当应用程序在Android api 28 (pie)中处于前台或后台时，在单击通知时“启动活动”会有额外的空值

Intent intent = getIntent();
if (intent != null && intent.getExtras() != null) {
    // 进行通知点击后的操作
} else {
    // 处理额外的空值情况，例如打开应用程序的主活动
}

Intent intent = new Intent(context, YourActivity.class);
PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, intent, 0);

NotificationCompat.Builder builder = new NotificationCompat.Builder(context)
        .setContentIntent(pendingIntent)
        .setContentTitle("标题")
        .setContentText("内容")
        .setSmallIcon(R.drawable.ic_notification);

NotificationManager notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
notificationManager.notify(notificationId, builder.build());