How to Pass custom object via intent in kotlin

问题

fun launchNextScreen(context: Context, people: People): Intent {
    val intent = Intent(context, NextScreenActivity::class.java)
    intent.putExtra(EXTRA_PEOPLE, (Parcelable) people)
    //intent.putExtra(EXTRA_PEOPLE, people as Parcelable)
    //intent.putExtra(EXTRA_PEOPLE, people)
    // tried above all three ways
    return intent
}

I tried the above code to pass an instance of the People class via intent using kotlin, but I am getting an error. What am I doing wrong?

回答1:

First, make sure the People class implements the Serializable interface:

class People : Serializable {
    // your stuff
}

Inner fields of People class must also implement the Serializable interface, otherwise you'll get runtime error.

Then it should work:

fun launchNextScreen(context: Context, people: People): Intent {
    val intent = Intent(context, NextScreenActivity::class.java)
    intent.putExtra(EXTRA_PEOPLE, people)
    return intent
}

To receive people back from Intent you'll need to call:

val people = intent.getSerializableExtra(EXTRA_PEOPLE) as? People

回答2:

Implement Serializable in the object:

data class Object (
        var param1: Int? = null,
        var param2: String? = null
) : Serializable

class Object : Serializable {
        var param1: Int? = null,
        var param2: String? = null
}

Then, you can pass the object using Intent:

val object = Object()
...
val intent = Intent(this, Activity2::class.java)
intent.putExtra("extra_object", object as Serializable)
startActivity(intent)

Finally, in Activity2 you get the object with:

val object = intent.extras.get("extra_object") as Object

回答3:

Found a better way of doing this:

In your gradle:

apply plugin: 'org.jetbrains.kotlin.android.extensions'

android {
    androidExtensions {
        experimental = true
    }
}

In your data class:

@Parcelize
data class Student(val id: String, val name: String, val grade: String) : Parcelable

In source activity:

val intent = Intent(context, Destination::class.java)
        intent.putExtra("student_id", student)
        context.startActivity(intent)

In destination activity:

student = intent.getParcelableExtra("student_id")

回答4:

`Parcelize` is no longer experimental, as of Kotlin 1.3.60+!

Define a data class, adding @Parcelize annotation and extending Parcelable:

@Parcelize
data class People(val id: String, val name: String) : Parcelable

To add to intent:

val intent = Intent(context, MyTargetActivity::class.java)
intent.putExtra("people_data", student)
context.startActivity(intent)

In MyTargetActivity:

val people: People = intent.getParcelableExtra("people_data")

If you haven't yet, enable extensions in your app's build.gradle. This also enables data binding and other great advanced features

apply plugin: 'kotlin-android-extensions'

回答5:

I found a better way to pass an object from one activity to another using Parcelable, it is faster than Serialization Android: Difference between Parcelable and Serializable?

first, add these lines of code inside build.gradle(app)

I got the answer from here

apply plugin: 'kotlin-android-extensions' in app.grable 

@Parcelize 
class Model(val title: String, val amount: Int) : Parcelable

passing with Intent--->

val intent = Intent(this, DetailActivity::class.java)
intent.putExtra(DetailActivity.EXTRA, model)
startActivity(intent)

Getting from intent --->

val model: Model = intent.getParcelableExtra(EXTRA)

回答6:

This post might be useful for what you intend to do:

Is there a convenient way to create Parcelable data classes in Android with Kotlin?

Basically, kotlin provides some little extras:

@Parcelize
class User(val firstName: String, val lastName: String) : Parcelable

See the post for more info.

回答7:

in kotlin to start activity and pass some data you could try something like this:

startActivity(intentFor<NameOfActivity>(STRING to data))

Have Fun

回答8:

Your People class needs to implement Parcelable like this:

class People(): Parcelable{
// stuff


}

android studio will show you an error. Simple move your cursor to "People" and hit alt+enter. It should now show the option to generate a Parcelable implementation.

This generated code will contain something like

parcel.writeString(member1)
parcel.writeInt(member2)

and somewhere else

member1=parcel.readString()
member2=parcel.readInt()

Make sure that all members are contained in these methods and when modifying it, make sure that read and write is happening in the exact same order.

来源：https://stackoverflow.com/questions/47593205/how-to-pass-custom-object-via-intent-in-kotlin

标签

android

android-intent

kotlin

kotlin-android-extensions