SkipFuseUI provides the SwiftUI API surface for Skip Fuse apps on Android. It acts as a thin Swift bridging layer that delegates rendering to SkipUI, which implements SwiftUI views as Jetpack Compose composables. On iOS, import SwiftUI resolves to Apple's framework as usual; on Android, it resolves to SkipFuseUI, giving you a single SwiftUI codebase that runs natively on both platforms.
SkipFuseUI sits between your SwiftUI code and SkipUI's Compose implementation. Your Swift views are compiled natively for Android by the Swift Android SDK, and at render time each view produces a Kotlin-side SkipUI counterpart that Compose renders on screen.
flowchart LR
A["Your SwiftUI Code"] --> B["SkipFuseUI\n(Swift on Android)"]
B -->|"Java_view"| C["SkipUI\n(Kotlin/Compose)"]
C --> D["Jetpack Compose\nUI on Screen"]
style A fill:#555555,stroke:#333,color:#fff
style B fill:#6b3fa0,stroke:#4a2d6e,color:#fff
style C fill:#2e6da4,stroke:#1a4a6e,color:#fff
style D fill:#2d7a2d,stroke:#1a5c1a,color:#fff
The key mechanism is the SkipUIBridging protocol. Every SkipFuseUI view type conforms to it by exposing a Java_view property that returns the equivalent SkipUI Kotlin object. When Compose needs to render your view hierarchy, it walks the tree of Java_view references — each one backed by SkipBridge JNI calls between Swift and Kotlin.
flowchart TB
subgraph "Your App"
APP["App SwiftUI Code"]
end
subgraph "SkipFuseUI Package"
SFUI["SkipFuseUI\n(re-exports SwiftUI\non Android)"]
SSU["SkipSwiftUI\n(Swift view types,\nproperty wrappers,\nmodifiers)"]
end
subgraph "Bridging Infrastructure"
SB["SkipBridge\n(JNI object lifecycle,\ntype conversion)"]
SF["SkipFuse\n(@Observable,\nOSLog, bridging\nsupport)"]
SAB["SkipAndroidBridge\n(Android-specific\nJNI helpers)"]
SJNI["SwiftJNI\n(low-level JNI\nC/Swift wrapper)"]
end
subgraph "Compose Implementation"
SUI["SkipUI\n(SwiftUI → Jetpack\nCompose mapping)"]
SM["SkipModel\n(Compose state\ntracking)"]
end
APP --> SFUI
SFUI --> SSU
SSU --> SB
SSU --> SF
SSU --> SUI
SB --> SAB
SB --> SJNI
SUI --> SM
style APP fill:#555555,stroke:#333,color:#fff
style SFUI fill:#6b3fa0,stroke:#4a2d6e,color:#fff
style SSU fill:#6b3fa0,stroke:#4a2d6e,color:#fff
style SB fill:#b33030,stroke:#8a1a1a,color:#fff
style SF fill:#b33030,stroke:#8a1a1a,color:#fff
style SAB fill:#b33030,stroke:#8a1a1a,color:#fff
style SJNI fill:#b33030,stroke:#8a1a1a,color:#fff
style SUI fill:#2e6da4,stroke:#1a4a6e,color:#fff
style SM fill:#2e6da4,stroke:#1a4a6e,color:#fff
On iOS, SkipFuseUI simply re-exports Apple's SwiftUI — the entire SkipSwiftUI layer is compiled away.
Every SwiftUI type in SkipFuseUI follows the same pattern: a Swift struct or class holds the view's parameters, and its Java_view property constructs the Kotlin equivalent on demand.
sequenceDiagram
participant App as Your View (Swift)
participant Fuse as SkipFuseUI VStack (Swift)
participant Bridge as SkipBridge (JNI)
participant UI as SkipUI VStack (Kotlin)
participant Compose as Jetpack Compose
App->>Fuse: VStack { Text("Hello") }
Note over Fuse: Stores alignment,<br/>spacing, content
Compose->>Fuse: Request Java_view
Fuse->>Bridge: Create SkipUI.VStack<br/>with bridged content
Bridge->>UI: JNI call → Kotlin object
UI->>Compose: Emit Column composable
Content views are recursively bridged via Java_viewOrEmpty, which walks the view tree and converts each Swift view into its Kotlin counterpart.
SwiftUI property wrappers (@State, @Binding, @AppStorage) are backed by bridge-aware box types that synchronize values between Swift and Compose's reactive state system:
flowchart LR
S["@State var count = 0\n(Swift)"] -->|"BridgedStateBox"| K["StateSupport\n(Kotlin/Compose)"]
K -->|"MutableState"| C["Compose\nRecomposition"]
C -->|"read triggers\naccess()"| S
style S fill:#6b3fa0,stroke:#4a2d6e,color:#fff
style K fill:#2e6da4,stroke:#1a4a6e,color:#fff
style C fill:#2d7a2d,stroke:#1a5c1a,color:#fff
When Swift code writes to a @State property, the BridgedStateBox notifies Compose's MutableState, triggering recomposition. When Compose reads the value, it calls back into Swift via the bridge. This two-way sync ensures that SwiftUI's declarative state model works identically on Android.
@Observable types require import SkipFuse to enable this state tracking. See the App Development guide for details.
SkipFuseUI mirrors the SwiftUI API surface for iOS 16+, including:
- Containers:
VStack,HStack,ZStack,List,ScrollView,LazyVGrid,LazyHGrid,NavigationStack,TabView,Form,Section,Group - Controls:
Button,Toggle,Slider,Stepper,Picker,DatePicker,TextField,SecureField,TextEditor - Components:
Text,Image,AsyncImage,Label,Link,ProgressView,Divider,ShareLink - Graphics:
Color,Gradient,Shape(Circle, Rectangle, Capsule, etc.),Path,Material - Layout:
GeometryReader,Alignment,EdgeInsets,ViewThatFits,Grid - State:
@State,@Binding,@Environment,@AppStorage,@FocusState - Modifiers:
.padding,.frame,.background,.overlay,.opacity,.rotation,.shadow,.clipShape,.sheet,.alert,.onAppear,.task, and many more - Navigation:
NavigationStack,NavigationLink,NavigationPath,.navigationTitle,.toolbar - Gestures:
TapGesture,LongPressGesture,DragGesture - Animation:
withAnimation,.animation,.transition,Spring - UIKit compatibility:
UIApplication,UIColor,UIImage,UIPasteboard
For the full list of supported SwiftUI components, see the SkipUI documentation.
- App Development — Building dual-platform apps with Skip, including UI and view model coding
- Skip Modes — Fuse vs. Lite mode and when to use each
- Bridging Reference — Supported Swift language features and types for bridging
- Cross-Platform Topics — Integrating platform-specific code with
#if SKIPand#if os(Android) - SkipUI Module — Supported SwiftUI components and Compose integration topics
- SkipBridge Module — The JNI bridging infrastructure that SkipFuseUI depends on
- SkipFuse Module — Observable state tracking and Android runtime support
This software is licensed under the Mozilla Public License 2.0.