Pass data between destinations

Navigation lets you attach data to a navigation operation by defining arguments for a destination. For example, a user profile destination might take a user ID argument to determine which user to display.

In general, you should strongly prefer passing only the minimal amount of data between destinations. For example, you should pass a key to retrieve an object rather than passing the object itself, as the total space for all saved states is limited on Android. If you need to pass large amounts of data, use a ViewModel as described in ViewModel overview.

Define destination arguments

To pass data between destinations, first define the argument by adding it to the destination that receives it by following these steps:

1. In the Navigation Editor, click the destination that receives the argument.
2. In the Attributes panel, click Add (+).
3. In the Add Argument Link window that appears, enter the argument name, argument type, whether the argument is nullable, and a default value, if needed.
4. Click Add. Notice that the argument now appears in the Arguments list in the Attributes panel.
5. Next, click the corresponding action that takes you to this destination. In the Attributes panel, you should now see your newly added argument in the Argument Default Values section.

6. You can also see that the argument was added in XML. Click the Text tab to toggle to XML view, and notice that your argument was added to the destination that receives the argument. An example is shown in the following:

    <fragment android:id="@+id/myFragment" >
        <argument
            android:name="myArg"
            app:argType="integer"
            android:defaultValue="0" />
    </fragment>
   

Supported argument types

The Navigation library supports the following argument types:

If an argument type supports null values, you can declare a default value of null by using android:defaultValue="@null".

Routes, deep links, and URIs with their arguments can be parsed from strings. This is not possible using custom data types such as Parcelables and Serializables as seen in the preceding table. To pass around custom complex data, store the data elsewhere such as a ViewModel or database and only pass an identifier while navigating; then retrieve the data in the new location after navigation has concluded.

When you choose one of the custom types, the Select Class dialog appears and prompts you to choose the corresponding class for that type. The Project tab lets you choose a class from your current project.

You can choose <inferred type> to have the Navigation library determine the type based on the provided value.

You can check Array to indicate that the argument should be an array of the selected Type value. Note the following:

• Arrays of enums and arrays of resource references are not supported.
• Arrays support nullable values, regardless of the support for nullable values of the underlying type. For example, using app:argType="integer[]" lets you use app:nullable="true" to indicate that passing a null array is acceptable.
• Arrays support a single default value, "@null". Arrays don't support any other default value.

Override a destination argument in an action

Destination-level arguments and default values are used by all actions that navigate to the destination. If needed, you can override the default value of an argument (or set one if it doesn't already exist) by defining an argument at the action level. This argument must be of the same name and type as the argument declared in the destination.

The following XML declares an action with an argument that overrides the destination-level argument from the preceding example:

<action android:id="@+id/startMyFragment"
    app:destination="@+id/myFragment">
    <argument
        android:name="myArg"
        app:argType="integer"
        android:defaultValue="1" />
</action>

Use Safe Args to pass data with type safety

The Navigation component has a Gradle plugin called Safe Args that generates simple object and builder classes for type-safe navigation and access to any associated arguments. Safe Args is strongly recommended for navigating and passing data, because it ensures type safety.

If you are not using Gradle, you can't use the Safe Args plugin. In these cases, you can use Bundles to directly pass data.

To add Safe Args to your project, include the following classpath in your top level build.gradle file:

buildscript {
    repositories {
        google()
    }
    dependencies {
        def nav_version = "2.8.5"
        classpath "androidx.navigation:navigation-safe-args-gradle-plugin:$nav_version"
    }
}

buildscript {
    repositories {
        google()
    }
    dependencies {
        val nav_version = "2.8.5"
        classpath("androidx.navigation:navigation-safe-args-gradle-plugin:$nav_version")
    }
}

You must also apply one of two available plugins.

To generate Java language code suitable for Java or mixed Java and Kotlin modules, add this line to your app or module's build.gradle file:

plugins {
  id 'androidx.navigation.safeargs'
}

plugins {
    id("androidx.navigation.safeargs")
}

Alternatively, to generate Kotlin code suitable for Kotlin-only modules add:

plugins {
  id 'androidx.navigation.safeargs.kotlin'
}

plugins {
    id("androidx.navigation.safeargs.kotlin")
}

You must have android.useAndroidX=true in your gradle.properties file as per Migrating to AndroidX.

After you've enabled Safe Args, your generated code contains the following type safe classes and methods for each action as well as with each sending and receiving destination.

• A class is created for each destination where an action originates. The name of this class is the name of the originating destination appended with the word "Directions". For example, if the originating destination is a fragment that is named SpecifyAmountFragment, the generated class is called SpecifyAmountFragmentDirections.

  This class has a method for each action defined in the originating destination.

• For each action used to pass the argument, an inner class is created whose name is based on the action. For example, if the action is called confirmationAction, the class is named ConfirmationAction. If your action contains arguments without a defaultValue, then you use the associated action class to set the value of the arguments.

• A class is created for the receiving destination. The name of this class is the name of the destination appended with the word "Args". For example, if the destination fragment is named ConfirmationFragment, the generated class is called ConfirmationFragmentArgs. Use this class's fromBundle() method to retrieve the arguments.

The following example shows you how to use these methods to set an argument and pass it to the navigate() method:

override fun onClick(v: View) {
   val amountTv: EditText = view!!.findViewById(R.id.editTextAmount)
   val amount = amountTv.text.toString().toInt()
   val action = SpecifyAmountFragmentDirections.confirmationAction(amount)
   v.findNavController().navigate(action)
}

@Override
public void onClick(View view) {
   EditText amountTv = (EditText) getView().findViewById(R.id.editTextAmount);
   int amount = Integer.parseInt(amountTv.getText().toString());
   ConfirmationAction action =
           SpecifyAmountFragmentDirections.confirmationAction();
   action.setAmount(amount);
   Navigation.findNavController(view).navigate(action);
}

In the code for the receiving destination, use the getArguments() method to retrieve the bundle and use its contents. When using the -ktx dependencies, Kotlin users can also use the by navArgs() property delegate to access arguments.

val args: ConfirmationFragmentArgs by navArgs()

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    val tv: TextView = view.findViewById(R.id.textViewAmount)
    val amount = args.amount
    tv.text = amount.toString()
}

@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
    TextView tv = view.findViewById(R.id.textViewAmount);
    int amount = ConfirmationFragmentArgs.fromBundle(getArguments()).getAmount();
    tv.setText(amount + "");
}

Use Safe Args with a global action

When using Safe Args with a global action, you must provide an android:id value for your root <navigation> element, as shown in the following example:

<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:app="http://schemas.android.com/apk/res-auto"
            xmlns:tools="http://schemas.android.com/tools"
            xmlns:android="http://schemas.android.com/apk/res/android"
            android:id="@+id/main_nav"
            app:startDestination="@id/mainFragment">

    ...

</navigation>

Navigation generates a Directions class for the <navigation> element that is based on the android:id value. For example, if you have a <navigation> element with android:id=@+id/main_nav, the generated class is called MainNavDirections. All destinations within the <navigation> element have generated methods for accessing all associated global actions using the same methods as described in the previous section.

Pass data between destinations with Bundle objects

If you aren't using Gradle, you can still pass arguments between destinations by using Bundle objects. Create a Bundle object and pass it to the destination using navigate(), as in the following example:

val bundle = bundleOf("amount" to amount)
view.findNavController().navigate(R.id.confirmationAction, bundle)

Bundle bundle = new Bundle();
bundle.putString("amount", amount);
Navigation.findNavController(view).navigate(R.id.confirmationAction, bundle);

In your receiving destination's code, use the getArguments() method to retrieve the Bundle and use its contents:

val tv = view.findViewById<TextView>(R.id.textViewAmount)
tv.text = arguments?.getString("amount")

TextView tv = view.findViewById(R.id.textViewAmount);
tv.setText(getArguments().getString("amount"));

Pass data to the start destination

You can pass data to your app's start destination. First, you must explicitly construct a Bundle that holds the data. Next, use one of the following approaches to pass the Bundle to the start destination:

• If you're creating your NavHost programmatically, call NavHostFragment.create(R.navigation.graph, args), where args is the Bundle that holds your data.
• Otherwise, you can set start destination arguments by calling one of the following overloads of NavController.setGraph():
  • Use the ID of the graph: navController.setGraph(R.navigation.graph, args)
  • Use the graph itself: navController.setGraph(navGraph, args)

To retrieve the data in your start destination, call Fragment.getArguments().

ProGuard considerations

If you are shrinking your code, you need to prevent your Parcelable, Serializable, and Enum class names from being obfuscated as part of the minification process. You can do this in one of two ways:

• Use @Keep annotations.
• Use keepnames rules.

The following subsections outline these approaches.

Use @Keep annotations

The following example adds @Keep annotations to model class definitions:

@Keep class ParcelableArg : Parcelable { ... }

@Keep class SerializableArg : Serializable { ... }

@Keep enum class EnumArg { ... }

@Keep public class ParcelableArg implements Parcelable { ... }

@Keep public class SerializableArg implements Serializable { ... }

@Keep public enum EnumArg { ... }

Use keepnames rules

You can also add keepnames rules to your proguard-rules.pro file, as shown in the following example:

proguard-rules.pro

...

-keepnames class com.path.to.your.ParcelableArg
-keepnames class com.path.to.your.SerializableArg
-keepnames class com.path.to.your.EnumArg

...

Additional resources

To learn more about navigation, consult the following additional resources.

Codelabs

• Learn Jetpack Navigation

Videos

• Android Jetpack: Manage UI navigation with navigation controller (Google I/O '18)