Passing enum or object through an intent (the best solution)

Question

I have an activity that when started needs access to two different ArrayLists. Both Lists are different Objects I have created myself.

Basically I need a way to pa

Answer 1

I think your best bet is going to be to convert those lists into something parcelable such as a string (or map?) to get it to the Activity. Then the Activity will have to convert it back to an array.

Implementing custom parcelables is a pain in the neck IMHO so I would avoid it if possible.

Answer 2

If you just want to send an enum you can do something like:

First declare an enum containing some value(which can be passed through intent):

 public enum MyEnum {
    ENUM_ZERO(0),
    ENUM_ONE(1),
    ENUM_TWO(2),
    ENUM_THREE(3);
    private int intValue;

    MyEnum(int intValue) {
        this.intValue = intValue;
    }

    public int getIntValue() {
        return intValue;
    }

    public static MyEnum getEnumByValue(int intValue) {
        switch (intValue) {
            case 0:
                return ENUM_ZERO;
            case 1:
                return ENUM_ONE;
            case 2:
                return ENUM_TWO;
            case 3:
                return ENUM_THREE;
            default:
                return null;
        }
    }
}

Then:

  intent.putExtra("EnumValue", MyEnum.ENUM_THREE.getIntValue());

And when you want to get it:

  NotificationController.MyEnum myEnum = NotificationController.MyEnum.getEnumByValue(intent.getIntExtra("EnumValue",-1);

Piece of cake!

Answer 3

It may be possible to make your Enum implement Serializable then you can pass it via the Intent, as there is a method for passing it as a serializable. The advice to use int instead of enum is bogus. Enums are used to make your code easier to read and easier to maintain. It would a large step backwards into the dark ages to not be able to use Enums.

Answer 4

Use Kotlin Extension Functions

inline fun <reified T : Enum<T>> Intent.putExtra(enumVal: T, key: String? = T::class.qualifiedName): Intent =
    putExtra(key, enumVal.ordinal)

inline fun <reified T: Enum<T>> Intent.getEnumExtra(key: String? = T::class.qualifiedName): T? =
    getIntExtra(key, -1)
        .takeUnless { it == -1 }
        ?.let { T::class.java.enumConstants[it] }

This gives you the flexibility to pass multiple of the same enum type, or default to using the class name.

// Add to gradle
implementation "org.jetbrains.kotlin:kotlin-reflect:$kotlin_version"

// Import the extension functions
import path.to.my.kotlin.script.putExtra
import path.to.my.kotlin.script.getEnumExtra

// To Send
intent.putExtra(MyEnumClass.VALUE)

// To Receive
val result = intent.getEnumExtra<MyEnumClass>()

Answer 5

Consider Following enum ::

public static  enum MyEnum {
    ValueA,
    ValueB
}

For Passing ::

 Intent mainIntent = new Intent(this,MyActivity.class);
 mainIntent.putExtra("ENUM_CONST", MyEnum.ValueA);
 this.startActivity(mainIntent);

To retrieve back from the intent/bundle/arguments ::

 MyEnum myEnum = (MyEnum) intent.getSerializableExtra("ENUM_CONST");

Answer 6

You can make your enum implement Parcelable which is quite easy for enums:

public enum MyEnum implements Parcelable {
    VALUE;


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

    @Override
    public void writeToParcel(final Parcel dest, final int flags) {
        dest.writeInt(ordinal());
    }

    public static final Creator<MyEnum> CREATOR = new Creator<MyEnum>() {
        @Override
        public MyEnum createFromParcel(final Parcel source) {
            return MyEnum.values()[source.readInt()];
        }

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

You can then use Intent.putExtra(String, Parcelable).

UPDATE: Please note wreckgar's comment that enum.values() allocates a new array at each call.

UPDATE: Android Studio features a live template ParcelableEnum that implements this solution. (On Windows, use Ctrl+J)