android - 如何使用 Intents 将对象从一个 Android Activity 发送到另一个？

Question

How can I pass an object of a custom type from one Activity to another using the putExtra() method of the class Intent?

Answer 1

如果您只是传递对象，那么 Parcelable是为此而设计的。使用它比使用 Java 的 native 序列化需要更多的努力，但它更快(我的意思是，WAY 更快)。

从文档中，如何实现的一个简单示例是:

// simple class that just has one member property as an example
public class MyParcelable implements Parcelable {
    private int mData;

    /* everything below here is for implementing Parcelable */

    // 99.9% of the time you can just ignore this
    @Override
    public int describeContents() {
        return 0;
    }

    // write your object's data to the passed-in Parcel
    @Override
    public void writeToParcel(Parcel out, int flags) {
        out.writeInt(mData);
    }

    // this is used to regenerate your object. All Parcelables must have a CREATOR that implements these two methods
    public static final Parcelable.Creator<MyParcelable> CREATOR = new Parcelable.Creator<MyParcelable>() {
        public MyParcelable createFromParcel(Parcel in) {
            return new MyParcelable(in);
        }

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

    // example constructor that takes a Parcel and gives you an object populated with it's values
    private MyParcelable(Parcel in) {
        mData = in.readInt();
    }
}

请注意，如果您要从给定的 Parcel 中检索多个字段，则必须按照放入它们的顺序(即采用 FIFO 方法)执行此操作。

一旦你的对象实现了Parcelable，只需将它们放入你的Intents与 putExtra() :

Intent i = new Intent();
i.putExtra("name_of_extra", myParcelableObject);

然后你可以用 getParcelableExtra() 把它们拉回来。 :

Intent i = getIntent();
MyParcelable myParcelableObject = (MyParcelable) i.getParcelableExtra("name_of_extra");

如果您的 Object Class 实现 Parcelable 和 Serializable，请确保您确实转换为以下之一:

i.putExtra("parcelable_extra", (Parcelable) myParcelableObject);
i.putExtra("serializable_extra", (Serializable) myParcelableObject);