我有一个名为 Order
的对象,我想在 Activity 之间传递它。目前我正在使用 Parcelable
来执行此操作。
public class Order implements Parcelable {
private String email;
private Long timestamp;
private List<OrderItem> items;
public Order() { }
private Order(Parcel in) {
email = in.readString();
timestamp = in.readLong();
}
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(email);
if (timestamp == null) {
dest.writeByte((byte) 0);
} else {
dest.writeByte((byte) 1);
dest.writeLong(timestamp);
}
dest.writeTypedList(items);
}
@Override
public int describeContents() {
return 0;
}
public static final Creator<Order> CREATOR = new Creator<Order>() {
@Override
public Order createFromParcel(Parcel in) {
return new Order(in);
}
@Override
public Order[] newArray(int size) {
return new Order[size];
}
};
// Getters
...
}
items
字段是实现 Parcelable
接口(interface)的 OrderItem
对象的 List
。
public class OrderItem implements Parcelable {
private String orderedClothingId;
private int quantity;
public OrderItem() { }
public OrderItem(String orderedClothingId, int quantity) {
this.orderedClothingId = orderedClothingId;
this.quantity = quantity;
}
private OrderItem(Parcel in) {
orderedClothingId = in.readString();
quantity = in.readInt();
}
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(orderedClothingId);
dest.writeInt(quantity);
}
@Override
public int describeContents() {
return 0;
}
public static final Creator<OrderItem> CREATOR = new Creator<OrderItem>() {
@Override
public OrderItem createFromParcel(Parcel in) {
return new OrderItem(in);
}
@Override
public OrderItem[] newArray(int size) {
return new OrderItem[size];
}
};
}
现在,要将名为 order
的 Order
对象从一个 Activity 传递到另一个 Activity ,我执行以下操作:
Intent intent = new Intent(mContext, ActivityTwo.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
intent.putExtra(ORDER_DETAIL_INTENT_EXTRA_KEY, order);
mContext.startActivity(intent);
在 ActivityTwo
中,我收集 Order
对象,如下所示:
Bundle data = getIntent().getExtras();
assert data != null;
mOrder = data.getParcelable(ORDER_DETAIL_INTENT_EXTRA_KEY);
但是,当我记录 ActivityTwo
中 Order
对象中包含的 items
字段时,它是 null
。如何在 Activity 之间传递原始非空 Order
对象,而 items
列表不为空?
最佳答案
首先,您错过了使用 dest = in.readTypedList(emptyList, CREATOR); 读回数组
但第二也是更重要的是,您需要写入/读取相同数量的参数,因为您的 writeToParcel 中有一个 if ,因此在读取时您需要相同的参数:
private Order(Parcel in) {
email = in.readString();
if(in.readByte() == 1)
timestamp = in.readLong(); //here to skip just like the writeToParcel
in.readTypedList(items = new ArrayList<OrderItem>(), OrderItem.CREATOR);
}
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(email);
if (timestamp == null) {
dest.writeByte((byte) 0);
} else {
dest.writeByte((byte) 1);
dest.writeLong(timestamp);
}
dest.writeTypedList(items);
}
关于java - 如何使用 Parcelable 在 Activity 之间传递带有其他对象列表的对象?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/47997457/