[shutter] shutter layout component (fractionallysizedbox component | stack layout component | positioned component)

One 、FractionallySizedBox Components

---

FractionallySizedBox Components : The controllable components are horizontal / Fill the parent container vertically ;

class FractionallySizedBox extends SingleChildRenderObjectWidget { 
      const FractionallySizedBox({ 
        Key key,    this.alignment = Alignment.center,    this.widthFactor,    this.heightFactor,    Widget child,  }) : assert(alignment != null),       assert(widthFactor == null || widthFactor >= 0.0),       assert(heightFactor == null || heightFactor >= 0.0),       super(key: key, child: child);}

FractionallySizedBox Component usage :

• Set the width to fill the parent container : widthFactor Field settings ;
• Set the height to fill the parent container : heightFactor Field settings ;
• Set tile components : child Field settings Widget Components ;

//  level / Tile components vertically FractionallySizedBox(  //  Set the width to fill the parent container   widthFactor: 1,  //  Set the height to fill the parent container   heightFactor: 1,  //  The level to set  /  Components of tile operation in vertical direction   child:  Components to control tiling  ( Widget  type  ),  ),)

Code example :

//  level / Tile components vertically FractionallySizedBox(  //  Set the width to fill the parent container   widthFactor: 1,  //  The level to set  /  Components of tile operation in vertical direction   child: Container(    decoration: BoxDecoration(color: Colors.black),    child: Text(      " Highly adaptive ,  The width fills the parent container ",      style: TextStyle(color: Colors.amberAccent),    ),  ),)

Two 、Stack Layout components

---

Stack Layout components : Equivalent to frame layout ;

class Stack extends MultiChildRenderObjectWidget { 
      /// Creates a stack layout widget.  ///  /// By default, the non-positioned children of the stack are aligned by their  /// top left corners.  Stack({ 
        Key key,    this.alignment = AlignmentDirectional.topStart,    this.textDirection,    this.fit = StackFit.loose,    this.overflow = Overflow.clip,    List<Widget> children = const <Widget>[],  }) : super(key: key, children: children);}

Stack Layout component usage : stay children Set several fields Widget Components , The last component is displayed at the top , Overwrite the previous components ;

Code example :

//  Frame layout Stack(  children: <Widget>[    Image.network("https://img-blog.csdnimg.cn/20210301145757946.png",      width: 100,      height: 100,    ),        Image.network("https://img-blog.csdnimg.cn/20210228180808133.png",        width: 25,        height: 25,      ),  ],),

3、 ... and 、Positioned Components

---

Positioned Components : Used in Stack Specify the location of a component in the layout

class Positioned extends ParentDataWidget<Stack> { 
      /// Creates a widget that controls where a child of a [Stack] is positioned.  ///  /// Only two out of the three horizontal values ([left], [right],  /// [width]), and only two out of the three vertical values ([top],  /// [bottom], [height]), can be set. In each case, at least one of  /// the three must be null.  ///  /// See also:  ///  /// * [Positioned.directional], which specifies the widget's horizontal  /// position using `start` and `end` rather than `left` and `right`.  /// * [PositionedDirectional], which is similar to [Positioned.directional]  /// but adapts to the ambient [Directionality].  const Positioned({ 
        Key key,    this.left, //  Set the distance from the component to the left     this.top, //  Set the distance from the component to the top     this.right, //  Set the distance from the component to the right     this.bottom, //  Set the distance between the component and the bottom     this.width, //  Set component width     this.height, //  Component height settings     @required Widget child,  }) : assert(left == null || right == null || width == null),       assert(top == null || bottom == null || height == null),       super(key: key, child: child);}

Positioned Component usage :

• Set component width : width Field ;
• Component height settings : height Field ;
• Set the distance from the component to the left : left Field ;
• Set the distance from the component to the top : top Field ;
• Set the distance from the component to the right : right Field ;
• Set the distance between the component and the bottom : bottom Field ;

Code example :

//  Frame layout Stack(  children: <Widget>[    Image.network("https://img-blog.csdnimg.cn/20210301145757946.png",      width: 100,      height: 100,    ),    //  Set the component location at  Stack  Relative position of     Positioned(      right: 0, //  From the right side  0  distance       bottom: 0, //  From the bottom  0  distance       //  Set the component position of the constraint       child: Image.network("https://img-blog.csdnimg.cn/20210228180808133.png",        width: 25,        height: 25,      ),    ),  ],),

Four 、 Complete code example

---

Complete code example :

import 'package:flutter/material.dart';class LayoutPage extends StatefulWidget { 
      @override  _LayoutPageState createState() => _LayoutPageState();}class _LayoutPageState extends State<LayoutPage> { 
      ///  The currently selected bottom navigation bar index   int _currentSelectedIndex = 0;  // This widget is the root of your application.  @override  Widget build(BuildContext context) { 
        //  Text component style  ,  Can be set to  Text  Text component     //  Set font size  20,  The color is red     TextStyle textStyle = TextStyle(fontSize: 20, color: Colors.red);    return MaterialApp(      title: ' Example layout components ',      theme: ThemeData(        primarySwatch: Colors.blue,      ),      home: Scaffold(        //  Top title bar         appBar: AppBar(title: Text(' Example layout components '),),        //  Bottom navigation bar  BottomNavigationBar  Set up         // items  You can set multiple  BottomNavigationBarItem        bottomNavigationBar: BottomNavigationBar(          //  Set the currently selected bottom navigation index           currentIndex: _currentSelectedIndex,          //  Set the callback event of clicking the navigation bar at the bottom  , index  The parameter is the index value of the click           onTap: (index){ 
                //  Callback  StatefulWidget  Component's  setState  Method of setting state  ,  Modify the currently selected index             //  after  BottomNavigationBar  The component will automatically update the currently selected tab             setState(() { 
                  //  change  int _currentSelectedIndex  The state of the variable               _currentSelectedIndex = index;            });          },          //  entry           items: [          //  Set the bottom navigation bar entry ,  Each entry can be set with an icon           BottomNavigationBarItem(            //  The default icon             icon: Icon(Icons.home, color: Colors.grey,),            //  Icon in active state             activeIcon: Icon(Icons.home, color: Colors.red,),            //  Set title             title: Text(" Home page ")          ),          //  Set the bottom navigation bar entry ,  Each entry can be set with an icon           BottomNavigationBarItem(            //  The default icon             icon: Icon(Icons.settings, color: Colors.grey,),            //  Icon in active state             activeIcon: Icon(Icons.settings, color: Colors.red,),              //  Set title               title: Text(" Set up ")          )        ],),        //  Set the levitation button         floatingActionButton: FloatingActionButton(          onPressed: (){ 
                print(" Click the hover button ");          },          child: Text(" Levitation button assembly "),        ),        // Container  Container usage         body:        _currentSelectedIndex == 0 ?        //  Refresh indicator component         RefreshIndicator(          //  Display content           child: ListView(            children: <Widget>[              Container( //  Corresponding to the bottom navigation bar settings tab                 //  Set the decorator of the container  , BoxDecoration  Is the most commonly used decorator                 //  You can check it by yourself  BoxDecoration  Properties that can be set in                 decoration: BoxDecoration(color: Colors.white),                //  Set up  child  How the sub components are centered ,  Center                 alignment: Alignment.center,                //  Child components ,  The subcomponent is set to a  Column  Components                 child: Column(                  // Column  Child components ,  Set up here  Text  Text component                   children: <Widget>[                    Text(" Main page tab ,  The drop-down refresh "),                    //  A linear layout arranged horizontally                     Row(                      children: <Widget>[                        //  Original picture ,  For comparison                         Image.network("https://img-blog.csdnimg.cn/20210301145757946.png",                          width: 100,                          height: 100,                        ),                        //  Circular clipping component  ,  take  child  Cut the layout into a circle                         ClipOval(                          //  Use  SizedBox  Component constrains layout size                           child: SizedBox(                            width: 100,                            height: 100,                            //  Use  SizedBox  Constrain this  Image  Component size                             child: Image.network("https://img-blog.csdnimg.cn/20210301145757946.png"),                          ),                        ),                        Padding(                          //  Set the inside margin  5                          padding: EdgeInsets.all(15),                          //  Square cutting component  ,  Cut the components into squares                           child: ClipRRect(                            //  Set the clipping fillet ,  Set the radius of the four corners to  10  Fillet of                             borderRadius: BorderRadius.all(Radius.circular(10)),                            //  Modify the transparency component  ,  Set up here  50%  transparency                             child: Opacity(                                opacity: 0.5,                                //  Set up  100x100  Size picture component                                 child: Image.network("https://img-blog.csdnimg.cn/20210301145757946.png",                                  width: 100,                                  height: 100,                                ),                            ),                          ),                        ),                      ],                    ),                    //  Set up a layout container  ,  For encapsulation  PageView  Components                     Container(                      //  Set height                       height: 200,                      //  Set margins                       margin: EdgeInsets.all(15),                      //  Set decoration ,  Dark orange background                       decoration: BoxDecoration(                          color: Colors.white                      ),                      //  Set up subcomponents  PageView  Cutting components for                       child:                      PhysicalModel(                        color: Colors.transparent,                        //  Set the fillet radius  15                        borderRadius: BorderRadius.circular(50),                        //  Set crop behavior  ,  Anti-Aliasing                         clipBehavior: Clip.antiAlias,                        //  Set up  PageView  Components                         child:                        PageView(                          //  Set up  PageView  Several components encapsulated in                           children: <Widget>[                            //  The first page component                             Container(                              //  Set the center mode  ,  centered                               alignment:Alignment.center,                              //  Decorator settings  ,  Green background                               decoration: BoxDecoration(color: Colors.green),                              //  Main text displayed                               child: Text(" page  0", style: TextStyle(fontSize: 20, color: Colors.black),),                            ),                            //  The second page component                             Container(                              //  Set the center mode  ,  centered                               alignment:Alignment.center,                              //  Decorator settings  ,  Green background                               decoration: BoxDecoration(color: Colors.red),                              //  Main text displayed                               child: Text(" page  1", style: TextStyle(fontSize: 20, color: Colors.white),),                            ),                            //  The third page component                             Container(                              //  Set the center mode  ,  centered                               alignment:Alignment.center,                              //  Decorator settings  ,  Green background                               decoration: BoxDecoration(color: Colors.black),                              //  Main text displayed                               child: Text(" page  2", style: TextStyle(fontSize: 20, color: Colors.yellow),),                            ),                          ],                        ),                      ),                    ),                    Container(                      child: Column(                        children: <Widget>[                          //  level / Tile components vertically                           FractionallySizedBox(                            //  Set the width to fill the parent container                             widthFactor: 1,                            //  The level to set  /  Components of tile operation in vertical direction                             child: Container(                              decoration: BoxDecoration(color: Colors.black),                              child: Text(                                " Highly adaptive ,  The width fills the parent container ",                                style: TextStyle(color: Colors.amberAccent),                              ),                            ),                          )                        ],                      ),                    ),                    //  Frame layout                     Stack(                      children: <Widget>[                        Image.network("https://img-blog.csdnimg.cn/20210301145757946.png",                          width: 100,                          height: 100,                        ),                        //  Set the component location at  Stack  Relative position of                         Positioned(                          right: 0, //  From the right side  0  distance                           bottom: 0, //  From the bottom  0  distance                           //  Set the component position of the constraint                           child: Image.network("https://img-blog.csdnimg.cn/20210228180808133.png",                            width: 25,                            height: 25,                          ),                        ),                      ],                    ),                  ],                ),              ),            ],          ),          //  Method of callback during refresh           //  When a drop-down operation occurs in the list ,  Call back the method           //  The callback is  Future  Type of           onRefresh: _refreshIndicatorOnRefresh,        )        :        Container( //  Corresponding to the bottom navigation bar settings tab           //  Set the decorator of the container  , BoxDecoration  Is the most commonly used decorator           //  You can check it by yourself  BoxDecoration  Properties that can be set in           decoration: BoxDecoration(color: Colors.white),          //  Set up  child  How the sub components are centered ,  Center           alignment: Alignment.center,          //  Child components ,  The subcomponent is set to a  Column  Components           child: Column(            // Column  Child components ,  Set up here  Text  Text component             children: <Widget>[              Text(" Set up page tabs ")            ],          ),        ) , //  This setting is related to  _currentSelectedIndex == 0?  Corresponding , ?:  Ternary operator       ),    );  }  /// RefreshIndicator  When a pull-down operation occurs ,  Call back the method   ///  This is an asynchronous method  ,  Add... Before the method body  async  keyword   Future<Null> _refreshIndicatorOnRefresh() async{ 
        //  Pause  500 ms ,  Use  await  Keyword implementation     //  Here  500 ms  Between  ,  The list is in refresh state     // 500 ms  after  ,  The list becomes non refreshed     await Future.delayed(Duration(milliseconds: 500));    return null;  }}

Operation effect display :

5、 ... and 、 Related resources

---

Reference material :

• Flutter Official website : https://flutter.dev/
• Flutter Developing documents : https://flutter.cn/docs ( Strongly recommend )
• official GitHub Address : https://github.com/flutter
• Flutter The Chinese community : https://flutter.cn/
• Flutter Practical tutorial : https://flutter.cn/docs/cookbook
• Flutter CodeLab : https://codelabs.flutter-io.cn/
• Dart Chinese document : https://dart.cn/
• Dart Developer website : https://api.dart.dev/
• Flutter Chinese net ( unofficial , The translation is very good ) : https://flutterchina.club/ , http://flutter.axuer.com/docs/
• Flutter Related issues : https://flutterchina.club/faq/ ( It is recommended to watch it at the introductory stage )

Blog source download :

• GitHub Address : https://github.com/han1202012/flutter_cmd ( Keep updating with the progress of the blog , There may not be the source code of this blog )

• Blog source snapshot : https://download.csdn.net/download/han1202012/15484718 ( The source code snapshot of this blog , You can find the source code of this blog )