[- Flutter必備 -] 聊聊那些彈框

對話方塊作為一個挺重要的東西，這裡來說一下，細細一數也蠻多的，本文包括

[1].SimpleDialog
[2].AlertDialog
[3].CupertinoAlertDialog
[4].Dialog中的元件狀態更新
[5].SnackBar
[6].BottomSheet
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0.搭個場子再說

class DialogShow extends StatefulWidget {
  @override
  _DialogShowState createState() => _DialogShowState();
}

class _DialogShowState extends State<DialogShow> {
  @override
  Widget build(BuildContext context) {
    var title = Container(
      alignment: AlignmentDirectional.center,
      child: Text(
        "Dialog Unit",
        style: TextStyle(fontSize: 30),
      ),
    );
    
    Map<String, Function> buttons = {
      "對話方塊SimpleDialog": _showSimpleDialog,
      "對話方塊AlertDialog": _showAlertDialog,
      "對話方塊CupertinoAlertDialog": _showCupertinoAlertDialog,
      "對話方塊顯示自己": _showWidgetDialog,
      "對話方塊顯示StatefulWidget": _showStatefulWidgetDialog,
      "Scaffold": _showScaffold,
      "BottomSheet": _showBottomSheet,
    };
    
    var btns=  buttons.keys.toList().map((str){//構建按鈕元件列表
      return RaisedButton(
        onPressed: () {
          buttons[str](context);
        },
        child: Text(str),
      );
    }).toList();

    var result =Column(children: <Widget>[title,Column(
      children: btns,
    )],) ;
    return result;
  }
}
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1.對話方塊:SimpleDialog

通過showDialog來建立對話方塊，傳入BuildContext物件，通過builder構造器來建立元件
簡單的對話方塊，只要一條條的東西可以選擇SimpleDialog，比如：

_showSimpleDialog(BuildContext context) {
  var strs=['雲深不知處內亥時息,卯時起',
    "雲深不知處內不可挑食留剩,不可境內殺生",
    "雲深不知處內不可私自鬥毆,不可淫亂",
    "雲深不知處禁止魏無羨入內,不可吹笛"];
  
  var title = Row(//標題
    children: <Widget>[
      Image.asset("images/icon_lwj.png", width: 30,height: 30,),
      SizedBox(width: 10,),
      new Text("藍氏家規")],
  );
  showDialog(
      context: context,
      builder: (context) {
        return SimpleDialog(
          title: title,
          children: strs.map((str){
            return SimpleDialogOption(
              child: Row(children: <Widget>[
                Icon(Icons.turned_in_not,color: Colors.blue,),Text(str)],) ,
              onPressed: () {
                Navigator.of(context).pop(str);
                print(str);
              },
            );
          }).toList(),
        );
      });
}
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3.對話方塊:AlertDialog

AlertDialog元件包括標題(title)、內容(content)、actions(行為)，還有一些陰影，顏色形狀等輔助屬性。

  _showAlertDialog(BuildContext context) {
    var title = Row(//標題
      children: <Widget>[
        Image.asset("images/icon_wwx.png", width: 30,height: 30,),
        SizedBox(width: 10,),
        new Text("表白")],
    );
    var content = Row(//內容
      children: <Widget>[
        Text("我?你，你是我的"),
        Image.asset("images/icon_ylm.png",width: 30, height: 30, )],
    );
    
    showDialog(
        context: context,
        builder: (context) => //構造器
            AlertDialog(title: title, content: content, actions: <Widget>[
              FlatButton(
                child: Text("不要鬧"),
                onPressed: () {
                  Navigator.of(context).pop();
                },
              ),
              FlatButton(
                child: Text("走開"),
                onPressed: () {
                  Navigator.of(context).pop();
                },
              )
            ]));
  }
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3.對話方塊:CupertinoAlertDialog

Cupertino風格的對話方塊

void _showCupertinoAlertDialog(BuildContext context) {
  var title = Row(//標題
    mainAxisAlignment: MainAxisAlignment.center,
    children: <Widget>[
      Image.asset("images/icon_wwx.png", width: 30,height: 30,),
      SizedBox(width: 10,),
      new Text("表白")],
  );
  var content = Row(
    children: <Widget>[
      Text("我?你，你是我的",style: TextStyle(fontSize: 20),),
      Image.asset("images/icon_ylm.png", width: 40, height: 40, ) ],
  );
  var dialog = CupertinoAlertDialog(
    content: content,
    title: title,
    actions: <Widget>[
      CupertinoButton( child: Text("不要鬧"),
        onPressed: () {
          Navigator.pop(context);
        },
      ),
      CupertinoButton( child: Text("走開"),
        onPressed: () {
          Navigator.pop(context);
        },
      ),
    ],
  );
  showDialog(context: context, builder: (context) => dialog);
}
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4.瞎玩一下

既然對話方塊裡面顯示的是一個Widget，那我把它自己顯示出了會怎麼樣?
現在Dialog應該不難玩了吧，既然什麼Widget都能放進去，還有什麼好怕的。

_showWidgetDialog(BuildContext context) {
  showDialog(
      context: context,
      builder: (context) {
        return this.widget;
      });
}
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5.對話方塊中的StatefulWidget

想要更新對話方塊裡的元件狀態，可以用StatefulBuilder，裡面回撥的StateSetter物件

_showStatefulWidgetDialog(BuildContext context) {
  var progress = 0.0;
  StateSetter stateSetter;

  Timer.periodic(Duration(milliseconds: 100), (timer) {//計時器模擬進度增加
    progress += 0.1;
    if (stateSetter != null) {
      stateSetter(() {});
    }
    if (progress >= 1) {
      timer.cancel();
      stateSetter = null;
      Navigator.of(context).pop();
    }
  });

  var statefulBuilder = StatefulBuilder(
    builder: (ctx, state) {
      stateSetter = state;
      return Center(
        child: SizedBox(width: 150, height: 150,
          child: Card(elevation: 24.0,
            color: Colors.blue.withAlpha(240),
            child: Column(
              mainAxisSize: MainAxisSize.min,
              crossAxisAlignment: CrossAxisAlignment.center,
              mainAxisAlignment: MainAxisAlignment.center,
              children: <Widget>[
                CircularProgressIndicator(
                  valueColor: AlwaysStoppedAnimation(Colors.white),
                  value: progress,
                ),
                SizedBox(height: 20,),
                Text("Loading...",
                  style: TextStyle(color: Colors.white),),
                SizedBox(height: 5,),
                Text("done ${((progress-0.1) * 100).toStringAsFixed(1)}%",
                  style: TextStyle(color: Colors.white),),
              ],
            ),
          ),
        ),
      );
    },
  );
  showDialog(context: context, builder: (ctx) => statefulBuilder);
}
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6.底部彈框:SnackBar

這個比較簡單，使用Scaffold.of方法獲取ScaffoldState呼叫showSnackBar

_showScaffold(BuildContext context) {
      var snackBar = SnackBar(
      backgroundColor: Color(0xffFB6431),//顏色
      content: Text('Hello!'),//內容
      duration: Duration(seconds: 3),//持續時間
      action: SnackBarAction(
          label: '確定',
          onPressed: () {
            print("Flutter之旅");
          }));
      Scaffold.of(context).showSnackBar(snackBar);//這樣就行了
}
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7.底部抽屜:BottomSheet

用法和SnackBar相似，更強的是底部欄的child你想放什麼都可以。

bool _showing=false;
_showBottomSheet(BuildContext context) {
  var bottomSheet = BottomSheet(
      onClosing: () {},
      builder: (context) => (Container(
            color: Color(0xdde3fbf6),
            height: 150,
            child: Center(
              child: Image.asset("images/wy_300x200_filter.jpg"),
            ),
          )));
  if(_showing){
    Navigator.of(context).pop();
  }else{
    Scaffold.of(context).showBottomSheet(bottomSheet.builder); //這樣就行了
  }
  _showing=!_showing;
}
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好了，本文就到這裡。

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結語

本文到此接近尾聲了，如果想快速嚐鮮Flutter，《Flutter七日》會是你的必備佳品;如果想細細探究它,那就跟隨我的腳步，完成一次Flutter之旅。
另外本人有一個Flutter微信交流群，歡迎小夥伴加入，共同探討Flutter的問題，本人微訊號:zdl1994328，期待與你的交流與切磋。