一个代码库，所有屏幕：Scapia 如何构建多平台 Flutter 应用

The final and most crucial step in achieving a truly single codebase was isolating every single platform-specific decision. While our PlatformWidget solved the high-level layout, we needed a robust system to prevent "platform-aware logic" from polluting individual UI components.

实现真正单一代码库的最终和最关键一步是隔离每一个平台特定的决策。虽然我们的 PlatformWidget 解决了高层布局，但我们需要一个强大的系统来防止 “平台感知逻辑” 污染单个 UI 组件。

The Problem: When `kIsWeb` Pollutes the Code

问题：当 `kIsWeb` 污染代码时

The moment a component has to ask, “Am I on the web?” it becomes tightly coupled to platform constraints and loses its portability.

一旦组件必须询问，“我是在网页上吗？”它就与平台约束紧密耦合，失去了可移植性。

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Our goal was to eliminate every single **kIsWeb** check from our presentation layer. We achieved this by implementing a powerful 3-Level Presentation System based on classic design patterns: Abstract Factory, Strategy, and Dependency Inversion.

我们的目标是消除 每一个 **kIsWeb** 检查从我们的展示层。我们通过实施一个强大的 3级展示系统，基于经典设计模式： 抽象工厂、策略和 依赖倒置 来实现这一目标。

The Solution: Abstraction is Liberation

解决方案：抽象即解放

We inverted the dependency: instead of the component asking the platform what to do, we inject the platform’s directives into the component.

我们反转了依赖关系：组件不再询问平台该做什么，而是我们注入平台的指令到组件中。

Level 1: The Abstraction Layer (Interfaces)

第 1 级：抽象层（接口）

This layer defines the contracts. Our high-level application logic only ever deals with abstract interfaces, ensuring it is platform-agnostic.

这一层定义了合同。我们的高层应用逻辑只处理抽象接口，确保其与平台无关。

**PlatformComponentFactory**: Defines contracts for platform-specific widgets (e.g., createDocumentUploadButton()).
**PlatformComponentFactory**: 定义平台特定小部件的合同（例如，createDocumentUploadButton()）。
**NavigationStrategy**: Defines contracts for platform-specific behaviour (e.g., MapsAfterUpload()).
**NavigationStrategy**: 定义平台特定行为的契约（例如，MapsAfterUpload()）。
**StyleProvider**: Defines contracts for simple style differences (e.g., defaultAlignment()).
**StyleProvider**: 定义简单样式差异的契约（例如，defaultAlignment()）。

abstract class PlatformComponentFactory {

抽象类 PlatformComponentFactory ...

一个代码库，所有屏幕：Scapia 如何构建多平台 Flutter 应用