Implementing Sticky Tabs Effect in HarmonyOS ArkTS

I. Core Implementation Principles

Achieving the sticky header effect through dual-level scroll nesting:

Outer Scroll container hosting top banners and tab area
Inner Tabs component bound with List for content scrolling
Utilizing nestedScroll property for scroll linkage control

// Key component structure
Scroll() {
  Column() {
    Banner() // Top banner
    Tabs({ 
      controller: this.tabsController,
      barPosition: BarPosition.Start,
      nestedScroll: { scrollForward: NestedScrollMode.PARENT_FIRST }
    }) {
      TabContent() {
        List() {
          // Content items
        }
      }
    }
  }
}

*Implementation reference: *

II. Implementation Steps

1. Layout Construction

@Entry
@Component
struct StickyTabs {
  @State currentIndex: number = 0
  private tabsController = new TabsController()

  build() {
    Scroll() {
      Column() {
        // Top banner
        Stack({ alignContent: Alignment.Top }) {
          Image("banner_bg.png")
            .width("100%")
            .height(200)
            .objectFit(ImageFit.Cover)
        }

        // Sticky tabs
        Tabs() {
          TabContent() {
            List() {
              ForEach(this.tabsData, (item) => {
                ListItem().text(item.title)
              })
            }
          }
        }
      }
    }
  }
}

*Layout pattern inspired by *

2. Scroll Monitoring

@State scrollY: number = 0
private onScroll = (event: ScrollEvent) => {
  this.scrollY = event.contentOffset.y
  this.updateStickyState()
}

// Sticky state determination
private updateStickyState() {
  if (this.scrollY > 150) { // Banner height threshold
    this.tabsController.setSticky(true)
  } else {
    this.tabsController.setSticky(false)
  }
}

*Scroll position detection method from *

3. Style Configuration

.tabs {
  .height(56)
  .backgroundColor(Color.White)
  .elevation(4)
  .sticky(StickyStyle.Header) // Core sticky property
  .scrollBar(BarState.Off)
}

*Style implementation reference: *

4. Interaction Coordination

// Tab click navigation
private handleTabChange(index: number) {
  this.tabsController.changeIndex(index)
  this.listScroller.scrollToIndex(index * 10) // Page calculation
}

// List scroll synchronization
private onListScroll = (event: ScrollEvent) => {
  const topItem = this.listRef.getScrollOffset()
  this.tabsController.setActiveTab(
    Math.floor(topItem / 100) // Position mapping
  )
}

*Interaction logic from *

5. Performance Optimization

// Virtual scroll implementation
List() {
  .virtualScroll({ 
    bufferSize: 5, 
    itemHeight: 80 
  })
}

*Optimization pattern from *

III. Key Considerations

Nested Scroll Limits
Avoid exceeding 3 scroll container nesting levels to prevent performance degradation
Edge Effect Conflicts
Set edgeEffect: EdgeEffect.None for inner lists to prevent scroll conflicts
Style Consistency
Maintain exact height consistency between tab components and CSS definitions
Event Throttling
Implement @throttle(200) decorator for scroll listeners
Dynamic Data Handling
Call tabsController.refreshLayout() after data updates

IV. Application Scenarios

Scenario Type	Implementation	Key Considerations
E-commerce	Category headers	Banner-tab height binding
News Channels	Multi-level tabs	Dynamic height calculation
Social Feeds	Variable content	Virtual scroll + position tracking

V. Debugging Techniques

Heatmap Visualization
Enable Layout Inspector's Show Touch Region option
Scroll Logging

   Scroll() {
     .onScroll((e) => {
       console.log(`[${new Date()}] Scroll position: ${e.contentOffset.y}`)
     })
   }

Performance Metrics Utilize PerformanceMonitor for FPS and memory tracking

VI. Extended Implementation

@Entry
@Component
struct AdvancedStickyTabs {
  @State currentIndex: number = 0
  private tabsController = new TabsController()
  private listData = Array.from({length: 100}, (_,i)=>`Item ${i+1}`)

  build() {
    Scroll() {
      Column() {
        // Dynamic banner
        Stack({ alignContent: Alignment.Top }) {
          Image("banner.png")
            .onScrollOffset((y) => {
              this.tabsController.setSticky(y > 150)
            })
        }

        // Sticky tabs with animations
        Tabs() {
          TabContent() {
            List() {
              ForEach(this.listData, (item) => {
                ListItem()
                  .height(80)
                  .onClick(() => this.handleItemClick())
              })
            }
            .nestedScroll({ scrollForward: NestedScrollMode.PARENT_FIRST })
          }
        }
      }
    }
  }
}

VII. Optimization Directions

Dynamic Height Adjustment Auto-calculate tab height using layout callbacks:

   onInit() {
     this.tabsController.onLayoutChanged((rect) => {
       this.tabHeight = rect.height
     })
   }

Smooth Transitions Implement sticky animation:

   .onStickyStateChanged((isSticky) => {
     animateTo({
       duration: 200,
       animation: Animation.Spring,
     })
   })

This implementation leverages HarmonyOS's native scroll coordination mechanisms while maintaining performance efficiency through virtual scrolling and optimized event handling. The solution effectively combines parent/child scroll interactions with dynamic layout adjustments to achieve professional-grade sticky header effects.

魔眼天王 @moyantianwang