[jnigen] closes https://github.com/dart-lang/jnigen/issues/280 (https://github.com/dart-lang/jnigen/issues/281)

pkgs/jni/example/android/build.gradle

diff --git a/pkgs/jni/example/android/build.gradle b/pkgs/jni/example/android/build.gradle
index 83ae220..3cdaac9 100644
--- a/pkgs/jni/example/android/build.gradle
+++ b/pkgs/jni/example/android/build.gradle
@@ -26,6 +26,6 @@
     project.evaluationDependsOn(':app')
 }
 
-task clean(type: Delete) {
+tasks.register("clean", Delete) {
     delete rootProject.buildDir
 }

pkgs/jni/lib/src/util/jlist.dart

diff --git a/pkgs/jni/lib/src/util/jlist.dart b/pkgs/jni/lib/src/util/jlist.dart
index 577ef89..eac7f20 100644
--- a/pkgs/jni/lib/src/util/jlist.dart
+++ b/pkgs/jni/lib/src/util/jlist.dart
@@ -112,8 +112,8 @@
       .getMethodIDOf(_class.reference, r"add", r"(Ljava/lang/Object;)Z");
   @override
   void add($E element) {
-    Jni.accessors.callMethodWithArgs(
-        reference, _addId, JniCallType.voidType, [element.reference]).check();
+    Jni.accessors.callMethodWithArgs(reference, _addId, JniCallType.booleanType,
+        [element.reference]).check();
   }
 
   static final _collectionClass = Jni.findJClass("java/util/Collection");