flutter基础布局之 对话框Dialogs

对话框Dialog主要包括AlertDialog 和 SimpleDialog

AlertDialog对话框主要用于可以返回结果。而SimpleDialog可以自己定义样式，如图标，内容等。

Dialogs主要分为三类：

Component	Priority	User action
Snackbar	Low priority	Optional: Snackbars disappear automatically
Banner	Prominent, medium priority	Optional: Banners remain until dismissed by the user, or if the state that caused the banner is resolved
Dialog	Highest priority	Required: Dialogs block app usage until the user takes a dialog action or exits the dialog (if available)

它们的优先级不同，使用的场景也不一样。

//网上好的代码段   
 showDialog(
      context: context,
      barrierColor: Colors.green,
      barrierDissmiss:false,//用户是否可以点击外边将其关闭
      builder: (_) => Dialog(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: <Widget>[
            ListTile(
              title: Text(
                'smart_select',
                style: Theme.of(context).textTheme.headline5,
              ),
              subtitle: Text('by davigmacode'),
              trailing: IconButton(
                icon: Icon(Icons.close),
                onPressed: () => Navigator.pop(context),
              ),
            ),
            Flexible(
              fit: FlexFit.loose,
              child: Container(
                padding: EdgeInsets.symmetric(horizontal: 15),
                child: Column(
                  mainAxisSize: MainAxisSize.min,
                  children: <Widget>[
                    Text(
                      'Smart select allows you to easily convert your usual form selects to dynamic pages with grouped radio or checkbox inputs. This widget is inspired by Smart Select component from Framework7',
                      style: Theme.of(context).textTheme.bodyText2,
                    ),
                    Container(height: 15),
                  ],
                ),
              ),
            )
          ],
        ),
      ),
    );

对话框的外观也是可以修改的

AlertDialog(
    title:Text("Accept?"),
    content:Text("Do you accept?),
    actions:[
        FlatButton('NO'),
        FlatButton("Yes"),
    ],
    elevation:24,
    BackgroundColor:Colors.blue,
    shap:CircleBorder(),//外观是可以修改的
)