save and restore previous backstack in order to 'undo' unwanted backs…

…tack operations
wealthfront · Feb 25, 2022 · 15e8651 · 15e8651
1 parent 38daf0d
commit 15e8651
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Showing 3 changed files with 29 additions and 18 deletions.
diff --git a/magellan-library/src/main/java/com/wealthfront/magellan/navigation/NavigationDelegate.kt b/magellan-library/src/main/java/com/wealthfront/magellan/navigation/NavigationDelegate.kt
@@ -77,25 +77,27 @@ public open class NavigationDelegate(
     direction: Direction,
     backStackOperation: (Deque<NavigationEvent>) -> MagellanTransition
   ) {
+    containerView?.setInterceptTouchEvents(true)
+    navigationPropagator.beforeNavigation()
+    val oldBackStack = backStack.map { it.navigable }
+    val oldBackStackCopy = ArrayDeque(backStack)
+
+    val transition = backStackOperation.invoke(backStack)
     navigationRequestHandler?.let { navRequestHandler ->
-      val backstackCopy = ArrayDeque(backStack)
-      backStackOperation.invoke(backstackCopy)
-      // onNavigationRequested implementation determines whether nav operation should be skipped
-      if (backstackCopy.currentNavigable != null &&
-        navRequestHandler.onNavigationRequested(this, backstackCopy.currentNavigable!!)
+      if (backStack.currentNavigable != null &&
+        navRequestHandler.shouldOverrideNavigation(this, backStack.currentNavigable!!)
       ) {
+        backStack.clear()
+        backStack.addAll(oldBackStackCopy)
+        navRequestHandler.overrideNavigationRequest(this, backStack.currentNavigable!!)
         return
       }
     }
 
-    containerView?.setInterceptTouchEvents(true)
-    navigationPropagator.beforeNavigation()
-    val from = navigateFrom(currentNavigable)
-    val oldBackStack = backStack.map { it.navigable }
-    val transition = backStackOperation.invoke(backStack)
+    val from = navigateFrom(oldBackStackCopy.currentNavigable)
     val newBackStack = backStack.map { it.navigable }
     findBackstackChangesAndUpdateStates(oldBackStack = oldBackStack, newBackStack = newBackStack)
-    val to = navigateTo(currentNavigable!!, direction)
+    val to = navigateTo(backStack.currentNavigable!!, direction)
     navigationPropagator.afterNavigation()
     animateAndRemove(from, to, direction, transition)
   }

diff --git a/magellan-library/src/main/java/com/wealthfront/magellan/navigation/Navigator.kt b/magellan-library/src/main/java/com/wealthfront/magellan/navigation/Navigator.kt
@@ -4,10 +4,16 @@ import android.content.Context
 import android.view.View
 
 public interface NavigationRequestHandler {
-  public fun onNavigationRequested(
+  public fun shouldOverrideNavigation(
     navigationDelegate: NavigationDelegate,
     navigable: NavigableCompat
   ): Boolean
+
+  // what if this supplied a backstack operation, instead?
+  public fun overrideNavigationRequest(
+    navigationDelegate: NavigationDelegate,
+    navigable: NavigableCompat
+  )
 }
 
 public interface ViewTemplateApplier {

diff --git a/...mple-advanced/src/main/java/com/wealthfront/magellan/sample/advanced/SampleApplication.kt b/...mple-advanced/src/main/java/com/wealthfront/magellan/sample/advanced/SampleApplication.kt
@@ -21,15 +21,18 @@ class SampleApplication : Application() {
       .build()
 
     Magellan.navigationRequestHandler = object : NavigationRequestHandler {
-      override fun onNavigationRequested(
+      override fun overrideNavigationRequest(
+        navigationDelegate: NavigationDelegate,
+        navigable: NavigableCompat
+      ) {
+        navigationDelegate.goTo(UpdateAppStep())
+      }
+
+      override fun shouldOverrideNavigation(
         navigationDelegate: NavigationDelegate,
         navigable: NavigableCompat
       ): Boolean {
-        if (navigable is SuggestExhibitJourney) {
-          navigationDelegate.goTo(UpdateAppStep())
-          return true
-        }
-        return false
+        return navigable is SuggestExhibitJourney
       }
     }
   }