Follow up fixed for EnabledMixin leaks state and listeners #318

Updated EnabledMixin#TestCase to include testMultiSetEnabledState()

Author: kevzlou7979

gwt-material/src/main/java/gwt/material/design/client/base/mixin/EnabledMixin.java

@@ -63,8 +63,13 @@ public boolean isEnabled() {
     }
 
     @Override
-    public void setEnabled(boolean enabled) {
-        if (!uiObject.isAttached() && handler == null) {
+    public void setEnabled(final boolean enabled) {
+        if (!uiObject.isAttached()) {
+            if (handler != null) {
+                handler.removeHandler();
+                handler = null;
+            }
+
             handler = uiObject.addAttachHandler(event -> {
                 if (event.isAttached()) {
                     applyEnabled(enabled, uiObject);

gwt-material/src/test/java/gwt/material/design/client/ui/base/MaterialWidgetTestCase.java

@@ -352,13 +352,13 @@ protected <H extends UIObject & HasEnabled> void checkEnabled(HasEnabled widget,
             assertFalse(element.hasClassName(CssName.DISABLED));
             assertFalse(element.hasAttribute(CssName.DISABLED));
         }
-        assertEquals(widget.isEnabled(), true);
+        assertTrue(widget.isEnabled());
         widget.setEnabled(false);
         if(checkElement) {
             assertTrue(element.hasClassName(CssName.DISABLED));
             assertTrue(element.hasAttribute(CssName.DISABLED));
         }
-        assertEquals(target.isEnabled(), false);
+        assertFalse(target.isEnabled());
     }
 
     // Generic Event Handling
@@ -1006,18 +1006,39 @@ public void testColor() {
     public void testEnabled() {
         // UiBinder
         // given
-        T widget = getWidget(false);
+        T widget = getWidget(true);
 
         // when / then
-        checkEnabled(widget, widget, false);
+        checkEnabled(widget, widget, true);
+    }
+
+    public void testMultiSetEnabledState() {
+        // given
+        T widget = getWidget();
+
+        // when / then
+        widget.setEnabled(false);
+        assertFalse(false);
+
+        // when / then
+        widget.setEnabled(true);
+        assertTrue(widget.isEnabled());
+
+        // when / then
+        widget.setEnabled(false);
+        assertFalse(widget.isEnabled());
 
-        // Standard
         // given
         attachWidget();
 
         // when / then
+        assertFalse(widget.isEnabled());
         widget.setEnabled(true);
-        checkEnabled(widget, widget, true);
+        assertTrue(widget.isEnabled());
+
+        // when / then
+        widget.setEnabled(false);
+        assertFalse(widget.isEnabled());
     }
 
     public void testId() {