Flutter 从另一个类访问和修改参数
我从Flatter开发开始,尝试从头开始构建一个简单的ToDo应用程序,而不是基于任何教程,这样我可以学得更好,但现在我无法从等效的小部件访问ToDo数组 为了使事情有条理,我有以下结构:Flutter 从另一个类访问和修改参数,flutter,Flutter,我从Flatter开发开始,尝试从头开始构建一个简单的ToDo应用程序,而不是基于任何教程,这样我可以学得更好,但现在我无法从等效的小部件访问ToDo数组 为了使事情有条理,我有以下结构: lib pages home.page.dart widgets todo-card.dart todo-empty.dart main.dart 该应用程序是每个待办事项的卡片列表和创建新待办事项的FAB。每张卡片都是一个删除按钮、todo文本的一部分和一个检查按钮。所
lib
pages
home.page.dart
widgets
todo-card.dart
todo-empty.dart
main.dart
该应用程序是每个待办事项的卡片列表和创建新待办事项的FAB。每张卡片都是一个删除按钮、todo文本的一部分和一个检查按钮。所有TODO项目都存储在HomePage类中:
页面/主页.page.dart
class HomePage extends StatefulWidget {
@override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
List todos = [
{'text': 'texto teste 1', 'checked': false},
{'text': 'texto teste 2', 'checked': true},
{'text': 'texto teste 3', 'checked': false},
];
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
...
),
backgroundColor: Theme.of(context).primaryColor,
body: this.todos.length > 0
? ListView.builder(
itemCount: this.todos.length,
itemBuilder: (context, index) {
Map item = this.todos[index];
return TodoCard(item['text'], item['checked']);
},
)
: TodoEmpty(),
floatingActionButton: FloatingActionButton(
...
),
);
}
}
class TodoCard extends StatefulWidget {
String text;
bool checked = false;
TodoCard(this.text, [this.checked = false]);
@override
_TodoCardState createState() => _TodoCardState();
}
class _TodoCardState extends State<TodoCard> {
@override
Widget build(BuildContext context) {
return Card(
child: Container(
padding: EdgeInsets.all(20),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
IconButton(
icon: Icon(Icons.delete),
onPressed: () {
},
),
Expanded(
child: Text(
widget.text,
),
),
IconButton(
icon: widget.checked
? Icon(Icons.check_box)
: Icon(Icons.check_box_outline_blank),
onPressed: () {
setState(() {
if (widget.checked == true) {
widget.checked = false;
} else {
widget.checked = true;
}
});
},
),
],
),
),
);
}
}
类主页扩展StatefulWidget{
@凌驾
_HomePageState createState()=>\u HomePageState();
}
类_HomePageState扩展状态{
列出待办事项=[
{'text':'texto teste 1','checked':false},
{'text':'texto teste 2','checked':true},
{'text':'texto teste 3','checked':false},
];
@凌驾
小部件构建(构建上下文){
返回脚手架(
appBar:appBar(
...
),
背景色:主题。背景色,
正文:this.todos.length>0
?ListView.builder(
itemCount:this.todos.length,
itemBuilder:(上下文,索引){
Map item=this.todos[index];
返回到文档(项目['text'],项目['checked']);
},
)
:TodoEmpty(),
浮动操作按钮:浮动操作按钮(
...
),
);
}
}
以及卡片结构:
widgets/todo card.dart
class HomePage extends StatefulWidget {
@override
_HomePageState createState() => _HomePageState();
}
class _HomePageState extends State<HomePage> {
List todos = [
{'text': 'texto teste 1', 'checked': false},
{'text': 'texto teste 2', 'checked': true},
{'text': 'texto teste 3', 'checked': false},
];
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
...
),
backgroundColor: Theme.of(context).primaryColor,
body: this.todos.length > 0
? ListView.builder(
itemCount: this.todos.length,
itemBuilder: (context, index) {
Map item = this.todos[index];
return TodoCard(item['text'], item['checked']);
},
)
: TodoEmpty(),
floatingActionButton: FloatingActionButton(
...
),
);
}
}
class TodoCard extends StatefulWidget {
String text;
bool checked = false;
TodoCard(this.text, [this.checked = false]);
@override
_TodoCardState createState() => _TodoCardState();
}
class _TodoCardState extends State<TodoCard> {
@override
Widget build(BuildContext context) {
return Card(
child: Container(
padding: EdgeInsets.all(20),
child: Row(
mainAxisAlignment: MainAxisAlignment.spaceBetween,
children: <Widget>[
IconButton(
icon: Icon(Icons.delete),
onPressed: () {
},
),
Expanded(
child: Text(
widget.text,
),
),
IconButton(
icon: widget.checked
? Icon(Icons.check_box)
: Icon(Icons.check_box_outline_blank),
onPressed: () {
setState(() {
if (widget.checked == true) {
widget.checked = false;
} else {
widget.checked = true;
}
});
},
),
],
),
),
);
}
}
类TodoCard扩展StatefulWidget{
字符串文本;
bool checked=false;
TodoCard(this.text[this.checked=false]);
@凌驾
_TodoCardState createState()=>U TodoCardState();
}
类_ToCardState扩展了状态{
@凌驾
小部件构建(构建上下文){
回程卡(
子:容器(
填充:边缘设置。全部(20),
孩子:排(
mainAxisAlignment:mainAxisAlignment.spaceBetween,
儿童:[
图标按钮(
图标:图标(Icons.delete),
已按下:(){
},
),
扩大(
子:文本(
widget.text,
),
),
图标按钮(
图标:widget.checked
?图标(图标。复选框)
:图标(图标。复选框\轮廓\空白),
已按下:(){
设置状态(){
if(widget.checked==true){
widget.checked=false;
}否则{
widget.checked=true;
}
});
},
),
],
),
),
);
}
}
我的问题是:如何从TodoCard
类访问和删除HomePage
属性,以便从todos
列表中删除索引?
现在我不想使用bloc、provider或其他类似的工具。由于我刚开始学习颤振,我想先掌握setState()
您可以像这样将函数作为参数传递给TodoCard类
class TodoCard extends StatefulWidget {
String text;
bool checked = false;
Function onTodoCardDeleted;
TodoCard(this.text, this.onTodoCardDeleted, [this.checked = false]);
@override
_TodoCardState createState() => _TodoCardState();
}
/* your code */
itemBuilder: (context, index) {
Map item = this.todos[index];
return TodoCard(item['text'], (){ _removeFromTodos(index); }, item['checked']);
},
/* your code */
_removeFromTodos(int index){
setState((){
todos.removeAt(index);
});
}
在主页中,您可以像这样创建TodoCard对象
class TodoCard extends StatefulWidget {
String text;
bool checked = false;
Function onTodoCardDeleted;
TodoCard(this.text, this.onTodoCardDeleted, [this.checked = false]);
@override
_TodoCardState createState() => _TodoCardState();
}
/* your code */
itemBuilder: (context, index) {
Map item = this.todos[index];
return TodoCard(item['text'], (){ _removeFromTodos(index); }, item['checked']);
},
/* your code */
_removeFromTodos(int index){
setState((){
todos.removeAt(index);
});
}
最后,您可以在删除图标上调用作为参数传递的函数
IconButton(
icon: Icon(Icons.delete),
onPressed: () {
widget.onTodoCardDeleted;
},
),
成功了!谢谢!我唯一需要改变的是:
widget.onTodoCardDeleted
to:widget.onTodoCardDeleted()代码>