由于NewEngineIntentBuilder内部类的构造无法外部访问(protected),无法继承BoostFlutterActivity自定义。将其改为public

android/src/main/java/com/idlefish/flutterboost/containers/BoostFlutterActivity.java

@@ -73,7 +73,7 @@ public class BoostFlutterActivity extends Activity
         private Map params = new HashMap();
 
 
-        protected NewEngineIntentBuilder(@NonNull Class<? extends BoostFlutterActivity> activityClass) {
+        public NewEngineIntentBuilder(@NonNull Class<? extends BoostFlutterActivity> activityClass) {
             this.activityClass = activityClass;
         }