public class MainActivity extends AppCompatActivity implements PermissionsApi.PermissionCallback {

    private static final int SMS_REQUEST = 101;
    private static final int STORAGE_REQUEST = 102;
    private static final int SOME_LIST_OF_PERMISSION = 103;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        PermissionsApi.getInstance().setPermissionCallback(this);
    }

/**
     * Permission rationale won't be shown when passed null. Its recommended to pass null for
     * those permissions which are optional.
     */
    private void onSmsPermission() {
        if (PermissionUtils.hasPermission(this, {Manifest.permission.RECEIVE_SMS}, 
        null, OPTIONAL_REQUEST))
        //Permission is already granted. Continue exuecuting your code.
    }

    private void onStoragePermission() {
        if (PermissionUtils.hasPermission(this,{Manifest.permission.READ_EXTERNAL_STORAGE,
        Manifest.permission.WRITE_EXTERNAL_STORAGE},
                getString(R.string.message_permission_rationale), REQUIRED_REQUEST))
            showToastMessage(getString(R.string.message_required_permission_granted));

    }

    /**
     * If a list of permissions needs to be granted, until the user grants 
     * all the permissions in the list the runtime dialogue will keep showing 
     * everytime user clicks on the button. Also, those permissions which are 
      * already granted won't be asked again.
     **/
    private void someListOfPermissions() {
        if (PermissionUtils.hasPermission(this, Utils.getPermissionList(),
                getString(R.string.message_permission_rationale), SOME_LIST_OF_PERMISSION))
            showToastMessage(getString(R.string.message_permission_list_granted));
    }

   
    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        if (this.isFinishing())
            return;
       switch (requestCode) {
            case SMS_REQUEST:
                /**
                 * Passing null here instead of rationale message will result in 
                  * permission being treated as denied instead of showing rationale message
                 */
                PermissionUtils.onRequestPermissionsResult(mContext, requestCode,
                permissions, grantResults, null);
                break;
            case STORAGE_REQUEST:
                PermissionUtils.onRequestPermissionsResult(mContext, requestCode, 
                permissions, grantResults, mContext.getString(R.string.message_permission_rationale));
                break;
            case SOME_LIST_OF_PERMISSION:
                PermissionUtils.onRequestPermissionsResult(mContext, requestCode, 
                permissions, grantResults, mContext.getString(R.string.message_permission_rationale));
                break;
        }
    }

    @Override
    public void onPermissionGranted(int requestCode) {
        switch (requestCode) {
            case SMS_REQUEST:
                showToastMessage(getString(R.string.message_optional_permission_granted));
                break;
            case STORAGE_REQUEST:
                showToastMessage(getString(R.string.message_required_permission_granted));
                break;
            case SOME_LIST_OF_PERMISSION:
                showToastMessage(getString(R.string.message_permission_list_granted));
                break;
        }
    }

    @Override
    public void onPermissionDenied(int requestCode) {
        if (requestCode == SMS_REQUEST)
            showToastMessage("Sms permission denied but can continue.");
        //Based on denied permission request code, handle the case accordingly.
    }