ListView的下拉刷新和上拉加载--XListView

分析XListView的源码，是因为其他开源控件代码都太多了（主要很多细微的地方都不懂，只能理解个大概），这个控件只是在原生ListView的基础上添加Header和Footer，代码很简单，可以随便折腾。

Github地址：Github上搜索这个就行-----XListView-Android

看Header代码：

/**
 * @file XListViewHeader.java
 * @create Apr 18, 2012 5:22:27 PM
 * @author Maxwin
 * @description XListView's header
 */
package me.maxwin.view;

import me.maxwin.R;
import android.content.Context;
import android.util.AttributeSet;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.RotateAnimation;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.ProgressBar;
import android.widget.TextView;

public class XListViewHeader extends LinearLayout {
	private LinearLayout mContainer;
	private ImageView mArrowImageView;
	private ProgressBar mProgressBar;
	private TextView mHintTextView;
	private int mState = STATE_NORMAL;

	private Animation mRotateUpAnim;
	private Animation mRotateDownAnim;
	
	private final int ROTATE_ANIM_DURATION = 180;

	// 正常状态 （箭头不动，进度条隐藏）
	public final static int STATE_NORMAL = 0;
	// 准备状态 （箭头向上或者向下旋转，进度条隐藏）
	public final static int STATE_READY = 1;
	// 刷新状态 （箭头隐藏，进度条旋转）
	public final static int STATE_REFRESHING = 2;

	public XListViewHeader(Context context) {
		super(context);
		initView(context);
	}

	/**
	 * @param context c
	 * @param attrs a
	 */
	public XListViewHeader(Context context, AttributeSet attrs) {
		super(context, attrs);
		initView(context);
	}

	/**
	 * 初始化整个布局：箭头、时间文字、进度条
	 * 布局宽为FILL_PARENT，Gravity为BOTTOM，这个是为了更新header高度的时候，布局始终在parent的底部
	 * 箭头的旋转动画
	 * @param context activity
	 */
	private void initView(Context context) {
		// 初始情况，设置下拉刷新view高度为0
		LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(
				LayoutParams.MATCH_PARENT, 0);
		mContainer = (LinearLayout) LayoutInflater.from(context).inflate(
				R.layout.xlistview_header, null);
		addView(mContainer, lp);
		setGravity(Gravity.BOTTOM);

		mArrowImageView = (ImageView)findViewById(R.id.xlistview_header_arrow);
		mHintTextView = (TextView)findViewById(R.id.xlistview_header_hint_textview);
		mProgressBar = (ProgressBar)findViewById(R.id.xlistview_header_progressbar);
		
		mRotateUpAnim = new RotateAnimation(0.0f, -180.0f,
				Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF,
				0.5f);
		mRotateUpAnim.setDuration(ROTATE_ANIM_DURATION);
		mRotateUpAnim.setFillAfter(true);
		mRotateDownAnim = new RotateAnimation(-180.0f, 0.0f,
				Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF,
				0.5f);
		mRotateDownAnim.setDuration(ROTATE_ANIM_DURATION);
		mRotateDownAnim.setFillAfter(true);
	}

	/**
	 * 设置刷新的状态：STATE_NORMAL / STATE_READY / STATE_REFRESHING
	 * 箭头和进度条的隐藏/显示 由上面的if语句判断
	 * 状态之间的变化由switch语句判断
	 * @param state state
	 */
	public void setState(int state) {
		// 与之前状态一样，什么都不干
		if (state == mState) return ;

		/**
		 * 正在刷新显示进度和文字
		 * 否则显示箭头和文字
		 * 也可以按自己需求做成别的样子
 		 */
		if (state == STATE_REFRESHING) {	// 显示进度
			mArrowImageView.clearAnimation();
			mArrowImageView.setVisibility(View.INVISIBLE);
			mProgressBar.setVisibility(View.VISIBLE);
		} else {	// 显示箭头图片
			mArrowImageView.setVisibility(View.VISIBLE);
			mProgressBar.setVisibility(View.INVISIBLE);
		}
		
		switch(state){
		case STATE_NORMAL:
			/**
			 * mState 记录的是之前的状态
			 * 这句代码的意思就是：由STATE_READY变为STATE_NORMAL
			 * 箭头向下旋转
			 */
			if (mState == STATE_READY) {
				mArrowImageView.startAnimation(mRotateDownAnim);
			}

			/**
			 * STATE_REFRESHING 变为 STATE_NORMAL
			 * 动画清除
			 */
			if (mState == STATE_REFRESHING) {
				mArrowImageView.clearAnimation();
			}
			mHintTextView.setText(R.string.xlistview_header_hint_normal);
			break;
		case STATE_READY:
			/**
			 * STATE_REFRESHING 变为 STATE_READY （没有这个状态变化）
			 * STATE_NORMAL 变为 STATE_READY
			 * 箭头向上旋转
			 */
			if (mState != STATE_READY) {
				mArrowImageView.clearAnimation();
				mArrowImageView.startAnimation(mRotateUpAnim);
				mHintTextView.setText(R.string.xlistview_header_hint_ready);
			}
			break;
		case STATE_REFRESHING:
			mHintTextView.setText(R.string.xlistview_header_hint_loading);
			break;
			default:
		}
		
		mState = state;
	}

	/**
	 * 设置头布局的高度
	 * @param height h
	 */
	public void setVisibleHeight(int height) {
		if (height < 0)
			height = 0;
		LinearLayout.LayoutParams lp = (LinearLayout.LayoutParams) mContainer
				.getLayoutParams();
		lp.height = height;
		mContainer.setLayoutParams(lp);
	}

	/**
	 * 获取头布局的高度
	 * @return h
	 */
	public int getVisibleHeight() {
		return mContainer.getLayoutParams().height;
	}

}

　　

看Footer的代码：

/**
 * @file XFooterView.java
 * @create Mar 31, 2012 9:33:43 PM
 * @author Maxwin
 * @description XListView's footer
 */
package me.maxwin.view;

import me.maxwin.R;
import android.content.Context;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.LinearLayout;
import android.widget.TextView;

/**
 * 上拉加载（显示出footer后，再继续往上拉才会出发上拉加载事件，或者直接点击footer）
 * 如果要做自动加载效果，可以自己监听ListView的滑动事件
 */
public class XListViewFooter extends LinearLayout {
	public final static int STATE_NORMAL = 0;
	public final static int STATE_READY = 1;
	public final static int STATE_LOADING = 2;

	private Context mContext;

	private View mContentView;
	private View mProgressBar;
	private TextView mHintView;
	
	public XListViewFooter(Context context) {
		super(context);
		initView(context);
	}
	
	public XListViewFooter(Context context, AttributeSet attrs) {
		super(context, attrs);
		initView(context);
	}

	/**
	 * 设置上拉状态
	 * @param state s
	 */
	public void setState(int state) {
		mHintView.setVisibility(View.INVISIBLE);
		mProgressBar.setVisibility(View.INVISIBLE);
		mHintView.setVisibility(View.INVISIBLE);
		/**
		 * STATE_READY：只显示准备文字
		 * STATE_LOADING：只显示进度条
		 * STATE_NORMAL：只显示正常文字
		 * 仍然可以根据自己需要调整
		 */
		if (state == STATE_READY) {
			mHintView.setVisibility(View.VISIBLE);
			mHintView.setText(R.string.xlistview_footer_hint_ready);
		} else if (state == STATE_LOADING) {
			mProgressBar.setVisibility(View.VISIBLE);
		} else {
			mHintView.setVisibility(View.VISIBLE);
			mHintView.setText(R.string.xlistview_footer_hint_normal);
		}
	}

	/**
	 * 设置footer的margin值
	 * @param height h
	 */
	public void setBottomMargin(int height) {
		if (height < 0) return ;
		LinearLayout.LayoutParams lp = (LinearLayout.LayoutParams)mContentView.getLayoutParams();
		lp.bottomMargin = height;
		mContentView.setLayoutParams(lp);
	}

	/**
	 * 获取footer的margin值
	 * @return
	 */
	public int getBottomMargin() {
		LinearLayout.LayoutParams lp = (LinearLayout.LayoutParams)mContentView.getLayoutParams();
		return lp.bottomMargin;
	}
	
	
	/**
	 * 正常状态
	 * normal status
	 */
	public void normal() {
		mHintView.setVisibility(View.VISIBLE);
		mProgressBar.setVisibility(View.GONE);
	}
	
	
	/**
	 * 上拉加载状态
	 * loading status 
	 */
	public void loading() {
		mHintView.setVisibility(View.GONE);
		mProgressBar.setVisibility(View.VISIBLE);
	}
	
	/**
	 * 隐藏footer，不需要上拉加载的时候
	 * hide footer when disable pull load more
	 */
	public void hide() {
		LinearLayout.LayoutParams lp = (LinearLayout.LayoutParams)mContentView.getLayoutParams();
		lp.height = 0;
		mContentView.setLayoutParams(lp);
	}
	
	/**
	 * 显示footer
	 * show footer
	 */
	public void show() {
		LinearLayout.LayoutParams lp = (LinearLayout.LayoutParams)mContentView.getLayoutParams();
		lp.height = LayoutParams.WRAP_CONTENT;
		mContentView.setLayoutParams(lp);
	}

	/**
	 * 初始化footer布局
	 * @param context activity
	 */
	private void initView(Context context) {
		mContext = context;
		LinearLayout moreView = (LinearLayout)LayoutInflater.from(mContext).inflate(R.layout.xlistview_footer, null);
		addView(moreView);
		moreView.setLayoutParams(new LinearLayout.LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.WRAP_CONTENT));
		
		mContentView = moreView.findViewById(R.id.xlistview_footer_content);
		mProgressBar = moreView.findViewById(R.id.xlistview_footer_progressbar);
		mHintView = (TextView)moreView.findViewById(R.id.xlistview_footer_hint_textview);
	}
	
	
}

　　

　　

看XListView的代码：

/**
 * @file XListView.java
 * @package me.maxwin.view
 * @create Mar 18, 2012 6:28:41 PM
 * @author Maxwin
 * @description An ListView support (a) Pull down to refresh, (b) Pull up to load more.
 * 		Implement IXListViewListener, and see stopRefresh() / stopLoadMore().
 */
package me.maxwin.view;

import me.maxwin.R;
import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewTreeObserver.OnGlobalLayoutListener;
import android.view.animation.DecelerateInterpolator;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.RelativeLayout;
import android.widget.Scroller;
import android.widget.TextView;

public class XListView extends ListView implements OnScrollListener {

	private float mLastY = -1; // save event y
	private Scroller mScroller; // used for scroll back
	private OnScrollListener mScrollListener; // user's scroll listener

	// the interface to trigger refresh and load more.
	private IXListViewListener mListViewListener;

	// -- header view
	private XListViewHeader mHeaderView;
	// header view content, use it to calculate the Header's height. And hide it
	// when disable pull refresh.
	private RelativeLayout mHeaderViewContent;
	private TextView mHeaderTimeView;
	private int mHeaderViewHeight; // header view's height
	private boolean mEnablePullRefresh = true;
	private boolean mPullRefreshing = false; // is refreashing.

	// -- footer view
	private XListViewFooter mFooterView;
	private boolean mEnablePullLoad;
	private boolean mPullLoading;
	private boolean mIsFooterReady = false;
	
	// total list items, used to detect is at the bottom of listview.
	private int mTotalItemCount;

	// for mScroller, scroll back from header or footer.
	private int mScrollBack;
	private final static int SCROLLBACK_HEADER = 0;
	private final static int SCROLLBACK_FOOTER = 1;

	private final static int SCROLL_DURATION = 400; // scroll back duration
	private final static int PULL_LOAD_MORE_DELTA = 50; // when pull up >= 50px
														// at bottom, trigger
														// load more.
	private final static float OFFSET_RADIO = 1.8f; // support iOS like pull
													// feature.

	public XListView(Context context) {
		super(context);
		initWithContext(context);
	}

	public XListView(Context context, AttributeSet attrs) {
		super(context, attrs);
		initWithContext(context);
	}

	public XListView(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
		initWithContext(context);
	}

	/**
	 * mScroller 用来处理滚动的
	 * 初始化header，添加header到ListView，获取header的高度
	 * 初始化footer，不添加到ListView，放在setAdapter里
	 * @param context activity
	 */
	private void initWithContext(Context context) {
		mScroller = new Scroller(context, new DecelerateInterpolator());
		// XListView need the scroll event, and it will dispatch the event to
		// user's listener (as a proxy).
		super.setOnScrollListener(this);

		// init header view
		mHeaderView = new XListViewHeader(context);
		mHeaderViewContent = (RelativeLayout) mHeaderView
				.findViewById(R.id.xlistview_header_content);
		mHeaderTimeView = (TextView) mHeaderView
				.findViewById(R.id.xlistview_header_time);
		addHeaderView(mHeaderView);

		// init footer view
		mFooterView = new XListViewFooter(context);

		// init header height
		mHeaderView.getViewTreeObserver().addOnGlobalLayoutListener(
				new OnGlobalLayoutListener() {
					@Override
					public void onGlobalLayout() {
						mHeaderViewHeight = mHeaderViewContent.getHeight();
						getViewTreeObserver()
								.removeGlobalOnLayoutListener(this);
					}
				});
	}

	/**
	 * 先addFooter再setAdapter，避免footer不显示（我遇到过）
	 * mIsFooterReady是判断footer添加过没有，footer只能添加一次
	 * @param adapter a
	 */
	@Override
	public void setAdapter(ListAdapter adapter) {
		// make sure XListViewFooter is the last footer view, and only add once.
		if (mIsFooterReady == false) {
			mIsFooterReady = true;
			addFooterView(mFooterView);
		}
		super.setAdapter(adapter);
	}

	/**
	 * 设置是否可以下拉刷新
	 *
	 * enable or disable pull down refresh feature.
	 * 
	 * @param enable e
	 */
	public void setPullRefreshEnable(boolean enable) {
		mEnablePullRefresh = enable;
		if (!mEnablePullRefresh) { // disable, hide the content
			mHeaderViewContent.setVisibility(View.INVISIBLE);
		} else {
			mHeaderViewContent.setVisibility(View.VISIBLE);
		}
	}

	/**
	 * 设置是否可以上拉加载
	 *
	 * enable or disable pull up load more feature.
	 * 
	 * @param enable e
	 */
	public void setPullLoadEnable(boolean enable) {
		mEnablePullLoad = enable;
		if (!mEnablePullLoad) {
			mFooterView.hide();
			mFooterView.setOnClickListener(null);
			//make sure "pull up" don't show a line in bottom when listview with one page 
			setFooterDividersEnabled(false);
		} else {
			mPullLoading = false;
			mFooterView.show();
			mFooterView.setState(XListViewFooter.STATE_NORMAL);
			//make sure "pull up" don't show a line in bottom when listview with one page  
			setFooterDividersEnabled(true);
			// both "pull up" and "click" will invoke load more.
			mFooterView.setOnClickListener(new OnClickListener() {
				@Override
				public void onClick(View v) {
					startLoadMore();
				}
			});
		}
	}

	/**
	 * 停止下拉刷新，重置header
	 * stop refresh, reset header view.
	 */
	public void stopRefresh() {
		if (mPullRefreshing == true) {
			mPullRefreshing = false;
			resetHeaderHeight();
		}
	}

	/**
	 * 停止上拉加载，重置footer
	 * stop load more, reset footer view.
	 */
	public void stopLoadMore() {
		if (mPullLoading == true) {
			mPullLoading = false;
			mFooterView.setState(XListViewFooter.STATE_NORMAL);
		}
	}

	/**
	 * 设置上拉刷新的时间
	 * set last refresh time
	 * 
	 * @param time
	 */
	public void setRefreshTime(String time) {
		mHeaderTimeView.setText(time);
	}

	/**
	 * 触发滑动事件（监听器需要实现OnXScrollListener）
	 */
	private void invokeOnScrolling() {
		if (mScrollListener instanceof OnXScrollListener) {
			OnXScrollListener l = (OnXScrollListener) mScrollListener;
			l.onXScrolling(this);
		}
	}

	/**
	 * 更新header的高度
	 * @param delta 手指拖动的距离
	 */
	private void updateHeaderHeight(float delta) {
		// 更新header的高度 = 之前的高度 + delta
		mHeaderView.setVisibleHeight((int) delta
				+ mHeaderView.getVisibleHeight());

		// 可以下拉刷新，并且不是正在刷新状态
		if (mEnablePullRefresh && !mPullRefreshing) { // 未处于刷新状态，更新箭头

			/**
			 * 更新后的高度 > header的初始高度了，状态变为准备状态
			 * 否则，仍然是普通状态
			 */
			if (mHeaderView.getVisibleHeight() > mHeaderViewHeight) {
				mHeaderView.setState(XListViewHeader.STATE_READY);
			} else {
				mHeaderView.setState(XListViewHeader.STATE_NORMAL);
			}
		}

		/**
		 * 这里是没有看懂的地方，为啥子？？？？
		 */
		setSelection(0); // scroll to top each time
	}

	/**
	 * 重置header的高度
	 * header没有完全显示，什么都不做
	 * header完全显示了，用mScroller实现滚动（从height到finalHeight - height），header刚好显示
	 * reset header view's height.
	 */
	private void resetHeaderHeight() {
		int height = mHeaderView.getVisibleHeight();
		if (height == 0) // not visible.
			return;
		// refreshing and header isn't shown fully. do nothing.
		if (mPullRefreshing && height <= mHeaderViewHeight) {
			return;
		}
		int finalHeight = 0; // default: scroll back to dismiss header.
		// is refreshing, just scroll back to show all the header.
		if (mPullRefreshing && height > mHeaderViewHeight) {
			finalHeight = mHeaderViewHeight;
		}
		mScrollBack = SCROLLBACK_HEADER;
		mScroller.startScroll(0, height, 0, finalHeight - height,
				SCROLL_DURATION);
		// trigger computeScroll
		invalidate();
	}

	/**
	 * 更新footer
	 * @param delta d
	 */
	private void updateFooterHeight(float delta) {
		int height = mFooterView.getBottomMargin() + (int) delta;
		if (mEnablePullLoad && !mPullLoading) {
			// 如果footer的margin + 手指拖动的距离 > 限定的距离, 认为触发了上拉加载事件
			if (height > PULL_LOAD_MORE_DELTA) { // height enough to invoke load
													// more.
				mFooterView.setState(XListViewFooter.STATE_READY);
			} else {
				mFooterView.setState(XListViewFooter.STATE_NORMAL);
			}
		}
		// 更新footer的margin值
		mFooterView.setBottomMargin(height);

//		setSelection(mTotalItemCount - 1); // scroll to bottom
	}

	/**
	 * 重置footer的margin
	 * 利用mScroller滚动 （从 bottomMargin 到 -bottomMargin）
	 */
	private void resetFooterHeight() {
		int bottomMargin = mFooterView.getBottomMargin();
		if (bottomMargin > 0) {
			mScrollBack = SCROLLBACK_FOOTER;
			mScroller.startScroll(0, bottomMargin, 0, -bottomMargin,
					SCROLL_DURATION);
			invalidate();
		}
	}

	/**
	 * 触发上拉加载更多事件，更新footer状态，触发回调
	 */
	private void startLoadMore() {
		mPullLoading = true;
		mFooterView.setState(XListViewFooter.STATE_LOADING);
		if (mListViewListener != null) {
			mListViewListener.onLoadMore();
		}
	}

	@Override
	public boolean onTouchEvent(MotionEvent ev) {
		if (mLastY == -1) {
			mLastY = ev.getRawY();
		}

		switch (ev.getAction()) {
		case MotionEvent.ACTION_DOWN:
			mLastY = ev.getRawY();
			break;
		case MotionEvent.ACTION_MOVE:
			final float deltaY = ev.getRawY() - mLastY;
			mLastY = ev.getRawY();

			/**
			 * ListView的第一个item在最顶部，并且手指向下拖动：更新header，触发header滑动监听（onXScrolling）
			 * ListView的最后一个item在底部，并且手指向上拖动：更新footer
			 *
			 */
			if (getFirstVisiblePosition() == 0
					&& (mHeaderView.getVisibleHeight() > 0 || deltaY > 0)) {
				// the first item is showing, header has shown or pull down.
				updateHeaderHeight(deltaY / OFFSET_RADIO);
				invokeOnScrolling();
			} else if (getLastVisiblePosition() == mTotalItemCount - 1
					&& (mFooterView.getBottomMargin() > 0 || deltaY < 0)) {
				// last item, already pulled up or want to pull up.
				updateFooterHeight(-deltaY / OFFSET_RADIO);
			}
			break;
		default:
			/**
			 * 这里的ev.getAction()应该是：
			 * UP 和 CANCEL
 			 */
			mLastY = -1; // reset
			if (getFirstVisiblePosition() == 0) {
				// invoke refresh
				/**
				 * 释放手指的之后，header的高度 > 最原本的高度，触发下拉刷新事件
				 * 更新状态，并回调
				 * 最后重置高度
				 */
				if (mEnablePullRefresh
						&& mHeaderView.getVisibleHeight() > mHeaderViewHeight) {
					mPullRefreshing = true;
					mHeaderView.setState(XListViewHeader.STATE_REFRESHING);
					if (mListViewListener != null) {
						mListViewListener.onRefresh();
					}
				}
				resetHeaderHeight();
			} else if (getLastVisiblePosition() == mTotalItemCount - 1) {
				// invoke load more.
				/**
				 * 释放手指之后，footer的margin > 限定的距离
				 * 触发上拉加载事件，并回调
				 * 最后重置高度
				 */
				if (mEnablePullLoad
				    && mFooterView.getBottomMargin() > PULL_LOAD_MORE_DELTA
				    && !mPullLoading) {
					startLoadMore();
				}
				resetFooterHeight();
			}
			break;
		}
		return super.onTouchEvent(ev);
	}

	/**
	 * mScroll 实现滚动必须要覆盖的方法
	 */
	@Override
	public void computeScroll() {
		if (mScroller.computeScrollOffset()) {
			if (mScrollBack == SCROLLBACK_HEADER) {
				mHeaderView.setVisibleHeight(mScroller.getCurrY());
			} else {
				mFooterView.setBottomMargin(mScroller.getCurrY());
			}
			postInvalidate();
			invokeOnScrolling();
		}
		super.computeScroll();
	}

	@Override
	public void setOnScrollListener(OnScrollListener l) {
		mScrollListener = l;
	}

	@Override
	public void onScrollStateChanged(AbsListView view, int scrollState) {
		if (mScrollListener != null) {
			mScrollListener.onScrollStateChanged(view, scrollState);
		}
	}

	@Override
	public void onScroll(AbsListView view, int firstVisibleItem,
			int visibleItemCount, int totalItemCount) {
		// send to user's listener
		mTotalItemCount = totalItemCount;
		if (mScrollListener != null) {
			mScrollListener.onScroll(view, firstVisibleItem, visibleItemCount,
					totalItemCount);
		}
	}

	public void setXListViewListener(IXListViewListener l) {
		mListViewListener = l;
	}

	/**
	 * you can listen ListView.OnScrollListener or this one. it will invoke
	 * onXScrolling when header/footer scroll back.
	 */
	public interface OnXScrollListener extends OnScrollListener {
		public void onXScrolling(View view);
	}

	/**
	 * implements this interface to get refresh/load more event.
	 */
	public interface IXListViewListener {
		public void onRefresh();

		public void onLoadMore();
	}
}

　　

结束，很简单啊。