WorkflowLayout.start now relies on Lifecycle.

Our sketchy homegrown `View.takeWhileAttached` somehow causes a strange issue
on API 30 devices where `View.onAttached` can be called twice, at least since
the recent change to introduce `View.start` landed in #602. We've seen
crashes on a variety of Samsung devices out in the wild, and can reproduce
the issue on API 30 AVDs via Android Studio's _Apply Changes and Restart
Activity_.

The fix is to be mainstream and use `Lifecycle`, which is added as a new
required parameter to `WorkflowLayout.start`. The old overloads are now
deprecated, and will be deleted soon.

We also promote `WorkflowLayout.show` to be publicly visible, to give apps the
option of taking control over how they collect their renderings.

Author: rjrjr

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).also { contentView -> contentView.start(lifecycle, model.renderings) }
     )
   }
 }

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

@@ -203,8 +203,11 @@ 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
 }
 

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

@@ -10,12 +10,17 @@ import android.view.View
 import android.view.ViewGroup
 import android.view.ViewGroup.LayoutParams.MATCH_PARENT
 import android.widget.FrameLayout
+import androidx.lifecycle.Lifecycle
+import androidx.lifecycle.coroutineScope
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.collect
 import kotlinx.coroutines.flow.launchIn
 import kotlinx.coroutines.flow.onEach
+import kotlinx.coroutines.launch
+import androidx.lifecycle.repeatOnLifecycle
 
 /**
  * A view that can be driven by a stream of renderings (and an optional [ViewRegistry])
@@ -43,31 +48,68 @@ public class WorkflowLayout(
 
   private var restoredChildState: SparseArray<Parcelable>? = null
 
+  @Suppress("DeprecatedCallableAddReplaceWith")
+  @Deprecated("Provide an androidx Lifecyle")
+  public fun start(
+    renderings: Flow<Any>,
+    registry: ViewRegistry
+  ) {
+    @Suppress("DEPRECATION")
+    start(renderings, ViewEnvironment(mapOf(ViewRegistry to registry)))
+  }
+
   /**
    * Subscribes to [renderings], and uses [registry] to
    * [build a new view][ViewRegistry.buildView] each time a new type of rendering is received,
    * making that view the only child of this one.
+   *
+   * @see [show]
    */
   public fun start(
+    lifecycle: Lifecycle,
     renderings: Flow<Any>,
     registry: ViewRegistry
   ) {
-    start(renderings, ViewEnvironment(mapOf(ViewRegistry to registry)))
+    start(lifecycle, renderings, ViewEnvironment(mapOf(ViewRegistry to registry)))
+  }
+
+  @Deprecated("Provide an androidx Lifecyle")
+  public fun start(
+    renderings: Flow<Any>,
+    environment: ViewEnvironment = ViewEnvironment()
+  ) {
+    takeWhileAttachedIfYouAreAnIdiotNoDoNotUseThis(renderings) { show(it, environment) }
   }
 
   /**
    * Subscribes to [renderings], and uses the [ViewRegistry] in the given [environment] to
    * [build a new view][ViewRegistry.buildView] each time a new type of rendering is received,
    * making that view the only child of this one.
+   *
+   * @see [show]
    */
   public fun start(
+    lifecycle: Lifecycle,
     renderings: Flow<Any>,
     environment: ViewEnvironment = ViewEnvironment()
   ) {
-    takeWhileAttached(renderings) { show(it, environment) }
+    lifecycle.coroutineScope.launch {
+      lifecycle.repeatOnLifecycle(Lifecycle.State.RESUMED) {
+        renderings.collect { show(it, environment) }
+      }
+    }
   }
 
-  private fun show(
+  /**
+   * Called from [start] as each rendering is collected from its `renderings: Flow<Any>`
+   * parameter. Updates the current child view from [newRendering] and [environment]
+   * if [newRendering] is [compatible] with the current one, or else replaces the
+   * current view with a new one.
+   *
+   * This method is exposed as an alternative to [start], to offer clients complete control
+   * over collecting their renderings.
+   */
+  public fun show(
     newRendering: Any,
     environment: ViewEnvironment
   ) {
@@ -131,7 +173,7 @@ public class WorkflowLayout(
   /**
    * Subscribes [update] to [source] only while this [View] is attached to a window.
    */
-  private fun <S : Any> View.takeWhileAttached(
+  private fun <S : Any> View.takeWhileAttachedIfYouAreAnIdiotNoDoNotUseThis(
     source: Flow<S>,
     update: (S) -> Unit
   ) {