Apple Newton Utilities Guia do Utilizador descarregar pdf (Página 118)

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CHAPTER 3

Views

3-34 Using Views

Showing a Hidden View 3

In many cases, you might think that you need to create a view dynamically. However,

if the template can be deﬁned at compile time, it’s easier to do that and ﬂag the

view as not visible. At the appropriate time, send it the

Open message to show it.

The typical example of this is a slip, which you can usually deﬁne at compile time.

Using the Newton Toolkit (NTK), simply do not check the

vVisible ﬂag in the

viewFlags slot of the view template. This will keep the view hidden when the

application is opened.

Also, it is important to declare this view in your application base view. For

information on declaring a view, see the section “View Instantiation” (page 3-26).

When you need to display the view, send it the

Open message using the name

under which you have declared it (for example,

myView:Open()).

This solution even works in cases where some template slots cannot be set until run

time. You can dynamically set slot values during view instantiation in any of the

following view methods: ViewSetupFormScript,

ViewSetupChildrenScript, and ViewSetupDoneScript. You can also set

values in a declared view before sending it the

Open message.

Adding to the stepChildren Array 3

If it is not possible to deﬁne the template for a view at compile time, the next best

solution is to create the template (either at compile time or run time) and add it to

the

stepChildren array of the parent view using the

ViewSetupChildrenScript method. This way, the view system takes care of

creating the view at the appropriate time (when the child views are shown).

For example, if you want to dynamically create a child view, you ﬁrst deﬁne the

view template as a frame. Then, in the

ViewSetupChildrenScript method of

its parent view, you add this frame to the

stepChildren array of the parent view.

To ensure that the

stepChildren array is in RAM, use this code:

if not HasSlot(self, 'stepChildren) then

self.stepChildren := Clone(self.stepChildren);

AddArraySlot(self.stepChildren, myDynamicTemplate);

The if statement checks whether the stepChildren slot already exists in the

current view (in RAM). If it does not, it is copied out of the template (in ROM)

into RAM. Then the new template is appended to the array.

All of this takes place in the

ViewSetupChildrenScript method of the parent

view, which is before the

stepChildren array is read and the child views are

created.

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