Ionic angular - update the code in MainActivity

Question

In my Ionic app after successfully run the application the MainActivity.java file has been generated inside the platform/android project folder. What I want is, I need to modify this file to handle android.permission.SYSTEM_ALERT_WINDOW permission. Since it is autogenerated file where we can implement this code in my ionic project (.ts file), so that it will reflect on MainActivity.java.

Basically I want to check permission in my.ts file and after compile and run the application, it should reflect on MainActivity.java.

Sample code which I want in MainActivity.java like below:

 @RequiresApi(api = Build.VERSION_CODES.M)
    @Override
    protected void onResume() {
        super.onResume();
        if (!Settings.canDrawOverlays(this)) {
            Intent intent = new Intent(Settings.ACTION_MANAGE_OVERLAY_PERMISSION,
                    Uri.parse("package:" + this.getPackageName()));
            startActivityForResult(intent, ACTION_MANAGE_OVERLAY_PERMISSION_REQUEST_CODE);
        }
    }

    @RequiresApi(api = Build.VERSION_CODES.M)
    @Override
    protected void onActivityResult(int requestCode, int resultCode,  Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

         if (requestCode == OVERLAY_PERMISSION_REQUEST_CODE) {
            if (Settings.canDrawOverlays(this)) {
                Toast.makeText(this, "permission granted display data",Toast.LENGTH_SHORT).show();
            } else {
                Toast.makeText(this, "you can't proceed without overlay permission", Toast.LENGTH_SHORT).show();
            }
        }
    }

I want this above code should be in MainActivity.java, so for that which file I need to modify in my Ionic angular project?