出自UXGuide.net

牢记平台间的差异

Platform Differences to Keep in Mind

An iPhone OS–based device is not a desktop or laptop computer, and an iPhone application is not the same as a desktop application. Although these seem merely common-sense statements, it is nonetheless paramount to keep them in mind as you embark on developing software for these devices.

基于 iPhone OS 的设备并非台式计算机或笔记本，且 iPhone 应用程序也不同于桌面应用程序。虽然这些似乎只是常识性的说明，尽管如此，但但当你基于这些设备开发软件的时候，最重要的是记住这些说明。

Designing software for iPhone OS–based devices requires a state of mind that may or may not be second nature to you. In particular, if the bulk of your experience lies in developing desktop applications, you should be aware of the significant differences between designing software for a mobile platform and for a computer.

为 iPhone 操作系统的设备设计软件需要一种思维方式，这种思维方式或许不是你所习惯的。尤其是当你的大部分经验都来源于开发桌面应用程序，你应该意识到设计移动平台软件和设计电脑软件的显著性差异。

This section summarizes the concrete differences that have the highest potential impact on your design decisions. For detailed information on how to handle these and other issues in your iPhone application development process, see iPhone Application Programming Guide.

这一部分概述了对于你设计决策潜在影响最大的不同点。有关如何处理你的iPhone应用程序开发过程中各种问题，参见《iPhone应用程序编程指南》（英文）的详细信息。

目录 1 紧凑的屏幕尺寸 Compact Screen Size 2 内存是有限的 Memory is Not Unlimited 3 同一时间只能显示一个页面 One Screen at a Time 4 同一时间只能运行一个应用程序 One Application at a Time 5 有限的用户帮助 Minimal User Help

紧凑的屏幕尺寸

Compact Screen Size

The small, high-resolution screens of iPhone OS–based devices make them powerful display devices that fit into users’ pockets. But that very advantage to users may be challenging to you, the developer, because it means that you must design a user interface that may be very different from those you’re accustomed to designing.

小巧，高分辨率的屏幕使iPhone操作系统设备成为具有强大显示能力且适合用户装进口袋使用的设备。对于用户来说这是个优势，但是对于你，开发人员来说这是个很大的挑战。因为这意味着你必须设计出一个不同于你习惯设计的用户界面。

Keep in mind the screen size of 480 x 320 pixels and use that as a motivation to focus the user interface on the essentials. You don’t have the room to include design elements that aren’t absolutely necessary, and crowding user interface elements makes your application unattractive and difficult to use.

要记住屏幕的尺寸只有480×320像素，所以要把重点放在用户界面必须具备的东西。你没有任何展示设计元素的空间，况且这些元素是完全没有必要的。拥挤的用户界面会使你的应用程序失去吸引力并且难以使用。

内存是有限的

Memory is Not Unlimited

Memory is a critical resource in iPhone OS, so managing memory in your application is crucial. Because the iPhone OS virtual memory model does not include disk swap space, you must take care to avoid allocating more memory than is available on the device. When low-memory conditions occur, iPhone OS warns the running application and may terminate the application if the problem persists. Be sure your application is responsive to memory usage warnings and cleans up memory in a timely manner.

内存是iPhone操作系统的重要资源，所以控制你的应用程序所占的内存是至关重要的。由于iPhone操作系统的虚拟内存模型不包括磁盘交换空间，所以你必须小心，不要给你的应用程序分配过多的内存。当内存不足的情况发生的时候，iPhone操作系统会对正在运行的程序发出警告，如果问题依然存在的话可能会终止程序。请确保你的应用程序能够即时响应内存使用警报并即时清理内存。

As you design your application, strive to reduce the application’s memory footprint by, for example, eliminating memory leaks, making resource files as small as possible, and loading resources lazily. See iPhone Application Programming Guide for extensive information about how to design iPhone applications that handle memory appropriately.

当你设计应用程序的时候，要严格地尽量降低应用程序的内存占用，例如，消除内存泄漏，尽量压缩资源文件大小，缓慢的装载资源等。《iPhone应用程序编程指南》中有大量有关如何设计iPhone应用程序使之合理的占用内存的资料。

同一时间只能显示一个页面

One Screen at a Time

One of the biggest differences between the iPhone OS environment and the computer environment is the window paradigm. With the exceptions of some modal views, users see a single application screen at a time on an iPhone OS–based device. iPhone applications can contain as many different screens as necessary, but users access and see them sequentially, never simultaneously.

iPhone操作系统与电脑操作系统在操作环境上最大的不同是窗口的模式。除了一些模态视图之外，用户在iPhone操作系统设备上同一时间只能看到单一的页面。iPhone应用程序能尽可能的包含所需要的不同的页面，但是用户是渐进方式看到它们，而不是同时看见。

If the desktop version of your application requires users to see several windows simultaneously, you need to decide if there’s a different way users can accomplish the same task in a single screen or a sequence of screens. If not, you should focus your iPhone application on a single subtask of your computer application, instead of trying to replicate a wider feature set.

如果你的应用程序对应的桌面版本要求用户同时浏览几个窗口，你就要决定是否有另外一种方法允许用户只打开一个页面或者打开一系列页面就可以完成任务。如果不能的话，你就要把你这个iPhone应用程序的重点放在这个电脑应用程序的下属子功能上，而不是去试图复制一个广泛的功能集合。

同一时间只能运行一个应用程序

One Application at a Time

Only one iPhone application can run at a time, and third-party applications never run in the background. This means that when users switch to another application, answer the phone, or check their email, the application they were using quits. It’s important to make sure that users do not experience any negative effects because of this reality. In other words, users should not feel that leaving your iPhone application and returning to it later is any more difficult than switching among applications on a computer.

同一时间只能运行一个iPhone应用程序，并且第三方应用程序不会在后台运行。这意味这当用户切换到其他应用程序的时候，如接听电话或者查看邮件等，他们现在之前所用的应用程序将会退出。确保用户不会因为遇到这种情况而感受到负面的影响是非常重要的，因为这是很自然的操作流程。换句话说，不应该让用户感觉到退出iPhone应用程序稍后再打开，会比在电脑程序之间切换更困难。

The most effective thing you can do to ensure that users have a positive application-switching experience is to pare the launch time of your application to the minimum. See iPhone Application Programming Guide for guidance on how to make your application’s launch time as short as possible.

为了确保用户能够拥有一个良好的程序切换体验，你所能做的最有效的事情就是降低应用程序的载入时间。关于如何尽可能的减少程序载入时间请参阅《iPhone应用程序编程指南》（英文）。

In general, users quit your application by switching to another application or service on the device; they take no specific action to close your application. Therefore, do not expect users to select Quit from a menu or click a close button. This means that your application is likely to quit without much warning, so you should be prepared to save user changes as they are made, as quickly as possible. Doing so allows a fast, smooth transition between applications and ensures that your application can reflect the user’s most recent changes the next time it starts.

一般情况下，用户通过切换到其他应用程序来退出你的应用程序，他们是不会做退出程序的确切行为。因此，不要期望用户会选择菜单中的“退出”选项或者点击关闭按钮。这种使用习惯就意味着：你的应用程序有可能在没有任何预警的情况下被关闭，所以你要时刻准备好尽可能快的保存用户做出的改动。这样做会使程序之间的转换快速而稳定，并且可以确保你的应用程序再次被打开的时候依然还是上次关闭前的状态。

Another important facet of the single application model is the way you handle application-specific preferences. On iPhone OS–based devices, users set preferences in the Settings application. Your iPhone application can supply such preferences, but this means that they must quit your application when they want to access them in Settings. If you follow the standard guidelines and offer settings that users need to set once, and then rarely, if ever, again, the user experience of your application should be smooth.

这种单一应用程序模式的另一个重要方面是你处理用户定制的偏爱的应用程序。在iPhone操作设备中，用户在“设置”这个应用程序中设置选项。你的iPhone应用程序也可以使用这种设置选项，但这意味着当用户想进行设置时，需进入“设置”应用程序，且必须退出你的应用程序。如果你遵循这个准则并提供设置选项，用户只要用过一次，就会逐渐的习惯并再次使用，你的应用程序将会拥有一个流畅的用户体验。

有限的用户帮助

Minimal User Help

Mobile users don’t have the time to read through a lot of help content before they can use your application. What’s more, you don’t want to give up valuable space to display or store it. A hallmark of the design of iPhone OS–based devices is ease of use, so it’s crucial that you meet users’ expectations and make the use of your application immediately obvious. There are a few things you can do to achieve this:

移动用户在使用你的应用程序之前没有时间去阅读大量的“帮助”内容。更何况你也不想放弃宝贵的屏幕空间去显示它们或存储这些内容。iPhone操作设备的一个标志性设计就是易用，所以有一点很重要，满足用户的期望并使应用程序的用法一目了然。想实现这些你要做的有以下几点：

• Use standard controls correctly. Users are familiar with the standard controls they see in the built-in applications, so they already know how to use them in your application.

正确使用标准控件。用户已经对内置应用程序中的标准控件非常熟悉了，所以他们清楚的知道该如何使用它们。

• Be sure the path through the information you present is logical and easy for users to predict. In addition, be sure to provide markers, such as back buttons, that users can use to find out where they are and how to retrace their steps.

确保通过你给出的信息得到的路径是符合逻辑且易于用户预知的。另外，确保提供像后退按钮这样的标记，这样用户可以知道他们在哪和如何追溯他们的操作步骤。