Google Script - Can't combine on the same script multiple selection from listBox and SubmitButton

Question

I'm trying to code on google app and I've encountered one issue. For example, let's consider this example code on google website ( link's here https://developers.google.com/apps-script/class_formpanel )

 function doGet() {
 var app = UiApp.createApplication();
 var form = app.createFormPanel();
 var flow = app.createFlowPanel();
 flow.add(app.createTextBox().setName("textBox"));
 flow.add(app.createListBox().setName("listBox").addItem("option 1").addItem("option 2"));
 flow.add(app.createSubmitButton("Submit"));
 form.add(flow);
 app.add(form);
 return app;
 }

 function doPost(eventInfo) {
 var app = UiApp.getActiveApplication();
 app.add(app.createLabel("Form submitted. The text box's value was '" +
   eventInfo.parameter.textBox +
   "' and the list box's value was '" +
   eventInfo.parameter.listBox + "'"));
 return app;
  }

My issue is that I want to select multiple values on the listbox. I change then line 6 in

 flow.add(app.createListBox(true).setName("listBox").addItem("option 1").addItem("option 2"));

to allow multiple selection. But the result is that only the last selected value is taken, preventing multiple selections. Apparently, it is due to the submitButton. I need to keep the formPanel because on a further code I'll like to combine uploading files and listBox multiple selection. How may I fix that? Thank you a lot

Answer 1

As a complement to Mogsdad's answer, note that this bug / issue is only concerning the doPost structured handler... if you don't need the file upload feature you could use a simple doGet + handler with callbackElement and in this case the multiselect list is available and works as expected.

test function :

function doGet() {
  var app = UiApp.createApplication().setTitle('test listBox');
  var panel = app.createHorizontalPanel().setStyleAttribute('padding','40px');
  var sHdlr = app.createServerHandler('validateList').addCallbackElement(panel);
  var items = ['category 1','category 2','category 3'];
  var list1 = app.createListBox(true).setName('list1');
  for(var i =0;i<items.length;++i){list1.addItem(items[i],i)}
  panel.add(list1).add(app.createButton('validate',sHdlr));
  app.add(panel);
  return app;
}

function validateList(e){
  var app = UiApp.getActiveApplication();
  app.add(app.createLabel("Value(s) in list : "+e.parameter.list1).setStyleAttribute('margin-left','40'));
  return app;
} 

and below is a working example of the workaround described in the issue tracker. I used a textBox to show the process, set it to visible(false) or use a hidden widget in a 'real' app. ( Test available here )

function doGet() {
  var app = UiApp.createApplication().setTitle('test listBox');
  var panel = app.createHorizontalPanel().setStyleAttribute('padding','40px');
  var listHandler = app.createServerHandler('updlistVal').addCallbackElement(panel);
  var items = ['category 1','category 2','category 3'];
  var list1 = app.createListBox(true).setName('list1').addChangeHandler(listHandler);
  for(var i =0;i<items.length;++i){list1.addItem(items[i])}
  panel.add(list1).add(app.createTextBox().setText(items[0]).setId('listboxVal').setName('listboxVal').setWidth('200'));// set a default value in case the user is happy with that and doesn't touch the listBox
  var submitBtn = app.createSubmitButton('test').setStyleAttribute('margin-left','40');
  app.add(app.createFormPanel().add(panel.add(submitBtn)));
  return app;
}

function doPost(e){
  var app = UiApp.getActiveApplication();
  app.add(app.createLabel().setStyleAttribute('padding','40').setText("Submitted value(s) from list : "+e.parameter.listboxVal));
  return app;
}

function updlistVal(e){
  var app = UiApp.getActiveApplication();
  app.getElementById('listboxVal').setValue(e.parameter.list1);
  return app;
}

---

EDIT 2 : As Mentioned in the comments on this post we must find a way to prevent going through the submission before the value of the hidden/text widget has been updated with a valid value. The "default value" I used above is a possible solution, another one is to use a client handler to validate the submit button only if the listValue (or its value in the hidden widget) is right. Here is a code that does it (only the doGet is reproduced, all other functions being identical.

function doGet() {
  var app = UiApp.createApplication().setTitle('test listBox');
  var panel = app.createHorizontalPanel().setStyleAttribute('padding','40px');
  var submitBtn = app.createSubmitButton('test').setStyleAttribute('margin-left','40').setEnabled(false);
  var listHandler = app.createServerHandler('updlistVal').addCallbackElement(panel);
  var items = ['category 1','category 2','category 3'];
  var listVal = app.createTextBox().setText('not defined yet').setId('listboxVal').setName('listboxVal').setWidth('200');
  var list1 = app.createListBox(true).setName('list1').addChangeHandler(listHandler).addItem('choose one or more item(s)');
  for(var i =0;i<items.length;++i){list1.addItem(items[i])}
  var clientH = app.createClientHandler().forTargets(submitBtn).setEnabled(true).validateMatches(list1, 'category');
  list1.addClickHandler(clientH);
  panel.add(list1).add(listVal);// set a default value in case the user is happy with that and doesn't touch the listBox
  app.add(app.createFormPanel().add(panel.add(submitBtn)));
  return app;
}

Using the hidden widget as validation source causes a small issue as we need to click twice on the listBox to make it work... in case there are other questions on the form this will be solved by triggering the client handler with every other widgets so that the double click won't be necessary anymore but this is becoming a bit "out of subject" I'm afraid.

---

EDIT 3 :

just for the fun of it, a last version that works apparently without issue...

test here

function doGet() {
  var app = UiApp.createApplication().setTitle('test listBox');
  var panel = app.createHorizontalPanel().setStyleAttribute('padding','40px');
  var submitBtn = app.createSubmitButton('test').setStyleAttribute('margin-left','40').setEnabled(false).setId('sbmt');
  var wait = app.createImage('https://dl.dropboxusercontent.com/u/211279/loading3T.gif').setId('wait').setVisible(false);
  var listHandler = app.createServerHandler('updlistVal').addCallbackElement(panel);
  var items = ['category 1','category 2','category 3'];
  var listVal = app.createTextBox().setText('not defined yet').setId('listboxVal').setName('listboxVal').setWidth('200');
  var list1 = app.createListBox(true).setName('list1').addChangeHandler(listHandler).addItem('choose one or more item(s)');
  for(var i =0;i<items.length;++i){list1.addItem(items[i])}
  var clientH = app.createClientHandler().forTargets(wait).setVisible(true).forTargets(submitBtn).setEnabled(false);
  list1.addChangeHandler(clientH);
  panel.add(list1).add(listVal);// set a default value in case the user is happy with that and doesn't touch the listBox
  app.add(app.createFormPanel().add(panel.add(submitBtn).add(wait)));
  return app;
}

function doPost(e){
  var app = UiApp.getActiveApplication();
  app.add(app.createLabel().setStyleAttribute('padding','40').setText("Submitted value(s) from list : "+e.parameter.listboxVal));
  return app;
}

function updlistVal(e){
  var app = UiApp.getActiveApplication();
  app.getElementById('listboxVal').setValue(e.parameter.list1);
  app.getElementById('sbmt').setEnabled(true);
  app.getElementById('wait').setVisible(false);
  return app;
}

Answer 2

This is a known bug in the issue tracker, Issue 959. Visit and star it for updates.

It's been known and "worked on" since Dec 2011, if you believe the notes added by the support team. Other users have provided a work-around, and a modified version of it appears below.

The idea is to attach a handler function to the ListBox, which will receive all the selected items from the ListBox. The handler will then write those values to a hidden element in the form. When the form is submitted, the list of selections will be available to the doPost(), via the hidden element.

  ...
  var listbox = app.createListBox(true).setName("listBox").addItem("option 1").addItem("option 2");
  flow.add(listbox);

  // Issue 959 ListBox Workaround: http://code.google.com/p/google-apps-script-issues/issues/detail?id=959
  var listboxHidden= app.createHidden("listboxHidden", "").setId("listboxHidden");
  flow.add(listboxHidden);
  var fixListBoxHandler = app.createServerHandler('fixListBoxHandler');
  fixListBoxHandler.addCallbackElement(listbox);
  listbox.addChangeHandler(fixListBoxHandler);

  ...
}

function fixListBoxHandler(e) {

  var app = UiApp.getActiveApplication();
  app.getElementById('listboxHidden').setValue(e.parameter.listbox);
  return app;

}

NOTE: Unfortunately, this work-around is time-sensitive; it can take several seconds for the handler to update the hidden value. If the submit button is hit before the handler completes its job, then post() receives what was in the hidden element before the call to the handler.