Apple Newton Utilities Betriebsanweisung PDF herunterladen (Seite 264)

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CHAPTER 7

Controls and Other Protos

7-4 Scroller Protos

viewRect, and dataRect. Each of these slots is a bounds frame with the

following form:

{left: 0, top: 0, right: 10, bottom: 10}

You usually create these bounds frame slots with the utility function SetBounds,

which is described in “SetBounds” (page 2-34) in Newton Programmer’s Reference.

When you use these slots, the scroller protos highlight the scrolling arrows

automatically to indicate to the user that more data can be viewed by tapping on the

highlighted arrows.

Each of the bounds frame slots serves a speciﬁc purpose in the scroller, as shown in

Table 7-1. The next section provides several examples of setting the values of these

slots for different scrolling effects.

Scrolling Examples 7

This section presents several simple examples of setting the bounds frame slots in

your scroller to allow scrolling.

Scrolling Lines of Text 7

To scroll lines of text, you set the values of the three scroller bounds frames as

required for your application. For example, if you have 20 text items in a vertical

list and you want to show 6 of the items at a time, you need to set the slot values

as follows:

scrollRect: SetBounds(0, 0, 0, 20) // 20 possible lines

viewRect: SetBounds(0, 0, 0, 6) // show 6 at a time

dataRect: SetBounds(0, 0, 0, 20)

Table 7-1 Scroller bounds frame slots

Slot name Description

scrollRect

Speciﬁes the scrollable area, which is the total area that the

user can see, or scroll over, with the scroller.

viewRect

Speciﬁes the part of the scrollable area that the user can

see at any one time. This is usually smaller than the area

speciﬁed by

scrollRect.

dataRect

Speciﬁes the portion of the scrollRect that contains

data. In simple cases, this is the same as

scrollRect.

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