Dynamic binding

1
Dynamic
Modifications
at Runtime

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© SAP AG 2005, ABAP Web Dynpro
Introduction
Modifying the context structure at runtime
Modifying the UI Element hierarchy at runtime
The use of dynamic actions
Contents:
Dynamic Modifications at Runtime

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Dynamic Modifications at Runtime: Objectives
After completing this lesson, you will be able to:
Understand what dynamic programming is
Dynamically modify and create UI elements
Dynamically create context elements
Dynamically bind UI element values to context
elements
Dynamically create actions

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Dynamic Runtime Modifications
Up till now, we have looked exclusively at the declarative approach to Web Dynpro
programming. Now, we will turn our attention to the programmatic techniques
needed to perform programmatically, the steps that have so far, only been done
declaratively.
What is type of dynamic modifications can be made at
runtime?
Dynamic Context Manipulation
The creation, modification and deletion of context nodes and
attributes
Dynamic UI Manipulation
The creation, modification and deletion of UI elements
Dynamic Assignment of Actions to UI Elements

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Usually, you would declare the structure of a controller’s context at design time,
and then create a static UI layout to display the data contained within the declared
context.
However, it is perfectly possible to create a context and UI layout hierarchy at
runtime. These techniques should only be used when they are required!
It is preferable to create as much of your context and UI layout hierarchy as
possible at design time.
There are several situations in which type of coding could be
required:
When the structure of your data is not known until runtime
When you want the behaviour of a screen to be generic – and
therefore dynamic
When you are writing utility components that must function in
a generic manner
Etc…
Under what circumstances should I write coding that
performs dynamic modifications?

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WDDOMODIFYVIEW
This Standard Hook method is called just before the view layout is rendered. It is
the only method in which the programmer is allowed direct access to the UI
element objects themselves.
The FIRSTTIME parameter is a boolean value that lets you know if the screen is
being rendered for the very first time, or re-rendered in response to an Action
event.
Standard Hook Method – View controller
Only a view controller has these hook methods.
The method WDDOMODIFYVIEW will only be called if:
The view is part of the current view assembly and this is the
first time the view is required, or
The view is part of the current view assembly and an action
belonging to the same view controller has been processed.

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Dynamic Context Data Creation
Example of context
metadata to be created
dynamically?Context Root (c=1..1, s=true)
FLIGHTS (c=0..n, s=true)
Context Metadata to be
created at runtime
BOOKINGS (c=0..n, s=false)
PRICE
CARRID
CONNID
FLDATE
BOOKID
CUSTOMID
CLASS
PASSNAME

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Context node creation
All context nodes created by the application developer must have some other
node acting as their parent. This is why a context is always supplied containing a
root node. The root node is the anchor point for all other nodes, irrespective of
whether they created statically at design time, or dynamically at runtime.
Node creation principle
1.Create the node’s metadata
2.Create the node instance based on the new metadata
Coding steps:
Obtain a reference to the metadata of
the context node that will act as the new
node’s parent. In this case, we are
creating an independent node, therefore
we get a reference to the metadata of
the root node.
Call static method
create_nodeinfo_from_struct( ) from
helper class cl_wd_dynamic_tool
A DDIC Structure can be used for the
attribute creation.
Dynamic Value Node Creation (1)
Context Root (c=1..1, s=true)
Context Metadata to be
created at runtime
BOOKINGS (c=0..n, s=false)
PRICE
CARRID
CONNID
FLDATE
BOOKID
CUSTOMID
CLASS
PASSNAME
DDIC Structure SFLIGHT

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Creating an value node
We are now dealing with the structure of the context not the contents, therefore we
must work with the metadata that describes the context nodes and attributes,
rather than the runtime data contained within node collections. This means we will
be working with if_wd_context_node_info objects.
1.Get a reference to the metadata of the node acting as the parent of the new node.
2.Use method create_nodeinfo_from_struct from helper class cl_wd_dynamic_tool to create a
node from a structure.
Dynamic Node Creation related to a structure
Coding steps:
Obtain a reference to the metadata of the context node that will act as the
new node’s parent.
Call static method create_nodeinfo_from_struct( ) from helper class
cl_wd_dynamic_tool to create from a DDIC structure a node.
DATA: rootnode_info TYPE REF TO if_wd_context_node_info,
table_name type string value 'SFLIGHT',
node_name type string value 'CONNECTIONS'.
* get root node info of context
rootnode_info = wd_context->get_node_info( ).
* create node named CONNECTIONS of sflight
cl_wd_dynamic_tool=>create_nodeinfo_from_struct(
parent_info = rootnode_info
node_name = node_name
structure_name = table_name
is_multiple = abap_false
is_mandatory = abap_true ).
Cardinality 1…1

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Dynamic Sub Node Creation related to a structure
DATA: dyn_node type ref to if_wd_context_node,
dyn_node_info TYPE REF TO if_wd_context_node_info,
. . .
* navigate from <CONTEXT> to <UI_ATTRIBUTES> via lead selection
dyn_node = wd_Context->get_Child_Node( Name = node_name ).
dyn_node_info = dyn_node->get_node_info( ).
* create sub node named BOOKINGS of sbook
parent_info = dyn_node_info
node_name = 'BOOKINGS'
structure_name = 'SBOOK'
is_multiple = abap_false
is_mandatory = abap_true ).
BOOKINGS (c=0..n,s=false)
PRICE
CARRID
CONNID
FLDATE
BOOKID
CUSTOMID
CLASS
PASSNAME
Structure SBOOK
Coding steps:
Obtain a reference to node and reference to the
metadata of the context node that will act as the new
node’s parent
Call static method create_nodeinfo_from_struct( ) to
create from a DDIC structure a node

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Add a Dynamic Attribute to a Node
UI_ATTRIBUTES
BUTTON_VISIBILITY
TEXT_VISIBILITY
* add context attribute to node
data: Ui_Attributes_info type ref to If_Wd_Context_Node_info.
data: ls_att type WDR_CONTEXT_ATTRIBUTE_INFO.
* get node info of context
Ui_Attributes_info = Node_Ui_Attributes->get_node_info( ).
ls_att-name = `TEXT_VISIBILITY`.
ls_att-TYPE_NAME = 'WDUI_VISIBILITY'.
Ui_Attributes_info->add_attribute( ATTRIBUTE_INFO = ls_att ).
Coding steps:
Obtain a reference to the metadata of the parent node
that will contain the attribute
Fill structure ( WDR_CONTEXT_ATTRIBUTE_INFO )
with attribute properties
Add attribute to parent node

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Principles of UI element manipulation
The following coding principles must be adhered to during UI element
manipulation:
1. Only perform direct manipulation of UI element objects when it is not
possible to control their behaviour through context binding.
2. UI manipulation is only permitted within the wdDoModifyView()
method of a view controller.
3. wdDoModifyView() has a boolean parameter called firstTime.
Typically, you will only build a dynamic UI element hierarchy when
firstTime == true. This avoids rebuilding the UI element hierarchy
unnecessarily.
4. Do NOT implement any coding in wdDoModifyView() that modifies
the context! The context should be considered “read-only” during the
execution of this method.

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Dynamic UI manipulation (1)
Context Root
Connections
PRICE
CARRID
CONNID
FLDATE
Context Metadata UI Element Hierarchy to
be created at runtime
RootUIElementContainer
CARRIDLabel
CARRIDInput
CONNIDLabel
CONNIDInput
FLDATELabel
FLDATEInput
PRICELabel
PRICEInput

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Coding steps:
Check that this is the
first time the view has
been rendered
Obtain a reference to
the root UI element
container
UI Element Hierarchy to
Context Root
Connections
PRICE
CARRID
CONNID
FLDATE
Context Metadata
method WDDOMODIFYVIEW .
data: wd_container type ref to cl_wd_uielement_container,
. . .
* Check if first time
check first_time = abap_true.
wd_container ?= view->get_element( 'ROOTUIELEMENTCONTAINER' ).

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Coding steps:
Create a new InputField UI
element object (bind to
context attribute
Create a new Label UI
element object
Set the Label’s properties
as required
Add the Label object to the
UI element container
Set the InputField’s
properties as required
Add the InputField to the
UI element container
InputField
InputField
Label
Label
bind
add
Context Root
Connections
PRICE
CARRID
CONNID
FLDATE
Context Metadata

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* Create label and input field
** create a input field
wd_input_field = cl_wd_input_field=>new_input_field( view = view
bind_value = 'CONNECTIONS.CARRID').
** create a label for the input field
wd_label = cl_wd_label=>new_label( label_for = wd_input_field->id ).
** set matrix_head_data for the label
cl_wd_matrix_head_data=>new_matrix_head_data( element = wd_label ).
** add label to container
wd_container->add_child( wd_label ).
cl_wd_matrix_data=>new_matrix_data( element = wd_input_field ).
** add input field to container
wd_container->add_child( wd_input_field ).

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Dynamic Actions
Certain UI elements can trigger client-side events (e.g. pressing enter
in an InputField, toggling a CheckBox or selecting the row of a
table).
In order for the client-side event to trigger the execution of a server-
side method, Web Dynpro uses the concept of Actions.
Actions can either be assigned declaratively to UI element events at
design time, or dynamically at runtime.
Actions assigned dynamically can only refer to existing server-side
action handler methods. It is not possible to define the coding of an
action event handler dynamically; only to define which existing action
handler will be called when a client-side event is trapped.

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The action can only be declared at design time.
Action Declaration
Declared action
Coding required
for dynamic
assigned action

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A button can be created and be added to the UI element container.
* Create button
** create button UI element
wd_button = cl_wd_button=>new_button( text = 'Show Flights'
on_action = 'SELECT_FLIGHTS' ).
cl_wd_matrix_head_data=>new_matrix_head_data( element = wd_button ).
** add button to container
wd_container->add_child( wd_button ).
Create a Dynamic Button
Coding steps:
Create a new Button UI
element object (assign an
predefined action)
Set the Button properties
as required
Add the Button to the UI
element container
Button
InputField
Label
Context Root
Connections
PRICE
CARRID
CONNID
FLDATE
Context Metadata
Button

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Was this a good approach?
Development Principle
Only if the required functionality of your application does not
permit design time declarations, then use a dynamic
modification approach.
All context node/attribute and UI elements which can be
created during design time should be created during design
time.

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Example for Dynamic Programming
Display the content of
ANY table
Dynamic Context
Dynamic table UI element
Dynamic data retrieval

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Example for Dynamic Programming I
DATA:
group_1 TYPE REF TO cl_wd_uielement_container,
new_tab TYPE REF TO cl_wd_table,
dyn_node TYPE REF TO if_wd_context_node,
tabname_node TYPE REF TO if_wd_context_node,
rootnode_info TYPE REF TO if_wd_context_node_info,
stru_tab TYPE REF TO data,
tablename TYPE string.
FIELD-SYMBOLS <tab> TYPE table.
* get node info of context root node
rootnode_info = wd_context->get_node_info( ).
* Get the name of the table to be created
tabname_node = wd_context->get_child_node( name = 'TABLE_DATA' ).
tabname_node->get_attribute( EXPORTING name = 'NAME' IMPORTING value =
tablename ).
translate tablename to upper case.
* create sub node of structure (tablename)
parent_info = rootnode_info
node_name = tablename
structure_name = tablename
is_multiple = abap_true ).

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Example for Dynamic Programming II
* remove "old" table UI element from view , if necessary
group_1 ?= view->get_element( 'GROUP_1' ).
group_1->remove_child( id = 'TESTTAB' ).
* * get instance of new node
dyn_node = wd_context->get_child_node( name = tablename ).
DATA new_tab TYPE REF TO cl_wd_table.
* create new UI element table
new_tab = cl_wd_dynamic_tool=>create_table_from_node(
ui_parent = group_1
table_id = 'TESTTAB'
node = dyn_node ).
** fill context node with data
* create internal table of (tabletype)
CREATE DATA stru_tab TYPE TABLE OF (tablename).
ASSIGN stru_tab->* TO <tab>.
* Get table content
SELECT * FROM (tablename) INTO CORRESPONDING FIELDS OF TABLE <tab>.
* Bind internal table to context node
dyn_node->bind_table( <tab> ).

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You should now be able to:
Understand what dynamic programming is
Dynamically modify and create UI elements
Dynamically create context elements
Dynamically bind UI element values to context
elements
Dynamically create actions
Web Dynpro Dynamic Programming: Summary

Dynamic binding

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