gWidgets (version 0.0-53)

gcombobox: Widgets to allow selection from a vector of items

Description

A combobox allows selection of a value from a list of items using a popup menu. Additionally, the widget can combine a text entry widget for user input outside of the pre-set list of items. A combobox is useful for selection from a moderate size of items (2-30, say). For smaller sets of items, a radio button group is a possibility, for larger sets of items, a scrollable (and perhaps searchable) table may be preferred.

Usage

gcombobox(items, selected = 1, editable = FALSE, coerce.with=NULL, handler = NULL, 
    action = NULL, container = NULL, ..., toolkit = guiToolkit())
gdroplist(items, selected = 1, editable = FALSE, coerce.with=NULL, handler = NULL, 
    action = NULL, container = NULL, ..., toolkit = guiToolkit())

Arguments

items

Vector of values to select from. This may also be a data frame, in which case the first column is the vector of values, the second (if present) indicates a stock icon to display with the item (not all toolkits), and the third (if present) will indicate a

selected

For gradio the initial selected value (as an index) For a drop list, the first selected value. Use 0 to leave blank

editable

A logical indicating if the user can add an entry to the list of available answers

coerce.with

Apply this function to selected value before returning

handler

Called when selection is changed

action

Passed to handler when called.

container

Optional container to attach widget to

...

Passed to add method of container

toolkit

Which GUI toolkit to use

Details

The initial items can be a vector or a data frame. Not all tool kits do something with the extra columns in the data frame.

The svalue method returns the selected value by name. Assume the value is a character vector. Use the coerce.with argument to return a value of a different type. If the extra argument index=TRUE is specified, the index of the selected value is given.

The svalue<- method can be used to set the selected value. This is done my name or if the argument index=TRUE is given by index. The value can be a data frame, in which case the first column is used to match against the current items.

The "[" method refers to the vector defining the items.

The "[<-" method can be used to change the vector defining the items.

The "length" method returns the number of items. For gcombobox the argument editable=TRUE adds a text-edit box where the user can type in a selection. By default this value is returned as a character by svalue. Use coerce.with to coerce this prior to returning.

See Also

A combobox is one of several ways to select a value of a set of items. See also gcheckbox, gradio, gcheckboxgroup, and gtable.

Methods for gComponent objects are detailed in gWidgets-methods.

Event Handlers are detailed in gWidgets-handlers.

Examples

flavors <- c("vanilla", "chocolate", "strawberry")

  f <- function(h,...) print(
      paste("Yum",
      paste(svalue(h$obj),collapse=" and "),
      sep = " "))

  w <- gwindow("combobox example")
  gp <- ggroup(container=w)
  glabel("Favorite flavor:", container=gp)
  cb <- gcombobox(flavors, editable=TRUE, container=gp, handler=f)

  svalue(cb) <- "vanilla"
  svalue(cb)
  cbg[3] <- "raspberry"