fix: prevent terminal sessions ListView crash by giving adapter a UI-thread-only snapshot instead of sharing TermuxService's live session list mutated off the UI thread

Author: jatezzz

termux/termux-app/src/main/java/com/termux/app/TermuxActivity.java

@@ -628,7 +628,7 @@ public void onResetTerminalSession() {
 
     private void setTermuxSessionsListView() {
         ListView termuxSessionsListView = findViewById(R.id.terminal_sessions_list);
-        mTermuxSessionListViewController = new TermuxSessionsListViewController(this, mTermuxService.getTermuxSessions());
+        mTermuxSessionListViewController = new TermuxSessionsListViewController(this, mTermuxService.getTermuxSessionsListSnapshot());
         termuxSessionsListView.setAdapter(mTermuxSessionListViewController);
         termuxSessionsListView.setOnItemClickListener(mTermuxSessionListViewController);
         termuxSessionsListView.setOnItemLongClickListener(mTermuxSessionListViewController);
@@ -974,14 +974,22 @@ public boolean isTerminalToolbarTextInputViewSelected() {
 
 
     public void termuxSessionListNotifyUpdated() {
-        if (mTermuxSessionListViewController == null) return;
+        // The session list may be mutated on a background thread (e.g. onCreateNewSession() runs
+        // createTermuxSession() on a background executor). Re-snapshotting the service's list into
+        // the adapter must therefore happen on the UI thread, so the adapter's own list is only
+        // ever read/written by the UI thread and the ListView can never observe a concurrent change.
         if (Looper.myLooper() == Looper.getMainLooper()) {
-            mTermuxSessionListViewController.notifyDataSetChanged();
+            refreshSessionsListView();
         } else {
-            TermuxExecutor.executeOnMain(mTermuxSessionListViewController::notifyDataSetChanged);
+            TermuxExecutor.executeOnMain(this::refreshSessionsListView);
         }
     }
 
+    private void refreshSessionsListView() {
+        if (mTermuxSessionListViewController == null || mTermuxService == null) return;
+        mTermuxSessionListViewController.updateSessions(mTermuxService.getTermuxSessionsListSnapshot());
+    }
+
     public boolean isVisible() {
         return mIsVisible;
     }

termux/termux-app/src/main/java/com/termux/app/TermuxService.java

@@ -896,6 +896,16 @@ public synchronized List<TermuxSession> getTermuxSessions() {
         return mShellManager.mTermuxSessions;
     }
 
+    /**
+     * Returns a consistent copy of the current {@link TermuxSession} list. Unlike
+     * {@link #getTermuxSessions()}, this does not expose the live backing list, so it is safe to
+     * iterate from any thread (e.g. to feed a UI adapter). The copy is taken under the same monitor
+     * that guards all session mutations, so it can never observe a half-applied add/remove.
+     */
+    public synchronized List<TermuxSession> getTermuxSessionsListSnapshot() {
+        return new ArrayList<>(mShellManager.mTermuxSessions);
+    }
+
     @Nullable
     public synchronized TermuxSession getTermuxSession(int index) {
         if (index >= 0 && index < mShellManager.mTermuxSessions.size())

termux/termux-app/src/main/java/com/termux/app/terminal/TermuxSessionsListViewController.java

@@ -22,6 +22,7 @@
 import com.termux.shared.theme.NightMode;
 import com.termux.shared.theme.ThemeUtils;
 import com.termux.terminal.TerminalSession;
+import java.util.ArrayList;
 import java.util.List;
 
 public class TermuxSessionsListViewController extends ArrayAdapter<TermuxSession> implements AdapterView.OnItemClickListener, AdapterView.OnItemLongClickListener {
@@ -32,10 +33,24 @@ public class TermuxSessionsListViewController extends ArrayAdapter<TermuxSession
     final StyleSpan italicSpan = new StyleSpan(Typeface.ITALIC);
 
     public TermuxSessionsListViewController(TermuxActivity activity, List<TermuxSession> sessionList) {
-        super(activity.getApplicationContext(), R.layout.item_terminal_sessions_list, sessionList);
+        // Defensively copy so the adapter owns its data instead of sharing the service's live list.
+        // The backing list is then only ever touched on the UI thread (here and in updateSessions),
+        // so a background session add/remove can never mutate it while the ListView is laying out.
+        super(activity.getApplicationContext(), R.layout.item_terminal_sessions_list, new ArrayList<>(sessionList));
         this.mActivity = activity;
     }
 
+    /**
+     * Replace the adapter's session snapshot with a copy of {@code sessions} and refresh the
+     * ListView in a single notification. Must be called on the UI thread.
+     */
+    public void updateSessions(@NonNull List<TermuxSession> sessions) {
+        setNotifyOnChange(false);
+        clear();
+        addAll(sessions);
+        notifyDataSetChanged();
+    }
+
     @SuppressLint("SetTextI18n")
     @NonNull
     @Override