Stefan Cameron on Forms
Building intelligent forms using Adobe LiveCycle Designer

Archive for May, 2006

Instantiating Subforms at Runtime

Something that’s often desired, when working with dynamic forms, is to let the user specify, at run time (in Acrobat), how many lines of information are required to specify what they want.

The classic example is a Purchase Order form on which there are objects (usually buttons) which let you add and remove item lines from the section of the form which calculates the total cost of the order based on how many items are being ordered and the quantity and cost of each item.

In order to achieve this, the use of the Instance Manager is required. The Instance Manager is an object which exists only on repeatable subforms (this could be a subform which is parented to a flowed subform and set to repeat for each data item or it could be a row in a table — since rows and tables are, essentially, subforms). With this special object, you can modify the set of instances of a repeatable (dynamic) subform.

You can access the Instance Manager in two ways. The first is by accessing the object from the dynamic (repeatable) subform:

// append a new instance of DynSubform within its parent container

// ensure that the new instance is included in
//  subsequent calculations

The second is by using the shortcut “underscore” syntax (note that this syntax is supported if the form is rendered to PDF):

// remove the third instance (zero-based) of DynSubform

// work-around for Acrobat 7.x bug (reported) where number of
//  instances isn't properly updated after calling removeInstance

The drawback to using the first syntax is that there must always be at least one instance of the dynamic subform which exists. If you have a form which must initially not have any instances of a particular dynamic subform, then you need to use the second syntax with the underscore since that special object is always “available” to you regardless of the current number of instances of the dynamic subform in question.

It’s also important to pay special attention to the minimum, maximum and initial number of instances of a dynamic subform. This is set on the Object palette’s Binding tab once you’ve specified that the subform is to Repeat for Each Data Item. The min and max limits must be repected at all times when using the Instance Manager. For example, if you set a min count of 1 and attempt to remove the last instance of a dynamic subform, an exception will be thrown which will result in a script error. You can check the current number of instances by using the Instance Manager’s count property and compare it to, for example,

// get the minimum number of instances that can be instantiated

There are other things you can do with the Instance Manager such as setting the number of instances (using its setInstance(int) method), move instances around (using its moveInstance(int, int) method) etc. These are covered in detail in the Adobe XML Form Object Model Reference (located in the XML section). Check-out the Manipulating instances of a subform section on page 675.

Posted by Stefan Cameron on May 18th, 2006
Filed under Instance Manager,Scripting

Calculate Scripts

I just learned something very interesting while answering a forum thread just now which I thought I should share with the rest of you.

In all the scripts I’ve written so far, I had never realized this simple rule: When writing calculation scripts to set the value of certain fields, the line in your script which assigns a value to the field on which the Calculate event was fired should always be the last line in your script. This is because the last-executed line in your script is the one that the XFA Object Model will use to determine the value of that field.

While it’s generally not recommended to do much more than set a field’s value in the Calculate event, reality is that most of us use it for much more than that: Since it fires on all fields on a form after a field’s value changes, we may use it to affect the presence, color, dimension, etc., of some fields which depend on the values of other fields. Therefore, it’s very easy to fall into this trap where your calculation script isn’t working probably simply because you haven’t structured it correctly.

Take the following FormCalc script as an example:

if (NumericField1 > 0) then
	NumericField1 * 10;
	$.presence = "visible";
	$.presence = "invisible";

This scripts runs in the Calculate event of a numeric field and, if NumericField1’s value is greater than zero (0), results in the field becoming visible and its value set to the product of NumericField1’s value multiplied by 10. If NumericField1’s value is zero (0) or less, its value is set to zero (0) and it becomes invisible. Note the order of the lines which set the field’s value and the ones which set its presence: The value is set before the presence is set.

The result of this script is that the presence is affected properly depending on the value of NumericField1 however, since the last-executed line is “$.presence = ‘visible’” (or “invisible”), the value acutally assigned to the field is “visible” (or “invisible”) which evaluates to “0” as a numerical value. Therefore, with this script, the value of the product field would always be zero (0).

If you change the order of the lines which set the field’s value and presence as follows:

if (NumericField1 > 0) then
	$.presence = "visible";
	NumericField1 * 10;
	$.presence = "invisible";

Then both the field’s presence and value will be set correctly because the last-executed lines in each block are the ones which set the field’s calculated value.

Posted by Stefan Cameron on May 15th, 2006
Filed under Events,Scripting

Data-Nominated Subforms

I thought I would post a little sample on data-nominated subforms tonight. This is a new feature, introduced in Designer 7.1, which can be a very powerful tool.

Since the feature essentially lets you define expressions against values from data being loaded into a form in order to control which subform, from a specified set (subform set containing subforms), will be used for the record currently being loaded into the form, you can do very interesting things. For example, you might have a table which lists data. Maybe you would like to use a row which has a yellow background to identify data which is not important, one with an orange background for data that’s important and one with a red background for data that’s very important. This can be easily achieved using Data-Nominated Subforms.

I’ve created a little sample based on the movie data I used for the Conditional Breaks Sample I posted a few days ago. In this sample, I have a subform set which contains 3 subforms, each capable of binding to a movie record. The twist is that I want to use the green subform for comedies, the red one for action movies and the blue one for dramas.

Download Sample [zip]

Minimum Requirements: Designer 7.1, Acrobat Pro 7.0.5.

Note: A basic understanding of Data Binding is required for this sample.

The trick in getting this to work is to first create a data connection which represents the data you’re loading into the form.

Then you need to create the subforms which each contain fields with names set to the data node names from a movie record so that Normal (“implicit”) binding works correctly once the subform is picked for the record.

The next step is to wrap all subforms into a subform set. You can do this by selecting them all in the Hierarchy palette and then choosing Wrap in Subform Set from the context menu.

At this point you’re almost done. All that’s missing are the expressions which tell the Object Model which subform from within the subform set to use for a particular data record.

The Data-Nominated Subform feature is accessed by selecting the subform set and going to the Object palette’s Subform Set tab. There, you’ll find a Type property from which you can select the Select One Subform From Alternatives item. When you select this option, an Edit Alternatives button will appear. Click on that to open the Data-Nominated Subform dialog. In there, you would elect to Choose Subform Using Expression, select your data connection from the drop down list and then specify an expression like

category == "Comedy"

for the “$” binding (which establishes the scope for your expression) on the comedy subform.

When you preview the form (if you just run it in Acrobat, you’ll have to import the data into the form using the commands under the File menu), you’ll see that the comedy subform is used only for records which have a “Comedy” category name.

Posted by Stefan Cameron on May 10th, 2006
Filed under Data-Nominated Subforms,Tutorials

Conditional Breaks

Some of you have requested a sample of the new Conditional Breaks feature in Designer 7.1.

This feature allows you to set conditions, based on imported data, which determine when breaks should occur.

For example, you may have data that you want to list by category and every time the category changes, you’d like to start the new category on a new page. Or, you may have a separator that you want to insert in between sets of data on your form.

I’ve created a little sample which demonstrates the Conditional Breaks feature by listing some movie data where each time the category changes, a new page starts. Don’t forget to import the data.xml file into the form when you open it in Acrobat.

Download Sample [zip]

Minimum Requirements: Designer 7.1, Acrobat 7.0.5.

Note: A basic understanding of Data Binding is required for this sample.

Since breaks are only really useful inside flowed subforms (there’s no point setting breaks on a subform inside a positioned container since the data won’t flow — it’ll all stay in one place instead of flowing left-to-right, top-to-bottom, for example), you can only get to the Conditional Break settings on the Object palette’s Pagination tab if you select a subform inside a flowed container (subform). The only exception is selecting a row or a section within a Table object since the content of Tables is always flowed.

Typically, after creating a new form, you would add a positioned subform (let’s call it the ContentSubform) to the page and add the fields you need into it. You would then make the page subform flowed (set the Content property on the Object palette’s Subform tab to Flowed), then select the ContentSubform and click on the Edit button on the Object palette’s Pagination tab. This will open the Conditional Breaks Dialog where you can add multiple conditions for that subform’s breaks.

In my sample, the data represents movies and each movie record has the following information:

  • Category
  • Title
  • Actor

Since I wanted to create a report-style form where a change in category breaks to a new page and a change in the actor’s name is preceeded by a separator, I created a movie subform which lists the data and then two other subforms:

  1. NewCategorySF which I want to insert every time the category changes.
  2. NewActorSF which I want to insert every time the actor’s name changes.

I then specified two conditional breaks on the movie subform:

  1. The first one checks for a change in the category data. When a change occurs, the layout will break to the top of a new instance of the “page 1” subform and, before starting to list the data for the new category, insert an instance of the NewCategorySF subform. This is what we call a Break Before Conditional Break (since the break occurs before the new record, which contains the new category name, is inserted into the form). Notice that the NewCategorySF subform is listed as a Leader for the Conditional Break because it’s meant to be inserted after the break but before the new record gets inserted into the form.
  2. The second checks for a change in the actor data. When a change occurs, the layout will not actually break because we simply want to use the Conditional Break to know when to insert the NewActorSF to separate the data set into sub-groups of actors. In this case, I specified NewActorSF to be a Leader for the Conditional Break because I wanted it to show-up after the actual break but before the new record is inserted into the form. You may wonder why I didn’t make it a Trailer but in this case, there wouldn’t be any difference since there isn’t an actual “physical” break in the data flow (to a new page or content area, for example).

Also notice that the NewCategorySF and NewActorSF subforms are both set to Repeat for Each Data Item (you can set this on the Object palette’s Binding tab) with a Min Count of 1 so that they always appear before the very first data record is inserted into the form. Otherwise, they wouldn’t appear until the first Conditional Break occurs.

Posted by Stefan Cameron on May 6th, 2006
Filed under Conditional Breaks,Tutorials

Samples! Give Me Samples!

One of the best places to look for Designer samples is on the LiveCycle Designer Samples Site. There, you’ll find lots of samples demonstrating various Designer techniques and features.

Although new samples are constantly be posted to the Designer Samples Site, they can’t always cover all topics or address all of our customer’s questions/issues. As such, I’ll be posting some of my own samples to my blog. Look for them under the Samples category.

Posted by Stefan Cameron on May 6th, 2006
Filed under Tutorials