在Android API 11+中,谷歌发布了一个名为Fragment的新类。

在视频中,谷歌建议,只要可能(link1, link2),我们应该使用片段而不是活动,但他们没有解释确切的原因。

片段的目的是什么以及它们的一些可能的用途(除了一些可以通过简单的视图/布局轻松实现的UI示例)?

我的问题是关于片段的:

使用片段的目的是什么? 与使用活动/视图/布局相比,使用片段的优点和缺点是什么?

奖金问题:

您能否为片段提供一些真正有趣的用途?谷歌在他们的视频里没有提到的事情? 在片段和包含它们的活动之间进行通信的最佳方式是什么? 当你使用片段时,最重要的事情是什么?从你的经验中有什么建议和警告吗?


当前回答

如果你以前写过前端,那么使用前端组件(React, Vue或Angular)。将片段视为活动中的可重用组件。

其他回答

#1 & #2使用片段的目的是什么 与使用片段相比,使用片段的优缺点 活动/视图/布局?

Fragments是Android用于创建可重用用户界面的解决方案。您可以使用活动和布局(例如使用include)来实现一些相同的功能。然而;fragments被连接到Android API中,从HoneyComb开始。让我详细说明;

The ActionBar. If you want tabs up there to navigate your app, you quickly see that ActionBar.TabListener interface gives you a FragmentTransaction as an input argument to the onTabSelected method. You could probably ignore this, and do something else and clever, but you'd be working against the API, not with it. The FragmentManager handles «back» for you in a very clever way. Back does not mean back to the last activity, like for regular activities. It means back to the previous fragment state. You can use the cool ViewPager with a FragmentPagerAdapter to create swipe interfaces. The FragmentPagerAdapter code is much cleaner than a regular adapter, and it controls instantiations of the individual fragments. Your life will be a lot easier if you use Fragments when you try to create applications for both phones and tablets. Since the fragments are so tied in with the Honeycomb+ APIs, you will want to use them on phones as well to reuse code. That's where the compatibility library comes in handy. You even could and should use fragments for apps meant for phones only. If you have portability in mind. I use ActionBarSherlock and the compatibility libraries to create "ICS looking" apps, that look the same all the way back to version 1.6. You get the latest features like the ActionBar, with tabs, overflow, split action bar, viewpager etc.

奖金2

片段之间最好的沟通方式是意图。当你在Fragment中按下一些东西时,你通常会调用StartActivity(),并在上面有数据。意图被传递到您启动的活动的所有片段。

片段是应用程序的用户界面或行为的一部分,可以放在活动中,从而实现更模块化的活动设计。如果我们说片段是一种子活动,那也不会错。

以下是关于片段的要点:

A fragment has its own layout and its own behavior with its own lifecycle callbacks. You can add or remove fragments in an activity while the activity is running. You can combine multiple fragments in a single activity to build a multi-pane UI. A fragment can be used in multiple activities. The fragment life cycle is closely related to the lifecycle of its host activity. When the activity is paused, all the fragments available in the acivity will also be stopped. A fragment can implement a behavior that has no user interface component. Fragments were added to the Android API in Android 3 (Honeycomb) with API version 11.

欲了解更多详情,请访问官方网站碎片。

如果你以前写过前端,那么使用前端组件(React, Vue或Angular)。将片段视为活动中的可重用组件。

我知道这个问题已经讨论得很激烈了,但我想再补充几点:

Frags can be used to populate Menus and can handle MenuItem clicks on their own. Thus giving futher modulation options for your Activities. You can do ContextualActionBar stuff and so on without your Activity knowing about it and can basically decouple it from the basic stuff your Activity handles (Navigation/Settings/About). A parent Frag with child Frags can give you further options to modulize your components. E.g. you can easily swap Frags around, put new Frags inside a Pager or remove them, rearrange them. All without your Activity knowing anything about it just focusing on the higher level stuff.

片段在某些情况下特别有用,比如我们想在所有页面中保留一个导航抽屉。你可以用你想要的任何片段来膨胀框架布局,并且仍然可以访问导航抽屉。

如果您使用了一个活动,那么您将不得不在所有活动中保留抽屉,这将导致冗余代码。这是片段的一个有趣用法。

我是Android的新手,仍然认为碎片是有帮助的。