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Android中传递对象的三种方法
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Android中，Activity和Fragment之間傳遞對象，可以通過將對象序列化并存入Bundle或者Intent中進行傳遞，也可以將對象轉化為JSON字符串，進行傳遞。
序列化對象可以使用Java的Serializable的接口、Parcelable接口。轉化成JSON字符串，可以使用Gson等庫。
1.Serializable
Model
public?class?Author?implements?Serializable{????private?int?id;?????private?String?name;?????//...}
public?class?Book?implements?Serializable{????private?String?title;????private?Author?author;????//...}
傳遞數據
??Book?book=new?Book();???book.setTitle("Java編程思想");???Author?author=new?Author();???author.setId(1);???author.setName("Bruce?Eckel");???book.setAuthor(author);???Intent?intent=new?Intent(this,SecondActivity.class);???intent.putExtra("book",book);???startActivity(intent);
接收數據
?Book?book=?(Book)?getIntent().getSerializableExtra("book");?Log.d(TAG,"book?title->"+book.getTitle());?Log.d(TAG,"book?author?name->"+book.getAuthor().getName());
2.轉化為JSON字符串
Model
public?class?Author{????private?int?id;?????private?String?name;?????//...}public?class?Book{????private?String?title;????private?Author?author;????//...}
傳遞數據
Book?book=new?Book();book.setTitle("Java編程思想");Author?author=new?Author();author.setId(1);author.setName("Bruce?Eckel");book.setAuthor(author);Intent?intent=new?Intent(this,SecondActivity.class);intent.putExtra("book",new?Gson().toJson(book));startActivity(intent);
接收數據
String?bookJson=getIntent().getStringExtra("book");Book?book=new?Gson().fromJson(bookJson,Book.class);Log.d(TAG,"book?title->"+book.getTitle());Log.d(TAG,"book?author?name->"+book.getAuthor().getName());
3.使用Parcelable
實現Parcelable接口需要實現兩個方法
除了要實現這兩個方法還必須創建一個Parcelable.Creator接口的實例，用于讀取Parcel容器中的數據
Model
public?class?Author?implements?Parcelable{????private?int?id;?????private?String?name;?????//setter?&?getter...?????@Override????public?int?describeContents()?{?????????return?0;????}?????@Override????public?void?writeToParcel(Parcel?dest,?int?flags)?{????????//該方法將類的數據寫入外部提供的Parcel中.即打包需要傳遞的數據到Parcel容器保存，????????//?以便從parcel容器獲取數據????????dest.writeString(name);????????dest.writeInt(id);?????}????public?static?final?Creator<Author>?CREATOR=new?Creator<Author>()?{????????@Override????????public?Author?createFromParcel(Parcel?source)?{????????????//從Parcel容器中讀取傳遞數據值，封裝成Parcelable對象返回邏輯層。????????????Author?author=new?Author();????????????author.setName(source.readString());????????????author.setId(source.readInt());????????????return?author;????????}?????????@Override????????public?Author[]?newArray(int?size)?{????????????//創建一個類型為T，長度為size的數組，僅一句話（return?new?T[size])即可。方法是供外部類反序列化本類數組使用。????????????return?new?Author[size];????????}????};}
?
public?class?Book?implements?Parcelable{????private?String?title;????private?Author?author;????//setter?&?getter...?????@Override????public?int?describeContents()?{????????return?0;????}?????@Override????public?void?writeToParcel(Parcel?dest,?int?flags)?{????????dest.writeString(title);????????dest.writeParcelable(author,flags);????}????public?static?final?Creator<Book>?CREATOR=new?Creator<Book>()?{????????@Override????????public?Book?createFromParcel(Parcel?source)?{????????????Book?book=new?Book();????????????book.setTitle(source.readString());????????????book.setAuthor(source.<Author>readParcelable(Author.class.getClassLoader()));????????????return?book;????????}?????????@Override????????public?Book[]?newArray(int?size)?{????????????return?new?Book[0];????????}????};}
傳遞數據
Book?book=new?Book();book.setTitle("Java編程思想");Author?author=new?Author();author.setId(1);author.setName("Bruce?Eckel");book.setAuthor(author);Intent?intent=new?Intent(this,SecondActivity.class);intent.putExtra("book",book);startActivity(intent);
接收數據
Book?book=getIntent().getParcelableExtra("book");Log.d(TAG,"book?title->"+book.getTitle());Log.d(TAG,"book?author?name->"+book.getAuthor().getName());
4.性能分析
經過測試，我們得到下圖的效果
可以看出，通過轉換為字符串的速度是最慢的。Seralizable次之，Parcelable比Seralizable快10倍。所以從性能上考 慮，我們必定優先選擇Parcelable。但是Parcelable有大量重復的模板代碼，如何簡化這些操作，將是下面主要講解的內容。
5.簡化Parcel操作
如果你使用android Studio 可以通過安裝android-parcelable-intellij-plugin插件，或者自己配置模板進行操作。
5.1 parceler
除了上面的操作，還有大量的第三方庫來簡化Parcelable操作。當然使用這些庫也許會降低Parcelable的性能。Parceler就是這樣一個庫。
Parceler使用非常簡單，在定義Model時用@Parcel進行注解，在傳遞數據的時候使用Parcels的wrap方法來包裝成一個Parcelable對象。獲取數據時用Parcels的unwrap方法來獲取對象。
Model
@Parcel?public?class?Author?{????int?id;?????String?name;?????//setter?&?getter...}
@Parcelpublic?class?Book?{????String?title;????Author?author;????//setter?&?getter}
傳遞對象
Book?book=new?Book();book.setTitle("Java編程思想");Author?author=new?Author();author.setId(1);author.setName("Bruce?Eckel");book.setAuthor(author);Intent?intent=new?Intent(this,SecondActivity.class);intent.putExtra("book",?Parcels.wrap(book));startActivity(intent);
接收對象
Book?book=?Parcels.unwrap(getIntent().getParcelableExtra("book"));Log.d(TAG,"book?title->"+book.getTitle());Log.d(TAG,"book?author?name->"+book.getAuthor().getName());
除了Parceler之外，還有如auto-parcel,ParcelableCodeGenerator,ParcelableGenerator等第三方庫，這里我將不進行講解，有興趣的朋友，可以自行研究。
轉自：Malinkang's Blog-Android中傳遞對象?
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