Wegpunkt-Pfeile mit Richtung und Info-Fenster; GPX-Schreib-Performance fix

- TrackDetailActivity: Zeigt zoom-adaptive Richtungspfeile (Bearing) als Marker auf der Karte; Klick öffnet Info-Fenster mit Geschwindigkeit und Kurs
- GPXManager: appendLocation schreibt nur noch per appendText statt Datei komplett neu zu schreiben (O(1) statt O(n))
- TrackingService: finalizeSession() beim Stoppen aufrufen, um GPX-Footer korrekt abzuschließen

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

mobile/src/main/java/de/tstratmann/gpstracker/TrackDetailActivity.kt

@@ -1,6 +1,10 @@
 package de.tstratmann.gpstracker
 
+import android.graphics.Bitmap
+import android.graphics.Canvas
 import android.graphics.Color
+import android.graphics.Paint
+import android.graphics.Path
 import android.os.Bundle
 import androidx.appcompat.app.AppCompatActivity
 import androidx.core.content.ContextCompat
@@ -18,6 +22,7 @@ class TrackDetailActivity : AppCompatActivity(), OnMapReadyCallback {
     private lateinit var binding: ActivityTrackDetailBinding
     private lateinit var googleMap: GoogleMap
     private lateinit var track: Track
+    private val waypointMarkers = mutableListOf<Marker>()
 
     companion object {
         const val EXTRA_TRACK_NAME = "track_name"
@@ -86,6 +91,93 @@ class TrackDetailActivity : AppCompatActivity(), OnMapReadyCallback {
         drawTrackWithSpeedGradient()
         addStartEndMarkers()
         fitMapToTrack()
+
+        googleMap.setOnCameraIdleListener {
+            displayWaypoints(googleMap.cameraPosition.zoom)
+        }
+
+        googleMap.setOnMarkerClickListener { marker ->
+            val point = marker.tag as? TrackPoint ?: return@setOnMarkerClickListener false
+            marker.title = formatWaypointSpeed(point.speed)
+            marker.snippet = "Kurs: ${point.bearing.toInt()}°"
+            marker.showInfoWindow()
+            true
+        }
+    }
+
+    private fun getWaypointStride(zoom: Float): Int = when {
+        zoom < 12f -> Int.MAX_VALUE
+        zoom < 13f -> 100
+        zoom < 14f -> 50
+        zoom < 15f -> 20
+        zoom < 16f -> 10
+        zoom < 17f -> 5
+        zoom < 18f -> 3
+        else -> 1
+    }
+
+    private fun createArrowBitmap(bearing: Float): BitmapDescriptor {
+        val size = 48
+        val bitmap = Bitmap.createBitmap(size, size, Bitmap.Config.ARGB_8888)
+        val canvas = Canvas(bitmap)
+        val cx = size / 2f
+        val cy = size / 2f
+
+        val fillPaint = Paint(Paint.ANTI_ALIAS_FLAG).apply {
+            color = Color.WHITE
+            style = Paint.Style.FILL
+        }
+        val strokePaint = Paint(Paint.ANTI_ALIAS_FLAG).apply {
+            color = Color.argb(220, 30, 100, 200)
+            style = Paint.Style.STROKE
+            strokeWidth = 3f
+        }
+
+        val path = Path().apply {
+            moveTo(cx, cy - size * 0.38f)
+            lineTo(cx + size * 0.22f, cy + size * 0.30f)
+            lineTo(cx, cy + size * 0.12f)
+            lineTo(cx - size * 0.22f, cy + size * 0.30f)
+            close()
+        }
+
+        canvas.rotate(bearing, cx, cy)
+        canvas.drawPath(path, fillPaint)
+        canvas.drawPath(path, strokePaint)
+
+        return BitmapDescriptorFactory.fromBitmap(bitmap)
+    }
+
+    private fun displayWaypoints(zoom: Float) {
+        waypointMarkers.forEach { it.remove() }
+        waypointMarkers.clear()
+
+        val stride = getWaypointStride(zoom)
+        if (stride == Int.MAX_VALUE) return
+
+        track.points.forEachIndexed { index, point ->
+            if (index % stride == 0) {
+                val marker = googleMap.addMarker(
+                    MarkerOptions()
+                        .position(LatLng(point.latitude, point.longitude))
+                        .icon(createArrowBitmap(point.bearing))
+                        .anchor(0.5f, 0.5f)
+                        .flat(true)
+                ) ?: return@forEachIndexed
+                marker.tag = point
+                waypointMarkers.add(marker)
+            }
+        }
+    }
+
+    private fun formatWaypointSpeed(speedMs: Float): String {
+        val useKnots = track.activityType?.useKnots == true
+        return if (useKnots) {
+            val knots = speedMs * 1.94384f
+            "%.1f kn".format(knots)
+        } else {
+            "${(speedMs * 3.6f).toInt()} km/h"
+        }
     }
 
     private fun drawTrackWithSpeedGradient() {

wear/src/main/java/de/tstratmann/gpstracker/GPXManager.kt

@@ -19,6 +19,11 @@ class GPXManager(private val context: Context) {
         return file
     }
 
+    fun finalizeSession() {
+        currentFile?.appendText(getGpxFooter())
+        currentFile = null
+    }
+
     fun appendLocation(location: Location) {
         currentFile?.let { file ->
             val time = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'", Locale.US).apply {
@@ -37,8 +42,7 @@ class GPXManager(private val context: Context) {
             }
             sb.append("</trkpt>")
 
-            val content = file.readText().removeSuffix(getGpxFooter())
-            file.writeText(content + sb.toString() + getGpxFooter())
+            file.appendText(sb.toString())
         }
     }
 

wear/src/main/java/de/tstratmann/gpstracker/TrackingService.kt

@@ -100,8 +100,9 @@ class TrackingService : Service() {
         speedCount = 0
         _trackingState.value = TrackingData()
 
-        val locationRequest = LocationRequest.Builder(Priority.PRIORITY_HIGH_ACCURACY, 1000)
-            .setMinUpdateIntervalMillis(1000)
+        val locationRequest = LocationRequest.Builder(Priority.PRIORITY_HIGH_ACCURACY, 5000)
+            .setMinUpdateIntervalMillis(5000)
+            .setMinUpdateDistanceMeters(10f)
             .build()
 
         try {
@@ -122,6 +123,7 @@ class TrackingService : Service() {
     fun stopTracking() {
         fusedLocationClient.removeLocationUpdates(locationCallback)
         job?.cancel()
+        gpxManager.finalizeSession()
         stopForeground(STOP_FOREGROUND_REMOVE)
         stopSelf()
     }