1 RaisedButton
RaisedButton组件主要用于文本布局。
2 构造函数
const RaisedButton({ Key key, @required VoidCallback onPressed, ValueChanged<boolonHighlightChanged, ButtonTextTheme textTheme, Color textColor, Color disabledTextColor, Color color, Color disabledColor, Color highlightColor, Color splashColor, Brightness colorBrightness, double elevation, double highlightElevation, double disabledElevation, EdgeInsetsGeometry padding, ShapeBorder shape, Clip clipBehavior = Clip.none, MaterialTapTargetSize materialTapTargetSize, Duration animationDuration, Widget child, })
3 常用属性
3.1 onPressed: 必填参数，按下按钮时触发的回调，接收一个方法，传null表示按钮禁用，会显示禁用相关样式
3.2 textColor：文本颜色
textColor: Colors.white,
3.3 color：按钮颜色
color: Colors.red,
3.4 splashColor：点击按钮时水波纹的颜色
splashColor: Colors.black,
3.5 highlightColor：高亮颜色，点击（长按）按钮后的颜色
highlightColor: Colors.green,
3.6 padding：内边距，其接收值的类型是EdgeInsetsGeometry类型的
3.6.1 一次性设置上下左右的间距
padding: EdgeInsets.all(20),
3.6.2 单独设置
3.6.2.1 上内边距
padding: EdgeInsets.only(top: 30),
3.6.2.2 下内边距
padding: EdgeInsets.only(bottom: 30),
3.6.2.3 左内边距
padding: EdgeInsets.only(left: 30),
3.6.2.4 右内边距
padding: EdgeInsets.only(right: 30),
3.6.3 一次性设置上下左右的间距 左上右下顺序设置
padding: EdgeInsets.fromLTRB(0,30,20,40),
3.7 shape：设置按钮的形状
3.7.1 borderRadius：设置圆角
shape: BeveledRectangleBorder( side: BorderSide( color: Colors.white, ), borderRadius: BorderRadius.all(Radius.circular(10)) ),
3.7.2 BeveledRectangleBorder：带斜角的长方形边框
shape: BeveledRectangleBorder( side: BorderSide( color: Colors.white, ), borderRadius: BorderRadius.all(Radius.circular(10)) ),
3.7.3 CircleBorder：圆形边框
shape: CircleBorder( side: BorderSide( color: Colors.white, ), ),
3.7.4 RoundedRectangleBorder：圆角矩形
shape: RoundedRectangleBorder( borderRadius: BorderRadius.all(Radius.circular(10)), ),
3.7.5 StadiumBorder：两端是半圆的边框
shape: StadiumBorder(),
