Solving Android Toast Restrictions and Crash Issues

Toast is a basic notification widget on Android that developers use for quick user feedback. Because it is provided by the system and does not depend on a foreground UI, Google has added restrictions in newer Android versions that can break normal business logic.

Problems encountered :

When the user disables the app’s Show notifications switch, Toast no longer appears.

On Android 7.1.2 (API 25) and below, calling Toast.show() may throw BadTokenException, causing a crash.

Custom windows of type TYPE_TOAST also throw token null is not valid on Android 7.1.1/7.1.2.

Root cause analysis – Toast display is not performed directly by the Toast object. In Toast#show() the framework calls the remote INotificationManager service (NotificationManagerService, NMS) to enqueue the toast. NMS creates a token and passes a tn object back to the app. The app then asks WindowManager to add a window of type TYPE_TOAST using that token. If the notification permission is disabled, NMS rejects the request and the toast is never shown.

Key source snippets:

@Aspect
public class ToastAspect {
    @Pointcut("call(* android.widget.Toast+.show(..))")
    public void toastShow() {}

    @Around("toastShow()")
    public void toastShow(ProceedingJoinPoint point) {
        Toast toast = (Toast) point.getTarget();
        Context context = (Context) ReflectUtils.getValue(toast, "mContext");
        if (Build.VERSION.SDK_INT >= 19 && NotificationManagerCompat.from(context).areNotificationsEnabled()) {
            point.proceed(point.getArgs());
        } else {
            floatToastShow(toast, context);
        }
    }

    private static void floatToastShow(Toast toast, Context context) {
        // replace with custom MToast that does not rely on NMS
        new MToast(context)
            .setDuration(mDuration)
            .setView(mNextView)
            .setGravity(mGravity, mX, mY)
            .setMargin(mHorizontalMargin, mVerticalMargin)
            .show();
    }
}

This AspectJ hook intercepts every Toast.show() call and, when notifications are disabled, replaces the system toast with a custom MToast that creates its own window, bypassing the NMS check.

Handling BadTokenException – The exception is thrown later in the message queue, not at the call site. Android 8.0 catches it internally. For pre‑8.0 devices we introduced a custom ToastHandler that catches the exception in the same way, preventing the crash.

Token‑null issue – Starting with Android 7.1.1 the system requires a valid token for TYPE_TOAST. Our custom MToast cannot obtain this token, so the exception cannot be avoided by simply changing the window type. The only viable path is to stop using TYPE_TOAST altogether.

Alternative solutions explored :

Use WindowManager with overlay types ( TYPE_PHONE, TYPE_APPLICATION_OVERLAY) – requires high‑level permissions and many OEM quirks.

Show a Dialog / DialogFragment / PopupWindow – tightly coupled to an Activity and heavyweight for simple notifications.

Replace Toast with Snackbar – the officially recommended Material Design component, lightweight and flexible.

We chose the Snackbar route and built a custom implementation that supports:

Custom styles, animations, and layout extensions.

Passing a specific parent view, Dialog, or PopupWindow to avoid being covered.

Cross‑page display via a local broadcast mechanism encapsulated in SnackbarHelper.

// Example of broadcasting a message for cross‑page Snackbar
Intent intent = new Intent(ACTION_SHOW_SNACKBAR);
intent.putExtra(EXTRA_MESSAGE, "Operation completed");
LocalBroadcastManager.getInstance(context).sendBroadcast(intent);

// In SnackbarHelper’s receiver
String msg = intent.getStringExtra(EXTRA_MESSAGE);
Snackbar.make(parentView, msg, Snackbar.LENGTH_LONG).show();

With this approach the notification appears even when the user has turned off the system notification switch, and the solution has been adopted widely across Meituan’s Android codebase.

Conclusion – By intercepting Toast calls with AspectJ, providing a custom MToast, handling system exceptions, and finally migrating to a robust Snackbar‑based implementation, we eliminated crashes related to Toast restrictions while preserving user experience.