How to Implement Parcelable In Kotlin?

12 minutes read

To implement Parcelable in Kotlin, you need to follow these steps:

  1. Import the necessary Android dependencies: import android.os.Parcel import android.os.Parcelable
  2. Create a Kotlin data class for the object you want to make Parcelable. Ensure that the class implements the Parcelable interface: data class MyObject(val name: String, val age: Int) : Parcelable { // Implement Parcelable methods here }
  3. Implement the writeToParcel() method to write the object's properties to a Parcel: override fun writeToParcel(parcel: Parcel, flags: Int) { parcel.writeString(name) parcel.writeInt(age) }
  4. Implement the describeContents() method and return 0: override fun describeContents(): Int { return 0 }
  5. Implement the CREATOR companion object, which provides a mechanism for creating instances of the Parcelable class from a Parcel: companion object CREATOR : Parcelable.Creator { override fun createFromParcel(parcel: Parcel): MyObject { return MyObject(parcel.readString(), parcel.readInt()) } override fun newArray(size: Int): Array { return arrayOfNulls(size) } }


That's it! Your Kotlin class is now Parcelable, and it can be passed between different components of your Android application using Intent or Bundle objects.


Note: When applying the Parcelable interface to a Kotlin data class, remember to consider potential limitations, such as using nullable types and handling possible null values when reading from and writing to the Parcel.

Best Kotlin Books to Read in December 2024

1
Atomic Kotlin

Rating is 5 out of 5

Atomic Kotlin

2
Kotlin Cookbook: A Problem-Focused Approach

Rating is 4.9 out of 5

Kotlin Cookbook: A Problem-Focused Approach

3
Head First Kotlin: A Brain-Friendly Guide

Rating is 4.8 out of 5

Head First Kotlin: A Brain-Friendly Guide

4
Kotlin in Action

Rating is 4.7 out of 5

Kotlin in Action

5
Kotlin In-Depth: A Guide to a Multipurpose Programming Language for Server-Side, Front-End, Android, and Multiplatform Mobile (English Edition)

Rating is 4.6 out of 5

Kotlin In-Depth: A Guide to a Multipurpose Programming Language for Server-Side, Front-End, Android, and Multiplatform Mobile (English Edition)

6
Kotlin Design Patterns and Best Practices: Build scalable applications using traditional, reactive, and concurrent design patterns in Kotlin, 2nd Edition

Rating is 4.5 out of 5

Kotlin Design Patterns and Best Practices: Build scalable applications using traditional, reactive, and concurrent design patterns in Kotlin, 2nd Edition

7
Kotlin Programming: The Big Nerd Ranch Guide (Big Nerd Ranch Guides)

Rating is 4.4 out of 5

Kotlin Programming: The Big Nerd Ranch Guide (Big Nerd Ranch Guides)

8
Java to Kotlin

Rating is 4.2 out of 5

Java to Kotlin

9
Kotlin Essentials (Kotlin for Developers)

Rating is 4.1 out of 5

Kotlin Essentials (Kotlin for Developers)


How to implement Parcelable in Kotlin when using data classes?

To implement Parcelable in Kotlin when using data classes, you can follow these steps:

  1. Import the required android.os.Parcelable package.
  2. Annotate the data class with @Parcelize.
  3. Ensure that all properties of the data class are Parcelable or supported types.
  4. Implement the Parcelable interface.


Here's an example of how to implement Parcelable in Kotlin for a data class:

1
2
3
4
5
import android.os.Parcelable
import kotlinx.android.parcel.Parcelize

@Parcelize
data class MyDataClass(val name: String, val age: Int) : Parcelable


In the example above, the @Parcelize annotation generates the required code to make MyDataClass parcelable.


How to make a Kotlin class Parcelable if it contains lists or arrays?

To make a Kotlin class Parcelable if it contains lists or arrays, you can follow these steps:


Step 1: Make your class implement the Parcelable interface.

1
2
3
class MyClass: Parcelable {
    // ...
}


Step 2: Implement the describeContents method. This method returns 0; ignore it for now.

1
2
3
override fun describeContents(): Int {
    return 0
}


Step 3: Implement the writeToParcel method. In this method, you need to write each property to the Parcel object.

1
2
3
4
5
override fun writeToParcel(dest: Parcel, flags: Int) {
    dest.writeList(myList)  // Replace myList with your actual list variable
    dest.writeArray(myArray) // Replace myArray with your actual array variable
    // Write other property values if needed
}


Step 4: Create a companion object with a CREATOR field that implements the Parcelable.Creator interface. In the createFromParcel method, read each property from the Parcel.

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
companion object CREATOR : Parcelable.Creator<MyClass> {
    override fun createFromParcel(parcel: Parcel): MyClass {
        val list = parcel.readArrayList(ClassLoader.getSystemClassLoader()) as ArrayList<MyItemType> // Replace MyItemType with the type of items in your list
        val array = parcel.readArray(ClassLoader.getSystemClassLoader()) as Array<MyItemType> // Replace MyItemType with the type of items in your array
        // Read other property values if needed
        return MyClass(list, array) // Replace list and array with the actual properties of your class
    }
    
    override fun newArray(size: Int): Array<MyClass?> {
        return arrayOfNulls(size)
    }
}


Step 5: Ensure that all the properties of your class are either Parcelable themselves or can be written to the Parcel. For example, if your list elements are not Parcelable, you need to make them implement Parcelable or use an alternative approach to serialize/deserialize them.


That's it! Your Kotlin class is now Parcelable, even if it contains lists or arrays.


How to create a Parcelable class in Kotlin?

To create a Parcelable class in Kotlin, follow the steps below:

  1. Add the androidx.parcel.Parcelize annotation to the class you want to make Parcelable.
1
2
3
4
@Parcelize
class MyClass(val name: String, val age: Int) : Parcelable {
    // Class definition
}


  1. Import the necessary dependencies in your build.gradle file.
1
2
3
4
5
implementation 'androidx.core:core-ktx:1.6.0'
implementation 'androidx.appcompat:appcompat:1.3.1'
implementation 'androidx.lifecycle:lifecycle-viewmodel-ktx:2.3.1'
implementation 'androidx.lifecycle:lifecycle-runtime-ktx:2.3.1'
implementation 'org.jetbrains.kotlinx:kotlinx-parcelize:1.7.2'


  1. Implement the Parcelable interface for the Parcelable class.
 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
@Parcelize
class MyClass(val name: String, val age: Int) : Parcelable {
    // Implement the Parcelable interface methods
    override fun describeContents() = 0

    override fun writeToParcel(dest: Parcel, flags: Int) {
        dest.writeString(name)
        dest.writeInt(age)
    }

    companion object CREATOR : Parcelable.Creator<MyClass> {
        override fun createFromParcel(parcel: Parcel): MyClass {
            return MyClass(parcel.readString(), parcel.readInt())
        }

        override fun newArray(size: Int): Array<MyClass?> {
            return arrayOfNulls(size)
        }
    }
}


Note: If you are using Android KTX, you can use the @Parcelize annotation instead of manually implementing the Parcelable interface.


That's it! You have now created a Parcelable class in Kotlin. You can use it to pass data between activities or fragments using Intent or Bundle.


How to implement Parcelable in Kotlin with nested objects?

To implement Parcelable in Kotlin with nested objects, you need to follow these steps:

  1. Import the required classes: import android.os.Parcel import android.os.Parcelable
  2. Create your data class and make it implement the Parcelable interface: data class OuterObject(val name: String, val innerObject: InnerObject) : Parcelable { // ... }
  3. Implement the necessary methods for the Parcelable interface: data class OuterObject(val name: String, val innerObject: InnerObject) : Parcelable { // ... // Parcelable Creator companion object CREATOR : Parcelable.Creator { override fun createFromParcel(parcel: Parcel): OuterObject { return OuterObject(parcel) } override fun newArray(size: Int): Array { return arrayOfNulls(size) } } // Write object's data to the parcel override fun writeToParcel(parcel: Parcel, flags: Int) { parcel.writeString(name) parcel.writeParcelable(innerObject, flags) } // Initialize object from the parcel data private constructor(parcel: Parcel) : this( parcel.readString(), parcel.readParcelable(InnerObject::class.java.classLoader) ) // Describe the kinds of special objects contained in the parcel override fun describeContents(): Int { return 0 } }
  4. Repeat the same steps for the nested object: data class InnerObject(val value: Int) : Parcelable { // ... companion object CREATOR : Parcelable.Creator { override fun createFromParcel(parcel: Parcel): InnerObject { return InnerObject(parcel) } override fun newArray(size: Int): Array { return arrayOfNulls(size) } } override fun writeToParcel(parcel: Parcel, flags: Int) { parcel.writeInt(value) } private constructor(parcel: Parcel) : this(parcel.readInt()) override fun describeContents(): Int { return 0 } }


Now you can use your Parcelable objects in your Kotlin code, and they can be passed between activities or fragments using intents or bundles.


What is the Parcelable.Creator.createFromParcel() method used for in Kotlin?

The Parcelable.Creator.createFromParcel() method in Kotlin is used to create an instance of the Parcelable object by unmarshalling it from a Parcel. It is a required method that needs to be implemented when using the Parcelable interface.


The createFromParcel() method is typically called when the Parcelable object needs to be reconstructed from a Parcel, such as when it is passed between different components of an Android application using the Intent system or when it is persisted and then retrieved later.


The implementation of createFromParcel() should read the values from the Parcel in the same order they were written during the writeToParcel() method. It is responsible for retrieving the data and constructing the object with the appropriate values.


Example:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
class ExampleParcelable : Parcelable {
    /* other code and parcelable implementation */

    companion object CREATOR : Parcelable.Creator<ExampleParcelable> {
        override fun createFromParcel(parcel: Parcel): ExampleParcelable {
            // Read the values from the Parcel and create a new instance of the ExampleParcelable object
            val stringValue = parcel.readString()
            val intValue = parcel.readInt()
            return ExampleParcelable(stringValue, intValue)
        }

        override fun newArray(size: Int): Array<ExampleParcelable?> {
            return arrayOfNulls(size)
        }
    }
}


In this example, the createFromParcel() method reads the String and Int values from the Parcel using the appropriate methods like readString() and readInt(). It then constructs a new instance of the ExampleParcelable object with the retrieved values and returns it.

Facebook Twitter LinkedIn Telegram Whatsapp Pocket

Related Posts:

In Kotlin, passing mutable lists of objects via intents allows you to share the list data between different activities or components in your Android application. Here&#39;s how you can achieve this:Create your custom object class: Begin by creating a custom ob...
To call a Kotlin function from JavaScript, you can use the Kotlin/JS plugin that allows you to compile Kotlin code to JavaScript. First, define your Kotlin function in a Kotlin file using the external keyword to tell the Kotlin compiler that this function will...
To run Kotlin on Ubuntu, you can follow these steps:Install Java Development Kit (JDK): Since Kotlin runs on the Java Virtual Machine (JVM), you need to have Java installed on your system. Open a terminal and run the following command to install the default JD...
To use a Kotlin function in Java, you can follow these steps:Create a Kotlin function that you want to use in Java. For example, let&#39;s consider a simple function named printMessage() that prints a message. fun printMessage() { println(&#34;Hello, world...
Working with Android extensions in Kotlin allows you to leverage the power of Kotlin&#39;s extension functions to easily enhance the functionality of Android classes. Here&#39;s how you can work with Android extensions in Kotlin.To create an Android extension,...
The Kotlin Standard Library functions are a collection of commonly used extension functions and top-level functions provided by the Kotlin programming language. These functions aim to simplify and enhance the development process by offering a set of utility fu...