Android 意图仅在startAtivityForResult时返回部分对象

我得给书和作者上课。和book类包含一个author数组。我使用startActivityForResult从主活动开始添加书本活动。在子活动中，我构建了一个author数组，并确保它包含刚刚初始化的author对象。然后把它传回去。代码如下：

Log.d("djdjdjjdjdjdjdjdjdj", authors[0].firstName);//could display the firstName;

intent.putExtra("book", new Book(title, authors, isbn, price));
setResult(Activity.RESULT_OK,intent);
finish();

在这种情况下，LogCat可以显示第一个名称

protected void onActivityResult(int requestCode, int resultCode,
        Intent intent) {
    super.onActivityResult(requestCode, resultCode, intent);
    if(requestCode == ADD_REQUEST) {
        if (resultCode == RESULT_OK) {
            Bundle data = intent.getExtras();
            Book book = (Book) data.getParcelable("book");
            Log.d("JJJJJJJJJJJJ", book.getTitle());//could display the title;
            Log.d("UUUUUUUUUUUU", book.getAuthors()[0].firstName);//NullPointerException: Attempt to read from null array;
            shoppingCart.add(book);
            viewHolderAdapter.notifyDataSetChanged();
        }
    }
}

当返回到主活动并提取图书对象时，它包含标题但不包含作者数组。为什么？ 这是图书课：

public class Book implements Parcelable{

public String title;
public Author[] authors;
public String isbn;
public String price;

public Book(String title, Author[] authors, String isbn, String price) {

    this.title = title;
    this.authors = authors;
    this.isbn = isbn;
    this.price = price;
}
public String getTitle()
{
    return title;
}
public Author[] getAuthors()
{
    return authors;
}
public String getIsbn()
{
    return isbn;
}
public String getPrice()
{
    return price;
}

public int describeContents(){
    return 0;
}

public Book(Parcel in)
{
    Parcelable[] parcelableArray =
            in.readParcelableArray(Author.class.getClassLoader());
    Author[] authors = null;
    if (parcelableArray != null) {
        authors = Arrays.copyOf(parcelableArray, parcelableArray.length, Author[].class);
    }

    this.title = in.readString();
    this.isbn = in.readString();
    this.price = in.readString();
}

public void writeToParcel(Parcel dest, int flags) {
    dest.writeParcelableArray(authors, flags);
    dest.writeString(title);
    dest.writeString(isbn);
    dest.writeString(price);
}

private void readFromParcel(Parcel in) {
    authors = in.createTypedArray(Author.CREATOR);
    title = in.readString();
    isbn = in.readString();
    price = in.readString();
}

public static final Parcelable.Creator<Book> CREATOR
        = new Parcelable.Creator<Book>() {
    public Book createFromParcel(Parcel in) {
        return new Book(in);
    }

    public Book[] newArray(int size) {
        return new Book[size];
    }
};
}

---

提前感谢。

请看一看《类构造函数：

Parcelable[] parcelableArray =
        in.readParcelableArray(Author.class.getClassLoader());
Author[] authors = null;
if (parcelableArray != null) {
    authors = Arrays.copyOf(parcelableArray, parcelableArray.length, Author[].class);
}

您已经创建了authors变量，为其分配了null，并将解析后的数组复制到该变量中。但您应该使用assing Book类变量

---

只需删除字符串Author[]authors=null；您的代码也会很好地工作。

我设法用另一个解决方案回答我自己的问题。。。 我只是替换：

Parcelable[] parcelableArray =
    in.readParcelableArray(Author.class.getClassLoader());
Author[] authors = null;
if (parcelableArray != null) {
    authors = Arrays.copyOf(parcelableArray, parcelableArray.length, Author[].class);
}

与：

并替换：

dest.writeParcelableArray(authors, flags);

与：

---

把你的书贴在课堂上

dest.writeParcelableArray(authors, flags);

dest.writeTypedArray(authors, flags);