小菜尝试做一个积分进度和类似物流进度的小组件，优先考虑的是自定义 ListView 但还是查阅了一下资料，发现神奇的 Stepper 步进器，虽不能完全满足需求，但提供了很好的思路，小菜仅就基本的 Stepper 学习一下；
源码分析
const Stepper({
Key key,
@required this.steps, // Step 列表
this.physics, // 滑动动画
this.type = StepperType.vertical, // 方向：横向/纵向
this.currentStep = 0, // 当前所在 Step
this.onStepTapped, // Step 点击回调
this.onStepContinue, // Step 继续按钮回调
this.onStepCancel, // Step 取消按钮回调
this.controlsBuilder, // 自定义控件
})
class Step
const Step({
@required this.title, // 标题
this.subtitle, // 副标题
@required this.content, // 内容
this.state = StepState.indexed, // 状态
this.isActive = false, // 是否高亮
})
}分析源码可知，Stepper 中存放的是 Step 列表，且 Step 数量不可变，其中包括了点击的回调等；Step 只是一个类而非 Widget 故不能单独使用；
案例尝试
Step
-
title 为描述性标题；content 为标题与副标题之下的内容，默认包含 continue 和 cancel 按钮；两者均为 Widget 且不可为 null；
return Stepper(steps: [ Step(title: Text('Step 标题一'), content: Container(color: Colors.orangeAccent.withOpacity(0.4), child: Text('Step 内容一'))), Step(title: Text('Step 标题二'), content: Container(color: Colors.blueAccent.withOpacity(0.4), child: Text('Step 内容二'))), Step(title: Text('Step 标题三'), content: Container(color: Colors.purple.withOpacity(0.4), child: Text('Step 内容三'))) ]);
-
subtitle 为副标题，在 title 之下，默认小一个字号；
return Stepper(steps: [ Step(title: Text('Step 标题一'), subtitle: Text('Step 副标题一'), content: Container(color: Colors.orangeAccent.withOpacity(0.4), child: Text('Step 内容一'))), Step(title: Text('Step 标题二'), subtitle: Text('Step 副标题二'), content: Container(color: Colors.blueAccent.withOpacity(0.4), child: Text('Step 内容二'))), Step(title: Text('Step 标题三'), subtitle: Text('Step 副标题三'), content: Container(color: Colors.purple.withOpacity(0.4), child: Text('Step 内容三'))) ]);
-
state 为状态，Flutter 默认提供了多种状态样式；
a. indexed: 在圆中展示每个 Step 数组下标(从 1 开始)；
b. editing: 编辑状态，在圆中展示铅笔图标；
c. complete: 完成状态，在圆中展示刻度图标；
d. disabled: 不可用状态，为灰色；
e. error: 错误状态，在红色三角中展示叹号图标；return Stepper(steps: [ Step(title: Text('Step state -> indexed'), state: StepState.indexed, content: Container()), Step(title: Text('Step state -> editing'), state: StepState.editing, content: Container()), Step(title: Text('Step state -> complete'), state: StepState.complete, content: Container()), Step(title: Text('Step state -> disabled'), state: StepState.disabled, content: Container()), Step(title: Text('Step state -> error'), state: StepState.error, content: Container()) ]);
- isActive 为设置当前 Step 是否高亮，仅图标高亮，其中 error 状态默认高亮，disabled 状态图标也可高亮；
return Stepper(steps: [ Step(isActive: true, title: Text('Step state -> indexed'), state: StepState.indexed, content: Container()), Step(isActive: true, title: Text('Step state -> editing'), state: StepState.editing, content: Container()), Step(isActive: true, title: Text('Step state -> complete'), state: StepState.complete, content: Container()), Step(isActive: true, title: Text('Step state -> disabled'), state: StepState.disabled, content: Container()), Step(isActive: true, title: Text('Step state -> error'), state: StepState.error, content: Container()) ]);
Stepper
-
type 包括横向 horizontal 展示与纵向 vertical 展示两类，默认是 vertical；
return Stepper(type: StepperType.horizontal, steps: [ Step(title: Text('Step 标题一'), content: Container()), Step(title: Text('Step 标题二'), content: Container()), Step(title: Text('Step 标题三'), content: Container()) ]);
-
currentStep 为当前 Step，注意数组下标从 0 开始；
return Stepper(type: StepperType.horizontal, currentStep: 1, steps: [ Step(title: Text('Step 标题一'), content: Container(child: Text('Step 内容一'))), Step(title: Text('Step 标题二'), content: Container(child: Text('Step 内容二'))), Step(title: Text('Step 标题三'), content: Container(child: Text('Step 内容三'))) ]);
-
onStepTapped 为 Step 点击回调，小菜尝试点击切换 Step 时获取当前 Step 高亮；
var _curStep = 0; return Stepper(currentStep: _curStep, onStepTapped: (step) { setState(() { _curStep = step; }); }, steps: [ Step(title: Text('Step 标题一'), content: Container(child: Text('Step 内容一')), isActive: _curStep >= 0 ? true : false), Step(title: Text('Step 标题二'), content: Container(child: Text('Step 内容二')), isActive: _curStep >= 1 ? true : false), Step(title: Text('Step 标题三'), content: Container(child: Text('Step 内容三')), isActive: _curStep >= 2 ? true : false) ]); -
onStepContinue 为 Step 中继续按钮点击回调；** 为 Step 中取消按钮点击回调；小菜尝试对继续和取消点击进行 Step** 切换；
return Stepper(currentStep: _curStep, onStepTapped: (step) { setState(() { _curStep = step; }); }, onStepContinue: () { setState(() { if (_curStep < 2) { _curStep++; } }); }, onStepCancel: () { setState(() { if (_curStep > 0) { _curStep--; } }); }, steps: [ Step(title: Text('Step 标题一'), content: Container(child: Text('Step 内容一')), isActive: _curStep >= 0 ? true : false), Step(title: Text('Step 标题二'), content: Container(child: Text('Step 内容二')), isActive: _curStep >= 1 ? true : false), Step(title: Text('Step 标题三'), content: Container(child: Text('Step 内容三')), isActive: _curStep >= 2 ? true : false) ]); -
controlsBuilder 用来自定义继续和取消按钮，若不需要展示则设置空 Widget 即可；
return Stepper(currentStep: _curStep, onStepTapped: (step) { setState(() { _curStep = step; }); }, onStepContinue: () { setState(() { if (_curStep < 2) { _curStep++; } }); }, onStepCancel: () { setState(() { if (_curStep > 0) { _curStep--; } }); }, controlsBuilder: (BuildContext context, {VoidCallback onStepContinue, VoidCallback onStepCancel}) { return Row(children: <Widget>[ Container( width: 100, child: Image.asset(_curStep == 0 ? 'images/icon_hzw01.jpg' : _curStep == 1 ? 'images/icon_hzw02.jpg' : 'images/icon_hzw03.jpg')), SizedBox(width: 30, height: 30), Column(children: <Widget>[ FlatButton(color: Colors.orangeAccent.withOpacity(0.4), onPressed: onStepContinue, child: Text('下一步')), FlatButton(color: Colors.purple.withOpacity(0.4), onPressed: onStepCancel, child: Text('上一步')) ]) ]); }, steps: [ Step(title: Text('Step 标题一'), content: Container(child: Text('Step 内容一')), isActive: _curStep >= 0 ? true : false), Step(title: Text('Step 标题二'), content: Container(child: Text('Step 内容二')), isActive: _curStep >= 1 ? true : false), Step(title: Text('Step 标题三'), content: Container(child: Text('Step 内容三')), isActive: _curStep >= 2 ? true : false) ]); - physics 为滑动属性，小菜测试将 Stepper 放在 ListView 中且不能完全展示时，设置 ClampingScrollPhysics() 可连续滑动；
physics: ClampingScrollPhysics(),
Stepper 使用方便快捷，虽样式相对固定无法满足所有需求，但给我们提供了很好的自定义思路；小菜对 Stepper 研究尚浅，如有错误请多多指导！
