多去看官方文档和注释!!!
/// The padding for the input decoration's container. /// /// The decoration's container is the area which is filled if [filled] is true /// and bordered per the [border]. It's the area adjacent to [icon] and above /// the widgets that contain [helperText], [errorText], and [counterText]. /// /// By default the `contentPadding` reflects [isDense] and the type of the /// [border]. /// /// If [isCollapsed] is true then `contentPadding` is [EdgeInsets.zero]. /// /// If `isOutline` property of [border] is false and if [filled] is true then /// `contentPadding` is `EdgeInsets.fromLTRB(12, 8, 12, 8)` when [isDense] /// is true and `EdgeInsets.fromLTRB(12, 12, 12, 12)` when [isDense] is false. /// If `isOutline` property of [border] is false and if [filled] is false then /// `contentPadding` is `EdgeInsets.fromLTRB(0, 8, 0, 8)` when [isDense] is /// true and `EdgeInsets.fromLTRB(0, 12, 0, 12)` when [isDense] is false. /// /// If `isOutline` property of [border] is true then `contentPadding` is /// `EdgeInsets.fromLTRB(12, 20, 12, 12)` when [isDense] is true /// and `EdgeInsets.fromLTRB(12, 24, 12, 16)` when [isDense] is false. final EdgeInsetsGeometry contentPadding;