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**yathish.venkatesh** · 29 Nov 2011, 22:50

I tried with Static data, which works fine but not with dynamic data(like populate from db etc..)

**yathish.venkatesh** · 30 Nov 2011, 03:40

I have changed by adding addDataArrivedHandlers as below. and it loads the correct desired values. But it is not allowing me to select Year and causing infinite call to addDataArrivedHandler()

Here is my code.

Code:

fromYear.addDataArrivedHandler(new DataArrivedHandler() {
            public void onDataArrived(DataArrivedEvent event) {
                    fromMonth.setOptionDataSource(DataSource.get("dateRange"));
                    Criteria criteriaFromMonth = new Criteria();
                    criteriaFromMonth.addCriteria("PRODUCT_ID","NA_ADB");
                    criteriaFromMonth.addCriteria("CLIENT_ID", 99);
                    int selectedFromYear = Integer.parseInt(fromYear.getValue().toString());
            //                (Integer)fromYear.getValue();
                    criteriaFromMonth.addCriteria("YEAR_NUM" ,selectedFromYear);
                    fromMonth.setOptionCriteria(criteriaFromMonth);
                    fromMonth.setOptionOperationId("monthFetch");
                    fromMonth.setValueField("MONTH_SHORT_NAME");
                    fromMonth.fetchData();
                    fromMonth.setDefaultToFirstOption(true);
            }
        });

As even Year combobox will be loaded from db, i added addDataArrivedHandler, so that based on the first Year, Month combobox gets populated(which works fine).

Now, if i want to change years(i mean when i click), it agains calls addDataArrivedHandler() and goes for infinite loop.

Please let me know how i can control this.

**Isomorphic** · 30 Nov 2011, 10:47

Wrong approach - take a look at the Databound Dependent Selects examples in the SmartGWT Showcase - they address specifically this use case.

**yathish.venkatesh** · 30 Nov 2011, 20:39

In showcase, you are using static data but here in my case, i am populating from db, hence i am using addDataArrivedHandler method.

**yathish.venkatesh** · 30 Nov 2011, 21:39

Isomorphic,

As data population takes time, i wont be getting value, which causes Null pointer exception as there wont be any value.
String category = (String) categoryItem.getValue();

Hence, i used an approach to wait till data loads by using addDataArrivedHandler. which works for the first time. but if i change the values, requests goes for infinite loop.

**Isomorphic** · 1 Dec 2011, 11:47

Incorrect, the Showcase example uses DataSources, it is already asynchronous and works with data loaded from a DB.

**yathish.venkatesh** · 1 Dec 2011, 21:50

Yes. I agree. In the showcase example, nothing would be selected by default, where as in my case, say year(2012) is selected and by default months(say jan-march) should be loaded in the dependent select item. I tried with the your approach but it leads to Null pointer exception when dependent select item tries to load the data based on selected independent select item.

**Isomorphic** · 1 Dec 2011, 22:03

This approach is used all the time for a wide variety of use cases and doesn't lead to NullPointerExceptions when applied as shown. If you're still having trouble with this and you think you've found a framework issue, you should prepare a standalone, minimal test case showing how applying the approach shown in the sample can lead to a NullPointerExceptions.

**yathish.venkatesh** · 1 Dec 2011, 22:31

To add to my previous post, in the showcase, by default, all the values would be loaded(like all the categories and items, regardless of any filter) But in my case, the first one should be selected and the corresponding items should be populated. But when i am trying to get the value of category, as there wont be any data populated, this exception occurs. I will prepare a test sample for you and post it.

Thanks,
Yathish

**Isomorphic** · 2 Dec 2011, 09:09

One again, the values are not loaded in advance in the Showcase sample. The selectItems are connected to a DataSource. They have no idea that the DataSource is working from a local cache - the DataSource is still asynchronous and they have no direct access to the DataSource's internal cache.

That's why this pattern works for remotely loaded data coming from a database or other source.

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Form Dependency - Select Item value population issue

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