modified UnityWebViewPostprocessBuild.cs to fix unity's incorrect theme setting for Android.

Author: KojiNakamaru

plugins/Editor/UnityWebViewPostprocessBuild.cs

@@ -23,6 +23,8 @@ public class UnityWebViewPostprocessBuild
     public void OnPostGenerateGradleAndroidProject(string basePath) {
         var changed = false;
         var androidManifest = new AndroidManifest(GetManifestPath(basePath));
+        changed = (androidManifest.SetApplicationTheme("@style/UnityThemeSelector") || changed);
+        changed = (androidManifest.SetActivityTheme("@style/UnityThemeSelector.Translucent") || changed);
         changed = (androidManifest.SetHardwareAccelerated(true) || changed);
 #if UNITYWEBVIEW_ANDROID_USES_CLEARTEXT_TRAFFIC
         changed = (androidManifest.SetUsesCleartextTraffic(true) || changed);
@@ -166,6 +168,25 @@ internal bool SetUsesCleartextTraffic(bool enabled) {
         return changed;
     }
 
+    internal bool SetApplicationTheme(string theme) {
+        bool changed = false;
+        if (ApplicationElement.GetAttribute("theme", AndroidXmlNamespace) != theme) {
+            ApplicationElement.SetAttribute("theme", AndroidXmlNamespace, theme);
+            changed = true;
+        }
+        return changed;
+    }
+
+    internal bool SetActivityTheme(string theme) {
+        bool changed = false;
+        var activity = GetActivityWithLaunchIntent() as XmlElement;
+        if (activity.GetAttribute("theme", AndroidXmlNamespace) != theme) {
+            activity.SetAttribute("theme", AndroidXmlNamespace, theme);
+            changed = true;
+        }
+        return changed;
+    }
+
     internal bool SetHardwareAccelerated(bool enabled) {
         bool changed = false;
         var activity = GetActivityWithLaunchIntent() as XmlElement;