A drop-down list is a GUI control which allows the user to choose one value from a list. When a drop-down list is inactive, it displays a single value. When activated, it displays (drops down) a list of values, from which the user may select one. When the user selects a new value, the control reverts to its inactive state, displaying the selected value. A drop-down list works similar to a list box but hides the complete list until the user initiate the drop down. The disadvantage of drop-down lists compared to related controls like radio buttons or lists is that the options are not visible without further interaction.
The list provides auto-complete feature for the whole string, independently of the "editable" property. Given the items of "bike", "boat", and "car":
- If one types "b", the list selects "bike".
- If one (rapidly) types "bo", it selects "boat".
- If one types "c", it selects "car".
One can repeatedly type a letter to cycle through items of the (read-only) drop-down list starting with this letter.
Is this the right control
- Use a drop-down list for single selection of one out of many items. If users should be able to add items use a combo box.
- For only a few options, consider to use a set of radio buttons.
- For a single selection out of a large number of items (n>20), use a list view.
- Prefer controls that show the options without further user interaction, except for the following cases:
- the list of options may change over time,
- the contents are obvious from the label and the one selected item, for example Month and January
- the control is part of a related sequence of controls. For example, to set a reminder to ring 5 hours or minutes before or after an event.
- Show a maximum of eight items at once (maxVisibleItems=8).
- When possible apply changes immediately but do not initiate an action (like print, send, delete) when the user selects an item from a drop-down list.
- Do not add controls to the drop-down (e.g. check boxes for each item).
- Place options that represent general options (e.g. all, none) at the beginning of the list.
- Sort list items in a logical order. Make sure sorting fits translation.
- Make sure the items are easily accessible via keyboard by moving distinctive letters to the beginning of each option. For example, in a list of countries on continents, write "Germany (Europe)" instead of "Europe/Germany".
- Do not have blank list items; use meta-options, e.g. (None) instead
- If activating a choice affects the appearance or the enabled state of other controls, place them next to the drop down.
- If certain controls in a configuration dialog are only relevant if a certain item is selected (i.e. they are dependent controls), disable them instead of hiding.
- Label the drop down with a descriptive caption to the left (cf. alignment).
- Create a buddy relation so access keys are assigned.
- End each label with a colon.
- Use sentence style capitalization for items.
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