From db33cf313cbd121b512826b479d29bc0f23ad25c Mon Sep 17 00:00:00 2001
From: Dick Smith <github@dicksmith.ca>
Date: Wed, 14 Nov 2018 10:53:38 -0500
Subject: [PATCH] fix: crash on Android Tab-View #6466 (#6467)

* fix: crash on Android Tab-View NativeScript#6466

This fix has been tested in production with no new issues occurring.

Long-term solution would be one of the following, though:
1. reintroduce overrides for `saveState`/`restoreState` in the current PagerAdapter implementation (removed on this commit NativeScript@ac04ede#diff-f1459d509d1432b432c29bcd30e462fbL97)
2. use FragmentPagerAdapter
3. use FragmentStatePagerAdapter

Both 2 and 3 manage the save/restore cycles. The main difference between 2 and 3 is that 2 uses more memory, but allows for quicker switching between Fragments than 3. Since tabs should usually be limited to 5 or less, this may be the best choice to maintain performance, which is important for top level navigation tabs.

When I have more time I may experiment with these options myself to see what the difference to performance and memory consumption is for each.

* refactor: _commitCurrentTransaction method+comment

* chore: fix typo

* fix: missing class definition
---
 .../ui/tab-view/tab-view.android.ts           | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/tns-core-modules/ui/tab-view/tab-view.android.ts b/tns-core-modules/ui/tab-view/tab-view.android.ts
index 3e2b0b816..c88133342 100644
--- a/tns-core-modules/ui/tab-view/tab-view.android.ts
+++ b/tns-core-modules/ui/tab-view/tab-view.android.ts
@@ -200,10 +200,7 @@ function initializeNativeClasses() {
         }
 
         finishUpdate(container: android.view.ViewGroup): void {
-            if (this.mCurTransaction != null) {
-                (<any>this.mCurTransaction).commitNowAllowingStateLoss();
-                this.mCurTransaction = null;
-            }
+            this._commitCurrentTransaction();
         }
 
         isViewFromObject(view: android.view.View, object: java.lang.Object): boolean {
@@ -211,6 +208,9 @@ function initializeNativeClasses() {
         }
 
         saveState(): android.os.Parcelable {
+            // Commit the current transaction on save to prevent "No view found for id 0xa" exception on restore.
+            // Related to: https://github.com/NativeScript/NativeScript/issues/6466
+            this._commitCurrentTransaction();
             return null;
         }
 
@@ -221,8 +221,15 @@ function initializeNativeClasses() {
         getItemId(position: number): number {
             return position;
         }
-    }
 
+        private _commitCurrentTransaction() {
+            if (this.mCurTransaction != null) {
+                this.mCurTransaction.commitNowAllowingStateLoss();
+                this.mCurTransaction = null;
+            }
+        }
+    }
+    
     PagerAdapter = FragmentPagerAdapter;
 }
 
@@ -713,4 +720,4 @@ function tryCloneDrawable(value: android.graphics.drawable.Drawable, resources:
     }
 
     return value;
-}
\ No newline at end of file
+}