如何在Flutter中制作AlertDialog？

Question

我正在学习在Flutter中构建应用程序。现在我来警报对话框。我之前在Android和iOS中完成过这些操作，但是如何在Flutter中发出警报？

以下是一些相关的SO问题：

• 如何在Flutter中设置AlertDialog操作的样式
• 在Flutter的警报对话框中添加下拉菜单
• 在应用程序主屏幕上显示警报对话框会自动加载
• 如何在Flutter中刷新AlertDialog
• 带有圆角的警报对话框

我想进行更一般的规范问答，所以我的答案如下。

Answer 1

我使用了类似的方法，但我想

1. 将 Dialog 代码作为小部件保存在单独的文件中，以便我可以重用它。
2. 显示对话框时模糊背景。

代码：1。 alertDialog_widget.dart

import 'dart:ui';
import 'package:flutter/material.dart';


class BlurryDialog extends StatelessWidget {

  String title;
  String content;
  VoidCallback continueCallBack;

  BlurryDialog(this.title, this.content, this.continueCallBack);
  TextStyle textStyle = TextStyle (color: Colors.black);

  @override
  Widget build(BuildContext context) {
    return BackdropFilter(
      filter: ImageFilter.blur(sigmaX: 6, sigmaY: 6),
      child:  AlertDialog(
      title: new Text(title,style: textStyle,),
      content: new Text(content, style: textStyle,),
      actions: <Widget>[
        new FlatButton(
          child: new Text("Continue"),
           onPressed: () {
            continueCallBack();
          },
        ),
        new FlatButton(
          child: Text("Cancel"),
          onPressed: () {
            Navigator.of(context).pop();
          },
        ),
      ],
      ));
  }
}

您可以通过创建一个新方法在 main（或任何您想要的地方）调用它，例如：

 _showDialog(BuildContext context)
{

  VoidCallback continueCallBack = () => {
 Navigator.of(context).pop(),
    // code on continue comes here

  };
  BlurryDialog  alert = BlurryDialog("Abort","Are you sure you want to abort this operation?",continueCallBack);


  showDialog(
    context: context,
    builder: (BuildContext context) {
      return alert;
    },
  );
}

Answer 2

一键式

showAlertDialog(BuildContext context) {

  // set up the button
  Widget okButton = FlatButton(
    child: Text("OK"),
    onPressed: () { },
  );

  // set up the AlertDialog
  AlertDialog alert = AlertDialog(
    title: Text("My title"),
    content: Text("This is my message."),
    actions: [
      okButton,
    ],
  );

  // show the dialog
  showDialog(
    context: context,
    builder: (BuildContext context) {
      return alert;
    },
  );
}

两个按钮

showAlertDialog(BuildContext context) {

  // set up the buttons
  Widget cancelButton = FlatButton(
    child: Text("Cancel"),
    onPressed:  () {},
  );
  Widget continueButton = FlatButton(
    child: Text("Continue"),
    onPressed:  () {},
  );

  // set up the AlertDialog
  AlertDialog alert = AlertDialog(
    title: Text("AlertDialog"),
    content: Text("Would you like to continue learning how to use Flutter alerts?"),
    actions: [
      cancelButton,
      continueButton,
    ],
  );

  // show the dialog
  showDialog(
    context: context,
    builder: (BuildContext context) {
      return alert;
    },
  );
}

三个按钮

showAlertDialog(BuildContext context) {

  // set up the buttons
  Widget remindButton = FlatButton(
    child: Text("Remind me later"),
    onPressed:  () {},
  );
  Widget cancelButton = FlatButton(
    child: Text("Cancel"),
    onPressed:  () {},
  );
  Widget launchButton = FlatButton(
    child: Text("Launch missile"),
    onPressed:  () {},
  );

  // set up the AlertDialog
  AlertDialog alert = AlertDialog(
    title: Text("Notice"),
    content: Text("Launching this missile will destroy the entire universe. Is this what you intended to do?"),
    actions: [
      remindButton,
      cancelButton,
      launchButton,
    ],
  );

  // show the dialog
  showDialog(
    context: context,
    builder: (BuildContext context) {
      return alert;
    },
  );
}

处理按钮按下

onPressed上面示例中按钮的回调为空，但是您可以添加如下内容：

Widget launchButton = FlatButton(
  child: Text("Launch missile"),
  onPressed:  () {
    Navigator.of(context).pop(); // dismiss dialog
    launchMissile();
  },
);

如果您进行回调null，则该按钮将被禁用。

onPressed: null,

补充代码

下面是代码，main.dart如果你没有得到上面运行的功能。

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter',
      home: Scaffold(
        appBar: AppBar(
          title: Text('Flutter'),
        ),
        body: MyLayout()),
    );
  }
}

class MyLayout extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return Padding(
      padding: const EdgeInsets.all(8.0),
      child: RaisedButton(
        child: Text('Show alert'),
        onPressed: () {
          showAlertDialog(context);
        },
      ),
    );
  }
}

// replace this function with the examples above
showAlertDialog(BuildContext context) { ... }

Answer 3

您可以使用此代码片段创建一个两个按钮的警报框，

import 'package:flutter/material.dart';

class BaseAlertDialog extends StatelessWidget {

  //When creating please recheck 'context' if there is an error!

  Color _color = Color.fromARGB(220, 117, 218 ,255);

  String _title;
  String _content;
  String _yes;
  String _no;
  Function _yesOnPressed;
  Function _noOnPressed;

  BaseAlertDialog({String title, String content, Function yesOnPressed, Function noOnPressed, String yes = "Yes", String no = "No"}){
    this._title = title;
    this._content = content;
    this._yesOnPressed = yesOnPressed;
    this._noOnPressed = noOnPressed;
    this._yes = yes;
    this._no = no;
  }

  @override
  Widget build(BuildContext context) {
    return AlertDialog(
      title: new Text(this._title),
      content: new Text(this._content),
      backgroundColor: this._color,
      shape:
          RoundedRectangleBorder(borderRadius: new BorderRadius.circular(15)),
      actions: <Widget>[
        new FlatButton(
          child: new Text(this._yes),
          textColor: Colors.greenAccent,
          onPressed: () {
            this._yesOnPressed();
          },
        ),
        new FlatButton(
          child: Text(this._no),
          textColor: Colors.redAccent,
          onPressed: () {
            this._noOnPressed();
          },
        ),
      ],
    );
  }
}

要显示对话框，您可以有一个方法在导入BaseAlertDialog 类后调用它

_confirmRegister() {
var baseDialog = BaseAlertDialog(
    title: "Confirm Registration",
    content: "I Agree that the information provided is correct",
    yesOnPressed: () {},
    noOnPressed: () {},
    yes: "Agree",
    no: "Cancel");
showDialog(context: context, builder: (BuildContext context) => baseDialog);
}

输出将是这样的

Answer 4

这是一个较短但完整的代码。

如果您需要一个只有一个按钮的对话框：

await showDialog(
      context: context,
      builder: (context) => new AlertDialog(
        title: new Text('Message'),
        content: Text(
                'Your file is saved.'),
        actions: <Widget>[
          new FlatButton(
            onPressed: () {
              Navigator.of(context, rootNavigator: true)
                  .pop(); // dismisses only the dialog and returns nothing
            },
            child: new Text('OK'),
          ),
        ],
      ),
    );

如果您需要一个带有是/否按钮的对话框：

onPressed: () async {
bool result = await showDialog(
  context: context,
  builder: (context) {
    return AlertDialog(
      title: Text('Confirmation'),
      content: Text('Do you want to save?'),
      actions: <Widget>[
        new FlatButton(
          onPressed: () {
            Navigator.of(context, rootNavigator: true)
                .pop(false); // dismisses only the dialog and returns false
          },
          child: Text('No'),
        ),
        FlatButton(
          onPressed: () {
            Navigator.of(context, rootNavigator: true)
                .pop(true); // dismisses only the dialog and returns true
          },
          child: Text('Yes'),
        ),
      ],
    );
  },
);

if (result) {
  if (missingvalue) {
    Scaffold.of(context).showSnackBar(new SnackBar(
      content: new Text('Missing Value'),
    ));
  } else {
    saveObject();
    Navigator.of(context).pop(_myObject); // dismisses the entire widget
  }
} else {
  Navigator.of(context).pop(_myObject); // dismisses the entire widget
}
}

Answer 5

警报对话框的最小代码

showDialog(
  context: context,
  builder: (_) => AlertDialog(
    title: Text('Title'),
    content: Text(
      'Content widget',
    ),
  ),
);

Answer 6

只需使用这个自定义对话框类，您不需要将其保留或使其为空，这样您就可以轻松获得此自定义。

import 'package:flutter/material.dart';

class CustomAlertDialog extends StatelessWidget {
  final Color bgColor;
  final String title;
  final String message;
  final String positiveBtnText;
  final String negativeBtnText;
  final Function onPostivePressed;
  final Function onNegativePressed;
  final double circularBorderRadius;

  CustomAlertDialog({
    this.title,
    this.message,
    this.circularBorderRadius = 15.0,
    this.bgColor = Colors.white,
    this.positiveBtnText,
    this.negativeBtnText,
    this.onPostivePressed,
    this.onNegativePressed,
  })  : assert(bgColor != null),
        assert(circularBorderRadius != null);

  @override
  Widget build(BuildContext context) {
    return AlertDialog(
      title: title != null ? Text(title) : null,
      content: message != null ? Text(message) : null,
      backgroundColor: bgColor,
      shape: RoundedRectangleBorder(
          borderRadius: BorderRadius.circular(circularBorderRadius)),
      actions: <Widget>[
        negativeBtnText != null
            ? FlatButton(
                child: Text(negativeBtnText),
                textColor: Theme.of(context).accentColor,
                onPressed: () {
                  Navigator.of(context).pop();
                  if (onNegativePressed != null) {
                    onNegativePressed();
                  }
                },
              )
            : null,
        positiveBtnText != null
            ? FlatButton(
                child: Text(positiveBtnText),
                textColor: Theme.of(context).accentColor,
                onPressed: () {
                  if (onPostivePressed != null) {
                    onPostivePressed();
                  }
                },
              )
            : null,
      ],
    );
  }
}

用法：

var dialog = CustomAlertDialog(
  title: "Logout",
  message: "Are you sure, do you want to logout?",
  onPostivePressed: () {},
  positiveBtnText: 'Yes',
  negativeBtnText: 'No');
showDialog(
  context: context,
  builder: (BuildContext context) => dialog);

输出：

Answer 7

或者您可以为此使用 RFlutter Alert 库。它易于定制且易于使用。它的默认样式包括圆角，您可以根据需要添加按钮。

基本警报：

Alert(context: context, title: "RFLUTTER", desc: "Flutter is awesome.").show();

带按钮的警报：

Alert(
    context: context,
    type: AlertType.error,
    title: "RFLUTTER ALERT",
    desc: "Flutter is more awesome with RFlutter Alert.",
    buttons: [
    DialogButton(
        child: Text(
        "COOL",
        style: TextStyle(color: Colors.white, fontSize: 20),
        ),
        onPressed: () => Navigator.pop(context),
        width: 120,
    )
    ],
).show();

您还可以定义通用警报样式。

*我是 RFlutter Alert 的开发者之一。

Answer 8

如果您想要漂亮且响应灵敏的警报对话框，那么您可以使用 flutter 包，例如

rflutter 警报，花哨的对话框，丰富的警报，甜蜜的警报对话框，简单的对话框和简单的警报

这些警报外观精美且反应灵敏。其中rflutteralert是最好的。目前我正在为我的应用程序使用 rflutter 警报。

Answer 9

showAlertDialog(BuildContext context, String message, String heading,
      String buttonAcceptTitle, String buttonCancelTitle) {
    // set up the buttons
    Widget cancelButton = FlatButton(
      child: Text(buttonCancelTitle),
      onPressed: () {},
    );
    Widget continueButton = FlatButton(
      child: Text(buttonAcceptTitle),
      onPressed: () {

      },
    );

    // set up the AlertDialog
    AlertDialog alert = AlertDialog(
      title: Text(heading),
      content: Text(message),
      actions: [
        cancelButton,
        continueButton,
      ],
    );

    // show the dialog
    showDialog(
      context: context,
      builder: (BuildContext context) {
        return alert;
      },
    );
  }

称为：

showAlertDialog(context, 'Are you sure you want to delete?', "AppName" , "Ok", "Cancel");