An TreeView implement in Android with RecyclerView written in kotlin.

Features

1. 100% written in kotlin.
2. Customise, in the future you can implement your own tree data structure.
3. Fetching data asynchronously(Lazy load), no need to load all data at once.
4. Horizontal scroll support. (with bug)
5. Built-in DSL

Screenshot

TODO

• [x] Select or Deselect Node
• [x] Better TreeNodeGenerator API
• [ ] More API to operate the node in the tree, such as expand, collapse, etc.
• [x] Draggable nodes

Usage

• Add the dependency to your gradle file

implementation("io.github.dingyi222666:treeview:1.3.1")

• Use the DataSource DSL to create tree used for the TreeView. Also you can use the TreeNodeGenerator to create the tree.

private fun createTree(): Tree<DataSource<String>> {
    val dataCreator: CreateDataScope<String> = { _, _ -> UUID.randomUUID().toString() }
    return buildTree(dataCreator) {
        Branch("app") {
            Branch("src") {
                Branch("main") {
                    Branch("java") {
                        Branch("com.dingyi.treeview") {
                            Leaf("MainActivity.kt")
                        }
                    }
                    Branch("res") {
                        Branch("drawable") {

                        }
                        Branch("xml") {}
                    }
                    Leaf("AndroidManifest.xml")
                }
            }
        }
    }
}

• Create a node binder to bind the node to the layout, and in most case also implement node click events in this class

  Note: For the indentation setting of the item, we recommend using a Space widget placed at the visual leftmost of your item layout.

• The width of this widget is the indentation width of the item.

inner class ViewBinder : TreeViewBinder<DataSource<String>>(),
    TreeNodeEventListener<DataSource<String>> {

    override fun createView(parent: ViewGroup, viewType: Int): View {
        return if (viewType == 1) {
            ItemDirBinding.inflate(layoutInflater, parent, false).root
        } else {
            ItemFileBinding.inflate(layoutInflater, parent, false).root
        }
    }

    override fun getItemViewType(node: TreeNode<DataSource<String>>): Int {
        if (node.isChild) {
            return 1
        }
        return 0
    }

    override fun bindView(
        holder: TreeView.ViewHolder,
        node: TreeNode<DataSource<String>>,
        listener: TreeNodeEventListener<DataSource<String>>
    ) {
        if (node.isChild) {
            applyDir(holder, node)
        } else {
            applyFile(holder, node)
        }

        val itemView = holder.itemView.findViewById<Space>(R.id.space)

        itemView.updateLayoutParams<ViewGroup.MarginLayoutParams> {
            width = node.depth * 22.dp
        }

    }

    private fun applyFile(holder: TreeView.ViewHolder, node: TreeNode<DataSource<String>>) {
        val binding = ItemFileBinding.bind(holder.itemView)
        binding.tvName.text = node.name.toString()
    }

    private fun applyDir(holder: TreeView.ViewHolder, node: TreeNode<DataSource<String>>) {
        val binding = ItemDirBinding.bind(holder.itemView)
        binding.tvName.text = node.name.toString()

        binding
            .ivArrow
            .animate()
            .rotation(if (node.expand) 90f else 0f)
            .setDuration(200)
            .start()
    }


    override fun onClick(node: TreeNode<DataSource<String>>, holder: TreeView.ViewHolder) {
        if (node.isChild) {
            applyDir(holder, node)
        } else {
            Toast.makeText(this@MainActivity, "Clicked ${node.name}", Toast.LENGTH_LONG).show()
        }
    }

    override fun onToggle(
        node: TreeNode<DataSource<String>>,
        isExpand: Boolean,
        holder: TreeView.ViewHolder
    ) {
        applyDir(holder, node)
    }
}

• If you want to implement horizontal scrolling, you need to set the supportHorizontalScroll to true

treeview.supportHorizontalScroll = true

• Now you can create the tree structure and set up the node generator and node binder for the TreeView, and then call refresh() to load the data

 val tree = createTree()

(binding.treeview as TreeView<DataSource<String>>).apply {
    bindCoroutineScope(lifecycleScope)
    this.tree = tree
    binder = ViewBinder()
    nodeEventListener = binder
}

lifecycleScope.launch {
    binding.treeview.refresh()
}

• If you want to load dynamic data (etc. local file), you can see this example here

• Done! Enjoy using it.

Special thanks

• Rosemoe (Help improve the TreeView horizontal scrolling support)
• HackerMadCat/Multimap (Multimap implementation in kotlin)