Runtime permission Request

PermissionRequest.java

import android.app.Activity;
import android.content.pm.PackageManager;
import android.support.annotation.Nullable;
import android.support.v4.app.ActivityCompat;
import android.support.v7.app.AlertDialog;

public class PermissionRequest {
  private static int RC = 1;
  private final String permission;
  @Nullable
  private String rationalExplanation;
  private Runnable onGranted;
  private Runnable onRejected;
  private int requestCode;

  private PermissionRequest(String permission) {
    this.permission = permission;
    requestCode = ++RC;
  }

  public static PermissionRequest of(String permission) {
    return new PermissionRequest(permission);
  }

  public PermissionRequest rationalExplanation(String rationalExplanation) {
    this.rationalExplanation = rationalExplanation;
    return this;
  }

  public PermissionRequest onGranted(Runnable onGranted) {
    this.onGranted = onGranted;
    return this;
  }

  public PermissionRequest onRejected(Runnable onRejected) {
    this.onRejected = onRejected;
    return this;
  }

  public void send(Activity activity) {
    if (ActivityCompat.checkSelfPermission(activity, permission) == PackageManager.PERMISSION_GRANTED) {
      postGranted();
    } else {
      requestPermission(activity);
    }
  }

  @SuppressWarnings("unused")
  public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
    if (requestCode == this.requestCode) {
      if (grantResults.length == 1 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
        postGranted();
      } else {
        postRejected();
      }
    }
  }

  private void requestPermission(Activity activity) {
    if (ActivityCompat.shouldShowRequestPermissionRationale(
        activity,
        permission)) {
      if (rationalExplanation == null) {
        postRejected();
      } else {
        new AlertDialog.Builder(activity)
            .setMessage(rationalExplanation)
            .setPositiveButton("OK", (dialog, which) -> {
              // Contact permissions have not been granted yet. Request them directly.
              ActivityCompat.requestPermissions(
                  activity,
                  new String[]{permission},
                  requestCode);
            })
            .show();
      }
    } else {
      ActivityCompat.requestPermissions(
          activity,
          new String[]{permission},
          requestCode);
    }
  }

  private void postGranted() {
    if (onGranted != null) {
      onGranted.run();
    }
  }

  private void postRejected() {
    if (onRejected != null) {
      onRejected.run();
    }
  }
}