Apple Newton Programmer’s Newton 2.0 (for Newton 2.0) User Manual

Page 230

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C H A P T E R 6

Pickers, Pop-up Views, and Overviews

6-30

Overview Protos

See “Column Specifications” (page 5-3) in Newton Programmer’s Reference for
details of the slots.

Having a Single Selection in a List Picker

The key to getting single selection is that single selection is part of the picker
definition and not an option of

protoListPicker

. That means the particular

class of

nameRef

you use must include single selection. In general, this requires

creating your own subclass of the particular name reference class.

The basic solution is to create a data definition that is a subclass of the particular
class your

protoListPicker

variant will view. That data definition will include

the

singleSelect

slot. As an example, suppose you want to use a

protoPeoplePopup

that just picks individual people. You could use the

following code to bring up a

protoPeoplePopup

that allows selecting only one

individual at a time:

// register the modified data definition
RegDataDef('|nameref.people.single:SIG|,
{_proto: GetDataDefs('|nameRef.people|), singleSelect:
true});

// then pop the thing
protoPeoplePopup:New('|nameref.people.single:SIG|,[],self,[
]);

// sometime later
UnRegDataDef('|nameref.people.single:SIG|);

For other types of

protoListPickers

and classes, create the appropriate

subclass. For example, a transport that uses

protoAddressPicker

for e-mail

messages might create a subclass of

'|nameRef.email|

and put that subclass

symbol in the class slot of the

protoAddressPicker

Since many applications are likely to do this, you may cut down on code in your

installScript

and

removeScript

by registering your

dataDef

only for the

duration of the picker. That would mean registering the class just before you pop
the picker and unregistering after the picker has closed. You can use the

pickActionScript

and

pickCanceledScript

methods to be notified when

to unregister the

dataDef

Having Preselected Items in a List Picker

If you want to have items that are initially selected in a list picker, use the

viewSetupDoneScript

to set up the selected array, rather than setting up

the selected array in your

viewSetupFormScript

viewSetupChildrenScript

, then send the

Update

message to

protoListPicker

to tell it to update the display.

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