(相关资料图)

import "package:flutter/material.dart";import "package:get/get.dart";import "logic.dart";class GetIndexPage extends StatefulWidget {  int count;  GetIndexPage({required this.count, Key? key}) : super(key: key);  @override  State createState() => _GetIndexPageState();}class _GetIndexPageState extends State {  late GetIndexLogic logic;  @override  void initState() {    super.initState();    logic = Get.put(GetIndexLogic(widget.count));  }  @override  Widget build(BuildContext context) {    return GetBuilder(builder: (_) {      return Scaffold(        body: Container(          child: Column(            children: [              Text("测试数据:"),              Expanded(child: _body),            ],          ),        ),      );    });  }  get _body {    if (logic.state.list.isEmpty) {      return Container(        child: Text("暂无数据"),        alignment: Alignment.center,      );    }    return GetBuilder(        builder: (_) {      return ListView.builder(        itemBuilder: (c, index) {          return Container(            child: Text(logic.state.list[index]),            alignment: Alignment.center,            height: 70,          );        },        itemCount: logic.state.list.length,      );    });  }  @override  void dispose() {    // TODO: implement dispose    Get.delete();    super.dispose();  }}

import "dart:math";import "package:get/get.dart";import "state.dart";class GetIndexLogic extends GetxController {  int count = 0;  GetIndexLogic(this.count);  final GetIndexState state = GetIndexState();  @override  void onInit() {    refreshData();    print("lw----onInit:$count");    super.onInit();  }  refreshData() {    state.list.clear();　　/// 模拟网络请求    Future.delayed(const Duration(milliseconds: 100), () {      bool res = Random().nextBool();      if (true) {        state.list.add("jack");        state.list.add("rose");        state.list.add(count.toString());      }      print("lw----res:$res--state.list:${state.list}");      update();    });  }  @override  void onClose() {    print("lw----onClose:$count");    super.onClose();  }}

class GetIndexState {  List list = [];  GetIndexState() {    ///Initialize variables  }}

以上是所有代码，也是使用getx 的常见场景。正常操作是不会有任何问题的。

但是如果网络数据响应时间变长，而且快速的进出页面，就会报错Null check operator used on a null value。

具体报错原因：由于快速的进出页面，当数据返回时，get内部已经delete了logic, 然后再重新创建新的

GetBuilder(        builder: (_) {      return ListView.builder(        itemBuilder: (c, index) {          return Container(            child: Text(logic.state.list[index]),            alignment: Alignment.center,            height: 70,          );        },        itemCount: logic.state.list.length,      );    });

getx内部，由于controller已经被释放，执行 GetInstance().put(controller!, tag: widget.tag); 的时候就会报错；

解决方式：新创建GetBuilder的时候，

return GetBuilder(      init: logic,        builder: (_) {      return ListView.builder(        itemBuilder: (c, index) {          return Container(            child: Text(logic.state.list[index]),            alignment: Alignment.center,            height: 70,          );        },        itemCount: logic.state.list.length,      );    });

总结：只要不是在初始化时就创建出的GetBuilder，就需要加上init: logic,但是logic应该是当前页面持有的logic，才能保持数据的准确性，