我如何通过一个自定义类型的对象从一个活动到另一个使用类意图的putExtra()方法?


当前回答

第一个活动:

intent.putExtra("myTag", yourObject);

在你的第二篇文章中:

myCustomObject myObject = (myCustomObject) getIntent().getSerializableExtra("myTag");

别忘了让你的自定义对象Serializable:

public class myCustomObject implements Serializable {
...
}

其他回答

你可以使用putExtra(Serializable..)和getSerializableExtra()方法来传递和检索你的类类型的对象;你必须将你的类标记为Serializable,并确保你所有的成员变量也是Serializable…

您需要将对象序列化为某种字符串表示形式。一种可能的字符串表示是JSON,如果你问我,在android中序列化JSON最简单的方法之一是通过谷歌GSON。

在这种情况下,你只需要输入字符串返回值from (new Gson()).toJson(myObject);并检索字符串值并使用fromJson将其转换回您的对象。

但是,如果您的对象不是非常复杂,那么可能不值得这样做,您可以考虑传递对象的单独值。

public class SharedBooking implements Parcelable{

    public int account_id;
    public Double betrag;
    public Double betrag_effected;
    public int taxType;
    public int tax;
    public String postingText;

    public SharedBooking() {
        account_id = 0;
        betrag = 0.0;
        betrag_effected = 0.0;
        taxType = 0;
        tax = 0;
        postingText = "";
    }

    public SharedBooking(Parcel in) {
        account_id = in.readInt();
        betrag = in.readDouble();
        betrag_effected = in.readDouble();
        taxType = in.readInt();
        tax = in.readInt();
        postingText = in.readString();
    }

    public int getAccount_id() {
        return account_id;
    }
    public void setAccount_id(int account_id) {
        this.account_id = account_id;
    }
    public Double getBetrag() {
        return betrag;
    }
    public void setBetrag(Double betrag) {
        this.betrag = betrag;
    }
    public Double getBetrag_effected() {
        return betrag_effected;
    }
    public void setBetrag_effected(Double betrag_effected) {
        this.betrag_effected = betrag_effected;
    }
    public int getTaxType() {
        return taxType;
    }
    public void setTaxType(int taxType) {
        this.taxType = taxType;
    }
    public int getTax() {
        return tax;
    }
    public void setTax(int tax) {
        this.tax = tax;
    }
    public String getPostingText() {
        return postingText;
    }
    public void setPostingText(String postingText) {
        this.postingText = postingText;
    }
    public int describeContents() {
        // TODO Auto-generated method stub
        return 0;
    }
    public void writeToParcel(Parcel dest, int flags) {
        dest.writeInt(account_id);
        dest.writeDouble(betrag);
        dest.writeDouble(betrag_effected);
        dest.writeInt(taxType);
        dest.writeInt(tax);
        dest.writeString(postingText);

    }

    public static final Parcelable.Creator<SharedBooking> CREATOR = new Parcelable.Creator<SharedBooking>()
    {
        public SharedBooking createFromParcel(Parcel in)
        {
            return new SharedBooking(in);
        }
        public SharedBooking[] newArray(int size)
        {
            return new SharedBooking[size];
        }
    };

}

传递数据:

Intent intent = new Intent(getApplicationContext(),YourActivity.class);
Bundle bundle = new Bundle();
i.putParcelableArrayListExtra("data", (ArrayList<? extends Parcelable>) dataList);
intent.putExtras(bundle);
startActivity(intent);

检索数据:

Bundle bundle = getIntent().getExtras();
dataList2 = getIntent().getExtras().getParcelableArrayList("data");

如果你只是传递对象,那么Parcelable就是为这个设计的。使用它需要比使用Java的本机序列化多一点努力,但它要快得多(我的意思是快得多)。

从文档中,一个简单的例子是如何实现的:

// 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,如果要从给定的Parcel中检索多个字段,则必须按照放入它们的相同顺序(即采用FIFO方法)执行此操作。

一旦你有你的对象实现Parcelable,这只是一个问题,把他们放入你的意图与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");

如果你的对象类实现了Parcelable和Serializable,那么请确保转换为以下类型之一:

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

对于你知道要在应用程序中传递数据的情况,使用“全局变量”(比如静态类)

以下是Dianne Hackborn (hackbod -谷歌安卓软件工程师)对此事的看法:

For situations where you know the activities are running in the same process, you can just share data through globals. For example, you could have a global HashMap<String, WeakReference<MyInterpreterState>> and when you make a new MyInterpreterState come up with a unique name for it and put it in the hash map; to send that state to another activity, simply put the unique name into the hash map and when the second activity is started it can retrieve the MyInterpreterState from the hash map with the name it receives.