Test of extending AutoCompleteTextField, after http://disq.us/p/21cvxbt

Test.java

AutoCompleteTextField field = new AutoCompleteTextField(listModel) {

            private Component popup;
            private Container lay;
            private Container parent;

            @Override
            protected boolean filter(String text) {
                return getCityFilter(listModel, resultQuery, isFullAddressSearch).filter(text);
            }

            // https://github.com/codenameone/CodenameOne/issues/2757#event-2268199434
            @Override
            protected boolean shouldShowPopup() {
                return isEditable();
            }

            @Override
            public void setEditable(boolean isEditable) {
                super.setEditable(isEditable);
                if (!isEditable) {
                    this.removePopup();
                }
            }

            /**
             * The original deinitialize() of AutoCompleteTextField executes its
             * own removePopup(), causing a NullPointerException if the popup
             * was already removed by my removePopup().This overidde solves this
             * issue.
             */
            @Override
            protected void deinitialize() {
                if (popup != null && popup.getParent() == null && parent != null && parent.getParent() == null && lay != null) {
                    parent.add(popup);
                    lay.add(parent);
                }
                super.deinitialize();
            }

            @Override
            protected void initComponent() {
                if (popup != null && parent != null) {
                    parent.setVisible(true);
                    parent.setHidden(false);
                    popup.setVisible(true);
                    popup.setHidden(false);
                    getComponentForm().revalidateWithAnimationSafety();
                }
                super.initComponent();
            }

            /**
             * Keep attention, flush animations, like explained here:
             * http://disq.us/p/21cb38g
             */
            private void removePopup() {
                Form f = getComponentForm();
                if (f != null) {
                    popup = ComponentSelector.$("AutoCompletePopup", f).asComponent();
                    if (popup != null) {
                        lay = f.getLayeredPane(super.getClass(), true);
                        parent = popup.getParent();
                        lay.getAnimationManager().flushAnimation(() -> {
                            popup.setVisible(false);
                            popup.setHidden(true);
                            parent.setVisible(false);
                            parent.setHidden(true);
                            lay.removeComponent(parent);
                            popup.remove();
                            f.revalidateWithAnimationSafety();
                        });
                    }
                }
            }
        };