当我尝试使用Parcelable额外传递Intent时，我不断收到NullPointerException。 我有两个可分类的类，author.java和Book.java。作者需要作为Parcelables数组包含在Book中。然后使用Intent将Book对象作为额外传递。
这是代码
import android.os.Parcel;
import android.os.Parcelable;
public class Author implements Parcelable{
public String firstName = null;
public String middleInitial = null;
public String lastName = null;
public Author(String[] authorName){
if(authorName.length == 1){
this.lastName = authorName[0];
}else if(authorName.length == 2){
this.firstName = authorName[0];
this.lastName = authorName[1];
}else if(authorName.length >= 3){
this.firstName = authorName[0];
this.middleInitial = authorName[1];
this.lastName = authorName[2];
}else if(authorName.length == 0){
//nothing needs to be done
}
}
public Author(String firstName, String middleInitial, String lastName){
this.firstName = firstName;
this.middleInitial = middleInitial;
this.lastName = lastName;
}
public Author(Parcel in){
String[] data = new String[3];
in.readStringArray(data);
this.firstName = data[0];
this.middleInitial = data[1];
this.lastName = data[2];
}
public static final Parcelable.Creator<Author> CREATOR = new Parcelable.Creator<Author>() {
public Author createFromParcel(Parcel in) {
return new Author(in);
}
public Author[] newArray(int size) {
return new Author[size];
}
};
@Override
public int describeContents() {
return 0;
}
@Override
public void writeToParcel(Parcel dest, int flags) {
String[] array = new String[3];
array[0] = this.firstName;
array[1] = this.middleInitial;
array[2] = this.lastName;
dest.writeStringArray(array);
}
}
import android.os.Parcel;
import android.os.Parcelable;
public class Book implements Parcelable{
// TODO Modify this to implement the Parcelable interface.
// TODO redefine toString() to display book title and price (why?).
public int id;
public String title;
public String isbn;
public String price;
public Author[] authors;
public Book(int id, String title, Author[] author, String isbn, String price) {
this.id = id;
this.title = title;
this.authors = new Author[author.length];
for(int i = 0; i < author.length; i++){
authors[i] = author[i];
}
this.isbn = isbn;
this.price = price;
}
public Book(Parcel in){
int intdata = in.readInt();
this.id = intdata;
String[] data = new String[3];
in.readStringArray(data);
this.title = data[0];
this.isbn = data[1];
this.price = data[2];
Author[] authorsT = (Author[]) in.readParcelableArray(Author.class.getClassLoader());
this.authors = new Author[authorsT.length];
for(int i = 0; i < authorsT.length; i++){
authors[i] = authorsT[i];
}
}
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];
}
};
@Override
public int describeContents() {
return 0;
}
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeInt(id);
String[] data = new String[3];
data[0] = title;
data[1] = isbn;
data[2] = price;
dest.writeStringArray(data);
if(authors == null){
authors = new Author[1];
}
dest.writeParcelableArray(authors, flags);
}
@Override
public String toString(){
return isbn;
}
}
以下是我发送意图的方式：
Intent result = new Intent();
result.putExtra(BOOK_RESULT_KEY, resultBook);
setResult(RESULT_OK, result);
finish();
并试图获得额外的收益：
Bundle data = getIntent().getExtras();
Book book = (Book)data.getParcelable(AddBookActivity.BOOK_RESULT_KEY);
String a = book.authors[0].lastName;
错误日志表示当我尝试访问对象簿时发生错误：
01-28 18:10:59.248: W/dalvikvm(1334): threadid=1: thread exiting with uncaught exception (group=0xb1a4cba8)
01-28 18:10:59.248: E/AndroidRuntime(1334): FATAL EXCEPTION: main
01-28 18:10:59.248: E/AndroidRuntime(1334): Process: edu.stevens.cs522, PID: 1334
01-28 18:10:59.248: E/AndroidRuntime(1334): java.lang.RuntimeException: Failure delivering result ResultInfo{who=null, request=1, result=-1, data=Intent { (has extras) }} to activity {edu.stevens.cs522/edu.stevens.cs522.BookStoreActivity}: java.lang.NullPointerException
01-28 18:10:59.248: E/AndroidRuntime(1334): at android.app.ActivityThread.deliverResults(ActivityThread.java:3365)
01-28 18:10:59.248: E/AndroidRuntime(1334): at android.app.ActivityThread.handleSendResult(ActivityThread.java:3408)
01-28 18:10:59.248: E/AndroidRuntime(1334): at android.app.ActivityThread.access$1300(ActivityThread.java:135)
01-28 18:10:59.248: E/AndroidRuntime(1334): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1244)
01-28 18:10:59.248: E/AndroidRuntime(1334): at android.os.Handler.dispatchMessage(Handler.java:102)
01-28 18:10:59.248: E/AndroidRuntime(1334): at android.os.Looper.loop(Looper.java:136)
01-28 18:10:59.248: E/AndroidRuntime(1334): at android.app.ActivityThread.main(ActivityThread.java:5017)
01-28 18:10:59.248: E/AndroidRuntime(1334): at java.lang.reflect.Method.invokeNative(Native Method)
01-28 18:10:59.248: E/AndroidRuntime(1334): at java.lang.reflect.Method.invoke(Method.java:515)
01-28 18:10:59.248: E/AndroidRuntime(1334): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
01-28 18:10:59.248: E/AndroidRuntime(1334): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
01-28 18:10:59.248: E/AndroidRuntime(1334): at dalvik.system.NativeStart.main(Native Method)
01-28 18:10:59.248: E/AndroidRuntime(1334): Caused by: java.lang.NullPointerException
01-28 18:10:59.248: E/AndroidRuntime(1334): at edu.stevens.cs522.BookStoreActivity.onActivityResult(BookStoreActivity.java:101)
01-28 18:10:59.248: E/AndroidRuntime(1334): at android.app.Activity.dispatchActivityResult(Activity.java:5423)
01-28 18:10:59.248: E/AndroidRuntime(1334): at android.app.ActivityThread.deliverResults(ActivityThread.java:3361)
01-28 18:10:59.248: E/AndroidRuntime(1334): ... 11 more
有人可以帮助我吗？
更新：以下是resultBook的创建方式：
public boolean onOptionsItemSelected(MenuItem item) {
super.onOptionsItemSelected(item);
// TODO
// SEARCH: return the book details to the BookStore activity
// CANCEL: cancel the search request
switch (item.getItemId()){
case R.id.search:
Book resultBook = searchBook();
Log.e("resulrBook:", resultBook.authors[0].lastName);
Intent result = new Intent();
result.putExtra(BOOK_RESULT_KEY, resultBook);
setResult(RESULT_OK, result);
finish();
case R.id.cancel:
setResult(RESULT_CANCELED, null);
finish();
default:
return
super.onOptionsItemSelected(item);
}
}
public Book searchBook(){
/*
* Search for the specified book.
*/
// TODO Just build a Book object with the search criteria and return that.
EditText editAuthor = (EditText) findViewById(R.id.search_author);
String authorString = editAuthor.getText().toString();
String[] authors = authorString.split(", ");
Author[] authorsArray = new Author[authors.length];
for(int i = 0; i < authors.length; i++){
authorsArray[i] = new Author(authors[i].split(" "));
}
EditText editTitle = (EditText) findViewById(R.id.search_title);
EditText editIsbn = (EditText) findViewById(R.id.search_isbn);
String title = editTitle.getText().toString();
String isbn = editIsbn.getText().toString();
Log.e(title, authorsArray[0].lastName);
Log.e("isbn:", isbn);
Book newBook = new Book(100, title, authorsArray, isbn, "10");
Log.e("Book author:", newBook.authors[0].lastName);
return newBook;
}
}
答案 0 :(得分：3)
问题解决了......
这是一个愚蠢的错误......
我实际上是想在OnActivityResult（）函数中获取传递的额外内容。但是，在该函数中，不应使用getIntent（）来获取子活动返回的意图。您应该直接使用在该函数中作为参数传递的intent：
protected void onActivityResult(int requestCode, int resultCode, Intent intent)
并写下这样的东西来获得额外的可分割：
Bundle data = intent.getExtra();
Book book = (Book)data.getParcelable(PARCELABLE_NAME);
希望它有所帮助。