How to read and write Enum into parcel on Android?

Question

Here is my model class:

public enum Action {
    RETRY, SETTINGS
}

private int imageId;
private String description;
private String actionName;
private Action action;

public NetworkError(int imageId, String description, String actionName, Action action ) {
    this.imageId = imageId;
    this.description = description;
    this.actionName = actionName;
    this.action = action;
}

public int getImageId() {
    return imageId;
}

public void setImageId(int imageId) {
    this.imageId = imageId;
}

public String getDescription() {
    return description;
}

public void setDescription(String description) {
    this.description = description;
}

public String getActionName() {
    return actionName;
}

public void setActionName(String actionName) {
    this.actionName = actionName;
}


@Override
public int describeContents() {
    return 0;
}

@Override
public void writeToParcel(Parcel dest, int flags) {
    dest.writeInt(this.imageId);
    dest.writeString(this.description);
    dest.writeString(this.actionName);
}

protected NetworkError(Parcel in) {
    this.imageId = in.readInt();
    this.description = in.readString();
    this.actionName = in.readString();
}

public static final Parcelable.Creator<NetworkError> CREATOR = new Parcelable.Creator<NetworkError>() {
    @Override
    public NetworkError createFromParcel(Parcel source) {
        return new NetworkError(source);
    }

    @Override
    public NetworkError[] newArray(int size) {
        return new NetworkError[size];
    }
};

Enums are `Serializable`. – CommonsWare Jul 03 '16 at 22:47 — CommonsWare, Jul 03 '16 at 22:47
http://www.parcelabler.com/ – tachyonflux Jul 03 '16 at 23:04 — tachyonflux, Jul 03 '16 at 23:04
have you tried `dest.writeValue()` – EpicPandaForce Sep 15 '16 at 12:33 — EpicPandaForce, Sep 15 '16 at 12:33

score 88 · Answer 1 · edited Sep 15 '16 at 12:11

88

I had similar problem and my solution was:

parcel.writeString(this.questionType.name());

and for reading :

this.questionType = QuestionType.valueOf(parcel.readString());

QuestionType is enum and remember that ordering of elements matters.

edited Sep 15 '16 at 12:11

Navoneel Talukdar

4,393
5
21
42

answered Sep 07 '16 at 08:26

milosnkb

1,523
12
15

Perfect Answer :) – Neo Apr 25 '20 at 14:09

score 46 · Answer 2 · answered Jan 31 '18 at 02:08

46

The most efficient - memory efficient - bundle is created by using the ENUM ordinal value.

Writing to Parcel dest.writeInt(enum_variable.ordinal());

Reading from parcel enum_variable = EnumName.values()[in.readInt()];

This should be fine unless you don't heed the documentation's admonitions:

Parcel is not a general-purpose serialization mechanism. This class (and the corresponding Parcelable API for placing arbitrary objects into a Parcel) is designed as a high-performance IPC transport. As such, it is not appropriate to place any Parcel data in to persistent storage: changes in the underlying implementation of any of the data in the Parcel can render older data unreadable.

In other words, you shouldn't pass Parcels between code versions because it may not work.

answered Jan 31 '18 at 02:08

Brendon Whateley

1,302
13
22

3

I can already see the people aggressively upvoting the `string` answer over this `ordinal` answer, because normally you're always discouraged from using `.ordinal()`, but given the caveat you mentioned, this is one of the acceptable use cases – avalancha Jan 23 '20 at 10:30
Yes, you have to be aware of the restrictions of Parcels. Personally try to use Protobufs as much as possible because they work in golang, kotlin, java, dart, etc. This means I don't have to deal with several different ways of packing and unpacking the same data. (Still no "Correct Answer" maked for this...) – Brendon Whateley Jan 24 '20 at 00:43

score 35 · Answer 3 · answered Oct 27 '17 at 15:46

35

Any enum is serializable.

You can do this in writeToParcel(): dest.writeSerializable(action)

And in the constructor: action = (Action) in.readSerializable()

answered Oct 27 '17 at 15:46

Geekarist

787
9
8

7

This is the easiest solution to implement but considering `serializable` interface is much slower than `parcelable`, I wonder if this has any effect on performance compared to the answers below where you cast the `enum` to a more primitive type. – mcy Nov 22 '17 at 14:31

score 5 · Answer 4 · answered Sep 15 '16 at 10:58

Enum decleration:

public enum Action {

    NEXT(1),
    OK(2);

    private int action;

    Action(int action) {
        this.action = action;
    }

}

Reading from Parcel:

protected ActionParcel(Parcel in) {
    int actionTmp = in.readInt();
    action = Tutorials.Action.values()[actionTmp];
}

Writing to parcel:

public void writeToParcel(Parcel dest, int flags) {
    int actionTmp = action == null ? -1 : action.ordinal();
    dest.writeInt(actionTmp);
}

Don't know why other methods were throwing exceptions. This method worked for me. — Dushyant Suthar, Dec 06 '19 at 16:10

score 5 · Answer 5 · answered Sep 20 '21 at 14:22

Now, you can write something like this using Kotlin Parcelize:

import android.os.Parcelable
import kotlinx.parcelize.Parcelize

@Parcelize
class NetworkError(
    var imageId: Int,
    var description: String,
    var actionName: String,
    private val action: Action
): Parcelable {

    @Parcelize
    enum class Action: Parcelable {
        RETRY, SETTINGS
    }
}

score 3 · Answer 6 · answered Jan 02 '20 at 12:23

Sample Kotlin-Code (null-safe):

writeInt(action?.ordinal ?: -1)

action = readInt().let { if (it >= 0) enumValues<MyEnum>()[it] else null }

Which can be encapsulated in a write/readEnum Methods as extensions to Parcel:

fun <T : Enum<T>> Parcel.writeEnum(value: T?) = 
    writeInt(value?.ordinal ?: -1)

inline fun <reified T : Enum<T>> Parcel.readEnum(): T? = 
    readInt().let { if (it >= 0) enumValues<T>()[it] else null }

score 2 · Answer 7 · answered Oct 10 '18 at 19:41

One way to do this is to write Actions in integer and read them properly as integer and convert them into Action. What I mean:

@Override
public void writeToParcel(Parcel dest, int flags) {
    dest.writeInt(this.imageId);
    dest.writeString(this.description);
    dest.writeString(this.actionName);

    int actionAsInt = action == Action.RETRY ? 1 : 0;
    dest.writeInt(actionAsInt);
}

protected NetworkError(Parcel in) {
    this.imageId = in.readInt();
    this.description = in.readString();
    this.actionName = in.readString();

    int actionAsInt = in.readInt();
    this.action = actionAsInt == 1 ? Action.RETRY : Action.SETTINGS;
}

Try it. Success ...

score 1 · Answer 8 · answered Aug 16 '21 at 05:59

1

Read parcel

action = Nav.valueOf(in.readString());

Write parcel

out.writeString(action.name());

answered Aug 16 '21 at 05:59

Googlian

6,077
3
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44

score 0 · Answer 9 · answered Dec 09 '21 at 14:42

0

Have you tried like this

@Parcelize enum class State {
    ON, OFF
}

@Parcelize
class PowerSwitch(var state: State) : Parcelable

Let me know it work for you or not?

answered Dec 09 '21 at 14:42

Sushant Gosavi

3,647
3
35
55

score 0 · Answer 10 · answered Apr 19 '22 at 21:12

Using the fact that enums are serializeable

My enum:

public enum HouseEnum {
    GRYFFINDOR, HUFFLEPUFF, RAVENCLAW, SLYTHERIN
}

When placing in bundle:

args.putSerializable(HOUSE, houseEnum);

When retrieving from bundle:

houseEnum = (HouseEnum) getArguments().getSerializable(HOUSE);

How to read and write Enum into parcel on Android?

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