| /* |
| * Copyright 2020 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| package androidx.compose.runtime.samples |
| |
| import androidx.annotation.Sampled |
| import androidx.compose.runtime.AbstractApplier |
| import androidx.compose.runtime.Composable |
| import androidx.compose.runtime.Composition |
| import androidx.compose.runtime.ExperimentalComposeApi |
| import androidx.compose.runtime.Recomposer |
| import androidx.compose.runtime.compositionFor |
| import androidx.compose.runtime.emit |
| import androidx.compose.runtime.getValue |
| import androidx.compose.runtime.setValue |
| import androidx.compose.runtime.state |
| |
| @Suppress("unused") |
| @OptIn(ExperimentalComposeApi::class) |
| @Sampled |
| fun CustomTreeComposition() { |
| // Provided we have a tree with a node base type like the following |
| abstract class Node { |
| val children = mutableListOf<Node>() |
| } |
| |
| // We would implement an Applier class like the following, which would teach compose how to |
| // manage a tree of Nodes. |
| class NodeApplier(root: Node) : AbstractApplier<Node>(root) { |
| override fun insert(index: Int, instance: Node) { |
| current.children.add(index, instance) |
| } |
| |
| override fun remove(index: Int, count: Int) { |
| current.children.remove(index, count) |
| } |
| |
| override fun move(from: Int, to: Int, count: Int) { |
| current.children.move(from, to, count) |
| } |
| |
| override fun onClear() { |
| root.children.clear() |
| } |
| } |
| |
| // A function like the following could be created to create a composition provided a root Node. |
| fun Node.setContent(content: @Composable () -> Unit): Composition { |
| return compositionFor(this, NodeApplier(this), Recomposer.current()).also { |
| setContent(content) |
| } |
| } |
| |
| // assuming we have Node sub-classes like "TextNode" and "GroupNode" |
| class TextNode : Node() { |
| var text: String = "" |
| var onClick: () -> Unit = {} |
| } |
| class GroupNode : Node() |
| |
| // Composable equivalents could be created |
| @Composable fun Text(text: String, onClick: () -> Unit = {}) { |
| emit<TextNode, NodeApplier>(::TextNode) { |
| set(text) { this.text = it } |
| set(onClick) { this.onClick = it } |
| } |
| } |
| |
| @Composable fun Group(content: @Composable () -> Unit) { |
| emit<GroupNode, NodeApplier>(::GroupNode, {}, content) |
| } |
| |
| // and then a sample tree could be composed: |
| fun runApp(root: GroupNode) { |
| root.setContent { |
| var count by state { 0 } |
| Group { |
| Text("Count: $count") |
| Text("Increment") { count++ } |
| } |
| } |
| } |
| } |