Flutter - 自定义Dialog

开发中，我们经常需要向用户展示信息，多数情况下，我们使用dialog展示提示信息，那么在Flutter中如何创建dialog, 并使用呢？现在就让我们来看看如何打造我们自己的dialog对象。

So Easy!

Dialog对象，我们需要重写build函数

自定义Dialog对象，需要继承Dialog类，尽管Dialog提供了child参数供写视图界面，但是往往会达不到我们想要的效果，因为默认的Dialog背景框是满屏的。。。那么我们就需要完全定义界面了，就需要重写build函数。下面我们编写一个加载对话框，如图示：

加载对话框

如图，我们需要打造一个类似的对话框，应该具体实现呢？首先，继承Dialog

import 'package:flutter/material.dart';

// ignore: must_be_immutable
class LoadingDialog extends Dialog {
  String text;

  LoadingDialog({Key key, @required this.text}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return new Material( //创建透明层
      type: MaterialType.transparency, //透明类型
      child: new Center( //保证控件居中效果
        child: new SizedBox(
          width: 120.0,
          height: 120.0,
          child: new Container(
            decoration: ShapeDecoration(
              color: Color(0xffffffff),
              shape: RoundedRectangleBorder(
                borderRadius: BorderRadius.all(
                  Radius.circular(8.0),
                ),
              ),
            ),
            child: new Column(
              mainAxisAlignment: MainAxisAlignment.center,
              crossAxisAlignment: CrossAxisAlignment.center,
              children: <Widget>[
                new CircularProgressIndicator(),
                new Padding(
                  padding: const EdgeInsets.only(
                    top: 20.0,
                  ),
                  child: new Text(
                    text,
                    style: new TextStyle(fontSize: 12.0),
                  ),
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}

上面我们已经创建了一个加载对话框，那么我们该如何展示这个dialog呢？showDialog函数

showDialog<Null>(
    context: context, //BuildContext对象
    barrierDismissible: false,
    builder: (BuildContext context) {
        return new LoadingDialog( //调用对话框
            text: '正在获取详情...',
        );
    });

对话框展示后，我们还需要关闭呀。关闭其实就很简单了！

Navigator.pop(context); //关闭对话框

不要着急，听我说完嘛

再来个栗子，看客请注意

// ignore: must_be_immutable
class MessageDialog extends Dialog {
  String title;
  String message;
  String negativeText;
  String positiveText;
  Function onCloseEvent;
  Function onPositivePressEvent;

  MessageDialog({
    Key key,
    @required this.title,
    @required this.message,
    this.negativeText,
    this.positiveText,
    this.onPositivePressEvent,
    @required this.onCloseEvent,
  }) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return new Padding(
      padding: const EdgeInsets.all(15.0),
      child: new Material(
        type: MaterialType.transparency,
        child: new Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            new Container(
              decoration: ShapeDecoration(
                color: Color(0xffffffff),
                shape: RoundedRectangleBorder(
                  borderRadius: BorderRadius.all(
                    Radius.circular(8.0),
                  ),
                ),
              ),
              margin: const EdgeInsets.all(12.0),
              child: new Column(
                children: <Widget>[
                  new Padding(
                    padding: const EdgeInsets.all(10.0),
                    child: new Stack(
                      alignment: AlignmentDirectional.centerEnd,
                      children: <Widget>[
                        new Center(
                          child: new Text(
                            title,
                            style: new TextStyle(
                              fontSize: 19.0,
                            ),
                          ),
                        ),
                        new GestureDetector(
                          onTap: this.onCloseEvent,
                          child: new Padding(
                            padding: const EdgeInsets.all(5.0),
                            child: new Icon(
                              Icons.close,
                              color: Color(0xffe0e0e0),
                            ),
                          ),
                        ),
                      ],
                    ),
                  ),
                  new Container(
                    color: Color(0xffe0e0e0),
                    height: 1.0,
                  ),
                  new Container(
                    constraints: BoxConstraints(minHeight: 180.0),
                    child: new Padding(
                      padding: const EdgeInsets.all(12.0),
                      child: new IntrinsicHeight(
                        child: new Text(
                          message,
                          style: TextStyle(fontSize: 16.0),
                        ),
                      ),
                    ),
                  ),
                  this._buildBottomButtonGroup(),
                ],
              ),
            ),
          ],
        ),
      ),
    );
  }

  Widget _buildBottomButtonGroup() {
    var widgets = <Widget>[];
    if (negativeText != null && negativeText.isNotEmpty) widgets.add(_buildBottomCancelButton());
    if (positiveText != null && positiveText.isNotEmpty) widgets.add(_buildBottomPositiveButton());
    return new Flex(
      direction: Axis.horizontal,
      children: widgets,
    );
  }

  Widget _buildBottomCancelButton() {
    return new Flexible(
      fit: FlexFit.tight,
      child: new FlatButton(
        onPressed: onCloseEvent,
        child: new Text(
          negativeText,
          style: TextStyle(
            fontSize: 16.0,
          ),
        ),
      ),
    );
  }

  Widget _buildBottomPositiveButton() {
    return new Flexible(
      fit: FlexFit.tight,
      child: new FlatButton(
        onPressed: onPositivePressEvent,
        child: new Text(
          positiveText,
          style: TextStyle(
            color: Color(Colors.teal.value),
            fontSize: 16.0,
          ),
        ),
      ),
    );
  }
}

效果图：

消息对话框