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 pass these objects to the activity from an Intent   I can use addExtras   but this requires a Parceable compatible class   I could make my classes to be passed serializable but as I understand this slows down the program  What are my options  Can I pass an Enum  As an aside  is there a way to pass parameters to an Activity Constructor from an Intent

User · Answer

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)

User · Answer

If you really need to  you could serialize an enum as a String  using name   and valueOf String   as follows    class Example implements Parcelable       public enum Foo   BAR  BAZ       public Foo fooValue      public void writeToParcel Parcel dest  int flags          parcel writeString fooValue    null   null   fooValue name              public static final Creator lt Example gt  CREATOR   new Creator lt Example gt           public Example createFromParcel Parcel source                   Example e   new Example           String s   source readString            if  s    null  e fooValue   Foo valueOf s          return e                   This obviously doesn t work if your enums have mutable state  which they shouldn t  really

User · Answer

You can pass an enum through as a string   public enum CountType       ONE      TWO      THREE    private CountType count  count   ONE   String countString   count name     CountType countToo   CountType valueOf countString     Given strings are supported you should be able to pass the value of the enum around with no problem

User · Answer

Don t use enums   Reason  78 to not use enums      Use integers  which can easily be remoted through Bundle and Parcelable

User · Answer

For passing an enum by intent  you can convert enum into integer   Ex   public enum Num A  B    Sending enum to integer    Num send   Num A  intent putExtra  TEST   send ordinal       Receiving integer to enum    Num rev  int temp   intent getIntExtra  TEST   -1   if temp  gt   0  amp  amp  temp  lt  Num values   length      rev   Num values   temp     Best regards

User · Answer

Most of the answers that are using Parcelable concept here are in Java code  It is easier to do it in Kotlin    Just annotate your enum class with   Parcelize and implement Parcelable interface    Parcelize enum class ViewTypes   Parcelable   TITLE  PRICES  COLORS  SIZES

User · Answer

This is an old question  but everybody fails to mention that Enums are actually Serializable and therefore can perfectly be added to an Intent as an extra  Like this   public enum AwesomeEnum     SOMETHING  OTHER     intent putExtra  AwesomeEnum   AwesomeEnum SOMETHING    AwesomeEnum result    AwesomeEnum  intent getSerializableExtra  AwesomeEnum      The suggestion to use static or application-wide variables is a really bad idea  This really couples your activities to a state managing system  and it is hard to maintain  debug and problem bound      ALTERNATIVES   A good point was noted by tedzyc about the fact that the solution provided by Oderik gives you an error  However  the alternative offered is a bit cumbersome to use  even using generics    If you are really worried about the performance of adding the enum to an Intent I propose these alternatives instead   OPTION 1   public enum AwesomeEnum     SOMETHING  OTHER    private static final String name   AwesomeEnum class getName      public void attachTo Intent intent        intent putExtra name  ordinal           public static AwesomeEnum detachFrom Intent intent        if  intent hasExtra name   throw new IllegalStateException        return values   intent getIntExtra name  -1            Usage      Sender usage AwesomeEnum SOMETHING attachTo intent      Receiver usage AwesomeEnum result   AwesomeEnum detachFrom intent     OPTION 2   generic  reusable and decoupled from the enum   public final class EnumUtil       public static class Serializer lt T extends Enum lt T gt  gt  extends Deserializer lt T gt            private T victim           SuppressWarnings  unchecked            public Serializer T victim                super  Class lt T gt   victim getClass                 this victim   victim                    public void to Intent intent                intent putExtra name  victim ordinal                         public static class Deserializer lt T extends Enum lt T gt  gt            protected Class lt T gt  victimType          protected String name          public Deserializer Class lt T gt  victimType                this victimType   victimType              this name   victimType getName                      public T from Intent intent                if   intent hasExtra name   throw new IllegalStateException                return victimType getEnumConstants   intent getIntExtra name  -1                        public static  lt T extends Enum lt T gt  gt  Deserializer lt T gt  deserialize Class lt T gt  victim            return new Deserializer lt T gt  victim             public static  lt T extends Enum lt T gt  gt  Serializer lt T gt  serialize T victim            return new Serializer lt T gt  victim             Usage      Sender usage EnumUtil serialize AwesomeEnum Something  to intent      Receiver usage AwesomeEnum result    EnumUtil deserialize AwesomeEnum class  from intent     OPTION 3  with Kotlin    It s been a while  but since now we have Kotlin  I thought I would add another option for the new paradigm  Here we can make use of extension functions and reified types  which retains the type when compiling    inline fun  lt reified T   Enum lt T gt  gt  Intent putExtra victim  T   Intent       putExtra T  class java name  victim ordinal   inline fun  lt reified T  Enum lt T gt  gt  Intent getEnumExtra    T        getIntExtra T  class java name  -1           takeUnless   it    -1             let   T  class java enumConstants it      There are a few benefits of doing it this way     We don t require the  overhead  of an intermediary object to do the serialization as it s all done in place thanks to inline which will replace the calls with the code inside the function  The functions are more familiar as they are similar to the SDK ones  The IDE will autocomplete these functions which means there is no need to have previous knowledge of the utility class    One of the downsides is that  if we change the order of the Emums  then any old reference will not work  This can be an issue with things like Intents inside pending intents as they may survive updates  However  for the rest of the time  it should be ok   It s important to note that other solutions  like using the name instead of the position  will also fail if we rename any of the values  Although  in those cases  we get an exception instead of the incorrect Enum value   Usage      Sender usage intent putExtra AwesomeEnum SOMETHING     Receiver usage val result   intent getEnumExtra lt AwesomeEnum gt

User · Answer

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

User · Answer

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

User · Answer

you can use enum constructor for enum to have primitive data type    public enum DaysOfWeek       MONDAY 1       TUESDAY 2       WEDNESDAY 3       THURSDAY 4       FRIDAY 5       SATURDAY 6       SUNDAY 7        private int value      private DaysOfWeek int value            this value   value             public int getValue             return this value             private static final SparseArray lt DaysOfWeek gt  map   new SparseArray lt DaysOfWeek gt          static                for  DaysOfWeek daysOfWeek   DaysOfWeek values                  map put daysOfWeek value  daysOfWeek              public static DaysOfWeek from int value            return map get value             you can use to pass int as extras then pull it from enum using its value

User · Answer

I like simple     The Fred activity has two modes -- HAPPY and SAD  Create a static IntentFactory that creates your Intent for you  Pass it the Mode you want  The IntentFactory uses the name of the Mode class as the name of the extra  The IntentFactory converts the Mode to a String using name   Upon entry into onCreate use this info to convert back to a Mode  You could use ordinal   and Mode values   as well  I like strings because I can see them in the debugger   public class Fred extends Activity        public static enum Mode           HAPPY          SAD                       public void onCreate Bundle savedInstanceState            super onCreate savedInstanceState           setContentView R layout betting           Intent intent   getIntent            Mode mode   Mode valueOf getIntent   getStringExtra Mode class getName              Toast makeText this   mode   mode toString    Toast LENGTH LONG  show               public static Intent IntentFactory Context context  Mode mode           Intent intent   new Intent            intent setClass context Fred class           intent putExtra Mode class getName   mode name              return intent

User · Answer

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

User · Answer

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

User · Answer

Use Kotlin Extension Functions  inline fun  lt reified T   Enum lt T gt  gt  Intent putExtra enumVal  T  key  String    T  class qualifiedName   Intent       putExtra key  enumVal ordinal   inline fun  lt reified T  Enum lt T gt  gt  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 lt MyEnumClass gt

User · Answer

about Oderik s post   You can make your enum implement Parcelable which is quite easy for enums  public enum MyEnum implements Parcelable         You can than use Intent putExtra String  Parcelable    If you define a MyEnum variable myEnum  then do intent putExtra  quot Parcelable1 quot   myEnum   you will get a  quot The method putExtra String  Parcelable  is ambiguous for the type Intent quot  error message  because there is also a Intent putExtra String  Parcelable  method  and original  Enum  type itself implements the Serializable interface  so compiler does not know choose which method intent putExtra String  Parcelable or Serializable    Suggest that remove the Parcelable interface from MyEnum  and move the core code into wrap class  Parcelable implementation  like this Father2 is a Parcelable and contain an enum field   public class Father2 implements Parcelable    AnotherEnum mAnotherEnum  int mField   public Father2 AnotherEnum myEnum  int field        mAnotherEnum   myEnum      mField   field     private Father2 Parcel in        mField   in readInt        mAnotherEnum   AnotherEnum values   in readInt        public static final Parcelable Creator lt Father2 gt  CREATOR   new Parcelable Creator lt Father2 gt           public Father2 createFromParcel Parcel in            return new Father2 in               Override     public Father2   newArray int size            return new Father2 size               Override public int describeContents         return 0      Override public void writeToParcel Parcel dest  int flags        dest writeInt mField       dest writeInt mAnotherEnum ordinal           then we can do  AnotherEnum anotherEnum   AnotherEnum Z  intent putExtra  quot Serializable2 quot   AnotherEnum X      intent putExtra  quot Parcelable2 quot   new Father2 AnotherEnum X  7

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

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