why i create a object which is extends container didn't show at list

[1506353029]

type FunBtn struct {
fyne.Container
Index int
AddBtn *widget.Button
DescBtn *widget.Button
Label *widget.Label
OnClick func(index int, CIndex int)
}

func NewFunBtn() *FunBtn {
btn := &FunBtn{}
btn.Layout = layout.NewHBoxLayout()
btn.Label = widget.NewLabel("")
btn.DescBtn = widget.NewButtonWithIcon("", theme.QuestionIcon(), func() { btn.onClick(0) })
btn.AddBtn = widget.NewButtonWithIcon("", theme.ContentAddIcon(), func() { btn.onClick(1) })
//btn.Objects = append(btn.Objects, btn.Label, btn.DescBtn, btn.AddBtn)
btn.Add(btn.Label)
btn.Add(btn.DescBtn)
btn.Add(btn.AddBtn)
btn.Index = -1
return btn
}

w2 := logic.CurApp.NewWindow("test")
tlist := widget.NewList(func() int {
	return 10
}, func() fyne.CanvasObject {
	return NewFunBtn()
},
	func(lii widget.ListItemID, co fyne.CanvasObject) {})
w2.SetContent(tlist)
w2.Show()

there is nothing at list
but if i change to "return btn.Container"，it can display nomally

[1506353029]

type BtnCard struct {
widget.Card
Index int
Queue int
init bool
}

func NewBtnCard() *BtnCard {
card := &BtnCard{}
card.SetTitle(" ")
card.SetSubTitle(" ")
card.SetContent(container.NewHBox(
widget.NewButtonWithIcon("单独执行", theme.MediaPlayIcon(), func() { card.onClick(5) }),
widget.NewButtonWithIcon("从此执行", theme.MediaPlayIcon(), func() { card.onClick(6) }),
widget.NewButtonWithIcon("命名", theme.InfoIcon(), func() { card.onClick(0) }),
widget.NewButtonWithIcon("修改", theme.DocumentCreateIcon(), func() { card.onClick(1) }),
widget.NewButtonWithIcon("删除", theme.DeleteIcon(), func() { card.onClick(2) }),
widget.NewButtonWithIcon("上移", theme.MoveUpIcon(), func() { card.onClick(3) }),
widget.NewButtonWithIcon("下移", theme.MoveDownIcon(), func() { card.onClick(4) }),
))
card.ExtendBaseWidget(card)
return card
}

and i create a object which is extends card also can display normally

[andydotxyz]

Container cannot be extended - only Widgets can.
fyne.Container and all objects in canvas package are concrete types which the drivers implement directly.