From caa4700487fa9c56a409e59f5758ae4147ec7362 Mon Sep 17 00:00:00 2001
From: Julian Winkler <julian.winkler1@web.de>
Date: Tue, 25 Mar 2025 19:55:31 +0100
Subject: [PATCH] ViewGroup: keep track of detachedChildren

Some ViewGroups like ViewPager2 call attachViewToParent() without
calling detachViewFromParent() first. This is not allowed according to
the Android API spec, but we need to handle it.
---
 src/api-impl/android/view/ViewGroup.java | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/api-impl/android/view/ViewGroup.java b/src/api-impl/android/view/ViewGroup.java
index 47bd3661..b8defa1d 100644
--- a/src/api-impl/android/view/ViewGroup.java
+++ b/src/api-impl/android/view/ViewGroup.java
@@ -15,6 +15,7 @@ import java.util.Objects;
 
 public class ViewGroup extends View implements ViewParent, ViewManager {
 	public ArrayList<View> children;
+	private ArrayList<View> detachedChildren;
 	private OnHierarchyChangeListener onHierarchyChangeListener;
 	private LayoutTransition transition;
 
@@ -34,6 +35,7 @@ public class ViewGroup extends View implements ViewParent, ViewManager {
 		super(context, attrs, defStyleAttr);
 
 		children = new ArrayList<View>();
+		detachedChildren = new ArrayList<View>();
 	}
 
 	public void addView(View child) {
@@ -136,10 +138,15 @@ public class ViewGroup extends View implements ViewParent, ViewManager {
 	}
 
 	public void detachViewFromParent(int index) {
-		children.remove(index).parent = null;
+		View child = children.remove(index);
+		child.parent = null;
+		detachedChildren.add(child);
 	}
 
 	public void attachViewToParent(View view, int index, LayoutParams params) {
+		if (!detachedChildren.remove(view)) {
+			addViewInternal(view, index, params);
+		}
 		if (!checkLayoutParams(params))
 			params = generateLayoutParams(params);
 
@@ -151,6 +158,9 @@ public class ViewGroup extends View implements ViewParent, ViewManager {
 	}
 
 	protected void removeDetachedView(View child, boolean animate) {
+		if (!detachedChildren.remove(child))
+			return;
+		child.parent = null;
 		native_removeView(widget, child.widget);
 		if (isAttachedToWindow())
 			child.detachFromWindowInternal();
@@ -388,6 +398,7 @@ public class ViewGroup extends View implements ViewParent, ViewManager {
 	public void detachViewFromParent(View view) {
 		children.remove(view);
 		view.parent = null;
+		detachedChildren.add(view);
 	}
 
 	public void setTouchscreenBlocksFocus(boolean touchscreenBlocksFocus) {}