java - 如何在两个 Activity 之间传递类对象？

Question

我有一个类Books.java，它实现一个Book.java列表，并且在MainActivity.java中我用书籍填充了对象库。我想将对象库从 MainActivity.java 发送到 ListActivity.java，但不适用于 i.putExtra。 我该怎么做？

书籍.java

import java.util.ArrayList;
import java.util.List;


public class Books implements DataAggregate <Book>{
private List<Book> books;

public Books(){};

public List<Book> getAll() {
    return this.getBooks();
}

public int size() {
    return this.getBooks().size();
}

public void insert(Book element) {
    this.getBooks().add(element);
}

public void delete(Book element) {
    this.getBooks().remove(element);
}

private List<Book> getBooks() {
    if (books==null){
        books=new ArrayList<Book>();
    }
    return books;
}

}

MainActivity.java

Books library;
for (int i = 0; i<db_books.size(); i++){
       String name = db_books.get(i).getBookName();
       String author = db_books.get(i).getBookAuthor();
       String epc = db_books.get(i).getBookEpc();
       Integer number = db_books.get(i).getNumBooks();
       Book myBook = new Book(name, author, epc, number);
       library.insert(myBook);
}
Intent i = new Intent(getApplicationContext(),ListActivity.class);
i.putExtra("library",library);
startActivity(i);

ListActivity.java

Books library = extras.getString("library");

Book.java

public class Book implements Serializable {

    private String bookName;
    private String bookAuthor;
    private String bookEpc;
    private Integer numBooks;


    public Book(){

    }

    public Book(String bname, String bauthor, String bepc, Integer nbooks){
        this.bookName = bname;
        this.bookAuthor = bauthor;
        this.bookEpc = bepc;
        this.numBooks = nbooks;
    }

    public String getBookName() {
        return bookName;
    }

    public void setBookName(String bookName) {
        this.bookName = bookName;
    }

    public String getBookAuthor() {
        return bookAuthor;
    }

    public void setBookAuthor(String bookAuthor) {
        this.bookAuthor = bookAuthor;
    }

    public String getBookEpc() {
        return bookEpc;
    }

    public void setBookEpc(String bookEpc) {
        this.bookEpc = bookEpc;
    }

    public Integer getNumBooks() {
        return numBooks;
    }

    public void setNumBooks(Integer numBooks) {
        this.numBooks = numBooks;
    }

    public void prettyPrint(){

        Log.d("Book:", this.bookName+" "+this.bookAuthor+" "+this.bookEpc+" "+this.numBooks.toString());
    }
}

Answer 1

而不是

Books library = extras.getString("library");

你应该这样做

Books library = (Books) extras. getSerializableExtra("library");