实现Parcelable接口

2019独角兽企业重金招聘Python工程师标准>>>

1 官方例子

public class MyParcelable implements Parcelable {private int mData;public int describeContents() {return 0;}public void writeToParcel(Parcel out, int flags) {out.writeInt(mData);}public static final Parcelable.Creator<MyParcelable> CREATOR= new Parcelable.Creator<MyParcelable>() {public MyParcelable createFromParcel(Parcel in) {return new MyParcelable(in);}public MyParcelable[] newArray(int size) {return new MyParcelable[size];}};private MyParcelable(Parcel in) {mData = in.readInt();}}

实现 Parcelable 的两个方法,同时还要实现静态变量CREATOR。

其他入门例子：

http://shri.blog.kraya.co.uk/2010/04/26/android-parcel-data-to-pass-between-activities-using-parcelable-classes/

2 Parcel里面有带classloader的方法可以直接填null，会使用默认的classloader,但是用null会报异常，原因有待查。

3 Parcel的writeValue方法可以写入Object类型的数据。

4 describeContents方法的用处

http://stackoverflow.com/questions/4778834/purpose-of-describecontents-of-parcelable-interface

主要就是用来区分子类的

父类抽象类子类复写describeContents方法

public XiangleTree createFromParcel(Parcel source) {
int description = source.readInt();
switch (description) {
case CATEGORY:
Category category = new Category();
category.setId(source.readString());
category.setLevel(source.readString());
category.setName(source.readString());
category.setParentId(source.readString());
category.setHasCoupon(source.readString());
return category;
case CIRCLE:
Circle circle = new Circle();
circle.setId(source.readString());
circle.setLevel(source.readString());
circle.setName(source.readString());
circle.setParentId(source.readString());
circle.setHasCoupon(source.readString());
return circle;
default:
return null;
}
}

http://stackoverflow.com/questions/4076946/parcelable-where-when-is-describecontents-used

回答者还笑称Parcelable 接口是个C++的程序员设计的，结果发现JAVA中没有多重继承。

5 Parcelable 的CONTENTS_FILE_DESCRIPTOR变量http://stackoverflow.com/questions/4076946/parcelable-where-when-is-describecontents-used

If you need to put FileDescriptor object into Parceable you should/must specify CONTENTS_FILE_DESCRIPTOR as return value of describeContents(),

i.e. by "special object" (indescribeContents()'s description) they really mean: FileDescriptor.

6 Parcelable 的PARCELABLE_WRITE_RETURN_VALUE变量用在writeToParcel (Parcel dest, int flags)方法。flags的值可以是0 or PARCELABLE_WRITE_RETURN_VALUE.

dest是某个方法的返回值such as "Parcelable someFunction()", "void someFunction(out Parcelable)", or "void someFunction(inout Parcelable)"

7 处理list：writeToParcel方法dest.writeTypedList(xxList) createFromParcel方法：source.readTypedList(xxList,XX.CREATOR)，或者参考《树形对象实现parcelable接口》

8 树形对象实现Parcelable 见笔记《树形对象实现parcelable接口》

转载于:https://my.oschina.net/dingbuoyi/blog/61903

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