Tree

The Tree widget in Fyne is used to display hierarchical data, such as file explorers, category lists, or nested menus. It allows expanding and collapsing nodes for better navigation.

Collapsible Tree

Show Code

package main

import (
  "fmt"

  "fyne.io/fyne/v2"
  "fyne.io/fyne/v2/app"
  "fyne.io/fyne/v2/container"
  "fyne.io/fyne/v2/widget"
)

func main() {
  a := app.New()
  w := a.NewWindow("Tree Collection")

  // Define the data for the tree
  data := map[string][]string{
    "":           {"Fruits", "Vegetables"}, // root nodes
    "Fruits":     {"Apple", "Banana", "Mango"},
    "Apple":      {"Red Apple", "Green Apple"}, // nested children
    "Banana":     {"Yellow Banana"},
    "Vegetables": {"Carrot", "Broccoli"},
  }

  // Create the tree
  tree := widget.NewTree(
    func(uid widget.TreeNodeID) []widget.TreeNodeID { // children
      return data[uid]
    },
    func(uid widget.TreeNodeID) bool { // is branch?
      children, ok := data[uid]
      return ok && len(children) > 0
    },
    func(branch bool) fyne.CanvasObject { // create template
      return widget.NewLabel("Template")
    },
    func(uid widget.TreeNodeID, branch bool, obj fyne.CanvasObject) { // update
      obj.(*widget.Label).SetText(uid)
    },
  )

  // Handlers
  tree.OnSelected = func(uid widget.TreeNodeID) {
    fmt.Println("Selected:", uid)
  }
  tree.OnBranchOpened = func(uid widget.TreeNodeID) {
    fmt.Println("Branch opened:", uid)
  }
  tree.OnBranchClosed = func(uid widget.TreeNodeID) {
    fmt.Println("Branch closed:", uid)
  }

  // Expand root
  tree.OpenAllBranches()

  w.SetContent(container.NewStack(tree))
  w.Resize(fyne.NewSize(400, 300))
  w.ShowAndRun()
}