HDC技术分论坛：HarmonyOS新一代UI框架的全面解读

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":10}},{"type":"color","attrs":{"color":"#40A9FF","name":"blue"}}],"text":"作者：yuzhiqiang，UI编程框架首席技术专家","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在Harmony 3.0.0开发者预览版中，包含了新一代的声明式UI框架ArkUI 3.0、多语言跨平台编译器ArkCompiler 3.0、跨端开发工具DevEco Studio3.0，以及基于TS/JS语言的API 7，全面提升开发者体验。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"本期，我们要为大家重点介绍HarmonyOS新一代声明式UI框架ArkUI 3.0。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"一、UI编程框架","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在介绍ArkUI 3.0之前，我们先来简要了解一下什么是UI编程框架。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"UI编程框架，是为应用开发者提供的开发UI的基础设施，主要包括UI控件（按钮/列表等），视图布局（摆放/排列相应的UI控件），动画机制（动画设计以及效果呈现），交互事件处理（点击/滑动等），以及相应的编程语言和编程模型等。从系统运行的维度来看，UI编程框架也包括一个运行时，负责应用在系统中执行时所需的资源加载、UI渲染和事件响应等。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"总体而言，UI编程框架提供了开发以及运行UI界面所需要的框架能力，主要架构如下图所示：","attrs":{}}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/be/beb97cd37e8eab23c0cdd4c7e84a039c.webp","alt":null,"title":"","style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":"","fromPaste":false,"pastePass":false}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":"center","origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":9}}],"text":"图1 UI编程框架","attrs":{}}]},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"开发模型：","attrs":{}},{"type":"text","text":"对开发者提供开发范式、UI控件/布局/动效/交互、编程语言等。它体现的是开发效率与难易程度。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"运行框架：","attrs":{}},{"type":"text","text":"UI界面渲染及交互的基础能力框架，包括相应的布局引擎、控件机制、动效引擎、事件机制、渲染管线等，并结合语言虚拟机和图形引擎，将开发者的程序运行在具体系统平台上。它体现的是应用运行的性能体验。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"平台适配：","attrs":{}},{"type":"text","text":"承载框架的具体操作系统或平台适配层。","attrs":{}}]}]}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"UI编程框架的关键需求，主要有以下两类：","attrs":{}}]},{"type":"numberedlist","attrs":{"start":1,"normalizeStart":1},"content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":1,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"开发效率：","attrs":{}},{"type":"text","text":"包括代码量、学习曲线、工具、社区、三方库完备度等。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":2,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"性能体验：","attrs":{}},{"type":"text","text":"包括启动速度、帧率、响应时延、酷炫效果、资源占用等。","attrs":{}}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"另外，随着智能设备的急剧增长，UI编程框架还需要考虑如何更好地适配不同设备的差异性，包括设备形态差异（比如屏幕形状、尺寸、分辨率、交互模式等），以及设备能力差异（比如内存、CPU、GPU等）。 ","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"二、ArkUI框架的演进","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"为了更好地满足开发效率和性能体验等相关的需求， ArkUI 3.0综合考虑了UI渲染以及语言和运行时，围绕着极简开发、高性能、跨设备跨平台进一步演进。下图描述了ArkUI整体架构的演进：","attrs":{}}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/00/0029cf6bc24092050dd3c39c08102918.webp","alt":null,"title":"","style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":"","fromPaste":false,"pastePass":false}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":"center","origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":9}}],"text":"图2 ArkUI框架演进","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"图的左侧是2020年发布的JS UI框架的架构示意图。它主要支持类Web的前端开发范式，通过DSL（domain-specific language，领域特定语言）转换层，跨语言对接到声明式UI后端引擎，并结合JS引擎完成整体UI渲染。图的右侧是新的ArkUI 3.0框架，","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"主要有以下几个关键的变化：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（1）引入了新一代的声明式UI开发范式，实现极简的UI描述语法。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（2）设计了统一的前后端扁平化渲染机制，进一步提升UI渲染的性能并降低内存消耗。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（3）深度结合ArkCompiler 3.0的方舟编译器和方舟运行时，提升语言的执行性能和跨语言通信能力。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（4）在工具方面，针对新一代的声明式UI开发范式构建了新的编译工具链和预览引擎，提供了所见即所得的实时预览机制。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"另外，在ArkUI 3.0框架中，类Web范式会继续保留，即类Web范式和新一代的声明式UI范式都可以支持，可以各自独立使用，但不能混用。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"三、ArkUI 3.0的关键特性","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"接下来我们展开详细介绍一下ArkUI 3.0的关键特性。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":12}},{"type":"strong","attrs":{}}],"text":"1. 新一代的声明式UI开发范式","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"具体而言，ArkUI 3.0中的新一代声明式UI开发范式，主要特征如下：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（1）基于TypeScript扩展的声明式UI描述语法，提供了类自然语言的UI描述和组合。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（2）开箱即用的多态组件。多态是指UI描述是统一的，UI呈现在不同类型设备上会有所不同。比如Button组件在手机和手表会有不同的样式和交互方式。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"（3）多维度的状态管理机制，支持灵活的数据驱动的UI变更。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"下面我们以一个具体的示例来说明新一代声明式UI开发范式的基本组成。如图3所示的代码示例，UI界面会显示一个“Hello World”的文本和一个“Click me”按钮。当用户点击“Click me”按钮时，字符串变量myText的值会从“World”变为“ACE”，文本最终显示为“Hello ACE”。","attrs":{}}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/1d/1dba164a29cb21ea9b570f0580936dd7.webp","alt":null,"title":"","style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":"","fromPaste":false,"pastePass":false}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":"center","origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":9}}],"text":"图3 声明式UI开发范式的基本概念","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"以上示例中所包含的","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"声明式UI开发范式的基本组成说明如下：","attrs":{}}]},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"装饰器：","attrs":{}},{"type":"text","text":"用来装饰类、结构体、方法以及变量，赋予其特殊的含义，如上述示例中@Entry、@Component、@State都是装饰器。@Component表示这是个自定义组件；@Entry则表示这是个入口组件；@State表示组件中的状态变量，这个状态变化会引起UI变更。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"自定义组件：","attrs":{}},{"type":"text","text":"可复用的UI单元，可组合其它组件，如上述被@Component装饰的struct Hello。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"UI描述：","attrs":{}},{"type":"text","text":"声明式的方式来描述UI的结构，如上述build()方法内部的代码块。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"内置组件：","attrs":{}},{"type":"text","text":"框架中默认内置的基础和布局组件，可直接被开发者调用，比如示例中的Column、Text、Divider、Button。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"事件方法：","attrs":{}},{"type":"text","text":"用于添加组件对事件的响应逻辑，统一通过事件方法进行设置，如跟随在Button后面的onClick()。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"属性方法：","attrs":{}},{"type":"text","text":"用于组件属性的配置，统一通过属性方法进行设置，如fontSize()、width()、height()、color()等，可通过链式调用的方式设置多项属性。","attrs":{}}]}]}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"上述示例中，用@State装饰过的变量myText，包含了一个基础的状态管理机制，即myText的值的变化，会引起相应的UI变更（Text组件）。ArkUI 3.0还提供多维度的状态管理机制。和UI相关联的数据，不仅仅在组件内使用，还可以在不同组件层级间传递，比如父子组件之间，爷孙组件之间，也可以是全局范围内的传递，还可以是跨设备传递。另外，从数据的传递形式来看，可以分为只读的单向传递和可变更的双向传递。开发者可以灵活的利用这些能力来实现数据和UI的联动。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"ArkUI采用嵌入式领域特定语言（embedded Domain Specific Language， eDSL）的形式，结合宿主语言能力实现UI开发。通过eDSL，结合语法糖或者语言原生的元编程能力，设计了统一的UI开发范式，并能够结合不同语言来实现应用的逻辑处理部分。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":12}},{"type":"strong","attrs":{}}],"text":"2. 关键渲染性能","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"下面通过一个简单的示例代码，为大家讲述从代码到UI显示的整体渲染流程。如图4所示，此示例会在UI界面显示一个“Click me”按钮，按钮下面同步显示按钮的点击次数。当用户点击按钮时，下面的点击次数会相应增加。","attrs":{}}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/60/60f38baddd376c4830727ac7aee08c09.webp","alt":null,"title":"","style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":"","fromPaste":false,"pastePass":false}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":"center","origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":9}}],"text":"图4 整体渲染流程","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"整个渲染过程分为两个阶段：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"（1）初始显示流程（步骤①~⑤）","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"① 源代码通过相应的工具链，编译为带有类型标志的目标文件，同时也包含了如何创建UI结构信息的指令流。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"② 通过跨语言调用并生成了C++层Component树（UI描述层）。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"③ 通过Component树进一步生成Element树。Element是Component的实例，表示一个具体的组件节点，它形成的Element树负责维持界面在整个运行时的树形结构，方便计算更新时的局部更新算法等。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"④ 对于每个可显示的Element都会为其创建对应的RenderNode。RenderNode负责一个节点的显示信息，它形成的Render树维护着整个界面渲染需要用到的信息，包括位置、大小、绘制命令等。后续的布局、绘制都是在Render树上进行的。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"⑤ 实现真正的渲染并显示绘制结果。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"（2）按钮被点击后的显示流程（步骤⑥~⑪）","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"⑥ 点击事件传递到组件，组件的onClick事件方法被触发执行。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"⑦ 由于onClick事件方法中@State注解过的变量改变了，相应getter/setter函数会被触发。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"⑧ 状态管理模块定位出关联的UI组件。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"⑨ 状态管理模块更新相应的Element树的信息。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"⑩ 更新相应的UI组件的渲染信息。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"⑪ 界面显示，与⑤类似。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"整个渲染过程中所需的关键能力，除了极简的开发范式本身，主要包含以下三个部分：","attrs":{}}]},{"type":"bulletedlist","content":[{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"编译优化以及跨语言调用。","attrs":{}},{"type":"text","text":"结合目标文件中的类型信息标志，ArkCompiler会实现相应的代码优化。另外，ArkCompiler也提供了高效的JS/TS -> C++跨语言调用机制。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"扁平化渲染机制以及小对象组合机制。","attrs":{}},{"type":"text","text":"组件信息的结构在前后端有基本一致的表示，进一步减少了转换开销，实现了扁平化的渲染。同时，UI组件内部都是通过轻量化对象来按需组合，内存消耗也进一步降低。","attrs":{}}]}]},{"type":"listitem","attrs":{"listStyle":null},"content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"状态管理机制。","attrs":{}},{"type":"text","text":"通过监听变量的存取操作，实现数据变化的自动化感知并计算出相应的最小化UI组件更新范围，实现高效的UI变更。","attrs":{}}]}]}],"attrs":{}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"除此之外，长列表渲染是一种典型的应用场景，里面可能会涉及到大量的数据，如果处理不当，会引起极大影响性能以及资源占用。ArkUI 3.0针对这类常用的场景，提供了一种","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"LazyForEach懒加载机制","attrs":{}},{"type":"text","text":"，会自动根据具体情况计算出合适的渲染数据，实现数据的按需加载，从而提升UI刷新效率。LazyForEach可以结合常用的列表类组件（比如List、Grid等）灵活配合使用。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":12}},{"type":"strong","attrs":{}}],"text":"3. 高级UI组件库","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"高级的UI组件库可以进一步助力高效的应用开发。HarmonyOS的欧洲研发团队基于ArkUI 3.0，构建了一些高阶组件示例，比如：常用的图表类组件、瀑布流布局组件等。开发者可以通过几行代码就可以实现复杂酷炫的UI效果，比如自适应的图片增删、行列变化，以及相应的酷炫动效效果。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"示例如下：","attrs":{}}]},{"type":"video","attrs":{"videoHTML":""}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":"center","origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":9}}],"text":"图5 图表组件","attrs":{}}]},{"type":"video","attrs":{"videoHTML":""}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":"center","origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":9}}],"text":"图6 瀑布流布局组件","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":12}},{"type":"strong","attrs":{}}],"text":"4. 多设备开发","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"除了UI开发套件，ArkUI 3.0围绕着多设备开发，还提供了多维度的方案，进一步简化开发：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"（1）基础能力层：","attrs":{}},{"type":"text","text":"包括基础的分层参数配置（比如色彩、字号、圆角、间距等），栅格系统，原子化布局能力（比如拉伸、折行、隐藏等）。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"（2）零部件组件层：","attrs":{}},{"type":"text","text":"包括多态控件，统一交互能力，以及在此基础上的组件组合。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"（3）面向典型场景：","attrs":{}},{"type":"text","text":"提供分类的页面组合模板以及示例代码。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"关于多设备开发，后面我们会有更详细的文章介绍，请大家持续关注。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":12}},{"type":"strong","attrs":{}}],"text":"5. 实时预览机制","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"整个开发流程中还有一个很重要的方面——预览能力，即可以在PC上通过IDE（集成开发环境）就可以实时看到应用的渲染效果，而无需通过具体设备来部署运行。","attrs":{}},{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"预览的关键需求主要包括：","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"（1）一致性渲染：","attrs":{}},{"type":"text","text":"和目标设备一致的UI呈现效果。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"（2）实时预览&双向预览：","attrs":{}},{"type":"text","text":"改动相应的代码，实时呈现出相应UI效果。另外，代码能够和UI双向联动，代码改动的同时UI也实时变更，UI改动的同时代码也相应地变更。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","marks":[{"type":"strong","attrs":{}}],"text":"（3）多维度预览：","attrs":{}},{"type":"text","text":"页面级预览、组件级预览、多设备预览。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"以上这些能力都需要UI编程框架具备相应的基础设施才能达成。ArkUI 3.0的预览器的整体架构如下图所示：","attrs":{}}]},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/e3/e3137a5af98c9db4c79c7aa76ca0b4e2.webp","alt":null,"title":"","style":[{"key":"width","value":"75%"},{"key":"bordertype","value":"none"}],"href":"","fromPaste":false,"pastePass":false}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":"center","origin":null},"content":[{"type":"text","marks":[{"type":"size","attrs":{"size":9}}],"text":"图7 ArkUI 3.0的预览器架构","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"ArkUI 3.0基于底层的画布通过自绘制实现了不同平台上一致化的渲染体验，并通过渲染侧的跨平台对接层完成了整体渲染效果。另外，ArkUI 3.0通过实时代码变化检测和增量编译机制，再配合前面所提到的高效渲染性能，实现了实时编写预览。","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"通过ArkUI 3.0的基础设施，结合IDE可视化工具（即预览器前端），就实现了上面的实时预览、双向预览等能力，进一步提升了开发者的开发效率。","attrs":{}}]},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"四、结束语","attrs":{}}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"总体而言，UI编程框架在应用开发中起了至关重要的作用。目前，拥有全新开发范式的新一代的UI框架——ArkUI 3.0走出了坚实的第一步，并已开始支撑更多的关键应用。接下来，除了基础设施的持续完善，我们会重点支持生态扩展，主要包括高级UI能力的提升，比如三方地图，游戏的融合，以及Web能力增强等。同时，我们也会围绕跨设备、性能体验持续地创新。欢迎广大的开发者加入进来，一起探索，一起改进，共建万物互联的应用生态！未来，有迹可循！","attrs":{}}]}]}