Parcelable其中/当describeContents（）使用？ [英] Parcelable where/when is describeContents() used?

问题描述

有谁知道在哪里/当Parcelable这种方法被称为？

Does anyone know where/when this method of a Parcelable is called?

 @Override
 public int describeContents() {
    return 0;
 }

它已被覆盖。但我应该考虑做一些有用的东西呢？

It has to be overriden. But should I consider doing something useful with it?

推荐答案

有一个在 Parcelable 定义的常量名为 CONTENTS_FILE_DESCRIPTOR 这意味着在 describeContents使用（）以创建位掩码返回值。

There is a constant defined in Parcelable called CONTENTS_FILE_DESCRIPTOR which is meant to be used in describeContents() to create bitmask return value.

说明为 CONTENTS_FILE_DESCRIPTOR 在 API参考是：

位掩码与describeContents（）使用：每一位再presents一种被认为有整理潜力时具有特殊意义的对象

Bit masks for use with describeContents(): each bit represents a kind of object considered to have potential special significance when marshalled.

这实际上意味着：如果你需要把的FileDescriptor 对象为Parcelable你应该/必须指定 CONTENTS_FILE_DESCRIPTOR 作为回报的describeContents（），即通过价值特殊对象（在 describeContents（）的说明）他们真正的意思是：的FileDescriptor 。

Which really means: If you need to put FileDescriptor object into Parcelable you should/must specify CONTENTS_FILE_DESCRIPTOR as return value of describeContents(), i.e. by "special object" (in describeContents()'s description) they really mean: FileDescriptor.

这整个的 Parcelable 功能查看未完成（读：有坏的设计）。还有另外一个奇怪的事情在docs：

This whole Parcelable functionality looks unfinished (read: has bad design). There is one other strange thing in the docs:

类实现Parcelable接口还必须有一个静态的，名为CREATOR，这是实现Parcelable.Creator接口的对象

Classes implementing the Parcelable interface must also have a static field called CREATOR, which is an object implementing the Parcelable.Creator interface

实施细则由人类可读的形式定义的多重继承？ ： - ）

Implementing multiple inheritance by rules defined in human readable form? :-)

这似乎是C ++程序员设计的 Parceable 并在某些时候，他意识到：哦，该死的，没有多重继承在Java中...： - ）

It seems like C++ programmer designed Parceable and at some point he realized: Oh, damn, there is no multiple inheritance in Java... :-)

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