Simpler, better back button handling.

`OverlayDialogHolder` now can provide an `onBackPressed: () -> Unit` function to be called in place of `Dialog.onBackPressed`, and we provide a default implementation that hooks in `OnBackPressedDispatcher`. This works for all kinds of dialogs, not just modal ones, and replaces `ModalScreenOverlayBackButtonHelper`. The other method that was on `ModalScreenOverlayBackButtonHelper`, which put the no-op `backPressedHandler` on the content view to ensure those on layer layers would not fire, is now built into the default implementation of `ScreenOverlayDialogFactory.buildDialogWithContent`, which is designed to be customized anyway.

Also locks down `AlertOverlayDialogFactory`, but moves all the interesting parts into a public function. Should be easier and safer for re-use.

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

@@ -429,16 +429,19 @@ public final class com/squareup/workflow1/ui/container/AlertDialogThemeResId : c
 	public synthetic fun getDefault ()Ljava/lang/Object;
 }
 
-public class com/squareup/workflow1/ui/container/AlertOverlayDialogFactory : com/squareup/workflow1/ui/container/OverlayDialogFactory {
+public final class com/squareup/workflow1/ui/container/AlertOverlayDialogFactory : com/squareup/workflow1/ui/container/OverlayDialogFactory {
 	public fun <init> ()V
 	public fun buildDialog (Lcom/squareup/workflow1/ui/container/AlertOverlay;Lcom/squareup/workflow1/ui/ViewEnvironment;Landroid/content/Context;)Lcom/squareup/workflow1/ui/container/OverlayDialogHolder;
 	public synthetic fun buildDialog (Lcom/squareup/workflow1/ui/container/Overlay;Lcom/squareup/workflow1/ui/ViewEnvironment;Landroid/content/Context;)Lcom/squareup/workflow1/ui/container/OverlayDialogHolder;
 	public fun getType ()Lkotlin/reflect/KClass;
 }
 
+public final class com/squareup/workflow1/ui/container/AlertOverlayDialogFactoryKt {
+	public static final fun toDialogHolder (Landroid/app/AlertDialog;Lcom/squareup/workflow1/ui/ViewEnvironment;)Lcom/squareup/workflow1/ui/container/OverlayDialogHolder;
+}
+
 public final class com/squareup/workflow1/ui/container/AndroidDialogBoundsKt {
 	public static final fun maintainBounds (Landroid/app/Dialog;Lcom/squareup/workflow1/ui/ViewEnvironment;Lkotlin/jvm/functions/Function1;)V
-	public static final fun maintainBounds (Landroid/app/Dialog;Lkotlinx/coroutines/flow/StateFlow;Lkotlin/jvm/functions/Function1;)V
 	public static final fun setBounds (Landroid/app/Dialog;Landroid/graphics/Rect;)V
 }
 
@@ -612,26 +615,6 @@ public final class com/squareup/workflow1/ui/container/LayeredDialogSessions$Sav
 	public synthetic fun newArray (I)[Ljava/lang/Object;
 }
 
-public abstract interface class com/squareup/workflow1/ui/container/ModalScreenOverlayBackButtonHelper {
-	public static final field Companion Lcom/squareup/workflow1/ui/container/ModalScreenOverlayBackButtonHelper$Companion;
-	public abstract fun onBackPressed (Landroid/view/View;)Z
-	public abstract fun onContentViewUpdate (Landroid/view/View;)V
-}
-
-public final class com/squareup/workflow1/ui/container/ModalScreenOverlayBackButtonHelper$Companion : com/squareup/workflow1/ui/ViewEnvironmentKey {
-	public fun getDefault ()Lcom/squareup/workflow1/ui/container/ModalScreenOverlayBackButtonHelper;
-	public synthetic fun getDefault ()Ljava/lang/Object;
-}
-
-public final class com/squareup/workflow1/ui/container/ModalScreenOverlayBackButtonHelper$DefaultImpls {
-	public static fun onBackPressed (Lcom/squareup/workflow1/ui/container/ModalScreenOverlayBackButtonHelper;Landroid/view/View;)Z
-	public static fun onContentViewUpdate (Lcom/squareup/workflow1/ui/container/ModalScreenOverlayBackButtonHelper;Landroid/view/View;)V
-}
-
-public final class com/squareup/workflow1/ui/container/ModalScreenOverlayBackButtonHelperKt {
-	public static final fun plus (Lcom/squareup/workflow1/ui/ViewEnvironment;Lcom/squareup/workflow1/ui/container/ModalScreenOverlayBackButtonHelper;)Lcom/squareup/workflow1/ui/ViewEnvironment;
-}
-
 public final class com/squareup/workflow1/ui/container/OverlayArea {
 	public static final field Companion Lcom/squareup/workflow1/ui/container/OverlayArea$Companion;
 	public fun <init> (Lkotlinx/coroutines/flow/StateFlow;)V
@@ -673,6 +656,7 @@ public abstract interface class com/squareup/workflow1/ui/container/OverlayDialo
 	public static final field Companion Lcom/squareup/workflow1/ui/container/OverlayDialogHolder$Companion;
 	public abstract fun getDialog ()Landroid/app/Dialog;
 	public abstract fun getEnvironment ()Lcom/squareup/workflow1/ui/ViewEnvironment;
+	public abstract fun getOnBackPressed ()Lkotlin/jvm/functions/Function0;
 	public abstract fun getOnUpdateBounds ()Lkotlin/jvm/functions/Function1;
 	public abstract fun getRunner ()Lkotlin/jvm/functions/Function2;
 }
@@ -691,24 +675,24 @@ public final class com/squareup/workflow1/ui/container/OverlayDialogHolder$Compa
 }
 
 public final class com/squareup/workflow1/ui/container/OverlayDialogHolderKt {
-	public static final fun OverlayDialogHolder (Lcom/squareup/workflow1/ui/ViewEnvironment;Landroid/app/Dialog;Lkotlin/jvm/functions/Function1;Lkotlin/jvm/functions/Function2;)Lcom/squareup/workflow1/ui/container/OverlayDialogHolder;
-	public static synthetic fun OverlayDialogHolder$default (Lcom/squareup/workflow1/ui/ViewEnvironment;Landroid/app/Dialog;Lkotlin/jvm/functions/Function1;Lkotlin/jvm/functions/Function2;ILjava/lang/Object;)Lcom/squareup/workflow1/ui/container/OverlayDialogHolder;
+	public static final fun OverlayDialogHolder (Lcom/squareup/workflow1/ui/ViewEnvironment;Landroid/app/Dialog;Lkotlin/jvm/functions/Function1;Lkotlin/jvm/functions/Function0;Lkotlin/jvm/functions/Function2;)Lcom/squareup/workflow1/ui/container/OverlayDialogHolder;
+	public static synthetic fun OverlayDialogHolder$default (Lcom/squareup/workflow1/ui/ViewEnvironment;Landroid/app/Dialog;Lkotlin/jvm/functions/Function1;Lkotlin/jvm/functions/Function0;Lkotlin/jvm/functions/Function2;ILjava/lang/Object;)Lcom/squareup/workflow1/ui/container/OverlayDialogHolder;
 	public static final fun canShow (Lcom/squareup/workflow1/ui/container/OverlayDialogHolder;Lcom/squareup/workflow1/ui/container/Overlay;)Z
 	public static final fun getShowing (Lcom/squareup/workflow1/ui/container/OverlayDialogHolder;)Lcom/squareup/workflow1/ui/container/Overlay;
 	public static final fun show (Lcom/squareup/workflow1/ui/container/OverlayDialogHolder;Lcom/squareup/workflow1/ui/container/Overlay;Lcom/squareup/workflow1/ui/ViewEnvironment;)V
 }
 
 public final class com/squareup/workflow1/ui/container/RealOverlayDialogHolder : com/squareup/workflow1/ui/container/OverlayDialogHolder {
-	public fun <init> (Lcom/squareup/workflow1/ui/ViewEnvironment;Landroid/app/Dialog;Lkotlin/jvm/functions/Function1;Lkotlin/jvm/functions/Function2;)V
+	public fun <init> (Lcom/squareup/workflow1/ui/ViewEnvironment;Landroid/app/Dialog;Lkotlin/jvm/functions/Function1;Lkotlin/jvm/functions/Function0;Lkotlin/jvm/functions/Function2;)V
 	public fun getDialog ()Landroid/app/Dialog;
 	public fun getEnvironment ()Lcom/squareup/workflow1/ui/ViewEnvironment;
+	public fun getOnBackPressed ()Lkotlin/jvm/functions/Function0;
 	public fun getOnUpdateBounds ()Lkotlin/jvm/functions/Function1;
 	public fun getRunner ()Lkotlin/jvm/functions/Function2;
 }
 
 public class com/squareup/workflow1/ui/container/ScreenOverlayDialogFactory : com/squareup/workflow1/ui/container/OverlayDialogFactory {
 	public fun <init> (Lkotlin/reflect/KClass;)V
-	public fun buildContent (Lcom/squareup/workflow1/ui/ScreenViewFactory;Lcom/squareup/workflow1/ui/Screen;Lcom/squareup/workflow1/ui/ViewEnvironment;Landroid/content/Context;)Lcom/squareup/workflow1/ui/ScreenViewHolder;
 	public synthetic fun buildDialog (Lcom/squareup/workflow1/ui/container/Overlay;Lcom/squareup/workflow1/ui/ViewEnvironment;Landroid/content/Context;)Lcom/squareup/workflow1/ui/container/OverlayDialogHolder;
 	public final fun buildDialog (Lcom/squareup/workflow1/ui/container/ScreenOverlay;Lcom/squareup/workflow1/ui/ViewEnvironment;Landroid/content/Context;)Lcom/squareup/workflow1/ui/container/OverlayDialogHolder;
 	public fun buildDialogWithContent (Lcom/squareup/workflow1/ui/container/ScreenOverlay;Lcom/squareup/workflow1/ui/ViewEnvironment;Lcom/squareup/workflow1/ui/ScreenViewHolder;)Lcom/squareup/workflow1/ui/container/OverlayDialogHolder;

workflow-ui/core-android/src/androidTest/java/com/squareup/workflow1/ui/container/DialogIntegrationTest.kt

@@ -1,7 +1,6 @@
 package com.squareup.workflow1.ui.container
 
 import android.app.Dialog
-import android.content.Context
 import android.view.View
 import android.widget.EditText
 import androidx.activity.ComponentActivity
@@ -55,24 +54,17 @@ internal class DialogIntegrationTest {
       object : ScreenOverlayDialogFactory<ContentRendering, DialogRendering>(
         type = DialogRendering::class
       ) {
-        override fun buildContent(
-          viewFactory: ScreenViewFactory<ContentRendering>,
-          initialContent: ContentRendering,
-          initialEnvironment: ViewEnvironment,
-          context: Context
-        ): ScreenViewHolder<ContentRendering> =
-          super.buildContent(viewFactory, initialContent, initialEnvironment, context).also {
-            latestContentView = it.view
-          }
-
         override fun buildDialogWithContent(
           initialRendering: DialogRendering,
           initialEnvironment: ViewEnvironment,
           content: ScreenViewHolder<ContentRendering>
-        ): OverlayDialogHolder<DialogRendering> =
-          super.buildDialogWithContent(initialRendering, initialEnvironment, content).also {
+        ): OverlayDialogHolder<DialogRendering> {
+          latestContentView = content.view
+
+          return super.buildDialogWithContent(initialRendering, initialEnvironment, content).also {
             latestDialog = it.dialog
           }
+        }
       }
   }
 

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

@@ -28,6 +28,9 @@ public interface ScreenViewHolder<in ScreenT : Screen> {
   /**
    * The function that is run by [show] to update [view] with a new [Screen] rendering and
    * [ViewEnvironment].
+   *
+   * Prefer calling [show] to using this directly, to ensure that [Showing] is
+   * maintained correctly, and [showing] keeps working.
    */
   public val runner: ScreenViewRunner<ScreenT>
 
@@ -103,6 +106,10 @@ public fun <ScreenT : Screen> ScreenViewHolder<ScreenT>.show(
 /**
  * Returns the [Screen] most recently used to update the receiver's [view][ScreenViewHolder.view]
  * via a call to [show].
+ *
+ * Note that the exact type of the returned [Screen] is likely not to match that of
+ * the receiver's `ScreenT` type parameter, e.g. if a
+ * [wrapping view factory][ScreenViewFactory.forWrapper] is in use.
  */
 @WorkflowUiExperimentalApi
 public val ScreenViewHolder<*>.showing: Screen

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

@@ -16,84 +16,98 @@ import com.squareup.workflow1.ui.container.AlertOverlay.Event.Canceled
 import kotlin.reflect.KClass
 
 /**
- * Default [OverlayDialogFactory] for [AlertOverlay].
+ * Default [OverlayDialogFactory] for [AlertOverlay], uses [AlertDialog].
+ * See [AlertDialog.toDialogHolder] to use [AlertDialog] for other purposes.
  *
- * This class is non-final for ease of customization of [AlertOverlay] handling,
- * see [OverlayDialogFactoryFinder] for details.
+ * - To customize [AlertDialog] theming, see [AlertDialogThemeResId]
+ * - To customize how [AlertOverlay] is handled more generally, set up a
+ *   custom [OverlayDialogFactoryFinder].
  */
 @WorkflowUiExperimentalApi
-public open class AlertOverlayDialogFactory : OverlayDialogFactory<AlertOverlay> {
+internal class AlertOverlayDialogFactory : OverlayDialogFactory<AlertOverlay> {
   override val type: KClass<AlertOverlay> = AlertOverlay::class
 
   override fun buildDialog(
     initialRendering: AlertOverlay,
     initialEnvironment: ViewEnvironment,
     context: Context
-  ): OverlayDialogHolder<AlertOverlay> {
-    return AlertDialog.Builder(context, initialEnvironment[AlertDialogThemeResId])
-      .create().let { alertDialog ->
-        for (button in Button.values()) {
-          // We want to be able to update the alert while it's showing, including to maybe
-          // show more buttons than were there originally. The API for Android's `AlertDialog`
-          // makes you think you can do that, but it actually doesn't work. So we force
-          // `AlertDialog.Builder` to show every possible button; then we hide them all;
-          // and then we manage their visibility ourselves at update time.
-          //
-          // We also don't want Android to tear down the dialog without our say so --
-          // again, we might need to update the thing. But there is a dismiss call
-          // built in to click handlers put in place by `AlertDialog`. So, when we're
-          // preflighting every possible button, we put garbage click handlers in place.
-          // Then we replace them with our own, again at update time, by setting each live
-          // button's click handler directly, without letting `AlertDialog` interfere.
-          //
-          // https://github.com/square/workflow-kotlin/issues/138
-          //
-          // Why " "? An empty string means no button.
-          alertDialog.setButton(button.toId(), " ") { _, _ -> }
-        }
+  ): OverlayDialogHolder<AlertOverlay> =
+    AlertDialog.Builder(context, initialEnvironment[AlertDialogThemeResId])
+      .create()
+      .toDialogHolder(initialEnvironment)
+}
 
-        OverlayDialogHolder(
-          initialEnvironment = initialEnvironment,
-          dialog = alertDialog,
-          onUpdateBounds = null
-        ) { rendering, _ ->
-          with(alertDialog) {
-            if (rendering.cancelable) {
-              setOnCancelListener { rendering.onEvent(Canceled) }
-              setCancelable(true)
-            } else {
-              setCancelable(false)
-            }
+/**
+ * Wraps the receiver in in an [OverlayDialogHolder] that is able to update its
+ * buttons as new [AlertOverlay] renderings are received.
+ */
+@WorkflowUiExperimentalApi
+public fun AlertDialog.toDialogHolder(
+  initialEnvironment: ViewEnvironment
+): OverlayDialogHolder<AlertOverlay> {
+  for (button in Button.values()) {
+    // We want to be able to update the alert while it's showing, including to maybe
+    // show more buttons than were there originally. The API for Android's `AlertDialog`
+    // makes you think you can do that, but it actually doesn't work. So we force
+    // `AlertDialog.Builder` to show every possible button; then we hide them all;
+    // and then we manage their visibility ourselves at update time.
+    //
+    // We also don't want Android to tear down the dialog without our say so --
+    // again, we might need to update the thing. But there is a dismiss call
+    // built in to click handlers put in place by `AlertDialog`. So, when we're
+    // preflighting every possible button, we put garbage click handlers in place.
+    // Then we replace them with our own, again at update time, by setting each live
+    // button's click handler directly, without letting `AlertDialog` interfere.
+    //
+    // https://github.com/square/workflow-kotlin/issues/138
+    //
+    // Why " "? An empty string means no button.
+    setButton(button.toId(), " ") { _, _ -> }
+  }
+
+  return OverlayDialogHolder(
+    initialEnvironment = initialEnvironment,
+    dialog = this,
+    onUpdateBounds = null,
+    onBackPressed = null
+  ) { rendering, _ ->
+    with(this) {
+      if (rendering.cancelable) {
+        setOnCancelListener { rendering.onEvent(Canceled) }
+        setCancelable(true)
+      } else {
+        setCancelable(false)
+      }
 
-            setMessage(rendering.message)
-            setTitle(rendering.title)
+      setMessage(rendering.message)
+      setTitle(rendering.title)
 
-            // The buttons won't actually exist until the dialog is showing.
-            if (isShowing) updateButtonsOnShow(rendering) else setOnShowListener {
-              updateButtonsOnShow(rendering)
-            }
-          }
-        }
+      // The buttons won't actually exist until the dialog is showing.
+      if (isShowing) updateButtonsOnShow(rendering) else setOnShowListener {
+        updateButtonsOnShow(rendering)
       }
+    }
   }
+}
 
-  private fun Button.toId(): Int = when (this) {
-    POSITIVE -> DialogInterface.BUTTON_POSITIVE
-    NEGATIVE -> DialogInterface.BUTTON_NEGATIVE
-    NEUTRAL -> DialogInterface.BUTTON_NEUTRAL
-  }
+@WorkflowUiExperimentalApi
+private fun Button.toId(): Int = when (this) {
+  POSITIVE -> DialogInterface.BUTTON_POSITIVE
+  NEGATIVE -> DialogInterface.BUTTON_NEGATIVE
+  NEUTRAL -> DialogInterface.BUTTON_NEUTRAL
+}
 
-  private fun AlertDialog.updateButtonsOnShow(rendering: AlertOverlay) {
-    setOnShowListener(null)
+@WorkflowUiExperimentalApi
+private fun AlertDialog.updateButtonsOnShow(rendering: AlertOverlay) {
+  setOnShowListener(null)
 
-    for (button in Button.values()) getButton(button.toId()).visibility = GONE
+  for (button in Button.values()) getButton(button.toId()).visibility = GONE
 
-    for (entry in rendering.buttons.entries) {
-      getButton(entry.key.toId())?.apply {
-        setOnClickListener { rendering.onEvent(ButtonClicked(entry.key)) }
-        text = entry.value
-        visibility = VISIBLE
-      }
+  for (entry in rendering.buttons.entries) {
+    getButton(entry.key.toId())?.apply {
+      setOnClickListener { rendering.onEvent(ButtonClicked(entry.key)) }
+      text = entry.value
+      visibility = VISIBLE
     }
   }
 }

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

@@ -43,7 +43,7 @@ internal fun <D : Dialog> D.maintainBounds(
 }
 
 @WorkflowUiExperimentalApi
-internal fun <D : Dialog> D.maintainBounds(
+private fun <D : Dialog> D.maintainBounds(
   bounds: StateFlow<Rect>,
   onBoundsChange: (Rect) -> Unit
 ) {

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

@@ -5,6 +5,9 @@ import android.os.Parcel
 import android.os.Parcelable
 import android.os.Parcelable.Creator
 import android.view.KeyEvent
+import android.view.KeyEvent.ACTION_UP
+import android.view.KeyEvent.KEYCODE_BACK
+import android.view.KeyEvent.KEYCODE_ESCAPE
 import android.view.MotionEvent
 import android.view.Window
 import androidx.core.view.doOnAttach
@@ -46,14 +49,17 @@ internal class DialogSession(
    * Wrap the given dialog holder to maintain [allowEvents] on each update.
    */
   val holder: OverlayDialogHolder<Overlay> = OverlayDialogHolder(
-    holder.environment, holder.dialog
+    holder.environment, holder.dialog, holder.onUpdateBounds, holder.onBackPressed
   ) { overlay, environment ->
     allowEvents = !environment[CoveredByModal]
     holder.show(overlay, environment)
   }
 
   val savedStateRegistryKey = Compatible.keyFor(holder.showing, index.toString())
 
+  private val KeyEvent.isBackPress: Boolean
+    get() = (keyCode == KEYCODE_BACK || keyCode == KEYCODE_ESCAPE) && action == ACTION_UP
+
   fun showDialog(
     parentLifecycleOwner: LifecycleOwner,
     stateRegistryAggregator: WorkflowSavedStateRegistryAggregator
@@ -68,7 +74,18 @@ internal class DialogSession(
         }
 
         override fun dispatchKeyEvent(event: KeyEvent): Boolean {
-          return !allowEvents || realWindowCallback.dispatchKeyEvent(event)
+          // Consume all events if we've been told to do so.
+          if (!allowEvents) return true
+
+          // If there is an onBackPressed handler invoke it instead of allowing
+          // the normal machinery to call Dialog.onBackPressed.
+          if (event.isBackPress) {
+            holder.onBackPressed?.invoke()
+            return true
+          }
+
+          // Allow the usual call to Dialog.onBackPressed.
+          return realWindowCallback.dispatchKeyEvent(event)
         }
       }
     }

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

@@ -155,19 +155,13 @@ public class LayeredDialogSessions private constructor(
         // with the new Overlay at that index. Just update it.
         sessions[i].also { it.holder.show(overlay, dialogEnv) }
       } else {
-        // We need a new dialog for this overlay. Time to build it.
-        // We wrap our Dialog instances in DialogHolder to keep them
-        // paired with their current overlay rendering and environment.
-        // It would have been nice to keep those in tags on the Dialog's
-        // decor view, more consistent with what ScreenViewFactory does,
-        // but calling Window.getDecorView has side effects, and things
-        // break if we call it to early. Need to store them somewhere else.
         overlay.toDialogFactory(dialogEnv)
           .buildDialog(overlay, dialogEnv, context)
           .let { holder ->
             holder.onUpdateBounds?.let { updateBounds ->
               holder.dialog.maintainBounds(holder.environment) { b -> updateBounds(b) }
             }
+
             DialogSession(i, holder).also { newSession ->
               // Prime the pump, make the first call to OverlayDialog.show to update
               // the new dialog to reflect the first rendering.