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Flutter Alarm Application Permissions

I am developing a flutter alarm application and I ran into a problem. Probably it is easy to solve, but as I do not know how I thought you might know. I attached a file showing the other permissions feed of the alarm application alarmy which I found in the playstore. In the file, you can see that the "Show on Lock screen" and the "Display pop-up windows while running in the background" permission are both accepted from the start. On the other hand in case of the alarm application "Ultra Alarm" I am developing the two permission are denied from the start and I do not know how to change that. Maybe you can help me. It is a mi device.

I'm not sure if it's disabled by the system or if you haven't asked for the permissions, in the second case I recommend you to use permission handler, on the other hand, if the system is blocking the app to grant the permission it's becasuse you haven't made the setup on your Info.plist
I recommend you to check this post

What happens when a permission is disabled at runtime?

I couldn't find any information about what happens when the user disables an app's permission while the app is running.
Is the application re-initilized?
I saw that in some apps if a Dialog or BottomSheet is open while I disable the permission, the dialog is no longer displayed when I return to the app.
Can anyone explain what happens in-detail when a permission is denied at runtime? Or does anyone have some useful links for me?
I would be especially interested in which lifecycle events are called when returning to the app.

When a previously granted permission is revoked through settings, the app is force stopped. You can see this by watching your app in the debugger. The app process is marked DEAD as soon as the permission is revoked.
Returning to the app will launch it from the main activity. I've never really looked into why this happens, but I assume it's because when a granted permission is revoked, the user could be deep into the app at a place where it is assumed the permission is granted. When the permission is revoked, there's no way to know if the screen they are currently in is even valid anymore.
Upon returning to the app, the app's state is restored and your current activity will be restarted, similar to a configuration change. If the activity you are in assumes a certain permission is granted, you should probably check that permission again in onCreate() to make sure you have it.

Simply put, That depends on what the app is trying to do when it needs permission.
For example: If we live in a country that requires you to be an adult to watch any video on YouTube, nothing will work with Location permissions denied
Another example: If you want to take photos using your phone via an app, the Camera permission should be permitted.
Under some circumstances, just part functions of app can not be used, but at an Extreme case, app would throw Security Exception and crash.

According to your point :
I saw that in some apps if a Dialog or BottomSheet is open while I
disable the permission, the dialog is no longer displayed when I
return to the app.
There is no lifecycle callback about what you do once permission is denied, but there's method on ActivityCompat which gives you flag if you want to show your own Dialog/BottomSheet
So, you can call shouldShowRequestPermissionRationale() method from ActivityCompat & make your own logic work when it's true.
shouldShowRequestPermissionRationale :
Gets whether you should show UI with rationale for requesting a permission. You should do this only if you do not have the permission and the context in which the permission is requested does not clearly communicate to the user what would be the benefit from granting this permission.
For example,
if you write a camera app, requesting the camera permission would be expected by the user and no rationale for why it is requested is needed.
If however, the app needs location for tagging photos then a non-tech savvy user may wonder how location is related to taking photos. In this case you may choose to show UI with rationale of requesting this permission.
While disabling permission for first time will give you callback in onRequestPermissionResult() method.

How to ask permissions from a Service

I am implementing a service that uses LocationManager to get and utilize the tablet location. This service is start and stop from an activity.
The latest Android requires that permissions are requested on runtime. Now I have managed to do this on an activity by using requestPermission in onCreate , checkSelfPermission everytime I use some Location manager function, and adding the requestPermission function and overriding the onRequestPermissionResult.
It works great.
Now for my service I need to do the same, but these functions seems to work only for activities. How can I activate permissions in a Service?
just in case, I have already asked for permissions in the activity that starts and stops the services

How can I activate permissions in a Service?
You don't. You activate (i.e., request) permissions from an activity. That is not negotiable.
Ideally, you request permissions before the activity starts the service or does something that will eventually cause the service to start (e.g., schedules the job with JobScheduler).
If you determine that your service no longer has the necessary permissions — perhaps the user revoked them from Settings — you could raise a Notification that leads the user to an activity where you re-request the permissions.
It is technically possible for a service to start an activity which requests the permissions. Usually, this is not a good idea, as you may not know what the user is doing at that moment, and the user may be unhappy to have you interrupt them with this permission request.

How can I activate permissions in a Service?
You can't request for permissions from services. Permissions should be asked explicitly which should be visible to the user in UI. However you can ask permission from activity and, if succeed, you can access those resources until user again turned off permission for your app.
how can you "transfer" these permissions to the service?
Permission is assigned for the entire app, so you don't need to transfer it from one activity to another or from one activity to service. Once you get a permission in an Activity, that permission is assigned to the entire app and your services can access the resources then after. cheers :)

Android 6.0 Permissions - Where to place permission requests?

with Androids new permission system, I was wondering how to implement it right. The tutorials about how and when to use the permissions seem to be pretty clear. However, I don't know who requests the permissions and where to request them.
So, basically my question is: should the Activity, who starts another Activity request the permission beforehand or should the Activity which requires the permission place the request?
If the Activity which requires the permission should request for it, should I call requestForPermission inside onCreate or in onStart?
Though it seems to be very simple questions, I haven't found any hints in the documentation.
Thanks.

should the Activity, who starts another Activity request the permission beforehand or should the Activity which requires the permission place the request?
That is up to you. The main guidance is that there should be a clear tie from something the user does to your request for permissions:
If your app needs certain permissions to do anything meaningful, ask for them when your app starts up, perhaps after any sort of "welcome" presentation to advise them about why you need the permissions.
If your app needs certain permissions to do something based on the user performing some in-app action, like tapping on an action bar item or ListView row, ask for the permission when the user performs that action.
Asking for permissions at semi-random points in the app will simply lead to user confusion ("what did I do? why is it asking me this? and why are these questions appearing in an Stack Overflow answer?!?").

If your app can't function properly without a particular permission might be good to have a welcome permission flow where you explain why need the permissions and ask for the grants. For example : Google maps and location permission
If some specific parts of the app need a separate permission you can call the permission check just before doing a method call that needs permission. In this case you can create a wrapper for your function that needs contact permission and always call that wrapper instead of the actual method. For example : Google maps and microphone permission when you try to use the search with voice functionality
More details http://inthecheesefactory.com/blog/things-you-need-to-know-about-android-m-permission-developer-edition/en
also check out https://github.com/permissions-dispatcher/PermissionsDispatcher could reduce a lot of permission code.

When ever your X task struck due to some "Y" permission then only ask for permission. There is no point of asking in onCreate or onStart method.
if you ask for "Y" permission at the start of Activity then there is no difference between Android M and below model. Exploit the beauty of Android M. for example if your require storage permission for creating a temp it's better make a temp file in App internal area i.e /data/data/your package name/files/ rather than asking for storage permission to users. Overall my point is exploit these options as much as you before it become necessary condition to ask for "Y" permission.
Regarding Activity concern , your task must be running be over some fragment or activity let that activity handle the onRequestPermission results.

Is there a way to get the currently running activity from a service without the GET_TASKS permission in Android?

I have a service which monitors the activity stack to get the top activity on the stack, and performs an action based on the top activity. I figured out a way to do this using the GET_TASKS permission. But the problem is that adding a new permission forces my users to manually update their application. So I wanted to know if there is any way to get the currently running activity without using the GET_TASKS permission?

No. The permission is there for a reason. The docs for that permission say:
Allows an application to get information about the currently or recently running tasks.
and clearly you want to get information about currently running tasks, so you need this permission. Just explain in your release notes why you require the new permission and if your application has enough value to your users, they'll update it anyway.