a sheme of using permissions on android

PermissionsManager.java

package com.jack.sparrow.mylauncher.model;

import android.Manifest;
import android.app.Activity;
import android.content.Context;
import android.content.pm.PackageManager;
import android.os.Build;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.util.Log;

import com.jack.sparrow.mylauncher.utils.Settings;
import com.jack.sparrow.mylauncher.utils.Tags;

import java.util.ArrayList;
import java.util.List;

public class PermissionsManager {
    private static PermissionsManager instance;
    private        Context            context;

    private PermissionsManager() {
    }

    private PermissionsManager(Context context) {
        this.context = context;
    }

    public static PermissionsManager getInstance(Context context) {
        if (instance == null) {
            instance = new PermissionsManager(context);
        }
        return instance;
    }

    public List<String> findUnAskedPermissions(List<String> wanted) {
        List<String> result = new ArrayList<>();
        for (String p : wanted) {
            if (!hasPermission(p) && shouldWeAskForPermission(p)) result.add(p);
        }
        return result;
    }

    /**
     * defines if permission is granted
     *
     * @param permission example:Manifest.permission.READ_CONTACTS
     * @return
     */
    public boolean hasPermission(String permission) {
        if (isPermissionModelHigherLollipop()) {
            return ((ContextCompat.checkSelfPermission(context,
                                                       permission)) == PackageManager.PERMISSION_GRANTED);
        }
        return true;
    }

    private boolean shouldWeAskForPermission(String permission) {
        // todo check if this permission is in shared preferences
        return true;
    }

    /**
     * checks if the permission model is as in Marshmallow or not
     *
     * @return
     */
    public boolean isPermissionModelHigherLollipop() {
        return (Build.VERSION.SDK_INT > Build.VERSION_CODES.LOLLIPOP_MR1);
    }

    /**
     * this method is called from activity
     * @param activity
     */
    private void exampleOfUsingPermission(Activity activity) {
        final String permission = Manifest.permission.READ_CONTACTS;
        // at this point of code we need to use a feature
        // make it as one function and call feature()
        if (hasPermission(permission)) {
            // we can use feature because have permissions
            feature();
        } else {
            if (shouldWeAskForPermission(permission)) {
                // display user that permission is denied
                // maybe at custom toast as in chrome when close tab
            } else {
                requestPermission(permission, RequestCodes.FEATURE_1, activity);
                markPermissionAsAsked(permission);
            }
        }
    }

    /**
     * its feature that needs a permission
     */
    public void feature() {

    }

    /**
     * check if permission is granted
     *
     * @param permission example: Manifest.permission.READ_CONTACTS
     * @param code       int constant
     * @return true if permission already granted and false if attempting to grant it
     */
    private boolean requestPermission(String permission, int code, Activity activity) {
        // Here, thisActivity is the current activity
        if (ContextCompat.checkSelfPermission(activity,
                                              permission) != PackageManager.PERMISSION_GRANTED) {
            if (Settings.DEBUG) Log.d(Tags.tag, "permission " + permission + " is granted");
            // Should we show an explanation?
            if (ActivityCompat.shouldShowRequestPermissionRationale(activity,
                                                                    Manifest.permission.READ_CONTACTS)) {

                // Show an explanation to the user *asynchronously* -- don't block
                // this thread waiting for the user's response! After the user
                // sees the explanation, try again to request the permission.

            } else {

                // No explanation needed, we can request the permission.
                ActivityCompat.requestPermissions(activity, new String[]{permission}, code);

                // MY_PERMISSIONS_REQUEST_READ_CONTACTS is an
                // app-defined int constant. The callback method gets the
                // result of the request.
            }
            return true;
        } else {
            if (Settings.DEBUG) Log.d(Tags.tag, "permission " + permission + " is not granted");
            return false;
        }
    }

    private void markPermissionAsAsked(String permission) {
        // todo sharedPreferences.edit().putBoolean(permission, false).apply();

    }

    public class RequestCodes {
        public static final int FEATURE_1 = 100;
    }
}
public class Launcher extends AppCompatActivity {

  @Override protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.launcher);
        ButterKnife.bind(this);
    
        permissionsManager = PermissionsManager.getInstance(this);
                permissionsManager.exampleOfUsingPermission(this);

  }
  
  
@Override public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
        switch (requestCode) {
            case PERMISSION_REQUEST_BIND_DEVICE_ADMIN: {
                // If request is cancelled, the result arrays are empty.
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    permissionsManager.feature();
                    // permission was granted, yay! Do the
                    // contacts-related task you need to do.

                } else {

                    // permission denied, boo! Disable the
                    // functionality that depends on this permission.

                    //display that permission is denied and feature cant be used
                }
                return;
            }

            // other 'case' lines to check for other
            // permissions this app might request
        }
    }
}