Tree views / Usage |
Create a form specification file containing a TREE container bound to a screen array. The screen array identifies the presentation elements to be used by the runtime system to display the tree-view and the additional columns.
A TREE container must be present in the LAYOUT section of the form, defining the columns of the tree-view list. The TREE container must hold at least one column defining the node texts (or names). This column will be used on the front-end side to display the tree-view widget. Additional columns can be added in the TREE container to display node information. The TREE container attributes must be declared in the ATTRIBUTES section of the form.
Secondary form fields have to be used to hold tree node information such as icon image, parent node id, current node id, expanded flag and parent flag. While these secondary fields can be defined as regular form fields and displayed in the tree-view list, we recommend that you use PHANTOM fields instead: Phantom fields can be listed in the screen-array but do not need to be part of the LAYOUT section. Phantom fields will only be used by the runtime system to build the tree of nodes.
LAYOUT TREE mytree ( PARENTIDCOLUMN=parentid, IDCOLUMN=id, EXPANDEDCOLUMN=expanded, ISNODECOLUMN=isnode ) { Tree [name |desc ] [name |desc ] [name |desc ] [name |desc ] [name |desc ] } END END ATTRIBUTES EDIT name = FORMONLY.name, IMAGECOLUMN=image; PHANTOM FORMONLY.image; PHANTOM FORMONLY.parentid; PHANTOM FORMONLY.id; PHANTOM FORMONLY.expanded; PHANTOM FORMONLY.isnode; EDIT desc = FORMONLY.description; END INSTRUCTIONS SCREEN RECORD sr( FORMONLY.* ); END
LAYOUT GRID { <Tree tv > Tree [name |desc ] [name |desc ] [name |desc ] [name |desc ] [name |desc ] < > } END END ATTRIBUTES TREE tv: mytree, PARENTIDCOLUMN=parentid, IDCOLUMN=id, EXPANDEDCOLUMN=expanded, ISNODECOLUMN=isnode; EDIT name = FORMONLY.name, IMAGECOLUMN=image; PHANTOM FORMONLY.image; PHANTOM FORMONLY.parentid; PHANTOM FORMONLY.id; PHANTOM FORMONLY.expanded; PHANTOM FORMONLY.isnode; EDIT desc = FORMONLY.description; END INSTRUCTIONS SCREEN RECORD sr( FORMONLY.* ); END
The first visual column ("name" in example) must be the field defining the node names, and the widget must be an EDIT or LABEL.
Several attributes are used to configure a TREE form element:
Tree-view definition must be completed with form fields declaration. These must be defined in the ATTRIBUTES section. The fields not used for display are declared as PHANTOM fields. The tree-view form fields must be grouped in a screen-array declared in the INSTRUCTIONS section.
The form fields required to declare a tree-view table are the following.
Description | Field type | Tree attribute to define the field | Mandatory | Default name |
---|---|---|---|---|
Text to be displayed for the node | EDIT | N/A | yes | N/A |
Id of the node | PHANTOM | IDCOLUMN | yes | id |
Id of the parent node | PHANTOM | PARENTIDCOLUMN | yes | parentid |
Icon image for a node | PHANTOM | IMAGECOLUMN | no | N/A |
Node expansion indicator | PHANTOM | EXPANDEDCOLUMN | no | no |
Parent node indicator | PHANTOM | ISNODECOLUMN | no | no |
The first three fields (node text, parent id and node id) are mandatory, and that the first visual (non-phantom) field listed in the screen array will be implicitly used to hold the text of tree-view nodes.
Additional fields (like the desc field in this example) can be defined to display details for each node in regular columns, that will appear on the right of the tree widget.
The order of the fields in the screen array of the tree-view does not matter, but it must of course match the order of the corresponding variables in the record-array of the program.
If you need to display node-specific images, define a phantom field to hold node images and attach it to the tree-view definition by using the IMAGECOLUMN attribute. Alternatively you can globally define images for all nodes with the IMAGEEXPANDED, IMAGECOLLAPSED and the IMAGELEAF attributes of the TREE form element.