Event Handling Guide for iOS--(一)--About Events in iOS

About Events in iOS

Users manipulate their iOS devices in a number of ways, such as touching the screen or shaking the device. iOS interprets when and how a user is manipulating the hardware and passes this information to your app. The more your app responds to actions in natural and intuitive ways, the more compelling the experience is for the user.

用户以多种方式操作他们的iOS设备，比如触摸屏幕或摇动设备。 iOS对用户操作设备的时间，如何操作做出解释并把该信息传递给应用程序。应用程序越以自然直观的方式响应动作，用户就能获得更吸引人的用户体验。

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At a Glance

一、概述

Events are objects sent to an app to inform it of user actions. In iOS, events can take many forms: Multi-Touch events, motion events, and events for controlling multimedia. This last type of event is known as a remote control eventbecause it can originate from an external accessory.

事件(Event)是发送给应用程序通知用户操作的对象。在iOS中，事件分为多种形式：多触摸事件，运动事件以及控制多媒体的事件。最后那种事件被称为远程控制事件，因为它可以从一个外部附件开启。

UIKit Makes It Easy for Your App to Detect Gestures

二、UIKit 使应用程序侦测手势(gesture)变得简单

iOS apps recognize combinations of touches and respond to them in ways that are intuitive to users, such as zooming in on content in response to a pinching gesture and scrolling through content in response to a flicking gesture. In fact, some gestures are so common that they are built in to UIKit. For example, UIControl subclasses, such as UIButtonand UISlider, respond to specific gestures—a tap for a button and a drag for a slider. When you configure these controls, they send an action message to a target object when that touch occurs. You can also employ the target-action mechanism on views by using gesture recognizers. When you attach a gesture recognizer to a view, the entire view acts like a control—responding to whatever gesture you specify.

iOS应用程序能辨认多种触摸的组合并把它们以各种方式直观地给用户响应，比如缩放内容来响应一个捏合(pinch)手势，滚动内容来响应一个轻扫(flick)手势。事实上，一些常用的手势都已经被内建在UIKit里。比如，UIControl 子类，比如UIButton 和 UISlider，它们用来响应指定的手势--点击按钮以及拖动滑动条。当你布置好这些控件后，它们会在触摸发生时给目标对象发送一个动作消息(action message)。你还可以在视图上使用目标-动作(target-action)机制，只要你使用手势识别器(gesture recognizers). 当你给视图加入手势识别器之后，整个视图就能像一个控件一样--响应你指定的任何手势。

Gesture recognizers provide a higher-level abstraction for complex event handling logic. Gesture recognizers are the preferred way to implement touch-event handling in your app because gesture recognizers are powerful, reusable, and adaptable. You can use one of the built-in gesture recognizers and customize its behavior. Or you can create your own gesture recognizer to recognize a new gesture.

手势识别器为复杂的事件处理逻辑提供了一个高层次的抽象。手势识别器(gesture recognizers)是应用程序中实现触摸事件处理(touch-event handling)的首选方法，因为手势识别器是强大的，可重用的，并且适应性强。你可以使用选择使用一个内建的手势识别器并自定义它的行为。或者你可以创建你自己的手势识别器来识别一个新手势。

Relevant Chapter: “Gesture Recognizers”

相关章节：“Gesture Recognizers”

An Event Travels Along a Specific Path Looking for an Object to Handle It

三、一个事件沿着一个指定的路径寻找能处理它的对象

When iOS recognizes an event, it passes the event to the initial object that seems most relevant for handling that event, such as the view where a touch occurred. If the initial object cannot handle the event, iOS continues to pass the event to objects with greater scope until it finds an object with enough context to handle the event. This sequence of objects is known as a responder chain, and as iOS passes events along the chain, it also transfers the responsibility of responding to the event. This design pattern makes event handling cooperative and dynamic.

当iOS识别了一个事件，它把事件传递给看起来最有可能处理该事件的初始对象，比如触摸发生的视图。如果初始对象不能处理该事件，iOS继续把它传递给更多的对象，直到找到能够处理该事件的对象。该对象序列就是一个响应链(responder chain)，当iOS沿着响应链传递时，它还转移响应该事件的职责(responsibility). 该设计模式让事件处理合作并动态(cooperative and dynamic)。

Relevant Chapter: “Event Delivery: The Responder Chain”

A UIEvent Encapsulates a Touch, Shake-Motion, or Remote-Control Event

四。UIEvent 对象封装了一个触摸，摇动，或远程控制事件

Many events are instances of the UIKit UIEvent class. A UIEvent object contains information about the event that your app uses to decide how to respond to the event. As a user action occurs—for example, as fingers touch the screen and move across its surface—iOS continually sends event objects to an app for handling. Each event object has a type—touch, “shaking” motion, or remote control—and a subtype.

很多事件都是UIKit UIEvent 类的实例。一个UIEvent 对象包含了应用程序决定如何响应该事件的事件信息。当一个用户操作发生时--比如，当手指触摸了屏幕并在界面上移动时---iOS 持续地给应用程序发送处理事件的事件对象。每个事件对象都有一个类型--触摸，“摇晃”运动，或者远程控制--和一个子类型。

Relevant Chapters: “Multitouch Events,” “Motion Events,” and “Remote Control Events”

An App Receives Multitouch Events When Users Touch Its Views

五、当多个用户触摸其多个视图时，应用程序接收多点触摸事件

Depending on your app, UIKit controls and gesture recognizers might be sufficient for all of your app’s touch event handling. Even if your app has custom views, you can use gesture recognizers. As a rule of thumb, you write your own custom touch-event handling when your app’s response to touch is tightly coupled with the view itself, such as drawing under a touch. In these cases, you are responsible for the low-level event handling. You implement the touch methods, and within these methods, you analyze raw touch events and respond appropriately.

取决于你的应用程序，UIKit控件和手势识别器可能已经能够处理应用程序的所有触摸事件。即使你的应用程序有自定义视图，你也可以使用手势识别器。根据经验(as a rule of thumb)，你在以下情况下可以编写你自己的自定义触摸事件处理--当你的应用程序需要的响应的触摸跟视图本身紧密关联时，比如手写绘图。这样的情况下，你是负责底层事件处理。你需要实现触摸方法，并在这些方法中分析原始触摸事件并做出正确的响应。

Relevant Chapter: “Multitouch Events”

An App Receives Motion Events When Users Move Their Devices

六、当用户移动他们的设备时，应用程序接收运动事件(Motion Events)

Motion events provide information about the device’s location, orientation, and movement. By reacting to motion events, you can add subtle, yet powerful features to your app. Accelerometer and gyroscope data allow you to detect tilting, rotating, and shaking.

运动事件提供了设备位置，方向，以及运动等信息。通过响应运动事件，你可以给应用程序添加巧妙(subtle)并强大的功能。加速器和陀螺仪数据(gyroscope data)可以检测倾斜(tilting), 旋转以及摇晃。

Motion events come in different forms, and you can handle them using different frameworks. When users shake the device, UIKit delivers a UIEvent object to an app. If you want your app to receive high-rate, continuous accelerometer and gyroscope data, use the Core Motion framework.

运动事件能以不同的形式出现，你可以使用不同的框架来处理它们。当用户摇晃设备时，UIKIt给应用程序传递一个UIEvent对象。如果你想让你的应用接收高速(high-rate)，连续的加速器和陀螺仪数据，使用Core Motion 框架。

Relevant Chapter: “Motion Events”

An App Receives Remote Control Events When Users Manipulate Multimedia Controls

七、当用户操作多媒体控件时，应用程序接收远程控制事件

iOS controls and external accessories send remote control events to an app. These events allow users to control audio and video, such as adjusting the volume through a headset. Handle multimedia remote control events to make your app responsive to these types of commands.

iOS 控件和外部附件(external accessories)能给应用程序发送远程控制事件。这些事件可以让用户控制音频和视频，比如通过一个耳机开调整音量。处理多媒体远程控制事件可以让你的应用程序响应这些类型的命令。

Relevant Chapter: “Remote Control Events”

相关章节：“Remote Control Events”

Prerequisites

八、前提

This document assumes that you are familiar with:

该文档假设你已经熟悉以下内容：

The basic concepts of iOS app development
iOS应用开发的基本概念
The different aspects of creating your app’s user interface
创建应用程序用户界面的方方面面
How views and view controllers work, and how to customize them
视图和视图控制器是如何工作的，以及如何自定义它们

If you are not familiar with those concepts, start by reading Start Developing iOS Apps Today. Then, be sure to read either View Programming Guide for iOS or View Controller Programming Guide for iOS, or both.

如果你还不熟悉那些概念，请先阅读Start Developing iOS Apps Today. 然后，确保你阅读了View Programming Guide for iOS 或 View Controller Programming Guide for iOS 的一篇或全部。