最近朋友想讓我實(shí)現(xiàn)一個(gè)仿蘋果相冊(cè)長(zhǎng)按下拉選中的效果，奈何度娘不給力，找不到任何的有關(guān)文章，索性就自己來實(shí)現(xiàn)吧。希望以后有此需求的朋友能借鑒借鑒自己的文章，這樣也不枉自己花些筆墨為大家來介紹實(shí)現(xiàn)的思路和方法。
實(shí)現(xiàn)效果：（長(zhǎng)按下拉選中后續(xù)選項(xiàng)）
2222.gif
首先，我們先來實(shí)現(xiàn)最基本的效果，單擊選中，再單擊，取消選中
import 'package:flutter/material.dart';
class AlbumDemo extends StatefulWidget {
const AlbumDemo({Key? key}) : super(key: key);
@override
State<AlbumDemo> createState() => _AlbumDemoState();
}
class _AlbumDemoState extends State<AlbumDemo> {
List selects = [];
@override
void initState() {
super.initState();
for(int i = 0; i < 400 ; i++){
selects.add(0);
}
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('AlbumDemo'),),
body: ListView.builder(itemBuilder: (BuildContext context,int index){
return GestureDetector(
onTap: (){
selects[index] = ((selects[index]??0)==0)?1:0;
setState(() {
});
},
child: Container(
color: Colors.white,
child: Column(
children: [
Container(
height: 80,
child: Row(
children: [
Icon( ((selects[index]??0) ==1)?Icons.check_box:Icons.check_box_outline_blank,),
SizedBox(width: 50,),
Text('$index'),
],
)
),
Container(
height: 0.5,
color: Colors.lightBlue,
)
],
),
)
);
},itemCount: 400,),
);
}
}
接下來利用手勢(shì)來判別滑動(dòng)軌跡,并且為listview添加controller控制滑動(dòng)
import 'package:flutter/material.dart';
enum PullDirection {
down,
up,
}
class AlbumDemo extends StatefulWidget {
const AlbumDemo({Key? key}) : super(key: key);
@override
State<AlbumDemo> createState() => _AlbumDemoState();
}
class _AlbumDemoState extends State<AlbumDemo> {
List selects = [];//選中的暫存數(shù)組
ScrollController _controller = ScrollController();
double origin_offset = 0;//原始的標(biāo)記位置，用來判別是上拉還是下滑
bool endDrap = false;//結(jié)束滑動(dòng)的標(biāo)志
bool isPullingUp = false;//是否正在上滑中
bool isPullingDown = false;//是否正在下滑中
bool isAnimationing = false;//是否處于自動(dòng)滾動(dòng)中
final GlobalKey _globalKey = GlobalKey();//用來獲取當(dāng)前的listview
Offset saveOffset = Offset(0, 0);
PullDirection direction = PullDirection.down;//滑動(dòng)方向
@override
void initState() {
super.initState();
for(int i = 0; i < 400 ; i++){
selects.add(0);
}
}
runloopScroll(bool down){
print("isPullingDown = $isPullingDown");
if(down){
origin_offset+=80;
}else{
origin_offset-=80;
if(origin_offset<0){
origin_offset = 0;
}
}
Future.delayed(Duration(milliseconds: 200),(){
if(down){
_controller.animateTo(origin_offset, duration: Duration(milliseconds: 200),curve:Curves.linear );
}else{
_controller.animateTo(origin_offset, duration: Duration(milliseconds: 200),curve:Curves.linear );
}
}).then((value){
RenderBox box = _globalKey.currentContext?.findRenderObject() as RenderBox;
var innerLocation = box.globalToLocal(saveOffset);
updateSelectionStatus(Offset(innerLocation.dx, innerLocation.dy+ (down?80:-80)),isSelected: direction==PullDirection.down);
if(endDrap == true){
}else{
if(down){//下滑中
if(isPullingDown) {
runloopScroll(true);
}
}else{
if(isPullingUp){
runloopScroll(false);
}
}
}
});
}
updateSelectionStatus(Offset offset,{bool isSelected = true}){
int index = (_controller.offset.toInt() + offset.dy.toInt()) ~/ 80 ;
// print('滑動(dòng)經(jīng)過的index=$index');
selects[index] = isSelected?1:0;
setState(() {
});
}
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: Text('AlbumDemo'),),
body: GestureDetector(
onLongPress: (){
print("長(zhǎng)按開始");
endDrap = false;
origin_offset = _controller.offset;
},
onLongPressEnd: (LongPressEndDetails details){
print("長(zhǎng)按結(jié)束");
endDrap = true;
isAnimationing = false;
},
onLongPressMoveUpdate:(LongPressMoveUpdateDetails details){
if(saveOffset.dy < details.globalPosition.dy){
//下滑
direction = PullDirection.down;
}else{
//上滑
direction = PullDirection.up;
}
saveOffset = details.globalPosition;
RenderBox box = _globalKey.currentContext?.findRenderObject() as RenderBox;
var innerLocation = box.globalToLocal(saveOffset);
updateSelectionStatus(innerLocation,isSelected: direction==PullDirection.down);
if(details.globalPosition.dy>=810){//下面的邊緣臨界點(diǎn)，目前寫死(這里應(yīng)該是導(dǎo)航欄與定點(diǎn)的距離)
if(isPullingUp){
isPullingUp = false;
}
isPullingDown = true;
if(isAnimationing){
}else{
runloopScroll(true);
isAnimationing = true;
}
}else if(details.globalPosition.dy<=120){//上面的臨界點(diǎn)，這里應(yīng)該是底部離定點(diǎn)的距離
if(isPullingDown){
isPullingDown = false;
isAnimationing = false;
}
isPullingUp = true;
if(isAnimationing){
}else{
runloopScroll(false);
isAnimationing = true;
}
}else{
if(isPullingDown){
isPullingDown = false;
isAnimationing = false;
}
if(isPullingUp){
isPullingUp = false;
}
}
},
child: ListView.builder(key: _globalKey,controller: _controller,itemBuilder: (BuildContext context,int index){
return GestureDetector(
onTap: (){
selects[index] = ((selects[index]??0)==0)?1:0;
setState(() {
});
},
child: Container(
color: Colors.white,
child: Column(
children: [
Container(
height: 80,
child: Row(
children: [
Icon( ((selects[index]??0) ==1)?Icons.check_box:Icons.check_box_outline_blank,),
SizedBox(width: 50,),
Text('$index'),
],
)
),
Container(
height: 0.5,
color: Colors.lightBlue,
)
],
),
)
);
},itemCount: 400,),
)
);
}
}
大功告成、樓主省略了講解步驟，請(qǐng)見下回分解 哈哈
