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| 1 | +# Example07DraggableMarkers - Draggable Markers with Drag Events |
| 2 | + |
| 3 | +[Back to README](../../README.md) |
| 4 | + |
| 5 | +This example demonstrates draggable markers in OpenMapView, showing how to enable marker dragging and handle drag event callbacks. |
| 6 | + |
| 7 | +## Features Demonstrated |
| 8 | + |
| 9 | +- Draggable markers with long-press activation |
| 10 | +- OnMarkerDragListener with start/drag/end callbacks |
| 11 | +- Toast notifications showing drag events |
| 12 | +- Add random markers with FAB button |
| 13 | +- Clear all markers with FAB button |
| 14 | +- Marker click listener alongside drag listener |
| 15 | +- Attribution click listener for OSM copyright |
| 16 | + |
| 17 | +## Screenshot |
| 18 | + |
| 19 | + |
| 20 | + |
| 21 | +## Quick Start |
| 22 | + |
| 23 | +### Option 1: Run in Android Studio |
| 24 | + |
| 25 | +1. Open the OpenMapView project in Android Studio |
| 26 | +2. Select `examples.Example07DraggableMarkers` from the run configuration dropdown |
| 27 | +3. Click Run (green play button) |
| 28 | +4. Deploy to your device or emulator |
| 29 | + |
| 30 | +### Option 2: Build and Install from Command Line |
| 31 | + |
| 32 | +```bash |
| 33 | +# From project root - build, install, and launch |
| 34 | +./gradlew :examples:Example07DraggableMarkers:installDebug |
| 35 | + |
| 36 | +# Launch the app |
| 37 | +adb shell am start -n de.afarber.openmapview.example07draggablemarkers/.MainActivity |
| 38 | +``` |
| 39 | + |
| 40 | +## Code Highlights |
| 41 | + |
| 42 | +### Creating Draggable Markers |
| 43 | + |
| 44 | +```kotlin |
| 45 | +val marker = Marker( |
| 46 | + position = LatLng(51.4661, 7.2491), |
| 47 | + title = "Marker 1", |
| 48 | + snippet = "Drag me!", |
| 49 | + draggable = true // Enable dragging |
| 50 | +) |
| 51 | +mapView.addMarker(marker) |
| 52 | +``` |
| 53 | + |
| 54 | +### Setting Up Drag Listener |
| 55 | + |
| 56 | +```kotlin |
| 57 | +mapView.setOnMarkerDragListener(object : OnMarkerDragListener { |
| 58 | + override fun onMarkerDragStart(marker: Marker) { |
| 59 | + Toast.makeText(context, "Started dragging: ${marker.title}", Toast.LENGTH_SHORT).show() |
| 60 | + } |
| 61 | + |
| 62 | + override fun onMarkerDrag(marker: Marker) { |
| 63 | + // Called continuously during drag - useful for real-time updates |
| 64 | + } |
| 65 | + |
| 66 | + override fun onMarkerDragEnd(marker: Marker) { |
| 67 | + val coordString = "%.4f, %.4f".format( |
| 68 | + marker.position.latitude, |
| 69 | + marker.position.longitude |
| 70 | + ) |
| 71 | + Toast.makeText(context, "${marker.title} at: $coordString", Toast.LENGTH_SHORT).show() |
| 72 | + } |
| 73 | +}) |
| 74 | +``` |
| 75 | + |
| 76 | +### Key Concepts |
| 77 | + |
| 78 | +- **draggable = true**: Enable dragging on individual markers |
| 79 | +- **OnMarkerDragListener**: Interface with three callbacks |
| 80 | +- **onMarkerDragStart()**: Called when long-press initiates drag |
| 81 | +- **onMarkerDrag()**: Called continuously during drag movement |
| 82 | +- **onMarkerDragEnd()**: Called when finger is lifted |
| 83 | +- **Marker position update**: Position is automatically updated during drag |
| 84 | + |
| 85 | +## What to Test |
| 86 | + |
| 87 | +1. **Add markers** - Click the refresh FAB to add 5 random draggable markers |
| 88 | +2. **Long-press to drag** - Press and hold a marker, then drag it |
| 89 | +3. **Observe start toast** - "Started dragging: Marker X" appears |
| 90 | +4. **Observe end toast** - New coordinates shown when released |
| 91 | +5. **Click markers** - Tap (don't hold) to see title and snippet |
| 92 | +6. **Clear all** - Click the clear FAB to remove all markers |
| 93 | +7. **Pan and zoom** - Markers remain draggable at all zoom levels |
| 94 | +8. **Attribution click** - Tap OSM attribution to open copyright page |
| 95 | + |
| 96 | +## Drag Interaction Details |
| 97 | + |
| 98 | +### How Dragging Works |
| 99 | + |
| 100 | +1. User long-presses on a draggable marker (~500ms) |
| 101 | +2. `onMarkerDragStart()` is called |
| 102 | +3. User moves finger while holding |
| 103 | +4. `onMarkerDrag()` is called continuously |
| 104 | +5. Marker visually follows the touch point |
| 105 | +6. User lifts finger |
| 106 | +7. `onMarkerDragEnd()` is called with final position |
| 107 | + |
| 108 | +### Drag vs Click vs Pan |
| 109 | + |
| 110 | +- **Click**: Quick tap on marker triggers click listener |
| 111 | +- **Long-press on marker**: Initiates drag (if draggable) |
| 112 | +- **Long-press on map**: Triggers map long-click listener |
| 113 | +- **Drag on map**: Pans the map |
| 114 | + |
| 115 | +## Technical Details |
| 116 | + |
| 117 | +### Marker State During Drag |
| 118 | + |
| 119 | +- Position is updated in real-time during drag |
| 120 | +- Marker's visual position follows the touch point |
| 121 | +- Final position is permanent after drag ends |
| 122 | + |
| 123 | +### Performance |
| 124 | + |
| 125 | +- Drag updates run on UI thread for responsiveness |
| 126 | +- No coordinate conversion until drag ends (efficient) |
| 127 | +- Smooth visual feedback during drag |
| 128 | + |
| 129 | +## Advanced Usage |
| 130 | + |
| 131 | +### Track Marker Movement |
| 132 | + |
| 133 | +```kotlin |
| 134 | +var startPosition: LatLng? = null |
| 135 | + |
| 136 | +mapView.setOnMarkerDragListener(object : OnMarkerDragListener { |
| 137 | + override fun onMarkerDragStart(marker: Marker) { |
| 138 | + startPosition = marker.position |
| 139 | + } |
| 140 | + |
| 141 | + override fun onMarkerDrag(marker: Marker) { |
| 142 | + // Update UI with current position |
| 143 | + } |
| 144 | + |
| 145 | + override fun onMarkerDragEnd(marker: Marker) { |
| 146 | + val distance = calculateDistance(startPosition!!, marker.position) |
| 147 | + Toast.makeText(context, "Moved: ${distance}m", Toast.LENGTH_SHORT).show() |
| 148 | + } |
| 149 | +}) |
| 150 | +``` |
| 151 | + |
| 152 | +### Combine with Click Listener |
| 153 | + |
| 154 | +```kotlin |
| 155 | +// Both listeners can coexist |
| 156 | +mapView.setOnMarkerClickListener { marker -> |
| 157 | + Toast.makeText(context, marker.title, Toast.LENGTH_SHORT).show() |
| 158 | + true |
| 159 | +} |
| 160 | + |
| 161 | +mapView.setOnMarkerDragListener(object : OnMarkerDragListener { |
| 162 | + // ... drag callbacks |
| 163 | +}) |
| 164 | +``` |
| 165 | + |
| 166 | +## Map Location |
| 167 | + |
| 168 | +**Default Center:** Bochum, Germany (51.4661°N, 7.2491°E) at zoom 13.0 |
| 169 | + |
| 170 | +Random markers are generated within ~2.5km of the center. |
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