教你自定义ListView实现下拉刷新，上拉加载更多

虽然listview 快被RecyclerView取代了，但作为新人的你有必要知道。网上其实已经有很多关于listview上下拉刷新的例子，今天想带大家写一个快速实现 并且简单例子。

我先上几张效果图吧









ok 我先说一下大体思路，

我们先分别写出头布局和脚布局，稍后用 addHeaderView(headView); addFootView(footView);加载到自定义的布局中，默认全部都隐藏

根据我们下滑的状态，来分别对应显示下拉 和上拉刷新的状态

在自定义的listiview,中设置回调 用于状态显示完之后数据的显示

我把主要的代码列出来

package com.example.administrator.listview_demo;

import android.annotation.TargetApi;
import android.content.Context;
import android.icu.text.SimpleDateFormat;
import android.os.Build;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.RotateAnimation;
import android.widget.AbsListView;
import android.widget.ListView;
import android.widget.ProgressBar;
import android.widget.TextView;

/**
* Created by Xavier on 2016/9/27.
*/
public class RefreshListView extends ListView implements AbsListView.OnScrollListener{
private  View footView;
private View headView;
private float downY; // 按下的y坐标
private float moveY; // 移动后的y坐标
private View mArrowView;        // 箭头布局
private TextView mTitleText;    // 头布局标题
private ProgressBar pb;         // 进度指示器
private TextView mLastRefreshTime; // 最后刷新时间
private Context mContext;
private int measuredHeighthead; //头布局高度
private  int measuredHeightfoot; //脚布局
private RotateAnimation rotateUpAnim; // 箭头向上动画
private RotateAnimation rotateDownAnim; // 箭头向下动画
public static final int PULL_TO_REFRESH = 0;// 下拉刷新
public static final int RELEASE_REFRESH = 1;// 释放刷新
public static final int REFRESHING = 2; // 刷新中
private int currentState = PULL_TO_REFRESH; // 当前刷新模式
private boolean isLoadingMore; // 是否正在加载更多
private OnRefreshListener mListener; // 刷新监听

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

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

public RefreshListView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
mContext=context;
init();
}

private void init() {
initAnimation();
initHead();
initFoot();
setOnScrollListener(this);
}
private void initHead() {
headView = View.inflate(mContext, R.layout.layout_header_list, null);
mArrowView = headView.findViewById(R.id.iv_arrow);
pb = (ProgressBar) headView.findViewById(R.id.pb);
mTitleText = (TextView) headView.findViewById(R.id.tv_title);
mLastRefreshTime = (TextView) headView.findViewById(R.id.tv_desc_last_refresh);
headView.measure(0,0);
measuredHeighthead = headView.getMeasuredHeight();
headView.setPadding(0,-measuredHeighthead,0,0);
addHeaderView(headView);
}

private void initFoot() {
footView = View.inflate(mContext, R.layout.layout_footer_list, null);
footView.measure(0,0);
measuredHeightfoot = footView.getMeasuredHeight();
footView.setPadding(0,-measuredHeightfoot,0,0);
addFooterView(footView);
}
@Override
public boolean onTouchEvent(MotionEvent ev) {
switch (ev.getAction()){
case MotionEvent.ACTION_DOWN:
downY=ev.getY();

break;
case  MotionEvent.ACTION_MOVE:

moveY=ev.getY();
if(currentState == REFRESHING){
return super.onTouchEvent(ev);
}

float offset = moveY - downY; // 移动的偏移量
if(offset > 0 && getFirstVisiblePosition() == 0){
//int paddingTop = -自身高度 + 偏移量
int paddingTop = (int) (- measuredHeighthead + offset);
headView.setPadding(0, paddingTop, 0, 0);

if(paddingTop >= 0 && currentState != RELEASE_REFRESH){// 头布局完全显示
System.out.println("切换成释放刷新模式: " + paddingTop);
// 切换成释放刷新模式
currentState = RELEASE_REFRESH;
updateHeader(); // 根据最新的状态值更新头布局内容
}else if(paddingTop < 0 && currentState != PULL_TO_REFRESH){ // 头布局不完全显示
System.out.println("切换成下拉刷新模式: " + paddingTop);
// 切换成下拉刷新模式
currentState = PULL_TO_REFRESH;
updateHeader(); // 根据最新的状态值更新头布局内容
}
return  true;
}
break;
case  MotionEvent.ACTION_UP:
// 根据刚刚设置状态
if(currentState == PULL_TO_REFRESH){
//          - paddingTop < 0 不完全显示, 恢复
headView.setPadding(0, -measuredHeighthead, 0, 0);
}else if(currentState == RELEASE_REFRESH) {
//          - paddingTop >= 0 完全显示, 执行正在刷新...
headView.setPadding(0, 0, 0, 0);
currentState = REFRESHING;
updateHeader();
}
break;
default:
break;
}

return super.onTouchEvent(ev);
}

/**
* 根据状态更新头布局内容
*/
private void updateHeader() {
switch (currentState) {
case PULL_TO_REFRESH: // 切换回下拉刷新
// 做动画, 改标题
mArrowView.startAnimation(rotateDownAnim);
mTitleText.setText("下拉刷新");

break;
case RELEASE_REFRESH: // 切换成释放刷新
// 做动画, 改标题
mArrowView.startAnimation(rotateUpAnim);
mTitleText.setText("释放刷新");

break;
case REFRESHING: // 刷新中...
mArrowView.clearAnimation();
mArrowView.setVisibility(View.INVISIBLE);
pb.setVisibility(View.VISIBLE);
mTitleText.setText("正在刷新中...");

if(mListener != null){
mListener.onRefresh(); // 通知调用者, 让其到网络加载更多数据.
}

break;

default:
break;
}
}
/**
* 初始化头布局的动画
*/
private void initAnimation() {
// 向上转, 围绕着自己的中心, 逆时针旋转0 -> -180.
rotateUpAnim = new RotateAnimation(0f, -180f,
Animation.RELATIVE_TO_SELF, 0.5f,
Animation.RELATIVE_TO_SELF, 0.5f);
rotateUpAnim.setDuration(300);
rotateUpAnim.setFillAfter(true); // 动画停留在结束位置

// 向下转, 围绕着自己的中心, 逆时针旋转 -180 -> -360
rotateDownAnim = new RotateAnimation(-180f, -360,
Animation.RELATIVE_TO_SELF, 0.5f,
Animation.RELATIVE_TO_SELF, 0.5f);
rotateDownAnim.setDuration(300);
rotateDownAnim.setFillAfter(true); // 动画停留在结束位置

}
@TargetApi(Build.VERSION_CODES.N)
private String getTime() {
long currentTimeMillis = System.currentTimeMillis();
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
return format.format(currentTimeMillis);
}

@Override
public void onScrollStateChanged(AbsListView view, int scrollState) {
// 最新状态是空闲状态, 并且当前界面显示了所有数据的最后一条. 加载更多
if(isLoadingMore){
return; // 已经在加载更多.返回
}
if(scrollState == SCROLL_STATE_IDLE && getLastVisiblePosition() >= (getCount() - 1)){
isLoadingMore = true;
System.out.println("scrollState: 开始加载更多");
footView.setPadding(0, 0, 0, 0);

setSelection(getCount()); // 跳转到最后一条, 使其显示出加载更多.

if(mListener != null){
mListener.onLoadMore();
}
}
}

@Override
public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {

}
public interface OnRefreshListener{

void onRefresh(); // 下拉刷新

void onLoadMore();// 加载更多
}

public void setRefreshListener(OnRefreshListener mListener) {
this.mListener = mListener;
}
/**
* 刷新结束, 恢复界面效果
*/
public void onRefreshComplete() {
if(isLoadingMore){
// 加载更多
footView.setPadding(0, -measuredHeightfoot, 0, 0);
isLoadingMore = false;
}else {
// 下拉刷新
currentState = PULL_TO_REFRESH;
mTitleText.setText("下拉刷新"); // 切换文本
headView.setPadding(0, -measuredHeighthead, 0, 0);// 隐藏头布局
pb.setVisibility(View.INVISIBLE);
mArrowView.setVisibility(View.VISIBLE);
String time = getTime();
mLastRefreshTime.setText("最后刷新时间: " + time);
}
}
}

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