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:
- In the Navigation Editor, click the destination that receives the argument.
- In the Attributes panel, click Add (+).
- 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.
- Click Add. Notice that the argument now appears in the Arguments list in the Attributes panel.
- 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.
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:
Type | app:argType syntax | Support for default values | Handled by routes | Nullable |
---|---|---|---|---|
Integer | app:argType="integer" | Yes | Yes | No |
Float | app:argType="float" | Yes | Yes | No |
Long | app:argType="long" | Yes - Default values must always end with an 'L' suffix (e.g. "123L"). | Yes | No |
Boolean | app:argType="boolean" | Yes - "true" or "false" | Yes | No |
String | app:argType="string" | Yes | Yes | Yes |
Resource Reference | app:argType="reference" | Yes - Default values must be in the form of "@resourceType/resourceName" (e.g. "@style/myCustomStyle") or "0" | Yes | No |
Custom Parcelable | app:argType="<type>", where <type> is the fully-qualified class name of the Parcelable |
Supports a default value of "@null". Does not support other default values. | No | Yes |
Custom Serializable | app:argType="<type>", where <type> is the fully-qualified class name of the Serializable |
Supports a default value of "@null". Does not support other default values. | No | Yes |
Custom Enum | app:argType="<type>", where <type> is the fully-qualified name of the enum | Yes - Default values must match the unqualified name (e.g. "SUCCESS" to match MyEnum.SUCCESS). | No | No |
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 useapp: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:
Groovy
buildscript { repositories { google() } dependencies { def nav_version = "2.8.2" classpath "androidx.navigation:navigation-safe-args-gradle-plugin:$nav_version" } }
Kotlin
buildscript { repositories { google() } dependencies { val nav_version = "2.8.2" classpath("androidx.navigation:navigation-safe-args-gradle-plugin:$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:
Groovy
plugins { id 'androidx.navigation.safeargs' }
Kotlin
plugins { id("androidx.navigation.safeargs") }
Alternatively, to generate Kotlin code suitable for Kotlin-only modules add:
Groovy
plugins { id 'androidx.navigation.safeargs.kotlin' }
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 calledSpecifyAmountFragmentDirections
.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 namedConfirmationAction
. If your action contains arguments without adefaultValue
, 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 calledConfirmationFragmentArgs
. Use this class'sfromBundle()
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:
Kotlin
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) }
Java
@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.
Kotlin
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() }
Java
@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:
Kotlin
val bundle = bundleOf("amount" to amount) view.findNavController().navigate(R.id.confirmationAction, bundle)
Java
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:
Kotlin
val tv = view.findViewById<TextView>(R.id.textViewAmount) tv.text = arguments?.getString("amount")
Java
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, callNavHostFragment.create(R.navigation.graph, args)
, whereargs
is theBundle
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)
- Use the ID of the graph:
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:
Kotlin
@Keep class ParcelableArg : Parcelable { ... } @Keep class SerializableArg : Serializable { ... } @Keep enum class EnumArg { ... }
Java
@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.