问题
I'm using Android Studio 3.2 Canary 14 and The Navigation Architecture Component. With this you can define transition animations pretty much as you would when using Intents.
But the animations are set as properties of the actions in the navigation graph, like so:
<fragment
android:id="@+id/startScreenFragment"
android:name="com.example.startScreen.StartScreenFragment"
android:label="fragment_start_screen"
tools:layout="@layout/fragment_start_screen" >
<action
android:id="@+id/action_startScreenFragment_to_findAddressFragment"
app:destination="@id/findAddressFragment"
app:enterAnim="@animator/slide_in_right"
app:exitAnim="@animator/slide_out_left"
app:popEnterAnim="@animator/slide_in_left"
app:popExitAnim="@animator/slide_out_right"/>
</fragment>
This gets tedious to define for all actions in the graph!
Is there a way to define a set of animations as default, on actions?
I've had no luck using styles for this.
回答1:
R.anim has the default animations defined (as final):
nav_default_enter_animnav_default_exit_animnav_default_pop_enter_animnav_default_pop_exit_anim
in order to change this behavior, you would have to use custom NavOptions,
because this is where those animation are being assigned to a NavAction.
one can assign these with the NavOptions.Builder:
protected NavOptions getNavOptions() {
NavOptions navOptions = NavOptions.Builder()
.setEnterAnim(R.anim.default_enter_anim)
.setExitAnim(R.anim.default_exit_anim)
.setPopEnterAnim(R.anim.default_pop_enter_anim)
.setPopExitAnim(R.anim.default_pop_exit_anim)
.build();
return navOptions;
}
most likely one would need to create a DefaultNavFragment, which extends class androidx.navigation.fragment (the documentation there does not seem completed yet).
So you can pass these NavOptions to the NavHostFragment like this:
NavHostFragment.findNavController(this).navigate(R.id.you_action_id, null, getNavOptions());
alternatively... when looking at the attrs.xml of that package; these animations are style-able:
<resources>
<declare-styleable name="NavAction">
<attr name="enterAnim" format="reference"/>
<attr name="exitAnim" format="reference"/>
<attr name="popEnterAnim" format="reference"/>
<attr name="popExitAnim" format="reference"/>
...
</declare-styleable>
</resources>
this means, one can define the according styles - and define these, as part of the theme...
one can define them in styles.xml:
<style name="Theme.Default" parent="Theme.AppCompat.Light.NoActionBar">
<!-- these should be the correct ones -->
<item name="NavAction_enterAnim">@anim/default_enter_anim</item>
<item name="NavAction_exitAnim">@anim/default_exit_anim</item>
<item name="NavAction_popEnterAnim">@anim/default_pop_enter_anim</item>
<item name="NavAction_popExitAnim">@anim/default_pop_exit_anim</item>
</style>
回答2:
As said, R.anim has the default animations defined:
nav_default_enter_anim
nav_default_exit_anim
nav_default_pop_enter_anim
nav_default_pop_exit_anim
But you can easily override them.
Just create your own four anim resources with the same names in your app module (just to clarify, the id of one of them is your.package.name.R.anim.nav_default_enter_anim) and write what animation you'd like.
回答3:
It is possible with custom androidx.navigation.fragment.Navigator.
I will demonstrate how to override fragment navigation. Here is our custom navigator. Pay attention to setAnimations() method
@Navigator.Name("fragment")
class MyAwesomeFragmentNavigator(
private val context: Context,
private val manager: FragmentManager, // Should pass childFragmentManager.
private val containerId: Int
): FragmentNavigator(context, manager, containerId) {
private val backStack by lazy {
this::class.java.superclass!!.getDeclaredField("mBackStack").let {
it.isAccessible = true
it.get(this) as ArrayDeque<Integer>
}
}
override fun navigate(destination: Destination, args: Bundle?, navOptions: NavOptions?, navigatorExtras: Navigator.Extras?): NavDestination? {
if (manager.isStateSaved) {
logi("Ignoring navigate() call: FragmentManager has already"
+ " saved its state")
return null
}
var className = destination.className
if (className[0] == '.') {
className = context.packageName + className
}
val frag = instantiateFragment(context, manager,
className, args)
frag.arguments = args
val ft = manager.beginTransaction()
navOptions?.let { setAnimations(it, ft) }
ft.replace(containerId, frag)
ft.setPrimaryNavigationFragment(frag)
@IdRes val destId = destination.id
val initialNavigation = backStack.isEmpty()
// TODO Build first class singleTop behavior for fragments
val isSingleTopReplacement = (navOptions != null && !initialNavigation
&& navOptions.shouldLaunchSingleTop()
&& backStack.peekLast()?.toInt() == destId)
val isAdded: Boolean
isAdded = if (initialNavigation) {
true
} else if (isSingleTopReplacement) { // Single Top means we only want one
instance on the back stack
if (backStack.size > 1) { // If the Fragment to be replaced is on the FragmentManager's
// back stack, a simple replace() isn't enough so we
// remove it from the back stack and put our replacement
// on the back stack in its place
manager.popBackStack(
generateBackStackName(backStack.size, backStack.peekLast()!!.toInt()),
FragmentManager.POP_BACK_STACK_INCLUSIVE)
ft.addToBackStack(generateBackStackName(backStack.size, destId))
}
false
} else {
ft.addToBackStack(generateBackStackName(backStack.size + 1, destId))
true
}
if (navigatorExtras is Extras) {
for ((key, value) in navigatorExtras.sharedElements) {
ft.addSharedElement(key!!, value!!)
}
}
ft.setReorderingAllowed(true)
ft.commit()
// The commit succeeded, update our view of the world
return if (isAdded) {
backStack.add(Integer(destId))
destination
} else {
null
}
}
private fun setAnimations(navOptions: NavOptions, transaction: FragmentTransaction) {
transaction.setCustomAnimations(
navOptions.enterAnim.takeIf { it != -1 } ?: android.R.anim.fade_in,
navOptions.exitAnim.takeIf { it != -1 } ?: android.R.anim.fade_out,
navOptions.popEnterAnim.takeIf { it != -1 } ?: android.R.anim.fade_in,
navOptions.popExitAnim.takeIf { it != -1 } ?: android.R.anim.fade_out
)
}
private fun generateBackStackName(backStackIndex: Int, destId: Int): String? {
return "$backStackIndex-$destId"
}
}
In the next step we have to add the navigator to NavController. Here is an example how to set it:
override fun onCreate(savedInstanceState: Bundle?) {
super.onCreate(savedInstanceState)
val navHostFragment = supportFragmentManager.findFragmentById(R.id.fragmentContainer)!!
with (findNavController(R.id.fragmentContainer)) {
navigatorProvider += MyAwesomeFragmentNavigator(this@BaseContainerActivity, navHostFragment.childFragmentManager, R.id.fragmentContainer)
setGraph(navGraphId)
}
}
And nothing special in xml :)
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<fragment
android:id="@+id/fragmentContainer"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true" />
</LinearLayout>
Now each fragment from graph will have alpha transitions
来源：https://stackoverflow.com/questions/50482095/how-do-i-define-default-animations-for-navigation-actions