Create An Observer For A Data Property; Create The Dialog Contents - Adobe 65007312 - Photoshop Lightroom Programmer's Manual

C 9: Getting Started: A Tutorial Example
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Create an observer for a data property

To make the text dynamic, we are going to add an observer for the
observer is notified whenever the observed property changes; we will tell it to update the text in
showValue_st
6. When the observer receives a notification it invokes a function. Create the function that will be used
by the observer:
local myCalledFunction = function()
showValue_st.title = updateField.value -- reflect the value entered in edit box
showValue_st.text_color = LrColor( 1, 0, 0 ) -- make the text red
end
This makes the
changes. It also turns the text red to show that it has fired.
7. Now add the observer to the observable table. This associates the function with a specific property in
the table:
props:addObserver( "myObservedString", myCalledFunction )
This observer is notified, and calls the response function, whenever the value of the key
myObservedString

Create the dialog contents

Now you will create the view hierarchy that defines the custom-UI portion of the dialog. This one uses a
as the top-level container, which contains two rows, which in turn contain the visible controls. In
column
this case, the controls include the
defined, along with additional labels and a push button.
8. Create the view hierarchy:
local c = f:column { --The top-level container, arranges all the rows vertically
9. We will add one more element, a push button. This demonstrates another way to define the behavior
of your UI, by specifying a direct action to be taken in response to clicking the button. In this case, the
.
text dynamic, by resetting its
showValue_st
is modified.
showValue
f:row { -- a group of labels arranged horizontally
fill_horizontal = 1, -- the row fills its parent's width
f:static_text { -- add a right-aligned label
alignment = "right",
width = LrView.share "label_width", -- all get the same width
title = "Bound value: "
},
showValue_st, -- the text box we already defined
}, -- end f:row
f:row { -- another group, a labeled edit box and button
f:static_text {
alignment = "right",
width = LrView.share "label_width", -- shared with other label
title = "New value: "
},
updateField, -- the edit box we already defined
-- add push button
}, -- end row
} -- end column
props.myObservedString
title
text box and the
updateField
Adding a data observer 181
value when the observed property
edit box that we already
key. The