Modality

Modality creates focus by preventing people from doing other things until they complete a task or dismiss a message or view. Action sheets, alerts, and activity views provide modal experiences. When a modal view appears onscreen, the user must make a choice by tapping a button or otherwise exiting the modal experience. Some apps implement modal views, such as while editing an event in Calendar or choosing a bookmark in Safari. A modal view can occupy the entire screen, an entire parent view, such as a popover, or a portion of the screen. A modal view typically includes completion and cancel buttons that exit the view.

模态通过阻止用户去做其他事直到他们完成一个任务或解散一条信息或视图来创建一个关注。操作面板、提醒和活动视图提供模态体验。当一个模态视图在屏幕上出现，用户必须通过敲击一个按钮或者其他令人兴奋的模态体验来做出一个选择。一个app实现模态视图，例如在日历上编辑一个事件或者在Safari选择一个书签。一个模态视图可以占据整个屏幕，整个父窗口，例如一个popover，或者屏幕的一部分。一个模态视图一般包括完成和取消按钮来离开视图。

Minimize the use of modality.

减少使用模态

Generally, people prefer to interact with apps in nonlinear ways. Consider creating a modal context only when it’s critical to get someone’s attention, when a task must be completed or abandoned to continue using the app, or to save important data.

一般，用户期望用非线性的方式来与app交互。考虑只有当一定要取得用户注意时才考虑创建一个模态环境，当一个任务必须完成或者放弃，然后才能继续使用app，或者来保存重要数据。

Provide an obvious and safe way to exit a modal task.Make sure people always know the outcome of their action when they dismiss a modal view.

同一个明显的和安全的方式来离开模态任务。确保当用户解除一个模态视图时清楚他们操作的结果。

Keep modal tasks simple, short, and narrowly focused.Don’t create an app within your app. If a modal task is too complex, people can lose sight of the task they suspended when they entered the modal context. Be especially wary of creating modal tasks that involve a hierarchy of views because users can get lost and forget how to retrace their steps. If a modal task must contain subviews, provide a single path through the hierarchy and a clear path to completion. Avoid using Done buttons for things other than completing the task.

保持模态任务简单，短小，高度聚焦。不要在你的app里再创建一个app。如果一个模态任务太复杂了，当用户进入模态环境时，可能无法聚焦悬浮在他们前面的任务。特别关注包含层级视图的创建模态任务因为用户可能丢失和忘记怎么重复他们的步骤。如果一个模态任务必须包含子视图，提供一个单一和清晰的途径去完成它。除了完成任务的地方，避免使用完成按钮。

Display a title that identifies a task, if appropriate.You might also provide text in other portions of the view that more fully describes the task or provides guidance.

如果合适，显示一个标题来标示一个任务。你也许在这个视图的其他部分提供文本来更全面的描述这个任务和提供指导。

Reserve alerts for delivering essential—and ideally actionable—information.An alert interrupts the experience and requires a tap to dismiss, so it’s important for people to feel that the intrusion is warranted. To learn more, seeAlerts.

用提醒来传递关键信息-最好是可操作的-信息。一个提醒打断体验和需要一个敲击来解散，所以感觉侵入是被批准的对用户来说很重要。

Respect notification preferences.In Settings, people specify how they want to receive notifications from your app. Abide by these preferences so they aren’t tempted to turn off your app’s notifications entirely.

遵守通知偏好。在设置中，用户设定从你的app怎么接收通知。遵守这些偏好，这样他们就不会想整个关掉你的通知。

Don’t display a modal view above a popover.With the possible exception of an alert, nothing should appear over a popover. In rare cases when you need to present a modal view after action is taken in a popover, close the popover before displaying the modal view.

不要在一个弹出框上显示模态视图。除了异常提醒，不要在弹出框上显示任何东西。在你在弹出框执行一个操作，很少情况你需要显示一个模态 视图，在显示模态视图前关掉弹出框。

Coordinate modal view appearance with your app.A modal view may include a navigation bar, for example. When this is the case, use the same appearance as the navigation bar in your app.

你的app与模态视图外观风格一致。一个模态视图也许包括一个导航条，例如。当发生这种情况时，使用你的app导航栏相同的外观。

Choose an appropriate modal view style.You can use any of these styles:

选择一种合适的模态视图样式。你可以选择使用以下样式：

全屏。覆盖整个屏幕。用于展示一个可能复杂的任务，可以在模态视图环境完成的。

页面sheet。在大设备上覆盖部分内容当设备是横放方向时。那些没覆盖的区域是无效来防止与它们交互。在小设备覆盖全部屏幕或者处于直立方向。用于展示一个可能复杂的任务，可以在模态视图环境完成的。

表单sheet。在屏幕正中间出现，如果一个键盘出现可能重定位。那些没覆盖的区域是无效来防止与它们交互。在小设备覆盖全部屏幕。用于收集信息。

当前环境。出现时和它的父视图一样大。用于显示在一个分隔视图窗格里、弹出框，或者其他不是全屏的视图的模态内容

Choose an appropriate transition style for revealing a modal view.Use a transition style that coordinates with your app and enhances the awareness of the temporary context shift. The default transition vertically slides the modal view up from the bottom of the screen and back down once dismissed. The flip-style transition appears to flip a view horizontally to reveal the modal view. Visually, the modal view looks like the back of the current view. It flips back once dismissed. Use consistent modal transition styles throughout your app.

为展示一个模态视图选择一个合适的转场。用一个与你的app风格相符的转场样式，增强临时环境变换的意识。初始转场从下到上垂直滑动模态视图,一旦解散从上到下出现。水平轻弹一个视图显示轻弹样式转场来显示模态视图。可见的，模态视图看起来像当前视图的背面。It flips back once dismissed. Use consistent modal transition styles throughout your app.

For modal view developer guidance, seeUIViewControllerandUIPresentationController.