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];
    }
};

Solution 1

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.

Solution 2

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.

Solution 3

Any enum is serializable.

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

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

Solution 4

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);
}

Solution 5

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 }

View more solutions