目標：
1.按下刪除按鈕時，會跳出提示框提醒是否要刪除
2.按下product_create頁面的save時，會跳出光箱

如此gif

1. pages/product.dart
   先定義好跳出提示框的function

  _showWarningDialog(BuildContext context) {
    showDialog(
        context: context,
        //一定要傳入基本訊息
        builder: (BuildContext context) {
          return AlertDialog(
            title: Text('Are you sure?'),
            content: Text('This action cannot be undone!'),
            actions: <Widget>[
              FlatButton(
                child: Text('DISCARD'),
                onPressed: () {
                  Navigator.pop(context);
                  //基本訊息在這用上了
                  //回到上一層而已，不做其他事
                },
              ),
              FlatButton(
                child: Text('CONTINUE'),
                onPressed: () {
                  Navigator.pop(context);
                  Navigator.pop(context, true);
                  //回到上一層
                  //然後傳一個true到products.dart的Navigator後的then那邊
                  //因為那邊有寫deleteProduct
                  //所以就進行刪除
                },
              ),
            ],
          );
        });
  }

再註冊即可

...
 child: RaisedButton(
   color: Theme.of(context).accentColor,
   child: Text('DELETE'),
   onPressed: () => _showWarningDialog(context),
 ),
...

2. pages/product_create.dart
   按下去以後叫出一個長在bottom的modal

child: RaisedButton(
  child: Text('Save'),
  onPressed: () {
    showModalBottomSheet(
        context: context,
        builder: (BuildContext context) {
          return Center(
            child: Text('This is a Modal!'),
          );
        });
  },
),

主題來源：
Learn Flutter & Dart to Build iOS & Android Apps