Utility class to assist with requesting permissions at run time on Android.

PermissionHandler.java

import android.content.pm.PackageManager;
import android.os.Build;

/**
 * {@link PermissionHandler} provides a simple API to request Android permissions
 * at runtime. The class exposes one static method: {@link #request} which the
 * requesting activity should call to request or check for permission. The requesting
 * activity must implement {@link PermissionActivity}.
 */
public class PermissionHandler {
    private static int[] grantedResult = new int[] { PackageManager.PERMISSION_GRANTED };

    /**
     * Request or check for a permission. The result of this should be handled in
     * onRequestPermissionResult, which must be implemented in the calling activity.
     * There are 3 cases here:
     * 1. If the permission is already granted, onRequestPermissionResult is called
     *    with {@link #grantedResult}
     * 2. If the permission is not already granted, and no rationale needs to be shown,
     *    the permission is requested by presenting the system dialog to the user,
     *    and onRequestPermissionResult is called with the result based on the selection of
     *    the user.
     * 3. If the permission is not already granted, and an explanation (rationale) needs to
     *    be shown, showRationale is called. Use it to show some explanation to the user (
     *    e.g. using a dialog or a snackbar), and possibly request the permission again using
     *    {@link #request}.
     * @param mActivity The activity requesting the permission. It should implement
     *                  the interface {@link PermissionActivity}
     * @param permission The permission to be requested
     * @param requestCode A unique request code to be used later for reference
     */
    public static void request(PermissionActivity mActivity, String permission, int requestCode) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M &&
                mActivity.checkSelfPermission(permission) != PackageManager.PERMISSION_GRANTED) {
            if (mActivity.shouldShowRequestPermissionRationale(permission)) {
                mActivity.showRationale(permission, requestCode);
            } else {
                mActivity.requestPermissions(new String[] { permission }, requestCode);
            }
        } else {
            mActivity.onRequestPermissionsResult(
                    requestCode,
                    new String[] { permission },
                    grantedResult);
        }
    }

    /**
     * Interface to be implemented by the calling activity. Only {@link #onRequestPermissionsResult}
     * and {@link #showRationale} actually need to be implemented. The other methods are already
     * implemented in {@link android.app.Activity}
     */
    public interface PermissionActivity {
        /** No need to implement this. Already implemented in {@link android.app.Activity}. */
        int checkSelfPermission(String permission);

        /** No need to implement this. Already implemented in {@link android.app.Activity}. */
        void requestPermissions(String[] permissions, int requestCode);

        /** No need to implement this. Already implemented in {@link android.app.Activity}. */
        boolean shouldShowRequestPermissionRationale(String permission);

        /** Implement this in your activity to handle the result of the {@link #request} **/
        void onRequestPermissionsResult(
                int requestCode, String[] permissions, int[] grantResults);

        /**
         * Implement this to show a rationale to the user for requesting a particular permission.
         * For instance, you can show a dialog or a toast explaining why you need the permission.
         * After showing the explanation, you can possibly request the permission again
         * using {@link #request}
         */
        void showRationale(String permission, int requestCode);
    }
}