我是 Flutter 新手，需要创建一个图库应用，该应用需要自定义对话框来显示所选图像。我该如何实现？
【问题讨论】：
一个通用的例子
showDialog(context: context,builder: (context) => _onTapImage(context)); // Call the Dialog.
_onTapImage(BuildContext context) {
return Stack(
alignment: Alignment.center,
children: <Widget>[
Image.network('https://via.placeholder.com/150',fit: BoxFit.contain,), // Show your Image
Align(
alignment: Alignment.topRight,
child: RaisedButton.icon(
color: Theme.of(context).accentColor,
textColor: Colors.white,
onPressed: () => Navigator.pop(context),
icon: Icon(
Icons.close,
color: Colors.white,
),
label: Text('Close')),
),
],
);
}
【讨论】：
使用 Dialog 类，它是 Flutter 中 AlertDialog 类的父类。对话框小部件有一个参数“shape”，您可以使用它来塑造对话框的边缘。
这是一个代码示例：
Dialog errorDialog = Dialog(
shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(12.0)), //this right here
child: Container(
height: 300.0,
width: 300.0,
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Padding(
padding: EdgeInsets.all(15.0),
child: Text('Cool', style: TextStyle(color: Colors.red),),
),
Padding(
padding: EdgeInsets.all(15.0),
child: Text('Awesome', style: TextStyle(color: Colors.red),),
),
Padding(padding: EdgeInsets.only(top: 50.0)),
TextButton(onPressed: () {
Navigator.of(context).pop();
},
child: Text('Got It!', style: TextStyle(color: Colors.purple, fontSize: 18.0),))
],
),
),
);
showDialog(context: context, builder: (BuildContext context) => errorDialog);}
【讨论】：
在按钮上单击显示对话框为 -
showDialog(
context: context,
builder: (_) => LogoutOverlay(),
);
带有两个按钮的对话框设计 -
class LogoutOverlay extends StatefulWidget {
@override
State<StatefulWidget> createState() => LogoutOverlayState();
}
class LogoutOverlayState extends State<LogoutOverlay>
with SingleTickerProviderStateMixin {
AnimationController controller;
Animation<double> scaleAnimation;
@override
void initState() {
super.initState();
controller =
AnimationController(vsync: this, duration: Duration(milliseconds: 450));
scaleAnimation =
CurvedAnimation(parent: controller, curve: Curves.elasticInOut);
controller.addListener(() {
setState(() {});
});
controller.forward();
}
@override
Widget build(BuildContext context) {
return Center(
child: Material(
color: Colors.transparent,
child: ScaleTransition(
scale: scaleAnimation,
child: Container(
margin: EdgeInsets.all(20.0),
padding: EdgeInsets.all(15.0),
height: 180.0,
decoration: ShapeDecoration(
color: Color.fromRGBO(41, 167, 77, 10),
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(15.0))),
child: Column(
children: <Widget>[
Expanded(
child: Padding(
padding: const EdgeInsets.only(
top: 30.0, left: 20.0, right: 20.0),
child: Text(
"Are you sure, you want to logout?",
style: TextStyle(color: Colors.white, fontSize: 16.0),
),
)),
Expanded(
child: Row(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Padding(
padding: const EdgeInsets.all(10.0),
child: ButtonTheme(
height: 35.0,
minWidth: 110.0,
child: RaisedButton(
color: Colors.white,
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(5.0)),
splashColor: Colors.white.withAlpha(40),
child: Text(
'Logout',
textAlign: TextAlign.center,
style: TextStyle(
color: Colors.green,
fontWeight: FontWeight.bold,
fontSize: 13.0),
),
onPressed: () {
setState(() {
Route route = MaterialPageRoute(
builder: (context) => LoginScreen());
Navigator.pushReplacement(context, route);
});
},
)),
),
Padding(
padding: const EdgeInsets.only(
left: 20.0, right: 10.0, top: 10.0, bottom: 10.0),
child: ButtonTheme(
height: 35.0,
minWidth: 110.0,
child: RaisedButton(
color: Colors.white,
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.circular(5.0)),
splashColor: Colors.white.withAlpha(40),
child: Text(
'Cancel',
textAlign: TextAlign.center,
style: TextStyle(
color: Colors.green,
fontWeight: FontWeight.bold,
fontSize: 13.0),
),
onPressed: () {
setState(() {
/* Route route = MaterialPageRoute(
builder: (context) => LoginScreen());
Navigator.pushReplacement(context, route);
*/ });
},
))
),
],
))
],
)),
),
),
);
}
}
【讨论】：
你只需将这个类放到你的项目中并调用它的方法来显示对话框。
使用这个类你不需要到处写对话框代码
class DialogUtils {
static DialogUtils _instance = new DialogUtils.internal();
DialogUtils.internal();
factory DialogUtils() => _instance;
static void showCustomDialog(BuildContext context,
{@required String title,
String okBtnText = "Ok",
String cancelBtnText = "Cancel",
@required Function okBtnFunction}) {
showDialog(
context: context,
builder: (_) {
return AlertDialog(
title: Text(title),
content: /* Here add your custom widget */,
actions: <Widget>[
FlatButton(
child: Text(okBtnText),
onPressed: okBtnFunction,
),
FlatButton(
child: Text(cancelBtnText),
onPressed: () => Navigator.pop(context))
],
);
});
}
}
你可以像这样调用这个方法：
GestureDetector(
onTap: () =>
DialogUtils.showCustomDialog(context,
title: "Gallary",
okBtnText: "Save",
cancelBtnText: "Cancel",
okBtnFunction: () => /* call method in which you have write your logic and save process */),
child: Container(),
)
【讨论】：
.internal？我想了解内部和工厂语义的背景
Error: The argument type 'Function' can't be assigned to the parameter type 'void Function()?'.
只要调用这个方法：
void showCustomDialog(BuildContext context) {
showGeneralDialog(
context: context,
barrierLabel: "Barrier",
barrierDismissible: true,
barrierColor: Colors.black.withOpacity(0.5),
transitionDuration: Duration(milliseconds: 700),
pageBuilder: (_, __, ___) {
return Center(
child: Container(
height: 240,
child: SizedBox.expand(child: FlutterLogo()),
margin: EdgeInsets.symmetric(horizontal: 20),
decoration: BoxDecoration(color: Colors.white, borderRadius: BorderRadius.circular(40)),
),
);
},
transitionBuilder: (_, anim, __, child) {
Tween<Offset> tween;
if (anim.status == AnimationStatus.reverse) {
tween = Tween(begin: Offset(-1, 0), end: Offset.zero);
} else {
tween = Tween(begin: Offset(1, 0), end: Offset.zero);
}
return SlideTransition(
position: tween.animate(anim),
child: FadeTransition(
opacity: anim,
child: child,
),
);
},
);
}
【讨论】：
您现在可以使用 AlertDialog 并在内容中构建您的小部件。
showDialog(
context: context,
builder: (BuildContext context) {
return AlertDialog(
shape: RoundedRectangleBorder(
borderRadius: BorderRadius.all(Radius.circular(20.0))),
backgroundColor: Colors.green,
content: Container(
height:200,
width:200,
decoration: BoxDecoration(
image: DecorationImage(
image: FileImage(filepath),
fit: BoxFit.cover))),}),
【讨论】：
参考：Flutter Alert Dialog to Custom Dialog | by Ishan Fernando | CodeChai | Medium
警报对话框
showDialog(
context: context,
builder: (BuildContext context){
return AlertDialog(
title: Text("Alert Dialog"),
content: Text("Dialog Content"),
);
},
actions:[
FlatButton(
child: Text("Close"),
onPressed: (){
Navigator.of(context).pop();
},
)
],
);
自定义对话框
showDialog(
context: context,
builder: (BuildContext context) {
return Dialog(
shape: RoundedRectangleBorder(
borderRadius:
BorderRadius.circular(20.0)), //this right here
child: Container(
height: 200,
child: Padding(
padding: const EdgeInsets.all(12.0),
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
crossAxisAlignment: CrossAxisAlignment.start,
children: [
TextField(
decoration: InputDecoration(
border: InputBorder.none,
hintText: 'What do you want to remember?'),
),
SizedBox(
width: 320.0,
child: RaisedButton(
onPressed: () {},
child: Text(
"Save",
style: TextStyle(color: Colors.white),
),
color: const Color(0xFF1BC0C5),
),
)
],
),
),
),
);
});
全屏对话框
showGeneralDialog(
context: context,
barrierDismissible: true,
barrierLabel: MaterialLocalizations.of(context)
.modalBarrierDismissLabel,
barrierColor: Colors.black45,
transitionDuration: const Duration(milliseconds: 200),
pageBuilder: (BuildContext buildContext,
Animation animation,
Animation secondaryAnimation) {
return Center(
child: Container(
width: MediaQuery.of(context).size.width - 10,
height: MediaQuery.of(context).size.height - 80,
padding: EdgeInsets.all(20),
color: Colors.white,
child: Column(
children: [
RaisedButton(
onPressed: () {
Navigator.of(context).pop();
},
child: Text(
"Save",
style: TextStyle(color: Colors.white),
),
color: const Color(0xFF1BC0C5),
)
],
),
),
);
});
【讨论】：
在我的情况下有一个可行的解决方案：
Future<void> _showMyDialog() async {
return showDialog<void>(
context: context,
barrierDismissible: false, // user must tap button!
builder: (BuildContext context) {
return AlertDialog(
title: Text('AlertDialog Title'),
content: SingleChildScrollView(
child: Column(
children: <Widget>[
Text('This is a demo alert dialog.'),
Text('Would you like to confirm this message?'),
],
),
),
actions: <Widget>[
TextButton(
child: Text('Confirm'),
onPressed: () {
print('Confirmed');
Navigator.of(context).pop();
},
),
TextButton(
child: Text('Cancel'),
onPressed: () {
Navigator.of(context).pop();
},
),
],
);
},
);
}
【讨论】：
希望这会有所帮助： 我在一个单独的类中创建了静态函数：
import 'package:flutter/material.dart';
import 'package:flutter_application_1/TGColors.dart';
class TGDialog
{
static doNothing() { } // stub needed for Function parameters
/// Returns an AlertDialog with most optional parameters
static AlertDialog dlg( BuildContext context,
{ String txtTitle = 'WHAT? no title?' ,
String txtMsg = 'WHAT? no content?',
String txtBtn1 = 'CANCEL' ,
String txtBtn2 = 'OK' ,
Function funcBtn1 = doNothing ,
Function funcBtn2 = doNothing ,
Color colBackground = TGColors.Orange ,
Color colText = TGColors.Indigo } )
{
return
AlertDialog(
backgroundColor : colBackground,
title : Text(txtTitle),
content : Text(txtMsg),
actions : <Widget>
[
TextButton(
onPressed : () => { funcBtn1(), Navigator.pop(context,'Cancel')},
child : Text(txtBtn1, style: TextStyle(color: colText)),
),
TextButton(
onPressed :() => { funcBtn2(),Navigator.pop(context) },
child : Text(txtBtn2, style: TextStyle(color: colText)),
),
],
);
}
}
一个例子：
Positioned( bottom: 1, left: (screenW / 5.6),
child : FloatingActionButton(
heroTag : 'clear',
onPressed :() => showDialog<String>
(
context : context,
builder : (BuildContext context) =>
///////////////////////////////////////////////////////
TGDialog.dlg( context,
txtTitle : 'Clear Order?',
txtMsg : 'This resets all item counts' ,
funcBtn2 : resetOrder)
///////////////////////////////////////////////////////
),
child : const Text('clear\nall', textAlign: TextAlign.center),
shape : RoundedRectangleBorder(
borderRadius: BorderRadius.circular(40),
),
),
),
等等。 顺便说一句：我喜欢 CSS webcolors，所以我在一个单独的类中定义了它们 像这样：
import 'dart:ui';
/// Contains mainly web colors (based on CSS)
///
/// Usage e.g: ... = TGcolors.CornFlowerBlue
class TGColors
{
static const PrimaryColor = Color(0xFF808080);
static const AliceBlue = Color(0xFFF0F8FF);
static const AntiqueWhite = Color(0xFFFAEBD7);
static const Aqua = Color(0xFF00FFFF);
static const Aquamarine = Color(0xFF7FFFD4);
// etc.
【讨论】：