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An alert dialog box is a special dialog box that is displayed in a graphical user interface when something unexpected occurred that requires immediate user action. The typical alert dialog provides information in a separate box to the user, after which the user can only respond in one way: by closing it. Closing an alert dialog will provide access to the original window, which is not available while the alert dialog is presented. Alert dialogs that block the application are regarded as a bad design solution by usability practitioners, since they are prone to produce mode errors. Also when used as error dialogs, they have been shown to be ineffective in their goals to inform users about an error condition or protect from a destructive operation. == Usage == Alerts have several typical uses:〔(Java Look and Feel Design Guidelines, second edition. )〕 * Error: informs the user than an operation could not continue or complete due to some insurmountable error. * Warning: alerts that the current course of action could be in some way dangerous or detrimental, often offering the option of not proceeding. * Info: presents a general notification about a recent event. * Question: elicits some kind of response from the user, required to complete the current process. ''Warning'' and ''question'' alerts typically offer two opposite options to close the dialog ("Allow/Deny", "OK/Cancel", "Yes/No") with the implicit assumption that one will proceed with the paused process that triggered the dialog, and the other one will interrupt the process without action. A good practice in interface design, often included in Human Interface Guidelines, is to label each option with the precise effect that it will have on the process (for example, "Save/Don't save" in a dialog triggered while editing a document with unsaved changes). The primary reason for using an alert dialogue instead of communicating via the main program window is Modality (human–computer interaction). A typical online form is non-modal. They present to a user many actions that can be performed in any sequence. By contrast an alert dialogue creates a modal state that isolates a particular element of the form and requires a user to address it before proceeding to the next step. The utility of the alert dialogue is increasing with mobile device penetration, because: * modal alerts are part of the native functionality of a mobile device, so can be deployed consistently across the device ecosystem as opposed to visual styling techniques that are prone to cross-platform inconsistency * smaller viewports (screens) make it more difficult to review the main program window looking for errors/information * smaller viewports have acclimatized users to interacting with a sequence of small screens each with a define action, rather than viewing all contextual info at once on a big screen 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Alert dialog box」の詳細全文を読む スポンサード リンク
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