中date.size爲顯示的加載條，可以自定義，date.size+1爲空白的View，我們設置其高度爲0 我們通過LinearLayoutManager的 findLastVisibleItemPosition判斷顯示的最後一條數據，如果是空白view，表示加載條已經完全展示，鬆開即可刷新。

回彈效果是通過在滑動時動態改變空白view的高度，達到阻尼效果 ，回彈時再動態將其改爲0，達到回彈效果，通過loading防止加載過程中滑動導致顯示問題 這裏的回調採用了Runnable傳參

public class RefreshFootAdapter extends
		RecyclerView.Adapter<RecyclerView.ViewHolder> {
	// 上拉加載更多
	public static final int SATUS_PULLUP_LOAD_MORE = 0;
	// 正在加載中
	public static final int SATUS_LOADING_MORE = 1;
	public static final int SATUS_UP_LOADING_MORE = 2;
	// 上拉加載更多狀態-默認爲0
	private int load_more_status = 0;
	private LayoutInflater mInflater;
	private List<String> mTitles = null;
	private static final int TYPE_ITEM = 0; // 普通Item View
	private static final int TYPE_FOOTER = 1; // 底部FootView
	private static final int TYPE_FOOTER_EMPTY = 2; // 底部空白View
	private static int pagesize;
	private int eview_height = 1;
	private long TimeFlag;// 回彈時間
	private RecyclerView parent;
	private boolean loadmare;// 判斷當前是可加載更多
	private boolean loading;// 判斷是否正在加載
	private int startY, nowY;// 滑動判斷
	//構造函數 處理滑動監聽 更新等功能
	public RefreshFootAdapter(Context context, RecyclerView parent,
			final LinearLayoutManager linearLayoutManager, int pagesize,
			final Runnable onloadmore) {
		this.parent = parent;
		this.mInflater = LayoutInflater.from(context);
		this.mTitles = new ArrayList<String>();
		for (int i = 0; i < 20; i++) {
			int index = i + 1;
			mTitles.add("item" + index);
		}
		this.pagesize = pagesize;
		parent.setOnTouchListener(new OnTouchListener() {

			@Override
			public boolean onTouch(View v, MotionEvent ev) {
				// TODO Auto-generated method stub

				switch (ev.getAction()) {

				case MotionEvent.ACTION_MOVE:

					nowY = (int) ev.getY();

					if (RefreshFootAdapter.this.getItemCount() == linearLayoutManager
							.findLastVisibleItemPosition() + 1) {
						if (startY == 0) {// 按下
							startY = nowY;
						}
						int changeY = nowY - startY;
						RefreshFootAdapter.this
								.notifyEmptyView((int) (-changeY / 1.3f));

						if (loading) {
							return false;
						}
						RefreshFootAdapter.this
								.changeMoreStatus(RefreshFootAdapter.this.SATUS_UP_LOADING_MORE);

						loadmare = true;
					} else {
						loadmare = false;
						if (loading) {
							return false;
						}
						RefreshFootAdapter.this
								.changeMoreStatus(RefreshFootAdapter.this.SATUS_PULLUP_LOAD_MORE);
						// 普通的滑動
						startY = 0;
					}

					break;
				case MotionEvent.ACTION_UP:
					RefreshFootAdapter.this.resetEmptyView();
					if (loadmare) {
						if (loading) {
							return false;
						} else {
							RefreshFootAdapter.this
									.changeMoreStatus(RefreshFootAdapter.this.SATUS_LOADING_MORE);
							if (onloadmore != null && !loading) {
								loading = true;
								onloadmore.run();
							}
						}
					}
					startY = 0;
					break;
				default:

					break;
				}
				return false;
			}
		});
	}

	/**
	 * item顯示類型
	 * 
	 * @param parent
	 * @param viewType
	 * @return
	 */
	public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent,
			int viewType) {
		// 進行判斷顯示類型，來創建返回不同的View
		if (viewType == TYPE_ITEM) {
			View view = mInflater.inflate(R.layout.item_recycler_layout,
					parent, false);
			// 這邊可以做一些屬性設置，甚至事件監聽綁定
			// view.setBackgroundColor(Color.RED);
			ItemViewHolder itemViewHolder = new ItemViewHolder(view);
			return itemViewHolder;
		} else if (viewType == TYPE_FOOTER) {
			View foot_view = mInflater.inflate(
					R.layout.recycler_load_more_layout, parent, false);
			// 這邊可以做一些屬性設置，甚至事件監聽綁定
			// view.setBackgroundColor(Color.RED);
			FootViewHolder footViewHolder = new FootViewHolder(foot_view);
			return footViewHolder;
		} else if (viewType == TYPE_FOOTER_EMPTY) {
			View foot_view_empty = mInflater.inflate(
					R.layout.recycler_load_more_layout_empty, parent, false);
			// 這邊可以做一些屬性設置，甚至事件監聽綁定
			// view.setBackgroundColor(Color.RED);
			FootEmptyHolder footEmptyViewHolder = new FootEmptyHolder(
					foot_view_empty);
			return footEmptyViewHolder;
		}
		return null;
	}

	/**
	 * 數據的綁定顯示
	 * 
	 * @param holder
	 * @param position
	 */
	public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
		if (holder instanceof ItemViewHolder) {
			((ItemViewHolder) holder).item_tv.setText(mTitles.get(position));
			holder.itemView.setTag(position);
		} else if (holder instanceof FootViewHolder) {
			FootViewHolder footViewHolder = (FootViewHolder) holder;
			switch (load_more_status) {
			case SATUS_PULLUP_LOAD_MORE:
				footViewHolder.foot_view_item_tv.setText("上拉加載更多...");
				break;
			case SATUS_LOADING_MORE:
				footViewHolder.foot_view_item_tv.setText("正在加載更多數據...");
				break;
			case SATUS_UP_LOADING_MORE:
				footViewHolder.foot_view_item_tv.setText("鬆開加載更多數據...");
				break;
			}
		} else if (holder instanceof FootEmptyHolder) {
			FootEmptyHolder footViewHolder = (FootEmptyHolder) holder;
			footViewHolder.empty.setLayoutParams(new ViewGroup.LayoutParams(
					111, eview_height));

		}
	}

	/**
	 * 進行判斷是普通Item視圖還是FootView視圖
	 * 
	 * @param position
	 * @return
	 */
	@Override
	public int getItemViewType(int position) {
		// 最後一個item設置爲footerView
		if (position + 1 == getItemCount()) {
			return TYPE_FOOTER_EMPTY;
		} else if (position + 2 == getItemCount()) {
			return TYPE_FOOTER;
		} else {
			return TYPE_ITEM;
		}
	}
	//如果是頁數的倍數 itemcount+2
	@Override
	public int getItemCount() {
		if (mTitles.size() % pagesize != 0) {
			return mTitles.size();
		} else {
			return mTitles.size() + 2;
		}
		// return mTitles.size()+1;
	}

	// 自定義的ViewHolder，持有每個Item的的所有界面元素
	public static class ItemViewHolder extends RecyclerView.ViewHolder {
		public TextView item_tv;

		public ItemViewHolder(View view) {
			super(view);
			item_tv = (TextView) view.findViewById(R.id.item_tv);
		}
	}

	/**
	 * 底部FootView佈局
	 */
	public static class FootViewHolder extends RecyclerView.ViewHolder {
		private TextView foot_view_item_tv;

		public FootViewHolder(View view) {
			super(view);
			foot_view_item_tv = (TextView) view
					.findViewById(R.id.foot_view_item_tv);
		}
	}
	//空白項
	public static class FootEmptyHolder extends RecyclerView.ViewHolder {
		private View empty;

		public FootEmptyHolder(View view) {
			super(view);
			empty = view.findViewById(R.id.empty);
		}
	}

	// 添加數據
	public void addItem(List<String> newDatas) {
		// mTitles.add(position, data);
		// notifyItemInserted(position);
		newDatas.addAll(mTitles);
		mTitles.removeAll(mTitles);
		mTitles.addAll(newDatas);
		notifyDataSetChanged();
	}
	//更新添加數據
	public void addMoreItem(List<String> newDatas) {
		mTitles.addAll(newDatas);
		notifyDataSetChanged();
	}
	//更新空白項高度
	private void notifyEmptyView(int height) {
		this.eview_height = height;
		notifyItemChanged(getItemCount() - 1);
	}
	//空白回彈 僞回彈動畫
	private void resetEmptyView() {
		final int dx = eview_height;
		new Thread(new Runnable() {

			@Override
			public void run() {
				// TODO Auto-generated method stub
				final int time = 500;
				final long startTime = new Date().getTime();
				TimeFlag = startTime;
				long nowTime = new Date().getTime();
				while (startTime + time > nowTime && TimeFlag == startTime) {
					nowTime = new Date().getTime();
					final int dt = (int) (nowTime - startTime);
					parent.post(new Runnable() {

						@Override
						public void run() {
							// TODO Auto-generated method stub
							eview_height = eview_height * (time - dt) / time;
							notifyDataSetChanged();
						}
					});

					try {
						Thread.sleep(10);
					} catch (InterruptedException e) {
						// TODO Auto-generated catch block
						e.printStackTrace();
					}
				}
				parent.post(new Runnable() {

					@Override
					public void run() {
						// TODO Auto-generated method stub
						eview_height = 0;
						notifyDataSetChanged();
					}
				});
			}
		}).start();
	}
	//停止加載更多 重置loading狀態和顯示文本
	public void stopLoadMore() {

		notifyDataSetChanged();
		loading = false;
		RefreshFootAdapter.this
		.changeMoreStatus(RefreshFootAdapter.this.SATUS_PULLUP_LOAD_MORE);
	}

	//改變加載條狀態
	private void changeMoreStatus(int status) {
		if (loading) {
			return;
		}
		load_more_status = status;
		notifyDataSetChanged();
	}
}

圖1爲滑動過程

圖2爲鬆開加載