Apple Newton Utilities Podręcznik Użytkownika Pobierz pdf (Strona 119)

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CHAPTER 3

Views

Using Views 3-35

If at some point after the child views have been created you want to modify the

contents of the

stepChildren array and build new child views from it, you can

use the

RedoChildren view method. First, make any changes you desire to the

stepChildren array, then send your view the RedoChildren message. All of

the view’s current children will be closed and removed. A new set of child views

will then be recreated from the

stepChildren array.

Also, note that reordering the

stepChildren array and then calling

RedoChildren or MoveBehind is the way to reorder the child views of a

view dynamically.

For details on an easy way to create a template dynamically, see “Creating

Templates” (page 3-36).

Using the AddStepView Function 3

If you need to create a template and add a view yourself at run time, use the

function

AddStepView. This function takes two parameters: the parent view to

which you want to add a view, and the template for the view you want to create.

The function returns a reference to the view it creates. Be sure to save this return

value so you can access the view later.

The

AddStepView function also adds the template to the parent’s

stepChildren array. This means that the stepChildren array needs to be

modiﬁable, or

AddStepView will fail. See the code in the previous section for an

example of how to ensure that the

stepChildren array is modiﬁable.

The

AddStepView function doesn’t force a redraw when the view is created, so

you must take one of the following actions yourself:

■ Send the new view a Dirty message.

■ Send the new view’s parent view a Dirty message. This is useful if you’re

using

AddStepView to create several views and you want to show them all at

the same time.

■ If you created the view template with the vVisible bit cleared, the new view

will remain hidden and you must send it the

Show message to make it visible.

This technique is useful if you want the view to appear with an animation effect

(speciﬁed in the

viewEffect slot in the template).

Do not use the

AddStepView function in a ViewSetupFormScript method or

ViewSetupChildrenScript method—it won’t work because that’s too early

in the view creation process of the parent for child views to be created. If you are

tempted to do this, you should instead use the second method of dynamic view

creation, in which you add your template to the

stepChildren array and let the

view system create the view for you.

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