Update chart after changing a field in an APEX form - apex

Question

How do I cause APEX to refresh a chart (graph) after I change the value in a text box/select list/etc that is used as a parameter in the chart's pl/sql statement?
I'd like it to look as professional as possible and minimize the portion of the page that must be refreshed (i.e., "ajax-like", which is the standard in 2018).

Answer 1

Create a dynamic action on the text box/select list/etc that is changed with event "change"
Create a true action and select pl/sql and write
Begin
null;
end;
In page items to submit select your items
Create a second true action after the first and select Refresh. Then select region as affected element and select your chart. Remember that the option 'Fire on initialization' must be set to NO

Answer 2

See Approach B, below, for the optimal solution.
Approach A
The simplest option (that is less professional) is to modify every text box/select list/etc of interest to submit the page when the value of the text box/select list/etc changes. As an example, for the select list, go to its settings->page action on selection and change the setting to submit page.
There are two main downsides to that approach:
Most of the page will refresh, which is jarring to your user, and
If you're using a plugin, or the type of item that you're using doesn't support that approach, then you're out of luck.
Approach B
A more complex solution that yields a more professional result follows. This solution involves dynamic actions, which I will probably not fully explain here. However, the information should be enough for the user to figure it out.
Let us suppose that you have two things: (1) a select list whose value is used as a parameter in a (2) chart's sql source statement.
To get the chart to update every time you make a new choice via the select list, you need to:
Create a dynamic action for the select list of interest. You do this by clicking on the select list, going to the dynamic action tab (the lightning bolt); right-click on the item; click select dynamic action; give it a name and set the event to change and make the selection type an item and set the item to the name of the select list you're watching.
Create a true action for that dynamic action that executes pl/sql code (you can do this by modifying the show action that was created by default in 1.). Set the pl/sql code to null;. Then under items to submit, specify the name of the select list of interest.
Create a second true action that refreshes the region that contains the chart.
You'll need to make sure that the sequence assigned to 2. is a smaller number than the sequence assigned to 3.. This should happen by default, but it's an area you can get tripped up.
Inapplicable Approach C
In Apex 5.something, they added a feature called Cascading List of Values. This feature allows you to specify that one item depends on another item for its values. For example, if you have a select list that allows the user to choose a department, and then you have a second select list that allows you to choose an employee from the chosen department (which presumably obtains its values from a query involving the value chosen in the first select list), you can tell APEX to refresh the second select list whenever you update the first.
You do this by editing the second select list. Under its settings goto list of values->cascading LOV parent item(s). Add the first select list as a "reverse" dependent (aka, "parent"). This will ensure that any time the first select list is updated, the second select list is also updated.
For better or for worse, charts do not have the cascading LOV parent item(s) setting. Thus, this solution does not apply to this question.