RecyclerView
RecyclerView - Efficient List Display
RecyclerView គឺជា advanced widget សម្រាប់បង្ហាញ large datasets ប្រកបដោយ performance ខ្ពស់។ វាជា improved version នៃ ListView ដែលផ្តល់ flexibility និង efficiency កាន់តែច្រើន។
🆚 RecyclerView vs ListView
| Feature | ListView | RecyclerView |
|---|---|---|
| ViewHolder | Optional (manual) | ✅ Mandatory (enforced pattern) |
| Layout Manager | Vertical list only | ✅ Linear, Grid, Staggered |
| Item Animations | None (manual) | ✅ Built-in (add, remove, move) |
| Item Decoration | Dividers only | ✅ Custom decorations |
| Performance | ⚠️ Moderate | ✅ Excellent (optimized recycling) |
| Flexibility | ⚠️ Limited | ✅ Highly customizable |
♻️ View Recycling Mechanism
RecyclerView recycles views ដើម្បី save memory និង improve performance:
[Screen displays 10 items]
┌─────────────────────────────┐
│ 📱 Visible Area (Screen) │
│ │
│ [Item 1] ← ViewHolder #1 │ ┐
│ [Item 2] ← ViewHolder #2 │ │
│ [Item 3] ← ViewHolder #3 │ │
│ [Item 4] ← ViewHolder #4 │ ├─ Visible items (on screen)
│ [Item 5] ← ViewHolder #5 │ │
│ [Item 6] ← ViewHolder #6 │ │
│ [Item 7] ← ViewHolder #7 │ │
│ [Item 8] ← ViewHolder #8 │ │
│ [Item 9] ← ViewHolder #9 │ │
│ [Item 10] ← ViewHolder #10 │ ┘
└─────────────────────────────┘
↓ User scrolls down ↓
┌─────────────────────────────┐
│ [Item 2] ← ViewHolder #2 │ ┐
│ [Item 3] ← ViewHolder #3 │ │
│ [Item 4] ← ViewHolder #4 │ │
│ [Item 5] ← ViewHolder #5 │ ├─ Same ViewHolders
│ [Item 6] ← ViewHolder #6 │ │ (recycled!)
│ [Item 7] ← ViewHolder #7 │ │
│ [Item 8] ← ViewHolder #8 │ │
│ [Item 9] ← ViewHolder #9 │ │
│ [Item 10] ← ViewHolder #10 │ │
│ [Item 11] ← ViewHolder #1 │ ┘ ← RECYCLED! (was Item 1)
└─────────────────────────────┘
Item 1 scrolled off screen
→ ViewHolder #1 recycled
→ Reused for Item 11!
💡 RecyclerView only creates ~12 ViewHolders
for a list of 1000 items!
✨ Memory Efficiency: បើ list មាន 1000 items ប៉ុន្តែ screen បង្ហាញតែ 10 items, RecyclerView creates ~12-15 ViewHolders only (not 1000!)។ ViewHolders ទាំងនោះ recycle រហូត!
🏗️ RecyclerView Architecture (4 Components)
| Component | តួនាទី | Responsibility |
|---|---|---|
| 1️⃣ RecyclerView | Container widget | • Display list on screen • Manage scrolling • Coordinate adapter & layout manager |
| 2️⃣ Adapter | Data → Views | • Hold data source (List, Array) • Create ViewHolders • Bind data to views |
| 3️⃣ ViewHolder | View cache | • Hold references to views (findViewById) • Prevent repeated findViewById() calls • Improve performance |
| 4️⃣ LayoutManager | Position items | • Determine item positions • Handle scrolling behavior • Types: Linear, Grid, Staggered |
📐 LayoutManager Types
| LayoutManager | ទម្រង់ | Use Case |
|---|---|---|
| LinearLayoutManager | Vertical or Horizontal list | News feed, Chat messages, Settings |
| GridLayoutManager | Grid (rows × columns) | Photo gallery, Product catalog |
| StaggeredGridLayoutManager | Staggered grid (Pinterest-like) | Pinterest layout, Masonry grid |
⚡ ViewHolder Pattern (Design Pattern)
ViewHolder pattern គឺជា design pattern ដើម្បី cache view references និង improve performance:
Without ViewHolder:
getView() called for each scroll
→ findViewById() called repeatedly ❌ SLOW!
→ Search view tree every time
→ 1000 items = 1000+ findViewById() calls
With ViewHolder:
ViewHolder created once
→ findViewById() called ONCE per ViewHolder ✅ FAST!
→ References cached in ViewHolder
→ 1000 items = ~12 findViewById() calls only!
Performance gain: 50-100x faster scrolling! 🚀
Java Code
Click "Run" to execute the Java code