Apple 2 manual Local Scroll Arrows

C H A P T E R 2

Container Views

Figure 2-31The universal scroll arrows at the bottom of a MessagePad screen

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Any view can have its scrolling controlled by user taps on the universal scroll arrows, but they only affect one of the open views. To be affected, a view must meet two requirements. First, the view must be set up during application development to receive taps on the universal scroll arrows. Second, it must be in front of all other open views that have also been set up to receive those taps. It is entirely possible for the view that is affected by the universal scroll arrows to be partially or completely covered by other open views that were not set up to receive scroll-arrow taps. (A view that receives scroll-arrow taps also receives taps on the Overview button, which is described in “Overview” on page 2-44).

There is no convention for indicating what will scroll when a user taps a universal scroll arrow. Users must learn by experience what will scroll when they tap the universal scroll arrows.

Generally, the universal scroll arrows should scroll most of the information in a view. An application should not use the universal scroll arrows to scroll part of the information embedded in a view. For instance, the built-in Date Book application uses the universal scroll arrows for scrolling from day to day, not for scrolling from hour to hour or month to month.

Local Scroll Arrows

For scrolling part of the information embedded in a view, an application should use local scroll arrows. For instance, the Date Book has a set of local scroll arrows for scrolling from hour to hour and another set for scrolling from month to month. Figure 2-32 illustrates the Date Book’s use of scroll arrows.

How Views Work 2-39