Android的 - 爪哇 - 通过意图，束或Parcelables并传递价值？ [英] android - java - pass values through intents, bundles or Parcelables?

问题描述

上下文：

Android版

我读了很多的净例子传递活动之间DATAS。

我所学到的：

• 通过意图传递原始DATAS（intent.putExtra（键，值））


• 捆绑原始DATAS并把它放在一个intent.putExtra（钥匙，包对象）


• Parcelables并 - >对复杂对象和原语

在你说，是的，我的确实的错过了一些东西。

问：

那么，它似乎有多种方式来达到同样的目标。

如果我想通过一个自定义的对象，Parcelable是我的男人。但我还是会要序列化，所以到最后，我也会有元，对吧？

要通过原语，我为什么要使用一个包时，直接以传递意图将使它呢？

Android的文档/论坛/博客的例子没有做对我来说。我的C背景仍持有我回了一下。

有3个不同的方式为什么要实现一个目标，顺便说一下？

解决方案

  

但我还是要序列化，所以到最后，我也会有元，对吧？

在Java的pretty所有事情最终还是归结到元。

  

要通过原语，我为什么要使用一个包时，直接以传递意图将使它呢？

无论哪种方式工作。使用哪种让你感觉更舒服。然而，就注意上的按键冲突（例如，你的活动，而且你继承你的一些基本活动，都试图把同样的事情在意图或捆绑）。

  

为什么有3种不同的方式来实现一个目标，顺便说一下？

我要猜一个目标就是从一个活动传递到另一个数据。涉及的进程间通信（IPC），即使这两种活动都在相同的过程中，作为芯OS过程参与路由。对于流之外pretty多凡事都从的ContentProvider 在标准的Andr​​oid，IPC意味着数据必须被放入包裹，这将会转换成字节数组传递跨进程边界。

Parcelable 重新presents可添加到自定义类的接口，让他们被放入一个包裹。

捆绑是一个具体的类，它实现 Parcelable 和再presents一个 HashMap的状结构，但强类型到被称为是能够进入一个包裹的东西。 捆绑比更方便的地块为开发者，因为它提供了通过键，其中<$ C $随机访问C>包裹没有。​​

意图演员只是一个捆绑，为此，意图暴露自己的访问方法。

  

有关我的所有的情况下，我应该忘记其他可能性，并且只使用Parcelable？

据我所知，有什么EpicPandaForce指的是序列化和 Parcelable 之间的比较。这两者都可以进入一个捆绑或包裹。在这两个，其他条件不变，序列化比较慢，因为它假定序列化形式必须是持久的，能够被数月或数年后再次读入。 Parcelable 假定每个人都在努力从相同的类定义的，可以绕过某些序列化开销的结果。

话虽这么说，这是一个微型的优化。

  

为什么其他仍然存在呢？

不是什么都可以做，延长 Parcelable ，特别是的java。* 类。 整数，例如，是不是 Parcelable 。然而，我们希望能够通过周围 INT 和整数值。因此，包裹支持 INT 一样，捆绑。

  

你的意思是我应该拿回来的东西R.blah

据我所知，在评论，Marconcini先生指的是ID作为一个笼统的概念，不是指 R.id 特别值。例如，如果你保持影像缓存，而不是绕过实际位图对象，通过周围的一些标识指向回缓存。

Context:

Android

I read a lot of examples on the net for passing datas between activities.

What I learned :

• Pass primitive datas through Intents (intent.putExtra(key,value))
• Bundle the primitive datas and put it in an intent.putExtra(key,bundle object)
• Parcelables -> for complex objects and primitives.

Before you say it, yes, I certainly missed something.

Question:

Well, it seems that there are multiple ways to achieve the same goal.

If I want to pass a custom object, a Parcelable is my man. BUT I will still have to "serialize" it, so in the end, I will also have primitives, right ?

To pass primitives, why should I use a bundle when passing directly in an intent will make it too ?

The android documentation / forums / blogs examples did not make it for me. My C background still holds me back a bit.

Why having 3 different ways to achieve one goal, by the way ?

解决方案

BUT I will still have to "serialize" it, so in the end, I will also have primitives, right ?

Pretty much everything in Java eventually boils down to primitives.

To pass primitives, why should I use a bundle when passing directly in an intent will make it too ?

Either way works. Use whichever makes you feel more comfortable. However, just watch out for collisions on keys (e.g., your activity, and a some base activity of yours that you inherit from, both trying to put the same thing in the same key of the Intent or Bundle).

Why having 3 different ways to achieve one goal, by the way ?

I am going to guess that "one goal" is "to pass data from one activity to another". That involves inter-process communication (IPC), even if the two activities are in the same process, as a core OS process is involved in the routing. For pretty much everything outside of streams from a ContentProvider in standard Android, IPC means that data has to be put into a Parcel, which gets converted into a byte array for passing across the process boundary.

Parcelable represents an interface that can be added to custom classes to allow them to be put into a Parcel.

Bundle is a concrete class that implements Parcelable and represents a HashMap-like structure, but strongly typed to things that are known to be able to go into a Parcel. Bundle is more convenient than a Parcel for developers, in that it offers random access by key, where Parcel does not.

Intent extras are merely a Bundle, for which Intent exposes its own accessor methods.

For all my cases, I should forget about the other possibilities and only use Parcelable ?

AFAIK, what EpicPandaForce was referring to was the comparison between Serializable and Parcelable. Either can go into a Bundle or a Parcel. Of the two, all else being equal, Serializable is slower, because it assumes that the serialized form has to be durable, able to be read in again months or years later. Parcelable assumes that everyone is working off of the same class definition and can bypass some Serializable overhead as a result.

That being said, it's a micro-optimization.

Why are the other still there then ?

Not everything can be made to extend Parcelable, notably java.* classes. Integer, for example, is not Parcelable. Yet, we would like to be able to pass int and Integer values around. Hence, Parcel supports int, as does Bundle.

you mean that I should get it back with the R.blah thing

AFAIK, in that comment, Mr. Marconcini was referring to "id" as a general concept, not referring to R.id values specifically. For example, if you are maintaining an image cache, rather than passing around actual Bitmap objects, pass around some identifier that points back to the cache.

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