Merge pull request #632 from square/ray/embrace-the-viewmodel

WorkflowLayout.start needs a Lifecycle, BackStackScreen is supported.

samples/compose-samples/src/main/java/com/squareup/sample/compose/hellocomposebinding/HelloBindingActivity.kt

@@ -36,10 +36,7 @@ class HelloBindingActivity : AppCompatActivity() {
     val model: HelloBindingModel by viewModels()
     setContentView(
       WorkflowLayout(this).apply {
-        start(
-          renderings = model.renderings,
-          environment = viewEnvironment
-        )
+        start(lifecycle, model.renderings, viewEnvironment)
       }
     )
   }

samples/compose-samples/src/main/java/com/squareup/sample/compose/hellocomposeworkflow/HelloComposeWorkflowActivity.kt

@@ -17,7 +17,7 @@ class HelloComposeWorkflowActivity : AppCompatActivity() {
     super.onCreate(savedInstanceState)
     val model: HelloComposeModel by viewModels()
     setContentView(
-      WorkflowLayout(this).apply { start(model.renderings) }
+      WorkflowLayout(this).apply { start(lifecycle, model.renderings) }
     )
   }
 

samples/compose-samples/src/main/java/com/squareup/sample/compose/inlinerendering/InlineRenderingActivity.kt

@@ -21,9 +21,7 @@ class InlineRenderingActivity : AppCompatActivity() {
 
     val model: HelloBindingModel by viewModels()
     setContentView(
-      WorkflowLayout(this).apply {
-        start(renderings = model.renderings)
-      }
+      WorkflowLayout(this).apply { start(lifecycle, model.renderings) }
     )
   }
 

samples/compose-samples/src/main/java/com/squareup/sample/compose/nestedrenderings/NestedRenderingsActivity.kt

@@ -38,10 +38,7 @@ class NestedRenderingsActivity : AppCompatActivity() {
     val model: NestedRenderingsModel by viewModels()
     setContentView(
       WorkflowLayout(this).apply {
-        start(
-          renderings = model.renderings,
-          environment = viewEnvironment
-        )
+        start(lifecycle, model.renderings, viewEnvironment)
       }
     )
   }

samples/containers/android/src/main/java/com/squareup/sample/container/SampleContainers.kt

@@ -8,5 +8,5 @@ import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 
 @OptIn(WorkflowUiExperimentalApi::class)
 val SampleContainers = ViewRegistry(
-  BackButtonViewFactory, OverviewDetailContainer, PanelContainer, ScrimContainer
+  OverviewDetailContainer, PanelContainer, ScrimContainer
 )

samples/containers/app-poetry/src/main/java/com/squareup/sample/poetryapp/PoetryActivity.kt

@@ -26,7 +26,7 @@ class PoetryActivity : AppCompatActivity() {
 
     val model: PoetryModel by viewModels()
     setContentView(
-      WorkflowLayout(this).apply { start(model.renderings, viewRegistry) }
+      WorkflowLayout(this).apply { start(lifecycle, model.renderings, viewRegistry) }
     )
   }
 

samples/containers/app-raven/src/main/java/com/squareup/sample/ravenapp/RavenActivity.kt

@@ -30,7 +30,7 @@ class RavenActivity : AppCompatActivity() {
 
     val model: RavenModel by viewModels()
     setContentView(
-      WorkflowLayout(this).apply { start(model.renderings, viewRegistry) }
+      WorkflowLayout(this).apply { start(lifecycle, model.renderings, viewRegistry) }
     )
 
     lifecycleScope.launch {

samples/containers/hello-back-button/src/main/java/com/squareup/sample/hellobackbutton/AreYouSureWorkflow.kt

@@ -1,7 +1,6 @@
 package com.squareup.sample.hellobackbutton
 
 import android.os.Parcelable
-import com.squareup.sample.container.BackButtonScreen
 import com.squareup.sample.hellobackbutton.AreYouSureWorkflow.Finished
 import com.squareup.sample.hellobackbutton.AreYouSureWorkflow.State
 import com.squareup.sample.hellobackbutton.AreYouSureWorkflow.State.Quitting
@@ -10,6 +9,7 @@ import com.squareup.workflow1.Snapshot
 import com.squareup.workflow1.StatefulWorkflow
 import com.squareup.workflow1.WorkflowAction.Companion.noAction
 import com.squareup.workflow1.action
+import com.squareup.workflow1.ui.BackButtonScreen
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow1.ui.modal.AlertContainerScreen
 import com.squareup.workflow1.ui.modal.AlertScreen

samples/containers/hello-back-button/src/main/java/com/squareup/sample/hellobackbutton/HelloBackButtonActivity.kt

@@ -27,7 +27,7 @@ class HelloBackButtonActivity : AppCompatActivity() {
 
     val model: HelloBackButtonModel by viewModels()
     setContentView(
-      WorkflowLayout(this).apply { start(model.renderings, viewRegistry) }
+      WorkflowLayout(this).apply { start(lifecycle, model.renderings, viewRegistry) }
     )
 
     lifecycleScope.launch {

samples/dungeon/app/src/main/java/com/squareup/sample/dungeon/DungeonActivity.kt

@@ -17,7 +17,7 @@ class DungeonActivity : AppCompatActivity() {
     val model: TimeMachineModel by viewModels { component.timeMachineModelFactory }
 
     setContentView(
-      WorkflowLayout(this).apply { start(model.renderings, component.viewRegistry) }
+      WorkflowLayout(this).apply { start(lifecycle, model.renderings, component.viewRegistry) }
     )
   }
 }

samples/hello-workflow-fragment/src/main/java/com/squareup/sample/helloworkflowfragment/HelloWorkflowFragment.kt

@@ -23,10 +23,10 @@ class HelloWorkflowFragment : Fragment() {
     // This ViewModel will survive configuration changes. It's instantiated
     // by the first call to ViewModelProvider.get(), and that original instance is returned by
     // succeeding calls, until this Fragment session ends.
-    val model: HelloViewModel = ViewModelProvider(this).get(HelloViewModel::class.java)
+    val model: HelloViewModel = ViewModelProvider(this)[HelloViewModel::class.java]
 
     return WorkflowLayout(inflater.context).apply {
-      start(model.renderings)
+      start(lifecycle, model.renderings)
     }
   }
 }

samples/hello-workflow/src/main/java/com/squareup/sample/helloworkflow/HelloWorkflowActivity.kt

@@ -21,7 +21,7 @@ class HelloWorkflowActivity : AppCompatActivity() {
     // succeeding calls.
     val model: HelloViewModel by viewModels()
     setContentView(
-      WorkflowLayout(this).apply { start(model.renderings) }
+      WorkflowLayout(this).apply { start(lifecycle, model.renderings) }
     )
   }
 }

samples/stub-visibility/src/main/java/com/squareup/sample/stubvisibility/StubVisibilityActivity.kt

@@ -18,7 +18,7 @@ class StubVisibilityActivity : AppCompatActivity() {
 
     val model: StubVisibilityModel by viewModels()
     setContentView(
-      WorkflowLayout(this).apply { start(model.renderings) }
+      WorkflowLayout(this).apply { start(lifecycle, model.renderings) }
     )
   }
 }

samples/tictactoe/app/src/androidTest/java/com/squareup/sample/TicTacToeEspressoTest.kt

@@ -36,6 +36,11 @@ import org.junit.rules.RuleChain
 import org.junit.runner.RunWith
 import java.util.concurrent.atomic.AtomicReference
 
+/**
+ * This app is our most complex sample, which makes it a great candidate for
+ * integration testing — especially of modals, back stacks, back button handling,
+ * and view state management.
+ */
 @OptIn(WorkflowUiExperimentalApi::class)
 @RunWith(AndroidJUnit4::class)
 class TicTacToeEspressoTest {
@@ -155,7 +160,7 @@ class TicTacToeEspressoTest {
       .check(matches(isDisplayed()))
   }
 
-  @Test fun canGoBackInModalView() {
+  @Test fun canGoBackInModalViewAndSeeRestoredViewState() {
     // Log in and hit the 2fa screen.
     inAnyView(withId(R.id.login_email)).type("foo@2fa")
     inAnyView(withId(R.id.login_password)).type("password")
@@ -168,7 +173,7 @@ class TicTacToeEspressoTest {
     inAnyView(withId(R.id.login_email)).check(matches(withText("foo@2fa")))
   }
 
-  @Test fun configChangePreservesBackStackViewStateCache() {
+  @Test fun canGoBackInModalViewAfterConfigChangeAndSeeRestoredViewState() {
     // Log in and hit the 2fa screen.
     inAnyView(withId(R.id.login_email)).type("foo@2fa")
     inAnyView(withId(R.id.login_password)).type("password")

samples/tictactoe/app/src/main/java/com/squareup/sample/mainactivity/TicTacToeActivity.kt

@@ -31,7 +31,7 @@ class TicTacToeActivity : AppCompatActivity() {
     idlingResource = component.idlingResource
 
     setContentView(
-      WorkflowLayout(this).apply { start(model.renderings, viewRegistry) }
+      WorkflowLayout(this).apply { start(lifecycle, model.renderings, viewRegistry) }
     )
 
     lifecycleScope.launch {

samples/todo-android/app/src/main/java/com/squareup/sample/todo/ToDoActivity.kt

@@ -26,7 +26,7 @@ class ToDoActivity : AppCompatActivity() {
 
     setContentView(
       WorkflowLayout(this).apply {
-        start(model.ensureWorkflow(traceFilesDir = filesDir), viewRegistry)
+        start(lifecycle, model.ensureWorkflow(traceFilesDir = filesDir), viewRegistry)
       }
     )
   }

workflow-ui/container-android/src/main/java/com/squareup/workflow1/ui/modal/ModalViewContainer.kt

@@ -10,11 +10,11 @@ import android.view.ViewGroup
 import android.view.ViewGroup.LayoutParams.MATCH_PARENT
 import android.view.ViewGroup.LayoutParams.WRAP_CONTENT
 import androidx.annotation.IdRes
+import com.squareup.workflow1.ui.BackButtonScreen
 import com.squareup.workflow1.ui.BuilderViewFactory
 import com.squareup.workflow1.ui.ViewEnvironment
 import com.squareup.workflow1.ui.ViewRegistry
 import com.squareup.workflow1.ui.WorkflowUiExperimentalApi
-import com.squareup.workflow1.ui.backPressedHandler
 import com.squareup.workflow1.ui.bindShowRendering
 import com.squareup.workflow1.ui.buildView
 import com.squareup.workflow1.ui.modal.ModalViewContainer.Companion.binding
@@ -62,22 +62,23 @@ public open class ModalViewContainer @JvmOverloads constructor(
     initialModalRendering: Any,
     initialViewEnvironment: ViewEnvironment
   ): DialogRef<Any> {
+    // Put a no-op backPressedHandler behind the given rendering, to
+    // ensure that the `onBackPressed` call below will not leak up to handlers
+    // that should be blocked by this modal session.
+    val wrappedRendering = BackButtonScreen(initialModalRendering) { }
+
     val view = initialViewEnvironment[ViewRegistry]
       // Notice that we don't pass a custom initializeView function to set the
       // WorkflowLifecycleOwner here. ModalContainer will do that itself, on the parent of the view
       // created here.
       .buildView(
-        initialRendering = initialModalRendering,
+        initialRendering = wrappedRendering,
         initialViewEnvironment = initialViewEnvironment,
         contextForNewView = this.context,
         container = this
       )
       .apply {
         start()
-        // If the modal's root view has no backPressedHandler, add a no-op one to
-        // ensure that the `onBackPressed` call below will not leak up to handlers
-        // that should be blocked by this modal session.
-        if (backPressedHandler == null) backPressedHandler = { }
       }
 
     return buildDialogForView(view)
@@ -109,7 +110,14 @@ public open class ModalViewContainer @JvmOverloads constructor(
   }
 
   override fun updateDialog(dialogRef: DialogRef<Any>) {
-    with(dialogRef) { (extra as View).showRendering(modalRendering, viewEnvironment) }
+    with(dialogRef) {
+      // Have to preserve the wrapping done in buildDialog. (We can't put the
+      // BackButtonScreen in the DialogRef because the superclass needs to be
+      // able to do compatibility checks against it when deciding whether
+      // or not to update the existing dialog.)
+      val wrappedRendering = BackButtonScreen(modalRendering) { }
+      (extra as View).showRendering(wrappedRendering, viewEnvironment)
+    }
   }
 
   @PublishedApi

workflow-ui/container-common/src/test/java/com/squareup/workflow1/ui/backstack/BackStackScreenTest.kt

@@ -6,7 +6,7 @@ import org.junit.Test
 import kotlin.test.assertFailsWith
 
 @OptIn(WorkflowUiExperimentalApi::class)
-class BackStackScreenTest {
+internal class BackStackScreenTest {
   @Test fun `top  is last`() {
     assertThat(BackStackScreen(1, 2, 3, 4).top).isEqualTo(4)
   }

workflow-ui/core-android/api/core-android.api

@@ -11,6 +11,15 @@ public abstract interface class com/squareup/workflow1/ui/AndroidViewRendering {
 	public abstract fun getViewFactory ()Lcom/squareup/workflow1/ui/ViewFactory;
 }
 
+public final class com/squareup/workflow1/ui/BackButtonScreen : com/squareup/workflow1/ui/AndroidViewRendering {
+	public fun <init> (Ljava/lang/Object;ZLkotlin/jvm/functions/Function0;)V
+	public synthetic fun <init> (Ljava/lang/Object;ZLkotlin/jvm/functions/Function0;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
+	public final fun getOnBackPressed ()Lkotlin/jvm/functions/Function0;
+	public final fun getShadow ()Z
+	public fun getViewFactory ()Lcom/squareup/workflow1/ui/ViewFactory;
+	public final fun getWrapped ()Ljava/lang/Object;
+}
+
 public final class com/squareup/workflow1/ui/BackPressHandlerKt {
 	public static final fun getBackPressedHandler (Landroid/view/View;)Lkotlin/jvm/functions/Function0;
 	public static final fun onBackPressedDispatcherOwnerOrNull (Landroid/content/Context;)Landroidx/activity/OnBackPressedDispatcherOwner;
@@ -203,8 +212,11 @@ public abstract interface class com/squareup/workflow1/ui/ViewStarter {
 public final class com/squareup/workflow1/ui/WorkflowLayout : android/widget/FrameLayout {
 	public fun <init> (Landroid/content/Context;Landroid/util/AttributeSet;)V
 	public synthetic fun <init> (Landroid/content/Context;Landroid/util/AttributeSet;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
+	public final fun start (Landroidx/lifecycle/Lifecycle;Lkotlinx/coroutines/flow/Flow;Lcom/squareup/workflow1/ui/ViewEnvironment;)V
+	public final fun start (Landroidx/lifecycle/Lifecycle;Lkotlinx/coroutines/flow/Flow;Lcom/squareup/workflow1/ui/ViewRegistry;)V
 	public final fun start (Lkotlinx/coroutines/flow/Flow;Lcom/squareup/workflow1/ui/ViewEnvironment;)V
 	public final fun start (Lkotlinx/coroutines/flow/Flow;Lcom/squareup/workflow1/ui/ViewRegistry;)V
+	public static synthetic fun start$default (Lcom/squareup/workflow1/ui/WorkflowLayout;Landroidx/lifecycle/Lifecycle;Lkotlinx/coroutines/flow/Flow;Lcom/squareup/workflow1/ui/ViewEnvironment;ILjava/lang/Object;)V
 	public static synthetic fun start$default (Lcom/squareup/workflow1/ui/WorkflowLayout;Lkotlinx/coroutines/flow/Flow;Lcom/squareup/workflow1/ui/ViewEnvironment;ILjava/lang/Object;)V
 	public final fun update (Ljava/lang/Object;Lcom/squareup/workflow1/ui/ViewEnvironment;)V
 }

workflow-ui/core-android/src/main/java/com/squareup/workflow1/ui/BackButtonScreen.kt

@@ -0,0 +1,43 @@
+package com.squareup.workflow1.ui
+
+/**
+ * Adds optional back button handling to a [wrapped] rendering, possibly overriding that
+ * the wrapped rendering's own back button handler.
+ *
+ * @param shadow If `true`, [onBackPressed] is set as the
+ * [backPressedHandler][android.view.View.backPressedHandler] after
+ * the [wrapped] rendering's view is built / updated, effectively overriding it.
+ * If false (the default), [onBackPressed] is set afterward, to allow the wrapped rendering to
+ * take precedence if it sets a `backPressedHandler` of its own -- the handler provided
+ * here serves as a default.
+ *
+ * @param onBackPressed The function to fire when the device back button
+ * is pressed, or null to set no handler -- or clear a handler that was set previously.
+ * Defaults to `null`.
+ */
+@WorkflowUiExperimentalApi
+public class BackButtonScreen<W : Any>(
+  public val wrapped: W,
+  public val shadow: Boolean = false,
+  public val onBackPressed: (() -> Unit)? = null
+) : AndroidViewRendering<BackButtonScreen<*>> {
+  override val viewFactory: ViewFactory<BackButtonScreen<*>> = DecorativeViewFactory(
+    type = BackButtonScreen::class,
+    map = { outer -> outer.wrapped },
+    doShowRendering = { view, innerShowRendering, outerRendering, viewEnvironment ->
+      if (!outerRendering.shadow) {
+        // Place our handler before invoking innerShowRendering, so that
+        // its later calls to view.backPressedHandler will take precedence
+        // over ours.
+        view.backPressedHandler = outerRendering.onBackPressed
+      }
+
+      innerShowRendering.invoke(outerRendering.wrapped, viewEnvironment)
+
+      if (outerRendering.shadow) {
+        // Place our handler after invoking innerShowRendering, so that ours wins.
+        view.backPressedHandler = outerRendering.onBackPressed
+      }
+    }
+  )
+}