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Flutter 重構(gòu)屬性透?jìng)骷昂瘮?shù)透?jìng)魇褂檬纠?/h1>

更新時(shí)間：2023年01月08日 15:22:01 作者：SoaringHeart

這篇文章主要為大家介紹了Flutter 重構(gòu)屬性透?jìng)骷昂瘮?shù)透?jìng)魇褂檬纠斀猓行枰呐笥芽梢越梃b參考下，希望能夠有所幫助，祝大家多多進(jìn)步，早日升職加薪

一、來(lái)源

今天在研究 flutter 相冊(cè)庫(kù) wechat_assets_picker 遇到一個(gè)問題：（我需要在第三方庫(kù)基礎(chǔ)上封裝一個(gè)組件，供項(xiàng)目?jī)?nèi)部調(diào)用，組件內(nèi)封裝一些公共邏輯。）但是 AssetPicker.pickAssets 的屬性太多了，一個(gè)個(gè)傳遞實(shí)在太麻煩，就想是否有 vue 中那種數(shù)據(jù)透?jìng)鞯慕鉀Q方法呢(已知 flutter 中目前不支持這種屬性透?jìng)?？苦苦思索5分鐘之后，靈光一閃：

函數(shù)透?jìng)?/h3>

/// pickAssets 方法源碼：
static Future<List<AssetEntity>?> pickAssets(
  BuildContext context, {
  List<AssetEntity>? selectedAssets,
  int maxAssets = 9,
  int pageSize = 80,
  int gridThumbSize = Constants.defaultGridThumbSize,
  int pathThumbSize = 80,
  int gridCount = 4,
  RequestType requestType = RequestType.image,
  List<int>? previewThumbSize,
  SpecialPickerType? specialPickerType,
  Color? themeColor,
  ThemeData? pickerTheme,
  SortPathDelegate<AssetPathEntity>? sortPathDelegate,
  AssetsPickerTextDelegate? textDelegate,
  FilterOptionGroup? filterOptions,
  WidgetBuilder? specialItemBuilder,
  IndicatorBuilder? loadingIndicatorBuilder,
  SpecialItemPosition specialItemPosition = SpecialItemPosition.none,
  bool allowSpecialItemWhenEmpty = false,
  AssetSelectPredicate<AssetEntity>? selectPredicate,
  bool? shouldRevertGrid,
  bool useRootNavigator = true,
  Curve routeCurve = Curves.easeIn,
  Duration routeDuration = const Duration(milliseconds: 300),
}) async {
...

二、 WechatPhotoPicker 使用示例

class WechatPhotoPickerDemo extends StatefulWidget {
  WechatPhotoPickerDemo({ Key? key, this.title}) : super(key: key);
  final String? title;
  @override
  _WechatPhotoPickerDemoState createState() => _WechatPhotoPickerDemoState();
}
class _WechatPhotoPickerDemoState extends State<WechatPhotoPickerDemo> {
  int maxCount = 9;
  List<AssetEntity> entitys = [];
  GlobalKey<WechatPhotoPickerState> _globalKey = GlobalKey();
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: Text(widget.title ?? "$widget"),
          actions: ['選擇',].map((e) => TextButton(
            child: Text(e,
              style: TextStyle(color: Colors.white),
            ),
            onPressed: onPicker,
          )).toList(),
        ),
        body: Column(
          children: [
            WechatPhotoPicker(
              key: _globalKey,
              selectedAssets: entitys,
              onChanged: (List<AssetEntity> selectedAssets) {
                print("selectedAssets: ${selectedAssets.length}");
              },
              onPicker: () => AssetPicker.pickAssets(
                  context,
                  maxAssets: 8,
                  selectedAssets: entitys,
                ),
            )
          ],
        )
    );
  }
  onPicker() async {
    _globalKey.currentState?.onPicker();
    print(entitys.length);
  }
}

二、 WechatPhotoPicker 組件源碼

/// 基于 wechat_assets_picker 的圖片選擇組件
class WechatPhotoPicker extends StatefulWidget {
  WechatPhotoPicker({
    Key? key,
    this.selectedAssets = const [],
    this.maxCount = 9,
    this.rowCount = 3,
    this.spacing = 10,
    this.decoration,
    this.addBuilder,
    required this.onChanged,
    this.onPicker,
  }) : super(key: key);
  /// 媒體對(duì)象數(shù)組
  List<AssetEntity> selectedAssets;
  /// 最大個(gè)數(shù)
  int maxCount;
  /// 每行元素個(gè)數(shù)
  int rowCount;
  /// 元素間距
  double spacing;
  /// 元素修飾器
  BoxDecoration? decoration;
  /// 添加圖片
  Widget Function(BuildContext context, double itemWidth)? addBuilder;
  /// 確認(rèn)選擇回調(diào)函數(shù)
  void Function(List<AssetEntity> selectedAssets) onChanged;
  /// 解決flutter數(shù)據(jù)無(wú)法透?jìng)鞯膯栴}(透?jìng)?AssetPicker.pickAssets 方法)
  Future<List<AssetEntity>?> Function()? onPicker;
  @override
  WechatPhotoPickerState createState() => WechatPhotoPickerState();
}
class WechatPhotoPickerState extends State<WechatPhotoPicker> {
  @override
  Widget build(BuildContext context) {
    return photoSection(
      selectedAssets: widget.selectedAssets,
      maxCount: widget.maxCount,
      rowCount: widget.rowCount,
      spacing: widget.spacing,
    );
  }
  photoSection({
    List<AssetEntity> selectedAssets = const [],
    int maxCount = 9,
    int rowCount = 3,
    double spacing = 10,
  }) {
    return LayoutBuilder(
        builder: (BuildContext context, BoxConstraints constraints){
          double itemWidth = ((constraints.maxWidth - spacing * (rowCount - 1))/rowCount).truncateToDouble();
          // print("itemWidth: $itemWidth");
          return Wrap(
              spacing: spacing,
              runSpacing: spacing,
              children: [
                ...selectedAssets.map((e) => Container(
                  clipBehavior: Clip.antiAlias,
                  decoration: widget.decoration ?? BoxDecoration(
                    // border: Border.all(width: 2),
                    borderRadius: BorderRadius.all(Radius.circular(4)),
                  ),
                  child: FadeInImage(
                    width: itemWidth,
                    height: itemWidth,
                    placeholder: AssetImage('images/img_placeholder.png'),
                    image: AssetEntityImageProvider(e, isOriginal: false),
                    fit: BoxFit.cover,
                  ),
                )).toList(),
                if (selectedAssets.length < maxCount)
                  InkWell(
                    onTap: () {
                      onPicker();
                    },
                    child: Container(
                      width: itemWidth,
                      height: itemWidth,
                      decoration: BoxDecoration(
                        color: Colors.black.withOpacity(0.1),
                        // border: Border.all(width: 1),
                        borderRadius: BorderRadius.all(Radius.circular(4)),
                      ),
                      child: widget.addBuilder != null ? widget.addBuilder!(context, itemWidth) : Icon(
                        Icons.add, 
                        size: itemWidth/3, 
                        color: Colors.black.withOpacity(0.3),
                      ),
                    ),
                  )
              ]
          );
        }
    );
  }
  onPicker() async {
    List<AssetEntity>? result = widget.onPicker != null ? await widget.onPicker!() :
    await AssetPicker.pickAssets(
      context,
      maxAssets: widget.maxCount,
      selectedAssets: widget.selectedAssets,
    );
    widget.selectedAssets = result ?? [];
    widget.onChanged(widget.selectedAssets);
    setState(() { });
  }
}

總結(jié)

1、onPicker 參數(shù)需要和調(diào)用方法搭配使用，即實(shí)現(xiàn)了函數(shù)透?jìng)?，函?shù)里的參數(shù)直接暴露給外部使用者，做二次定制開發(fā)；如果默認(rèn)參數(shù)（可以適量添加）能夠滿足通用需求，則無(wú)需使用 onPicker 可選參數(shù)；

  onPicker: () => AssetPicker.pickAssets(
      context,
      maxAssets: 8,
      selectedAssets: entitys,
    ),

    List<AssetEntity>? result = widget.onPicker != null ? await widget.onPicker!() :
    await AssetPicker.pickAssets(
      context,
      maxAssets: widget.maxCount,
      selectedAssets: widget.selectedAssets,
    );

2、WechatPhotoPickerState，沒有使用下?lián)Q線（私有）實(shí)現(xiàn)是為了向外部暴露 State，可以通過 GlobalKey 獲取 State 實(shí)例對(duì)象，進(jìn)而調(diào)用一些封裝方法；達(dá)到更高的代碼復(fù)用；

聲明 GlobalKey：

 GlobalKey：<WechatPhotoPickerState> _globalKey = GlobalKey();

調(diào)用 State 方法：

_globalKey.currentState?.onPicker();

3、所有自定義組件原則上都要支持 key 屬性，才是一個(gè)完整的組件 Widget；

無(wú)論是移動(dòng)原生、前端 h5 或者 flutter 跨平臺(tái)，各種數(shù)據(jù)透?jìng)鞯乃枷胧窍嘟谝欢巳〉猛黄浦?，其他端基本都是平移?shí)現(xiàn)，這些可以減少代碼量又不損失功能，而且維護(hù)性和擴(kuò)展性更優(yōu)的實(shí)現(xiàn)方式就是代碼重構(gòu)的本質(zhì)。

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