Added parentFragmentViewModel()

mvrx/src/main/kotlin/com/airbnb/mvrx/MvRxExtensions.kt

@@ -1,10 +1,10 @@
 package com.airbnb.mvrx
 
-import androidx.lifecycle.ViewModelProviders
 import androidx.annotation.RestrictTo
 import androidx.annotation.RestrictTo.Scope.LIBRARY
 import androidx.fragment.app.Fragment
 import androidx.fragment.app.FragmentActivity
+import androidx.lifecycle.ViewModelProviders
 import kotlin.properties.ReadOnlyProperty
 import kotlin.reflect.KClass
 import kotlin.reflect.KProperty
@@ -29,6 +29,60 @@ inline fun <T, reified VM : BaseMvRxViewModel<S>, reified S : MvRxState> T.fragm
         .apply { subscribe(this@fragmentViewModel, subscriber = { postInvalidate() }) }
 }
 
+/**
+ * Gets or creates a ViewModel scoped to a parent fragment. This delegate will walk up the parentFragment hierarchy
+ * until it finds a Fragment that can provide the correct ViewModel. If no parent fragments can provide the ViewModel,
+ * a new one will be created in top-most parent Fragment.
+ */
+inline fun <T, reified VM : BaseMvRxViewModel<S>, reified S : MvRxState> T.parentFragmentViewModel(
+    viewModelClass: KClass<VM> = VM::class,
+    crossinline keyFactory: () -> String = { viewModelClass.java.name }
+): Lazy<VM> where T : Fragment, T : MvRxView = lifecycleAwareLazy(this) {
+    requireNotNull(parentFragment) { "There is no parent fragment for ${this::class.java.simpleName}!" }
+    val notFoundMessage by lazy { "There is no ViewModel of type ${VM::class.java.simpleName} for this Fragment!" }
+    val factory = MvRxFactory { error(notFoundMessage) }
+    var fragment: Fragment? = parentFragment
+    val key = keyFactory()
+    while (fragment != null) {
+        try {
+            return@lifecycleAwareLazy ViewModelProviders.of(fragment, factory).get(key, viewModelClass.java)
+                .apply { subscribe(this@parentFragmentViewModel, subscriber = { postInvalidate() }) }
+        } catch (e: java.lang.IllegalStateException) {
+            if (e.message == notFoundMessage) {
+                fragment = fragment.parentFragment
+            } else {
+                throw e
+            }
+        }
+    }
+
+    // ViewModel was not found. Create a new one in the top-most parent.
+    var topParentFragment = parentFragment
+    while (topParentFragment?.parentFragment != null) {
+        topParentFragment = topParentFragment.parentFragment
+    }
+    val viewModelContext = FragmentViewModelContext(this.requireActivity(), _fragmentArgsProvider(), topParentFragment!!)
+    return@lifecycleAwareLazy MvRxViewModelProvider.get(viewModelClass.java, S::class.java, viewModelContext, keyFactory())
+        .apply { subscribe(this@parentFragmentViewModel, subscriber = { postInvalidate() }) }
+}
+
+/**
+ * Gets or creates a ViewModel scoped to a target fragment. Throws [IllegalStateException] if there is no target fragment.
+ */
+inline fun <T, reified VM : BaseMvRxViewModel<S>, reified S : MvRxState> T.targetFragmentViewModel(
+    viewModelClass: KClass<VM> = VM::class,
+    crossinline keyFactory: () -> String = { viewModelClass.java.name }
+): Lazy<VM> where T : Fragment, T : MvRxView = lifecycleAwareLazy(this) {
+    val targetFragment = requireNotNull(targetFragment) { "There is no target fragment for ${this::class.java.simpleName}!" }
+    MvRxViewModelProvider.get(
+        viewModelClass.java,
+        S::class.java,
+        FragmentViewModelContext(this.requireActivity(), targetFragment._fragmentArgsProvider(), targetFragment),
+        keyFactory()
+    )
+        .apply { subscribe(this@targetFragmentViewModel, subscriber = { postInvalidate() }) }
+}
+
 /**
  * [activityViewModel] except it will throw [IllegalStateException] if the ViewModel doesn't already exist.
  * Use this for screens in the middle of a flow that cannot reasonably be an entrypoint to the flow.

mvrx/src/test/kotlin/com/airbnb/mvrx/ViewSubscriberTest.kt → mvrx/src/test/kotlin/com/airbnb/mvrx/FragmentSubscriberTest.kt

@@ -5,6 +5,7 @@ import android.os.Bundle
 import android.view.LayoutInflater
 import android.view.View
 import android.view.ViewGroup
+import android.widget.FrameLayout
 import androidx.fragment.app.Fragment
 import org.junit.Assert.assertEquals
 import org.junit.Test
@@ -463,4 +464,122 @@ class FragmentSubscriberTest : BaseTest() {
     fun duplicateUniqueOnlySubscribeThrowIllegalStateException() {
          createFragment<DuplicateUniqueSubscriberFragment, TestActivity>(containerId = CONTAINER_ID)
     }
+
+    class ParentFragment : BaseMvRxFragment() {
+
+        val viewModel: ViewSubscriberViewModel by fragmentViewModel()
+
+        override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?) = FrameLayout(requireContext())
+
+        override fun invalidate() {
+        }
+    }
+
+    class ChildFragmentWithParentViewModel : BaseMvRxFragment() {
+
+        val viewModel: ViewSubscriberViewModel by parentFragmentViewModel()
+
+        override fun invalidate() {
+        }
+    }
+
+    @Test
+    fun testParentFragment() {
+        val (_, parentFragment) = createFragment<ParentFragment, TestActivity>(containerId = CONTAINER_ID)
+        val childFragment = ChildFragmentWithParentViewModel()
+        parentFragment.childFragmentManager.beginTransaction().add(childFragment, "child").commit()
+        assertEquals(parentFragment.viewModel, childFragment.viewModel)
+    }
+
+    class ParentFragmentWithoutViewModel : BaseMvRxFragment() {
+
+        override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?) = FrameLayout(requireContext())
+
+        override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+            childFragmentManager.beginTransaction()
+                .add(ChildFragmentWithParentViewModel(), "child1")
+                .commit()
+            childFragmentManager.beginTransaction()
+                .add(ChildFragmentWithParentViewModel(), "child2")
+                .commit()
+        }
+
+        override fun invalidate() {
+        }
+    }
+
+    @Test
+    fun testChildFragmentsCanShareViewModelWithoutParent() {
+        val (_, parentFragment) = createFragment<ParentFragmentWithoutViewModel, TestActivity>(containerId = CONTAINER_ID)
+        val childFragment1 = parentFragment.childFragmentManager.findFragmentByTag("child1") as ChildFragmentWithParentViewModel
+        val childFragment2 = parentFragment.childFragmentManager.findFragmentByTag("child2") as ChildFragmentWithParentViewModel
+        assertEquals(childFragment1.viewModel, childFragment2.viewModel)
+    }
+
+    class EmptyMvRxFragment : BaseMvRxFragment() {
+        override fun invalidate() {
+        }
+    }
+
+    @Test
+    fun testCreatesViewModelInTopMostFragment() {
+        val (_, parentFragment) = createFragment<ParentFragmentWithoutViewModel, TestActivity>(containerId = CONTAINER_ID)
+        val middleFragment = Fragment()
+        parentFragment.childFragmentManager.beginTransaction().add(middleFragment, "middle").commitNow()
+        val childFragment1 = ChildFragmentWithParentViewModel()
+        middleFragment.childFragmentManager.beginTransaction().add(childFragment1, "child1").commitNow()
+
+        val childFragment2 = ChildFragmentWithParentViewModel()
+        parentFragment.childFragmentManager.beginTransaction().add(childFragment2, "child2").commitNow()
+
+        assertEquals(childFragment1.viewModel, childFragment2.viewModel)
+    }
+
+    class FragmentWithTarget : BaseMvRxFragment() {
+        val viewModel: ViewSubscriberViewModel by targetFragmentViewModel()
+
+        var invalidateCount = 0
+
+        override fun invalidate() {
+            invalidateCount++
+        }
+    }
+
+    @Test
+    fun testTargetFragment() {
+        val (_, parentFragment) = createFragment<EmptyMvRxFragment, TestActivity>(containerId = CONTAINER_ID)
+        val targetFragment = EmptyMvRxFragment()
+        parentFragment.childFragmentManager.beginTransaction().add(targetFragment, "target").commitNow()
+        val fragmentWithTarget = FragmentWithTarget()
+        fragmentWithTarget.setTargetFragment(targetFragment, 123)
+        parentFragment.childFragmentManager.beginTransaction().add(fragmentWithTarget, "fragment-with-target").commitNow()
+        // Make sure subscribe works.
+        assertEquals(1, fragmentWithTarget.invalidateCount)
+        fragmentWithTarget.viewModel.setFoo(1)
+        assertEquals(2, fragmentWithTarget.invalidateCount)
+    }
+
+    @Test
+    fun testTargetFragmentsShareViewModel() {
+        val (_, parentFragment) = createFragment<EmptyMvRxFragment, TestActivity>(containerId = CONTAINER_ID)
+        val targetFragment = EmptyMvRxFragment()
+        parentFragment.childFragmentManager.beginTransaction().add(targetFragment, "target").commitNow()
+        val fragmentWithTarget1 = FragmentWithTarget()
+        fragmentWithTarget1.setTargetFragment(targetFragment, 123)
+        parentFragment.childFragmentManager.beginTransaction().add(fragmentWithTarget1, "fragment-with-target1").commitNow()
+        val fragmentWithTarget2 = FragmentWithTarget()
+        fragmentWithTarget2.setTargetFragment(targetFragment, 123)
+        parentFragment.childFragmentManager.beginTransaction().add(fragmentWithTarget2, "fragment-with-target2").commitNow()
+        assertEquals(fragmentWithTarget1.viewModel, fragmentWithTarget2.viewModel)
+    }
+
+    /**
+     * This would be [IllegalStateException] except it fails during the Fragment transaction so it's a RuntimeException.
+     */
+    @Test(expected = RuntimeException::class)
+    fun testTargetFragmentWithoutTargetCrashes() {
+        val (_, parentFragment) = createFragment<EmptyMvRxFragment, TestActivity>(containerId = CONTAINER_ID)
+        val fragmentWithTarget = FragmentWithTarget()
+        parentFragment.childFragmentManager.beginTransaction().add(fragmentWithTarget, "fragment-with-target").commitNow()
+    }
 }

sample/src/main/java/com/airbnb/mvrx/sample/MainFragment.kt

@@ -28,6 +28,13 @@ class MainFragment : BaseFragment() {
             clickListener { _ -> navigateTo(R.id.action_main_to_helloWorldEpoxyFragment) }
         }
 
+        basicRow {
+            id("parent_fragments")
+            title("Parent/Child ViewModel")
+            subtitle(demonstrates("parentFragmentViewModel"))
+            clickListener { _ -> navigateTo(R.id.action_main_to_parentFragment) }
+        }
+
         basicRow {
             id("random_dad_joke")
             title("Random Dad Joke")

sample/src/main/java/com/airbnb/mvrx/sample/features/parentfragment/ChildFragment.kt

@@ -0,0 +1,30 @@
+package com.airbnb.mvrx.sample.features.parentfragment
+
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import com.airbnb.mvrx.BaseMvRxFragment
+import com.airbnb.mvrx.parentFragmentViewModel
+import com.airbnb.mvrx.sample.R
+import com.airbnb.mvrx.withState
+import kotlinx.android.synthetic.main.fragment_parent.textView
+
+class ChildFragment : BaseMvRxFragment() {
+
+    private val viewModel: CounterViewModel by parentFragmentViewModel()
+
+    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
+        return inflater.inflate(R.layout.fragment_child, container, false)
+    }
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        textView.setOnClickListener {
+            viewModel.incrementCount()
+        }
+    }
+
+    override fun invalidate() = withState(viewModel) { state ->
+        textView.text = "ChildFragment: Count: ${state.count}"
+    }
+}

sample/src/main/java/com/airbnb/mvrx/sample/features/parentfragment/ParentFragment.kt

@@ -0,0 +1,44 @@
+package com.airbnb.mvrx.sample.features.parentfragment
+
+import android.os.Bundle
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import androidx.navigation.fragment.findNavController
+import androidx.navigation.ui.setupWithNavController
+import com.airbnb.mvrx.BaseMvRxFragment
+import com.airbnb.mvrx.MvRxState
+import com.airbnb.mvrx.fragmentViewModel
+import com.airbnb.mvrx.sample.R
+import com.airbnb.mvrx.sample.core.MvRxViewModel
+import com.airbnb.mvrx.withState
+import kotlinx.android.synthetic.main.fragment_parent.textView
+import kotlinx.android.synthetic.main.fragment_parent.toolbar
+
+data class CounterState(val count: Int = 0) : MvRxState
+class CounterViewModel(state: CounterState) : MvRxViewModel<CounterState>(state) {
+    fun incrementCount() = setState { copy(count = count + 1) }
+}
+
+class ParentFragment : BaseMvRxFragment() {
+
+    private val viewModel: CounterViewModel by fragmentViewModel()
+
+    override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
+        return inflater.inflate(R.layout.fragment_parent, container, false)
+    }
+
+    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
+        toolbar.setupWithNavController(findNavController())
+        textView.setOnClickListener {
+            viewModel.incrementCount()
+        }
+        childFragmentManager.beginTransaction()
+            .replace(R.id.childContainer, ChildFragment())
+            .commit()
+    }
+
+    override fun invalidate() = withState(viewModel) { state ->
+        textView.text = "ParentFragment: Count: ${state.count}"
+    }
+}

sample/src/main/res/layout/fragment_child.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="match_parent"
+    android:layout_height="match_parent">
+
+    <TextView
+        android:id="@+id/textView"
+        android:layout_width="match_parent"
+        android:layout_height="match_parent"
+        android:gravity="center" />
+
+</FrameLayout>

sample/src/main/res/layout/fragment_parent.xml

@@ -0,0 +1,25 @@
+<?xml version="1.0" encoding="utf-8"?>
+<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">
+    <androidx.appcompat.widget.Toolbar
+        android:id="@+id/toolbar"
+        android:layout_width="match_parent"
+        android:layout_height="?attr/actionBarSize"
+        app:navigationIcon="@drawable/ic_arrow_back"
+        />
+    <TextView
+        android:id="@+id/textView"
+        android:layout_width="match_parent"
+        android:layout_height="0dp"
+        android:gravity="center"
+        android:layout_weight="1" />
+
+    <FrameLayout
+        android:id="@+id/childContainer"
+        android:layout_width="match_parent"
+        android:layout_height="0dp"
+        android:layout_weight="4" />
+</LinearLayout>

sample/src/main/res/navigation/nav_graph.xml

@@ -40,6 +40,9 @@
             app:exitAnim="@anim/anim_exit"
             app:popEnterAnim="@anim/anim_pop_enter"
             app:popExitAnim="@anim/anim_pop_exit" />
+        <action
+            android:id="@+id/action_main_to_parentFragment"
+            app:destination="@id/parentFragment" />
     </fragment>
 
     <fragment
@@ -79,4 +82,8 @@
     <fragment
         android:id="@+id/helloWorldFragment"
         android:name="com.airbnb.mvrx.sample.features.helloworld.HelloWorldFragment" />
+    <fragment
+        android:id="@+id/parentFragment"
+        android:name="com.airbnb.mvrx.sample.features.parentfragment.ParentFragment"
+        android:label="ParentFragment" />
 </navigation>