【Flutter】StatefulWidget 组件 ( 创建 StatefulWidget 组件 | MaterialApp 组件

【Flutter】StatefulWidget 组件 ( 创建 StatefulWidget 组件 | MaterialApp 组件 | Scaffold 组件 )（二）

2022-01-29 254

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简介： 【Flutter】StatefulWidget 组件 ( 创建 StatefulWidget 组件 | MaterialApp 组件 | Scaffold 组件 )（二）

三、MaterialApp 组件

MaterialApp 组件是材料设计 ( Material Design ) APP 组件 , 通常用作页面的根节点 ;

MaterialApp 组件是 StatefulWidget 的子类 ;

通过 MaterialApp 组件很容易实现符合 Material Design 规范的应用 ;

MaterialApp 组件中的 tittle 字段就是标题设置 , theme 字段设置的是主题 , home 字段设置的是界面的主要子组件 ; 在上述示例中

下面的代码是 MaterialApp 构造函数源码 , 其中构造函数的可选参数就是可设置的选项 :

class MaterialApp extends StatefulWidget {
  /// Creates a MaterialApp.
  ///
  /// At least one of [home], [routes], [onGenerateRoute], or [builder] must be
  /// non-null. If only [routes] is given, it must include an entry for the
  /// [Navigator.defaultRouteName] (`/`), since that is the route used when the
  /// application is launched with an intent that specifies an otherwise
  /// unsupported route.
  ///
  /// This class creates an instance of [WidgetsApp].
  ///
  /// The boolean arguments, [routes], and [navigatorObservers], must not be null.
  const MaterialApp({
    Key key,
    this.navigatorKey,
    this.home,// 主页面组件 
    this.routes = const <String, WidgetBuilder>{},
    this.initialRoute,
    this.onGenerateRoute,
    this.onUnknownRoute,
    this.navigatorObservers = const <NavigatorObserver>[],
    this.builder,
    this.title = '',// 标题
    this.onGenerateTitle,
    this.color,
    this.theme,// 主题 
    this.darkTheme,
    this.themeMode = ThemeMode.system,
    this.locale,
    this.localizationsDelegates,
    this.localeListResolutionCallback,
    this.localeResolutionCallback,
    this.supportedLocales = const <Locale>[Locale('en', 'US')],
    this.debugShowMaterialGrid = false,
    this.showPerformanceOverlay = false,
    this.checkerboardRasterCacheImages = false,
    this.checkerboardOffscreenLayers = false,
    this.showSemanticsDebugger = false,
    this.debugShowCheckedModeBanner = true,
  }) : assert(routes != null),
       assert(navigatorObservers != null),
       assert(title != null),
       assert(debugShowMaterialGrid != null),
       assert(showPerformanceOverlay != null),
       assert(checkerboardRasterCacheImages != null),
       assert(checkerboardOffscreenLayers != null),
       assert(showSemanticsDebugger != null),
       assert(debugShowCheckedModeBanner != null),
       super(key: key);
}

四、Scaffold 组件

Scaffold 组件是一个完整的页面组件 , 封装有 AppBar , 底部导航栏 BottomNavigationBar , 侧边栏组件 , 使用该组件可以很容易实现一个复杂的导航页面 ;

Scaffold 组件常用设置选项 :

顶部标题栏设置 : appBar ;

界面主体子组件设置 : body ;

悬浮按钮设置 : floatingActionButton ;

底部导航栏设置 : bottomNavigationBar ;

侧边栏设置 : drawer ;

Scaffold 组件构造函数源码 : 构造函数中的可选参数就是组件的可设置选项 ;

class Scaffold extends StatefulWidget {
  /// Creates a visual scaffold for material design widgets.
  const Scaffold({
    Key key,
    this.appBar,// 顶部标题栏设置
    this.body,// 界面主体组件设置
    this.floatingActionButton,// 悬浮按钮设置 
    this.floatingActionButtonLocation,
    this.floatingActionButtonAnimator,
    this.persistentFooterButtons,
    this.drawer,// 侧边栏
    this.endDrawer,
    this.bottomNavigationBar,// 底部导航栏
    this.bottomSheet,
    this.backgroundColor,
    this.resizeToAvoidBottomPadding,
    this.resizeToAvoidBottomInset,
    this.primary = true,
    this.drawerDragStartBehavior = DragStartBehavior.start,
    this.extendBody = false,
    this.extendBodyBehindAppBar = false,
    this.drawerScrimColor,
    this.drawerEdgeDragWidth,
  }) : assert(primary != null),
       assert(extendBody != null),
       assert(extendBodyBehindAppBar != null),
       assert(drawerDragStartBehavior != null),
       super(key: key);
}