Android----单纯的下拉刷新ListView
目录 
文章图片
无标题.png 演示 
文章图片
gif5新文件 (1).gif 思路
【Android----单纯的下拉刷新ListView】1.设置can控制现在是不是可以滑动。
2.如果现在第一个可见元素position是0，设置可以滑动。
3.滑动的实现，本质上是用header的高度去控制。
4.全局只用currentHeight去控制当前滑动的量
demo
github:https://github.com/pgyCode/PullUpAndPullDown
ListView的代码
package com.example.rtyui.androidteach.PullRefreshList;
import android.animation.Animator;
import android.animation.ObjectAnimator;
import android.animation.ValueAnimator;
import android.content.Context;
import android.graphics.drawable.AnimationDrawable;
import android.os.AsyncTask;
import android.util.AttributeSet;
import android.util.TypedValue;
import android.view.LayoutInflater;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;
import com.example.rtyui.androidteach.R;
/**
* Created by rtyui on 2018/5/3.
*/public class PullRefreshListView extends ListView {private final int HEADER_DP = 100;
private View header;
private float currentHeight = 0;
private float lastPosition = 0;
private PullRefreshInterface pullRefreshInterface;
private boolean can = false;
private ImageView imgHead;
private TextView tipHead;
public PullRefreshListView(Context context, AttributeSet attrs) {
super(context, attrs);
initHead(context);
addHeaderView(header, null, true);
setHeaderHeight();
setVerticalScrollBarEnabled(false);
setPadding(getPaddingLeft(), getPaddingTop() -1,getPaddingRight(), getPaddingBottom());
}public void setPullRefreshInterface(PullRefreshInterface pullRefreshInterface) {
this.pullRefreshInterface = pullRefreshInterface;
can = true;
}@Override
protected void onFinishInflate() {
super.onFinishInflate();
}//处理touch事件
@Override
public boolean onTouchEvent(MotionEvent ev) {
if (can){
switch (ev.getAction()) {
case MotionEvent.ACTION_MOVE:
System.out.println(getFirstVisiblePosition() + " " + currentHeight);
if (getFirstVisiblePosition() == 0) {
if (lastPosition != 0) {
float temp = ev.getY() - lastPosition;
if (temp > -60 && temp < 60) {
currentHeight += temp > 0 ? calculateHeight(temp) : temp;
}
lastPosition = ev.getY();
if (currentHeight > 0) {
setHeaderHeight();
if (currentHeight > dp2px(HEADER_DP))
headStatu1();
else
headStatu0();
} else {
currentHeight = 0;
setHeaderHeight();
}
return true;
} else {
lastPosition = ev.getY();
}
}
break;
case MotionEvent.ACTION_UP:
lastPosition = 0;
if (currentHeight > dp2px(HEADER_DP)){
new MyAsyncTask().execute();
headStatu2();
can = false;
}
else if (currentHeight > 0){
replyView(currentHeight, 0);
}else{
currentHeight = 0;
setHeaderHeight();
}
break;
}
}
return super.onTouchEvent(ev);
}/**
* dp转为px
* @param dp dp值
* @return
*/
private int dp2px(int dp) {
return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp, getResources().getDisplayMetrics());
}//下拉刷新
private void headStatu0(){
imgHead.setImageResource(R.drawable.down);
tipHead.setText("下拉刷新");
}//释放立即刷新
private void headStatu1(){
imgHead.setImageResource(R.drawable.up);
tipHead.setText("释放立即刷新");
}//正在刷新
private void headStatu2(){
imgHead.setImageResource(R.drawable.ss);
AnimationDrawable animationDrawable = (AnimationDrawable) imgHead.getDrawable();
animationDrawable.start();
tipHead.setText("正在刷新...");
}//刷新成功
private void headStatu3(){
imgHead.setImageResource(R.drawable.succeed);
tipHead.setText("刷新成功");
}/*
* 回弹
* @param distance 距离
* @param origin 终点
*/
private void replyView(final float distance, final int origin) {
// 设置动画
ValueAnimator anim = ObjectAnimator.ofFloat(distance - origin, 0.0F).setDuration(300);
anim.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
currentHeight = (int) (origin + (Float) animation.getAnimatedValue());
System.out.println(currentHeight + "w wewe ");
setHeaderHeight();
if (currentHeight == 0)
can = true;
}
});
anim.start();
}//初始化头部
private void initHead(Context context){
header = LayoutInflater.from(context).inflate(R.layout.pull_refresh_header, this, false);
//我的头部
imgHead = header.findViewById(R.id.img);
//我的头部图标
tipHead = header.findViewById(R.id.tip);
//我的头部提示
}private void setHeaderHeight(){
ViewGroup.LayoutParams layoutParams = header.getLayoutParams();
if (currentHeight <= 1)
layoutParams.height = 1;
else
layoutParams.height = (int) currentHeight;
header.setLayoutParams(layoutParams);
}/**
* 计算滑动高度与实际要移动的高度的关系
* @param move 滑动高度
* @return
*/
private float calculateHeight(float move){
return move / 2;
}private class MyAsyncTask extends AsyncTask {@Override
protected Boolean doInBackground(Void... voids) {
boolean result = pullRefreshInterface.load_PullRefresh();
publishProgress(result);
if (result)
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
return result;
}@Override
protected void onProgressUpdate(Boolean... values) {
super.onProgressUpdate(values);
if (values[0]){
headStatu3();
}else{
replyView(currentHeight, 0);
}
}@Override
protected void onPreExecute() {
super.onPreExecute();
replyView(currentHeight, dp2px(HEADER_DP));
pullRefreshInterface.beforeLoad_PullRefresh();
}@Override
protected void onPostExecute(Boolean aBoolean) {
super.onPostExecute(aBoolean);
replyView(currentHeight, 0);
pullRefreshInterface.afterLoad_PullRefresh(aBoolean);
}
}
}
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