add badge showing how many filters are active

app/src/main/java/net/vonforst/evmap/fragment/MapFragment.kt

@@ -10,6 +10,7 @@ import android.content.res.Configuration
 import android.os.Bundle
 import android.view.*
 import android.view.inputmethod.InputMethodManager
+import android.widget.TextView
 import androidx.activity.OnBackPressedCallback
 import androidx.core.app.SharedElementCallback
 import androidx.core.content.ContextCompat
@@ -505,7 +506,21 @@ class MapFragment : Fragment(), OnMapReadyCallback, MapsActivity.FragmentCallbac
 
     override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
         inflater.inflate(R.menu.map, menu)
-        super.onCreateOptionsMenu(menu, inflater)
+
+        val filterItem = menu.findItem(R.id.menu_filter)
+        val filterView = filterItem.actionView
+
+        val filterBadge = filterView?.findViewById<TextView>(R.id.filter_badge)
+        if (filterBadge != null) {
+            // set up badge showing number of active filters
+            vm.filtersCount.observe(viewLifecycleOwner, Observer {
+                filterBadge.visibility = if (it > 0) View.VISIBLE else View.GONE
+                filterBadge.text = it.toString()
+            })
+        }
+        filterView?.setOnClickListener {
+            onOptionsItemSelected(filterItem)
+        }
     }
 
     override fun onOptionsItemSelected(item: MenuItem): Boolean {

app/src/main/java/net/vonforst/evmap/viewmodel/FilterViewModel.kt

@@ -169,7 +169,18 @@ data class MultipleChoiceFilterValue(
     @PrimaryKey override val key: String,
     var values: MutableSet<String>,
     var all: Boolean
-) : FilterValue()
+) : FilterValue() {
+    override fun equals(other: Any?): Boolean {
+        if (other == null || other !is MultipleChoiceFilterValue) return false
+        if (key != other.key) return false
+
+        return if (all) {
+            other.all
+        } else {
+            !other.all && values == other.values
+        }
+    }
+}
 
 @Entity
 data class SliderFilterValue(

app/src/main/java/net/vonforst/evmap/viewmodel/MapViewModel.kt

@@ -45,6 +45,17 @@ class MapViewModel(application: Application, geApiKey: String) : AndroidViewMode
     private val filtersWithValue: LiveData<List<FilterWithValue<out FilterValue>>> by lazy {
         filtersWithValue(filters, filterValues)
     }
+
+    val filtersCount: LiveData<Int> by lazy {
+        MediatorLiveData<Int>().apply {
+            value = 0
+            addSource(filtersWithValue) { filtersWithValue ->
+                value = filtersWithValue.count {
+                    it.filter.defaultValue() != it.value
+                }
+            }
+        }
+    }
     val chargepoints: MediatorLiveData<Resource<List<ChargepointListItem>>> by lazy {
         MediatorLiveData<Resource<List<ChargepointListItem>>>()
             .apply {