自定义ListView下拉刷新上拉加载功能（面试）

ListView下拉刷新上拉加载的原理：

添加一个头和一个脚，然后对头和脚进行一些具体的处理，还要提供回调方法在外界进行具体的逻辑实现想要的功能。

对头进行的处理，即执行下拉加载：

在onTouchEvent方法的ACTION_DOWN,ACTION_MOVE和ACTION_UP的三种触摸状态中进行具体的业务处理

对脚的处理，即执行上拉加载：

在onScrollStateChanged（）方法中进行具体的处理

触发上拉加载必须要满足两个条件：
（1）匀速滚动到最后一个条目的位置

（2）飞速滚动到最后一个条目的位置

下面是布局和代码：

layout_refresh_listview_footer的布局

<span style="font-size:18px;"><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="wrap_content"    android:gravity="center"    android:orientation="horizontal" >    <ProgressBar         android:layout_width="wrap_content"        android:layout_height="wrap_content"/><TextView     android:text="正在加载..."    android:textSize="20sp"    android:layout_marginLeft="25dp"    android:layout_width="wrap_content"        android:layout_height="wrap_content"/></LinearLayout></span>

layout_refresh_listview_header的布局：

<span style="font-size:18px;"><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:id="@+id/ll_root"    android:orientation="vertical" >    <LinearLayout         android:id="@+id/ll_refresh_header"        android:orientation="horizontal"        android:layout_width="match_parent"        android:layout_height="wrap_content">        <FrameLayout             android:layout_width="wrap_content"            android:layout_height="wrap_content">            <ProgressBar                android:id="@+id/bar"                android:visibility="invisible"                 android:layout_width="wrap_content"                android:layout_height="wrap_content"/>            <ImageView                android:id="@+id/red_arrow"                android:layout_gravity="center"                android:src="@drawable/common_listview_headview_red_arrow"                android:layout_width="wrap_content"                android:layout_height="wrap_content"/>        </FrameLayout>        <LinearLayout             android:orientation="vertical"            android:gravity="center"            android:layout_width="match_parent"            android:layout_height="match_parent">            <TextView                 android:gravity="center"                android:id="@+id/refresh_state_tv"                android:text="下拉刷新"                android:layout_width="match_parent"                android:layout_height="wrap_content"/>            <TextView                 android:gravity="center"                android:id="@+id/refresh_time_tv"                android:text="1990-10-10"                android:layout_width="match_parent"                android:layout_height="wrap_content"/>        </LinearLayout>    </LinearLayout></LinearLayout></span>

具体的代码：

<span style="font-size:18px;">package com.itcast.zhbj.view;import java.text.SimpleDateFormat;import java.util.Date;import android.content.Context;import android.os.Handler;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.View;import android.view.animation.RotateAnimation;import android.widget.AbsListView;import android.widget.AbsListView.OnScrollListener;import android.widget.ImageView;import android.widget.LinearLayout;import android.widget.ListView;import android.widget.ProgressBar;import android.widget.TextView;import com.itcast.zhbj.R;public class RefreshListView extends ListView implements OnScrollListener {private LinearLayout ll_root;private ProgressBar bar;private ImageView red_arrow;private TextView refresh_state_tv,refresh_time_tv;private View customerView;private LinearLayout ll_refresh_header;private int headerHeight;private RotateAnimation upAnimation,downAnimation;private int downY = -1;private int mfirstVisibleItem = -1;private Handler handler = new Handler(){public void handleMessage(android.os.Message msg) {finish();};};//1,下拉刷新private static final int PULL_DOWN = 1; //2,释放刷新状态private static final int RELEASE_REFRESH = 2;//3,正在刷新private static final int IS_REFRESHING = 3;//当前所处状态private int CURRENTSTATE = PULL_DOWN;private OnRefreshListener onRefreshListener;private int footerHeight;//没有做加载动作private boolean isLoad = false;private View viewFooter;public RefreshListView(Context context, AttributeSet attrs) {super(context, attrs);//准备初始化ListView的头,并且默认将其头部的 view添加进来initHeader();initFooter();setOnScrollListener(this);}private void initFooter() {viewFooter = View.inflate(getContext(), R.layout.layout_refresh_listview_footer, null);//脚底默认隐藏//测量脚底高度,有多高隐藏多少viewFooter.measure(0, 0);footerHeight = viewFooter.getMeasuredHeight();viewFooter.setPadding(0,-footerHeight, 0, 0);addFooterView(viewFooter);}//刷新完成后要去做的处理public void finish(){if(CURRENTSTATE == IS_REFRESHING){//当前状态还原成下拉刷新CURRENTSTATE = PULL_DOWN;//文字要切换会下拉刷新refresh_state_tv.setText("下拉刷新");//进度条隐藏bar.setVisibility(View.INVISIBLE);//红色箭头需要显示red_arrow.setVisibility(View.VISIBLE);//隐藏刷新头ll_refresh_header.setPadding(0, -headerHeight, 0, 0);}if(isLoad){isLoad = false;viewFooter.setPadding(0,-footerHeight, 0, 0);}}//定义一个接口public interface OnRefreshListener{//定义一个为实现的下拉刷新业务逻辑方法public void pullDownRefresh();//定义一个上拉加载的业务逻辑public void loadMore();}public void setOnRefreshListener(OnRefreshListener onRefreshListener){this.onRefreshListener = onRefreshListener;}private void initHeader() {View viewHeader = View.inflate(getContext(),R.layout.layout_refresh_listview_header, null);//用作添加轮播图所在view的线性布局对象ll_root = (LinearLayout) viewHeader.findViewById(R.id.ll_root);ll_refresh_header = (LinearLayout) viewHeader.findViewById(R.id.ll_refresh_header);bar = (ProgressBar) viewHeader.findViewById(R.id.bar);red_arrow = (ImageView) viewHeader.findViewById(R.id.red_arrow);refresh_state_tv = (TextView) viewHeader.findViewById(R.id.refresh_state_tv);refresh_time_tv = (TextView)viewHeader.findViewById(R.id.refresh_time_tv);addHeaderView(viewHeader);//刷新头的隐藏操作//测量刷新头对应的高度,有多高就隐藏掉多少ll_refresh_header.measure(0, 0);headerHeight = ll_refresh_header.getMeasuredHeight();//完整的隐藏掉刷新头ll_refresh_header.setPadding(0, -headerHeight, 0, 0);initAnimation();}private void initAnimation() {upAnimation = new RotateAnimation(0, -180, RotateAnimation.RELATIVE_TO_SELF, 0.5f,RotateAnimation.RELATIVE_TO_SELF, 0.5f);upAnimation.setDuration(300);upAnimation.setFillAfter(true);downAnimation = new RotateAnimation(-180, -360,RotateAnimation.RELATIVE_TO_SELF, 0.5f,RotateAnimation.RELATIVE_TO_SELF, 0.5f);downAnimation.setDuration(300);downAnimation.setFillAfter(true);}//提供一个给刷新头底部添加轮播图所在view对象的方法public void addCustomerView(View view){ customerView = view; ll_root.addView(view);}@Overridepublic boolean onTouchEvent(MotionEvent ev) {switch (ev.getAction()) {case MotionEvent.ACTION_DOWN://获取按下点的y轴的坐标downY = (int) ev.getY();break;case MotionEvent.ACTION_MOVE:if(downY == -1){//就在刚刚开始移动的时候就去获取y轴的坐标位置,并且将其作为按下点的y轴的坐标downY = (int) ev.getX();}//获取移动过程中Y轴的坐标int moveY = (int) ev.getY();//获取listview在屏幕上面左上角的y轴坐标int[] listViewLocation = new int[2];this.getLocationOnScreen(listViewLocation);int listViewLocationY = listViewLocation[1];//获取轮播图对应view在屏幕上面左上角的Y轴坐标int[] customerViewLocation = new int[2];customerView.getLocationOnScreen(customerViewLocation);int customerViewLocationY = customerViewLocation[1];if(listViewLocationY>customerViewLocationY){break;}//1,向下拖拽 2,第0个条目可见if(moveY-downY>0 && mfirstVisibleItem == 0){//满足下拉刷新的触发条件了//下拉刷新--->释放刷新int padding = -headerHeight+moveY-downY;//padding>0代表刷新头完整的拖拽出来if(padding>0 && CURRENTSTATE == PULL_DOWN){CURRENTSTATE = RELEASE_REFRESH;setCurrentOption();}//padding<0代表刷新头没有被完整的拖拽出来if(padding<0 && CURRENTSTATE == RELEASE_REFRESH){CURRENTSTATE = PULL_DOWN;setCurrentOption();}//维护界面必须跟着手势去做移动,根据手势去给刷新头设置一个距顶端的间距(还隐藏的距离)ll_refresh_header.setPadding(0, padding, 0, 0);//如果移动过程中触发了状态的改变,那就必须在手势抬起的时候,去根据不同的当前状态做,不同的逻辑处理//让抬起事件做相应return true;}break;case MotionEvent.ACTION_UP:downY = -1;//当前状态所处释放刷新的时候放手if(CURRENTSTATE == RELEASE_REFRESH){//就真的需要去做刷新操作,刷新头在刷新过程中可见,刷新完成后,就需要隐藏CURRENTSTATE = IS_REFRESHING;setCurrentOption();ll_refresh_header.setPadding(0, 0, 0, 0);//做listview真正的刷新动作,刷新的业务逻辑,不能确定业务逻辑的具体实现,但是必须得去调用.(回调)//1,定义一个接口//2,在接口的内部定义一个为实现的业务路基的方法//3,传递一个实现了了接口的类的对象进来(实现了业务逻辑方法)//4,调用已经实现好的业务逻辑方法if(onRefreshListener!=null){onRefreshListener.pullDownRefresh();}handler.sendEmptyMessageDelayed(0, 3000);}//当前状态所处下拉刷新的时候放手if(CURRENTSTATE == PULL_DOWN){//弹回相应的刷新头ll_refresh_header.setPadding(0, -headerHeight, 0, 0);}break;}return super.onTouchEvent(ev);}public void setCurrentOption(){switch (CURRENTSTATE) {case RELEASE_REFRESH:refresh_state_tv.setText("释放刷新");red_arrow.startAnimation(upAnimation);break;case PULL_DOWN:refresh_state_tv.setText("下拉刷新");red_arrow.startAnimation(downAnimation);break;case IS_REFRESHING:refresh_state_tv.setText("正在刷新");red_arrow.clearAnimation();bar.setVisibility(View.VISIBLE);red_arrow.setVisibility(View.GONE);refresh_time_tv.setText(getFormatTime());break;}}private String getFormatTime() {//获取刷新的当前时间Date date = new Date();//格式化SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");return simpleDateFormat.format(date);}@Overridepublic void onScroll(AbsListView arg0, int firstVisibleItem, int arg2, int arg3) {mfirstVisibleItem  = firstVisibleItem;}@Overridepublic void onScrollStateChanged(AbsListView view, int scrollState) {//1,获取最后的一个可见条目的索引值,如果等于当前数据适配器中最后一个条目索引值,说明滚动到了最后//getLastVisiblePosition() == getAdapter().getCount()-1//2,匀速滚动到最后或者是飞速滚动到最后才可以触发上加载动作//scrollState == OnScrollListener.SCROLL_STATE_FLING 飞速滚动//scrollState == OnScrollListener.SCROLL_STATE_TOUCH_SCROLL 匀速滚动if(scrollState == OnScrollListener.SCROLL_STATE_FLING ||scrollState == OnScrollListener.SCROLL_STATE_TOUCH_SCROLL){if(getLastVisiblePosition() == getAdapter().getCount()-1 && !isLoad){//满足上拉加载的条件//将是否加载的判断标示维护成trueisLoad = true;//加载过程中要去展示底部的加载进度条viewFooter.setPadding(0, 0, 0, 0);//加载业务逻辑处理(回调)if(onRefreshListener!=null){onRefreshListener.loadMore();}handler.sendEmptyMessageDelayed(0, 3000);}}}}</span>