项目中需要下拉刷新的功能，但是这个View不是ListView这类的控件，需要ViewGroup实现这个功能，一开始网上大略找了一下，没发现特别合适的，代码也是没怎么看懂，所以决定还是自己写一个。

于是翻出XlistView的源码看是一点一点看，再大致理解了XLisview源码，终于决定自己动手啦

为了省事，headView还是用了XListView的HeadView，省了很多事：）

下拉刷新，下拉刷新，肯定是先实现下拉功能，最开始我是打算通过 extends ScrollView 来实现，因为有现成的滚动效果嘛，可是实际因为两个原因放弃了：

1、ScrollView下只能有一个子控件View ,虽然在 Scroll下添加一个ViewGroup，然后讲headView动态添加进前面的ViewGroup，但是我还是比较习惯studio的可视化预览，总觉得不直观！

2、 ScrollView内嵌ListView时会发生 冲突，还需要去重写ListView。于是放弃换个思路！

关于上面的原因1：动态添加headView进ScrollView的中GroupView中，可以在重写ScrollView的onViewAdded（）方法，将初始化时解析的headView添加进子GroupView

@Override public void onViewAdded(View child) { super.onViewAdded(child); //因为headView要在最上面，最先想到的就是Vertical的LinearLayout LinearLayout linearLayout = (LinearLayout) getChildAt(0); linearLayout.addView(view, 0); }

换个思路，通过extends LinearLayout来实现吧！

先做准备工作，我们需要一个HeaderView以及要获取到HeaderView的高度，还有初始时Layout的高度

private void initView(Context context) { mHeaderView = new SRefreshHeader(context); mHeaderViewContent = (RelativeLayout) mHeaderView.findViewById(R.id.slistview_header_content); setOrientation(VERTICAL); addView(mHeaderView, 0); getHeaderViewHeight(); getViewHeight(); }

mHeaderView = new SRefreshHeader(context);

通过构造方法实例化HeaderView

mHeaderViewContent = (RelativeLayout)

mHeaderView.findViewById(R.id.slistview_header_content);

这是解析headerView内容区域iew,等会儿要获取这个view的高度，你肯定会问为啥不用上面的mHeaderView来获取高度，点进构造方法里可以看到如下代码

// 初始情况，设置下拉刷新view高度为0 LayoutParams lp = new LayoutParams(LayoutParams.MATCH_PARENT, 0); mContainer = (LinearLayout) LayoutInflater.from(context).inflate(R.layout.listview_head_view_layout, null); w(mContainer, lp);

如果直接获取mHeaderView的高度 那肯定是0

getHeaderViewHeight();

getViewHeight();

分别是获取HeaderView的高度和Layout的初始高度

/** * 获取headView高度 */ private void getHeaderViewHeight() { ViewTreeObserver vto2 = mHeaderViewContent.getViewTreeObserver(); vto2.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() { @Override public void onGlobalLayout() { mHeaderViewHeight = mHeaderViewContent.getHeight(); mHeaderViewContent.getViewTreeObserver().removeGlobalOnLayoutListener(this); } }); } /** * 获取SRefreshLayout当前实例的高度 */ private void getViewHeight() { ViewTreeObserver thisView = getViewTreeObserver(); thisView.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() { @Override public void onGlobalLayout() { SRefreshLayout.this.mHeight = SRefreshLayout.this.getHeight(); SRefreshLayout.this.getViewTreeObserver().removeGlobalOnLayoutListener(this); } }); }

准备工作完成了，接下来就是要成下拉操作了

到这里，肯定一下就想到了onTouchEvent（）方法，是的！现在就开始在这里施工

实现下拉一共 会经历三个过程

ACTION_UP→ACTION_MOVE→ACTION_UP

在ACTION_UP事件中，也就是手指按下的时候，我们需要做的只是记录按下时候的坐标

switch (ev.getAction()) { case MotionEvent.ACTION_DOWN: //记录起始高度 mLastY = ev.getRawY();//记录按下时的Y坐标 break;

然后就是ACTION_MOVE事件了，这里是最重要的，因为下拉时HeadView和Layout的高度变化都在这里进行

case MotionEvent.ACTION_MOVE: if (!isRefreashing) isRefreashing = true; final float deltaY = ev.getRawY() - mLastY; mLastY = ev.getRawY(); updateHeaderViewHeight(deltaY / 1.8f);//按一定比例缩小移动距离 updateHeight(); break;

里面的updateHeaderViewHeight和updateHeight分别是改变HeaderView的高度和Layout的高度

private void updateHeight() { ViewGroup.LayoutParams lp = getLayoutParams(); //更新当前layout实例高度为headerView高度加上最初的layout高度 //如果不更新layout 会造成内容高度压缩 无法保持比例 lp.height = (mHeight + mHeaderView.getVisiableHeight()); setLayoutParams(lp); } private void updateHeaderViewHeight(float space) { // if (space < 0) // space = 0; // int factHeight = (int) (space - mHeaderViewHeight); if (mHeaderView.getStatus() != SRefreshHeader.STATE_REFRESHING) { //如果不处于刷新中同时如果高度 if (mHeaderView.getVisiableHeight() < mHeaderViewHeight * 2 && mHeaderView.getStatus() != SRefreshHeader.STATE_NORMAL) { mHeaderView.setState(SRefreshHeader.STATE_NORMAL); } if (mHeaderView.getVisiableHeight() > mHeaderViewHeight * 2 && mHeaderView.getStatus() != SRefreshHeader.STATE_READY) { mHeaderView.setState(SRefreshHeader.STATE_READY); } } mHeaderView.setVisiableHeight((int) space + mHeaderView.getVisiableHeight()); }

更新Header高度时，通过下拉的距离来判断是否到达刷新的距离，上面代码中我设定的是到达mHeaderView初始高度的两倍，就进入“释放刷新”的状态，如果没有达到则保持“下拉刷新”的状态

HeaderView中的状态一共设定了3个分别是

public final static int STATE_NORMAL = 0;//下拉刷新 public final static int STATE_READY = 1;//释放刷新 public final static int STATE_REFRESHING = 2;//刷新中

更新高度的方法headerView和layout都是相同的，就是原高度加上移动的距离重新赋给headerView或者layout

mHeaderView.setVisiableHeight((int) space

+ mHeaderView.getVisiableHeight());

最后就是ACTION_UP事件了就是手指离开屏幕的时候，在这里我们需要根据headerView目前状态来决定headerView的最终状态！

case MotionEvent.ACTION_UP: //松开时 //避免点击事件触发 if (!isRefreashing) break; //如果headView状态处于READY状态 则说明松开时应该进入REFRESHING状态 if (mHeaderView.getStatus() == SRefreshHeader.STATE_READY) { mHeaderView.setState(SRefreshHeader.STATE_REFRESHING); } //根据状态重置SrefreshLayout当前实例和headView高度 resetHeadView(mHeaderView.getStatus()); reset(mHeaderView.getStatus()); mLastY = -1;//重置坐标 break;

resetHeadView和reset分别是重置headerView高度和layout高度的方法

private void reset(int status) { ViewGroup.LayoutParams lp = getLayoutParams(); switch (status) { case SRefreshHeader.STATE_REFRESHING: lp.height = mHeight + mHeaderViewHeight; break; case SRefreshHeader.STATE_NORMAL: lp.height = mHeight; break; } setLayoutParams(lp); } private void resetHeadView(int status) { switch (status) { case SRefreshHeader.STATE_REFRESHING: mHeaderView.setVisiableHeight(mHeaderViewHeight); break; case SRefreshHeader.STATE_NORMAL: mHeaderView.setVisiableHeight(0); break; } }

实现方式也是一样的。根据状态来判断，如果是处于刷新中，那headerView应该正常显示，并且高度是初始的高度，如果处于NORMAL，也就是"下拉刷新"状态，那么说未触发刷新，重置时，headerView应该被隐藏，也就是高度重置为0

到这里下拉刷新操作也基本完成了，还需要加一个回调接口进行通知

interface OnRefreshListener { void onRefresh(); }

case MotionEvent.ACTION_UP: //松开时 //避免点击事件触发 if (!isRefreashing) break; //如果headView状态处于READY状态 则说明松开时应该进入REFRESHING状态 if (mHeaderView.getStatus() == SRefreshHeader.STATE_READY) { mHeaderView.setState(SRefreshHeader.STATE_REFRESHING); if (mOnRefreshListener != null) mOnRefreshListener.onRefresh(); } //根据状态重置SrefreshLayout当前实例和headView高度 resetHeadView(mHeaderView.getStatus()); reset(mHeaderView.getStatus()); mLastY = -1;//重置坐标 break;

好，到这里就基本完成了，试试效果吧。咦，发现一个问题，嵌套ListView的时候为什么这个Layout不能执行下拉刷新！仔细想想应该是事件分发的问题，还需要处理一下事件的拦截！

关于事件拦截的处理，阅读了鸿洋大神写的viewgroup事件分发的博客和Android-Ultra-Pull-To-Refresh的部分源码，从中找到了解决办法：

@Override public boolean onInterceptTouchEvent(MotionEvent ev) { AbsListView absListView = null; for (int n = 0; n < getChildCount(); n++) { if (getChildAt(n) instanceof AbsListView) { absListView = (ListView) getChildAt(n); Logs.v("查找到listView"); } } if (absListView == null) return super.onInterceptTouchEvent(ev); switch (ev.getAction()) { case MotionEvent.ACTION_DOWN: mStartY = ev.getRawY(); break; case MotionEvent.ACTION_MOVE: float space = ev.getRawY() - mStartY; Logs.v("space:" + space); if (space > 0 && !absListView.canScrollVertically(-1) && absListView.getFirstVisiblePosition() == 0) { Logs.v("拦截成功"); return true; } else { Logs.v("不拦截"); return false; } } return super.onInterceptTouchEvent(ev); }

其中

if (space > 0 && !absListView.canScrollVertically(-1) && absListView.getFirstVisiblePosition() == 0)

space即移动的距离 canScrollVertically（）是判断ListView能否在垂直方向上滚动，参数为负数时代表向上，为正数时代码向下滚动，最后一个就是ListView第一个可见的item的postion

加上上面的事件拦截处理，一个可以满足开头提到的需求的Viewgroup也就完成了！

下面贴上Layout的源码和HeaderView(直接使用的XlistView的HeaderView)的源码

public class SRefreshLayout extends LinearLayout { private SRefreshHeader mHeaderView; private RelativeLayout mHeaderViewContent; private boolean isRefreashing; private float mLastY = -1;//按下的起始高度 private int mHeaderViewHeight;//headerView内容高度 private int mHeight;//布局高度 private float mStartY; interface OnRefreshListener { void onRefresh(); } public OnRefreshListener mOnRefreshListener; public SRefreshLayout(Context context) { super(context); initView(context); } public SRefreshLayout(Context context, AttributeSet attrs) { super(context, attrs); initView(context); } public SRefreshLayout(Context context, AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); initView(context); } private void initView(Context context) { mHeaderView = new SRefreshHeader(context); mHeaderViewContent = (RelativeLayout) mHeaderView.findViewById(R.id.slistview_header_content); setOrientation(VERTICAL); addView(mHeaderView, 0); getHeaderViewHeight(); getViewHeight(); } /** * 获取headView高度 */ private void getHeaderViewHeight() { ViewTreeObserver vto2 = mHeaderViewContent.getViewTreeObserver(); vto2.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() { @Override public void onGlobalLayout() { mHeaderViewHeight = mHeaderViewContent.getHeight(); mHeaderViewContent.getViewTreeObserver().removeGlobalOnLayoutListener(this); } }); } /** * 获取SRefreshLayout当前实例的高度 */ private void getViewHeight() { ViewTreeObserver thisView = getViewTreeObserver(); thisView.addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() { @Override public void onGlobalLayout() { SRefreshLayout.this.mHeight = SRefreshLayout.this.getHeight(); SRefreshLayout.this.getViewTreeObserver().removeGlobalOnLayoutListener(this); } }); } @Override public boolean onInterceptTouchEvent(MotionEvent ev) { AbsListView absListView = null; for (int n = 0; n < getChildCount(); n++) { if (getChildAt(n) instanceof AbsListView) { absListView = (ListView) getChildAt(n); Logs.v("查找到listView"); } } if (absListView == null) return super.onInterceptTouchEvent(ev); switch (ev.getAction()) { case MotionEvent.ACTION_DOWN: mStartY = ev.getRawY(); break; case MotionEvent.ACTION_MOVE: float space = ev.getRawY() - mStartY; Logs.v("space:" + space); if (space > 0 && !absListView.canScrollVertically(-1) && absListView.getFirstVisiblePosition() == 0) { Logs.v("拦截成功"); return true; } else { Logs.v("不拦截"); return false; } } return super.onInterceptTouchEvent(ev); } @Override public boolean onTouchEvent(MotionEvent ev) { if (mLastY == -1) mLastY = ev.getRawY(); switch (ev.getAction()) { case MotionEvent.ACTION_DOWN: //记录起始高度 mLastY = ev.getRawY();//记录按下时的Y坐标 break; //手指离开屏幕时 case MotionEvent.ACTION_UP: //松开时 //避免点击事件触发 if (!isRefreashing) break; //如果headView状态处于READY状态 则说明松开时应该进入REFRESHING状态 if (mHeaderView.getStatus() == SRefreshHeader.STATE_READY) { mHeaderView.setState(SRefreshHeader.STATE_REFRESHING); if (mOnRefreshListener != null) mOnRefreshListener.onRefresh(); } //根据状态重置SrefreshLayout当前实例和headView高度 resetHeadView(mHeaderView.getStatus()); reset(mHeaderView.getStatus()); mLastY = -1;//重置坐标 break; case MotionEvent.ACTION_MOVE: if (!isRefreashing) isRefreashing = true; final float deltaY = ev.getRawY() - mLastY; mLastY = ev.getRawY(); updateHeaderViewHeight(deltaY / 1.8f);//按一定比例缩小移动距离 updateHeight(); break; } return super.onTouchEvent(ev); } private void reset(int status) { ViewGroup.LayoutParams lp = getLayoutParams(); switch (status) { case SRefreshHeader.STATE_REFRESHING: lp.height = mHeight + mHeaderViewHeight; break; case SRefreshHeader.STATE_NORMAL: lp.height = mHeight; break; } setLayoutParams(lp); } private void resetHeadView(int status) { switch (status) { case SRefreshHeader.STATE_REFRESHING: mHeaderView.setVisiableHeight(mHeaderViewHeight); break; case SRefreshHeader.STATE_NORMAL: mHeaderView.setVisiableHeight(0); break; } } private void updateHeight() { ViewGroup.LayoutParams lp = getLayoutParams(); //更新当前layout实例高度为headerView高度加上最初的layout高度 //如果不更新layout 会造成内容高度压缩 无法保持比例 lp.height = (mHeight + mHeaderView.getVisiableHeight()); setLayoutParams(lp); } private void updateHeaderViewHeight(float space) { // if (space < 0) // space = 0; // int factHeight = (int) (space - mHeaderViewHeight); if (mHeaderView.getStatus() != SRefreshHeader.STATE_REFRESHING) { //如果不处于刷新中同时如果高度 if (mHeaderView.getVisiableHeight() < mHeaderViewHeight * 2 && mHeaderView.getStatus() != SRefreshHeader.STATE_NORMAL) { mHeaderView.setState(SRefreshHeader.STATE_NORMAL); } if (mHeaderView.getVisiableHeight() > mHeaderViewHeight * 2 && mHeaderView.getStatus() != SRefreshHeader.STATE_READY) { mHeaderView.setState(SRefreshHeader.STATE_READY); } } mHeaderView.setVisiableHeight((int) space + mHeaderView.getVisiableHeight()); } public void stopRefresh() { if (mHeaderView.getStatus() == SRefreshHeader.STATE_REFRESHING) { mHeaderView.setState(SRefreshHeader.STATE_NORMAL); resetHeadView(SRefreshHeader.STATE_NORMAL); reset(SRefreshHeader.STATE_NORMAL); } } public void setOnRefreshListener(OnRefreshListener onRefreshListener) { this.mOnRefreshListener = onRefreshListener; } }

public class SRefreshHeader extends LinearLayout { private LinearLayout mContainer; private int mState = STATE_NORMAL; private Animation mRotateUpAnim; private Animation mRotateDownAnim; private final int ROTATE_ANIM_DURATION = 500; public final static int STATE_NORMAL = 0;//下拉刷新 public final static int STATE_READY = 1;//释放刷新 public final static int STATE_REFRESHING = 2;//刷新中 private ImageView mHeadArrowImage; private TextView mHeadLastRefreashTimeTxt; private TextView mHeadHintTxt; private TextView mHeadLastRefreashTxt; private ProgressBar mRefreshingProgress; public SRefreshHeader(Context context) { super(context); initView(context); } /** * @param context * @param attrs */ public SRefreshHeader(Context context, AttributeSet attrs) { super(context, attrs); initView(context); } private void initView(Context context) { // 初始情况，设置下拉刷新view高度为0 LayoutParams lp = new LayoutParams(LayoutParams.MATCH_PARENT, 0); mContainer = (LinearLayout) LayoutInflater.from(context).inflate(R.layout.listview_head_view_layout, null); addView(mContainer, lp); setGravity(Gravity.BOTTOM); mHeadArrowImage = (ImageView) findViewById(R.id.slistview_header_arrow); mHeadLastRefreashTimeTxt = (TextView) findViewById(R.id.slistview_header_time); mHeadHintTxt = (TextView) findViewById(R.id.slistview_header_hint_text); mHeadLastRefreashTxt = (TextView) findViewById(R.id.slistview_header_last_refreash_txt); mRefreshingProgress = (ProgressBar) findViewById(R.id.slistview_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); } public void setState(int state) { if (state == mState) return; if (state == STATE_REFRESHING) { // 显示进度 mHeadArrowImage.clearAnimation(); mHeadArrowImage.setVisibility(View.INVISIBLE); mRefreshingProgress.setVisibility(View.VISIBLE); } else { // 显示箭头图片 mHeadArrowImage.setVisibility(View.VISIBLE); mRefreshingProgress.setVisibility(View.INVISIBLE); } switch (state) { case STATE_NORMAL: if (mState == STATE_READY) { mHeadArrowImage.startAnimation(mRotateDownAnim); } if (mState == STATE_REFRESHING) { mHeadArrowImage.clearAnimation(); } mHeadHintTxt.setText("下拉刷新"); break; case STATE_READY: if (mState != STATE_READY) { mHeadArrowImage.clearAnimation(); mHeadArrowImage.startAnimation(mRotateUpAnim); mHeadHintTxt.setText("松开刷新"); } break; case STATE_REFRESHING: mHeadHintTxt.setText("正在刷新"); break; default: } mState = state; } public void setVisiableHeight(int height) { if (height < 0) height = 0; LayoutParams lp = (LayoutParams) mContainer .getLayoutParams(); lp.height = height; mContainer.setLayoutParams(lp); } public int getStatus() { return mState; } public int getVisiableHeight() { return mContainer.getHeight(); } }

最后是布局文件

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="wrap_content" android:gravity="bottom"> <RelativeLayout android:id="@+id/slistview_header_content" android:layout_width="match_parent" android:layout_height="60dp"> <LinearLayout android:id="@+id/slistview_header_text" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_centerInParent="true" android:gravity="center" android:orientation="vertical"> <TextView android:id="@+id/slistview_header_hint_text" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="下拉刷新" /> <LinearLayout android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginTop="3dp"> <TextView android:id="@+id/slistview_header_last_refreash_txt" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="上次刷新时间" android:textSize="12sp" /> <TextView android:id="@+id/slistview_header_time" android:layout_width="wrap_content" android:layout_height="wrap_content" android:textSize="12sp" /> </LinearLayout> </LinearLayout> <ProgressBar android:id="@+id/slistview_header_progressbar" android:layout_width="30dp" android:layout_height="30dp" android:layout_centerVertical="true" android:layout_toLeftOf="@id/slistview_header_text" android:visibility="invisible" /> <ImageView android:id="@+id/slistview_header_arrow" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignLeft="@id/slistview_header_progressbar" android:layout_centerVertical="true" android:layout_toLeftOf="@id/slistview_header_text" android:src="@drawable/mmtlistview_arrow" /> </RelativeLayout> </LinearLayout>

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持查字典教程网。