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Set the dependent dropdown's default value in select2 using JavaScript

In a wicket application, I have two dependent dropdowns using Select2. Now, I want to set the default value of both dropdowns. The default value should be the first element of the choiceList.
Second dropdown's default value should be updated accordingly if I select other option from the choice in the first dropdown.
I have used Placeholder but didn't succeed. How can I update the placeholder value dynamically?
I tried the below code but the second dropdown's default value is not updating automatically.
private static class ValueEditor extends Select2Choice<String> {
private static final long serialVersionUID = SingleFiniteValueEditor.serialVersionUID;
ValueEditor(String id, EditableSingleFiniteModel<?> model, ChoiceProvider<String> provider) {
super(id, model.valueModel(), provider);
setOutputMarkupId(true);
getSettings().setDropdownAutoWidth(true);
getSettings().setCloseOnSelect(true);
getSettings().setPlaceholder("");
getSettings().setAllowClear(!model.mandatory());
if(!model.choices().getObject().isEmpty()) {
model.valueModel().setObject(model.choices().getObject().get(0));
}
}
#Override
protected void onInitialize() {
super.onInitialize();
add(new OnChangeAjaxBehavior() {
private static final long serialVersionUID = SingleFiniteValueEditor.serialVersionUID;
#Override
protected void onUpdate(AjaxRequestTarget target) {
target.add(getComponent().getParent());
target.prependJavaScript(JQuery.execute("$('#%s').select2('destroy');", getJquerySafeMarkupId()));
target.appendJavaScript(JQuery.execute("$('#%s').select2('focus');", getJquerySafeMarkupId()));
send(getComponent(), Broadcast.BUBBLE, new ValueChangedEvent());
}
});
// FIXME append a class and style in stylesheet?
add(AttributeModifier.append("style", "min-width:200px;"));
}
#Override
protected void onComponentTag(ComponentTag tag) {
tag.setName("select");
super.onComponentTag(tag);
}
}
I am new to the wicket framework so please help me with this problem.
First, two dropdowns are dependent dropdowns as shown in the fig enter image description here. Second dropdown's choice list is depend on first dropdown's selected value.

What is the Vaadin 8 way of adding code to the html head tag?

Other SO answers suggest overriding ApplicationServlet.writeAjaxPageHtmlHeader, but I cannot find those classes and methods in Vaadin 8.
I cannot find anything similar in com.vaadin.server.VaadinServlet or com.vaadin.ui.UI.
There is the #JavaScript annotation, but if I put that on my UI class, the script would be loaded for every page of my application. I need it only on one specific page.

The initial HTML page is called bootstrap page in Vaadin. There is some documentation that hints you to right direction in Book of Vaadin.
In Vaadin 8, you need to add BootstrapListener to session. You can get created sessions by adding SessionInitListener in VaadinServlet.
Register Session
This example is using Vaadin with Spring Boot but the same principle applies when not using Spring Boot.
#Component("vaadinServlet")
#WebServlet(urlPatterns = "/*", name = "BootstrapVaadinServlet", asyncSupported = true)
#VaadinServletConfiguration(ui = BoostrapUi.class, productionMode = false)
public class BootstrapVaadinServlet extends SpringVaadinServlet {
private static final Logger logger = LoggerFactory.getLogger(BootstrapVaadinServlet.class);
#Override
protected void servletInitialized() throws ServletException {
super.servletInitialized();
getService().addSessionInitListener(this::addBoostrapListenerOnSessionInit);
}
private void addBoostrapListenerOnSessionInit(SessionInitEvent sessionInitEvent) {
sessionInitEvent.getSession().addBootstrapListener(new AppBootstrapListener());
}
}
Implement html head tag modification
public class AppBootstrapListener implements BootstrapListener {
#Override
public void modifyBootstrapFragment(BootstrapFragmentResponse bootstrapFragmentResponse) {
}
#Override
public void modifyBootstrapPage(BootstrapPageResponse res) {
Elements headTags = res.getDocument().getElementsByTag("head");
Element head = headTags.get(0);
head.appendChild(metaExample(res.getDocument()));
}
private Node metaExample(Document document) {
Element meta = document.createElement("meta");
meta.attr("author", "Me");
return meta;
}
}

If using add-on is ok, try HeaderTags
Overview
Using this add-on, you can define tags to add to the host page by
adding annotation to your UI class.
Sample from add ons usage example
#MetaTags({
// Replaces the Vaadin X-UA-Compatible header
#Meta(httpEquiv = "X-UA-Compatible", content = "hello"),
#Meta(name = "test", content = "test") })
// And showing how to create a link tag as well
#Link(rel = "foobar", href = "about:blank")
public class DemoUI extends UI {
...
}

WebView not load when open one url(android)

Sorry for my english. I have one activity and one fragment(fragment have webView). In activity i have items menu, if i click for item reload link in fragment. Each time when i click for item in menu, i call this code
ItemMenuFragment fragment = new ItemMenuFragment();
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.frame_layout, fragment);
fragmentTransaction.commit();
Fragment reload and then he get new link for webView. In fragment load page html like this
webView.getSettings().setJavaScriptEnabled(true);
webView.getSettings().setLoadWithOverviewMode(true);
webView.getSettings().setUseWideViewPort(true);
webView.loadUrl(Global.URL_MAIN + ((MainActivity) getActivity()).getLink());
Everything work fine. But in html link i have profile page, in this profile page i have button "load image", when i click this button show popup and after this all items menu cant load url. Its show white page and its all.
My ways of solving:
I think, need reload my fragment every times and i add this code when load fragment:
ItemMenuFragment fragment = new ItemMenuFragment();
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
if(!fragmentTransaction.isEmpty()) fragmentTransaction.remove(fragment);
fragmentTransaction.add(R.id.frame_layout, fragment);
fragmentTransaction.commit();
its not work, then i add this code:
ItemMenuFragment fragment = new ItemMenuFragment();
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.add(R.id.frame_layout, fragment);
fragmentTransaction.detach(fragment);
fragmentTransaction.attach(fragment);
fragmentTransaction.commit();
It does not work either. Then I add in fragment code, which the clean webView:
CookieSyncManager.createInstance(getActivity());
CookieManager cookieManager = CookieManager.getInstance();
cookieManager.removeAllCookie();
webView.clearCache(true);
webView.clearHistory();
It does not work either. I don't know how to solve my problem. Once again about my problem: after popup window in webView i cant any more load url in webView. It show me white pages.
UPD:
This is simple code my project. My left menu create dynamicly and in left menu i have listView. I have only one fragment, this fragment reload link each time when i click some item in menu
MainActivity
public class MainActivity extends AppCompatActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//menuItems - listview
//item - object in menu(contains link and name)
//adapterMenuItems adapter for lisView
menuItems.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
setLink(item.getUrl());
setFragment();
adapterMenuItems.notifyDataSetChanged();
if(menu.isMenuShowing()) menu.toggle();
}
});
}
public void setFragment(){
ItemMenuFragment fragment = new ItemMenuFragment();
FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
fragmentTransaction.add(R.id.frame_layout, fragment);
fragmentTransaction.commit();
}
//set link for fragment
public void setLink(String link){
this.link = link;
}
//return link for fragment
public String getLink(){
return link;
}
}
Fragment
public class ItemMenuFragment extends Fragment {
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View containerView = inflater.inflate(R.layout.fragment_item_menu, container, false);
webView.getSettings().setJavaScriptEnabled(true);
webView.getSettings().setLoadWithOverviewMode(true);
webView.getSettings().setUseWideViewPort(true);
webView.loadUrl(Global.URL_MAIN + ((MainActivity) getActivity()).getLink());
}}

Wicket Ajax Error Log: ERROR: Cannot bind a listener for event "click" on element "AjaxCheckBox" because the element is not in the DOM

Hey when I run my program, I want to dynamically add Panels to the mainpage and therfore work with "setVisible(boolean)".
But not I get the error:
ERROR: Cannot bind a listener for event "click" on element "institutCheck7" because the element is not in the DOM
In the Ajax Debugger.
I saw that it has something to do with the visibility in this
post, but I didn't get what I have to do, it says, that this is being resolved in Wicket 7, but I'm still running 6.20.
adminUIForm.add(myPanel= new MyPanel("myPanel", allThings));
myPanel.setOutputMarkupId(true);
myPanel.setVisible(false);
//Note: Setting the OutputMarkupId allows actions such as setting components in/visible
List<IColumn<ContactInfo, String>> columns = new ArrayList<IColumn<ContactInfo, String>>();
columns = initializeColumns(columns);
DataTable<ContactInfo, String> datatable = new DataTable<ContactInfo, String>("datatable", columns, provider, 10){
private static final long serialVersionUID = 1L;
#Override
protected Item<ContactInfo> newRowItem(final String id, final int index,
final IModel<ContactInfo> model) {
Item<ContactInfo> rowItem = new Item<ContactInfo>(id, index, model);
rowItem.add(new AjaxEventBehavior("onclick") {
private static final long serialVersionUID = 1L;
#Override
protected void onEvent(AjaxRequestTarget target) {
System.out.println("click");
myPanel.setSelectedKontakt(model);
myPanel.setVisible(true);
target.add(myPanel);
}
});
return rowItem;
}
};
setTableProperties(datatable);
adminUIForm.add(datatable);
}
I override the newRowItem method to add an onClick event. I get "click" in the console each time I hit a column, but I get this error log:
ERROR: Wicket.Ajax.Call.processComponent: Component with id [[institutTablePanel6]] was not found while trying to perform markup update. Make sure you called component.setOutputMarkupId(true) on the component whose markup you are trying to update.
ERROR: Cannot bind a listener for event "click" on element "institutCheck7" because the element is not in the DOM
ERROR: Cannot bind a listener for event "click" on element "cont8" because the element is not in the DOM
ERROR: Cannot bind a listener for event "click" on element "institutCheck9" because the element is not in the DOM
ERROR: Cannot bind a listener for event "click" on element "conta" because the element is not in the DOM
ERROR: Cannot bind a listener for event "click" on element "institutCheckb" because the element is not in the DOM
ERROR: Cannot bind a listener for event "click" on element "contc" because the element is not in the DOM
ERROR: Cannot bind a listener for event "click" on element "institutCheckd" because the element is not in the DOM
ERROR: Cannot bind a listener for event "click" on element "conte" because the element is not in the DOM
Those error all bind with components in "myPanel", I don't know how to resolve this. If I set it to visible earlier I get the same problem, including all elements, which will be hidden later in the workflow.
Edit:
public class MyPanel extends Panel {
private static final long serialVersionUID = 1L;
private Form<Void> institutForm = new Form<Void>("institutForm");
private ListView<Institut> listView;
private IModel<ContactInfo> selectedKontakt;
private Set<Institut> allInstitut;
#Override
protected void onModelChanged() {
//TODO maybe here
super.onModelChanged();
}
public InstitutTablePanel(String id, final Set<Institut> allInstitut) {
super(id);
this.allInstitut = allInstitut;
this.add(institutForm);
List<Institut> allInstitutList = new ArrayList<Institut>(allInstitut);
institutForm.add(listView = new ListView<Institut>("listView", allInstitutList) {
private static final long serialVersionUID = 1L;
protected void populateItem(final ListItem<Institut> item) {
final IModel<Boolean> checked = Model.of(Boolean.FALSE);
final IModel<String> expandState = Model.of("+");
#SuppressWarnings("unused")
final Label institutLabel;
final Institut institut = item.getModelObject();
// Define variables which concern only one item in populateItem
final WebMarkupContainer div = createMarkUpContainer("cont");
final WebMarkupContainer container = createMarkUpContainer("container");
container.setEnabled(false);
compareInstitute(checked, institut, container);
item.add(container);
div.add(new AjaxEventBehavior("onclick") {
private static final long serialVersionUID = 1L;
#Override
protected void onEvent(AjaxRequestTarget target) {
expandOrCollapse(expandState, container);
target.add(institutForm);
}
});
item.add(div);
div.add(new AjaxCheckBox("institutCheck", checked) {
private static final long serialVersionUID = 1L;
#Override
protected void onUpdate(AjaxRequestTarget target) {
//Not Important for this
target.add(institutForm);
}
});
container.add(new ErhebungMatrixPanel("erhebungMatrix", institut, selectedKontakt));
container.setVisible(false);
div.add(institutLabel = new Label("institutLabel", new PropertyModel<Institut>(institut, "langName")));
}
});
listView.setOutputMarkupId(true);
listView.setReuseItems(true);
institutForm.setOutputMarkupId(true);
}}
I edited my setSelectedKontakt method like this:
public void setSelectedKontakt(IModel<ContactInfo> model) {
this.selectedKontakt = model;
modelChanged();
}
to trigger the change if necessary.
The problem is target.add(myPanel); won't trigger populateItem again.

The error message says it pretty clearly and a look into the DOM tells that the markup for the panel is not there. Thats because setVisible(false) doens't even render the component with CSS display: none; as expected. It's just not there so it can't be modified afterwards. But you can tell Wicket to render a placeholder instead with setOutputMarkupPlaceholderTag(true). Wicket then creates an invisible markup e.g. <span style="display: none;" id="mypanel1a"></span>, which then is swaped with the real component when setting the visiblity to true later.

Just a tip to those that do get this error that a common mistake is to use:
<wicket:container wicket:id="panel"/>
...instead of...
<div wicket:id="panel"/>
...for where you put the panel. The method call setOutputMarkupId will not inform you that it is unable to add an id to a wicket:container, and hence your target.add(panel) will also fail.

Pulling a single variable off a webview in android?

I need to pull a value from a hidden div tag when using a webview. I have turned on javascript in my webview activity but its not liking the "". HOW can I achieve my goal?
public class buttonOne extends Activity{
WebView wb = null;
/** Called when the activity is first created. */
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.buttons);
wb = new WebView(this);
wb.getSettings().setJavaScriptEnabled(true);
wb.setWebViewClient(new HelloWebViewClient());
wb.getSettings().setJavaScriptEnabled(true);
wb.loadUrl("http://ishopstark.com/mobileapp.php?category=1");
setContentView(wb);
}
private class HelloWebViewClient extends WebViewClient {
public boolean shouldOverrideUrlLoading(WebView view, String url) {
view.loadUrl(url);
<script type="text/javascript">
{
var varSendText = document.getElementById("sendtextcoupon").value;
}
</script>
return true;
}
}

Here's a short example of how to inject Javascript into a WebView.
If you actually want to get the value and use it in your Java code, you're going to have to register a JavascriptInterface like in this example - extracting HTML from a WebView