Step 2: A First View

A message box is not much of a UI. UI5 apps describe their screens as XML views — and in abap2UI5 you write that view in ABAP, with z2ui5_cl_ui5_view_builder:

CLASS zcl_app_walkthrough DEFINITION PUBLIC.
  PUBLIC SECTION.
    INTERFACES z2ui5_if_app.
ENDCLASS.

CLASS zcl_app_walkthrough IMPLEMENTATION.
  METHOD z2ui5_if_app~main.

    DATA(view) = z2ui5_cl_ui5_view_builder=>factory(
        )->ele( n = `View` ns = `mvc`
            )->a( n = `xmlns`     v = `sap.m`
            )->a( n = `xmlns:mvc` v = `sap.ui.core.mvc`

            )->ele( `Shell`
                )->ele( `Page`
                    )->a( n = `title` v = `Walkthrough - Step 2`

                    )->tag( `Text`
                        )->a( n = `text` v = `Hello World` ).

    client->view_display( view->stringify( ) ).

  ENDMETHOD.
ENDCLASS.

The Four Verbs

You are writing a UI5 XML view, one control per call. The builder has four verbs and no list of controls to look up — every UI5 control, property and aggregation is available, because the builder never knew any of them by name:

ele( )	add a control and descend into it — for a container
tag( )	add a control and stay — for a leaf
a( )	set one attribute on the control the chain points at
end( )	ascend to the parent

The single rule: a( ) applies to the control the chain currently points at, so attributes follow their control — and a control gets them before its first child. The root mvc:View and its xmlns declarations are written by hand, exactly as in a real UI5 view. stringify( ) renders the XML from the root, and view_display( ) sends it to the browser.

The indentation mirrors the XML tree — Text sits inside Page inside Shell — which is what makes the chain readable as the view it builds. The full layout rules are on the View → Definition page.

Want to see the XML this chain produced? Press Ctrl+F12 in the running app and open the view tab — the developer tools show the generated view, the model and the payload of every roundtrip.

Next, the app gets its first button — and with it, the app lifecycle.