Reduce duplicate drawing of polylines and polygons + fix feature removing in Google Maps

androidshared/src/main/java/org/odk/collect/androidshared/livedata/LiveDataUtils.java

@@ -62,6 +62,7 @@ private static class CombinedLiveData<T> extends MediatorLiveData<T> {
 
         private final Object[] values;
         private final Function<Object[], T> map;
+        private T lastEmitted;
 
         CombinedLiveData(LiveData<?>[] sources, Function<Object[], T> map) {
             this.map = map;
@@ -79,7 +80,12 @@ private static class CombinedLiveData<T> extends MediatorLiveData<T> {
         }
 
         private void update() {
-            setValue(map.apply(values));
+            T newValue = map.apply(values);
+
+            if (lastEmitted == null || !lastEmitted.equals(newValue)) {
+                lastEmitted = newValue;
+                setValue(newValue);
+            }
         }
     }
 

androidshared/src/test/java/org/odk/collect/androidshared/livedata/LiveDataUtilsTest.kt

@@ -34,4 +34,19 @@ class LiveDataUtilsTest {
 
         assertThat(combined.getOrAwaitValue(), equalTo(Pair("one-updated", "two")))
     }
+
+    @Test
+    fun `#combine skips emission when result is equal to previous`() {
+        val one = MutableLiveData("one")
+        val combined = one.combine(MutableLiveData<String>())
+
+        var counter = 0
+        LiveDataUtils.observe(combined) {
+            counter++
+        }
+
+        one.value = "one"
+
+        assertThat(counter, equalTo(1))
+    }
 }

geo/src/main/java/org/odk/collect/geo/geopoly/GeoPolyFragment.kt

@@ -15,7 +15,6 @@ import androidx.lifecycle.asLiveData
 import androidx.lifecycle.viewmodel.viewModelFactory
 import com.google.android.material.dialog.MaterialAlertDialogBuilder
 import com.google.android.material.snackbar.Snackbar
-import org.odk.collect.androidshared.livedata.LiveDataExt.combine
 import org.odk.collect.androidshared.ui.DialogFragmentUtils.showIfNotShowing
 import org.odk.collect.androidshared.ui.FragmentFactoryBuilder
 import org.odk.collect.androidshared.ui.SnackbarUtils
@@ -253,8 +252,7 @@ class GeoPolyFragment @JvmOverloads constructor(
             },
             displayDismissButton = true
         )
-        val viewData = viewModel.points.asLiveData().combine(viewModel.invalidMessage)
-        viewData.observe(viewLifecycleOwner) { (points, invalidMessage) ->
+        viewModel.viewData.observe(viewLifecycleOwner) { (points, invalidMessage) ->
             val isValid = invalidMessage == null
             if (!isValid) {
                 snackbar.setText(invalidMessage)

geo/src/main/java/org/odk/collect/geo/geopoly/GeoPolyViewModel.kt

@@ -2,10 +2,12 @@ package org.odk.collect.geo.geopoly
 
 import androidx.lifecycle.LiveData
 import androidx.lifecycle.ViewModel
+import androidx.lifecycle.asLiveData
 import androidx.lifecycle.map
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import org.odk.collect.androidshared.data.Consumable
+import org.odk.collect.androidshared.livedata.LiveDataExt.combine
 import org.odk.collect.androidshared.livedata.LiveDataExt.withLast
 import org.odk.collect.async.Cancellable
 import org.odk.collect.async.Scheduler
@@ -53,6 +55,8 @@ class GeoPolyViewModel(
         }
     }
 
+    val viewData = _points.asLiveData().combine(invalidMessage)
+
     private var accuracyThreshold: Int = 0
     private var recording: Cancellable? = null
 

geo/src/test/java/org/odk/collect/geo/geopoly/GeoPolyViewModelTest.kt

@@ -7,13 +7,17 @@ import org.hamcrest.Matchers.equalTo
 import org.junit.Rule
 import org.junit.Test
 import org.mockito.Mockito.mock
+import org.odk.collect.androidtest.MainDispatcherRule
 import org.odk.collect.testshared.getOrAwaitValue
 
 class GeoPolyViewModelTest {
 
     @get:Rule
     val instantTaskExecutorRule = InstantTaskExecutorRule()
 
+    @get:Rule
+    val mainDispatcherRule = MainDispatcherRule()
+
     @Test
     fun `#fixedAlerts is null until after invalid message is non-null`() {
         val invalidMessage = MutableLiveData<String?>(null)

google-maps/src/main/java/org/odk/collect/googlemaps/GoogleMapFragment.java

@@ -850,6 +850,7 @@ public void dispose() {
 
         private void clearPolyline() {
             if (polyline != null) {
+                polyline.setVisible(false);
                 polyline.remove();
                 polyline = null;
             }
@@ -1024,6 +1025,7 @@ public List<MapPoint> getPoints() {
 
         private void clearPolygon() {
             if (polygon != null) {
+                polygon.setVisible(false);
                 polygon.remove();
                 polygon = null;
             }