获取当前应用程序的版本号

/**
     * 获取当前应用程序的版本号
     */
    private String getVersion() {
        String st = getResources().getString(R.string.Version_number_is_wrong);
        PackageManager pm = getPackageManager();
        try {
            PackageInfo packinfo = pm.getPackageInfo(getPackageName(), 0);
            String version = packinfo.versionName;
            return version;
        } catch (NameNotFoundException e) {
            e.printStackTrace();
            return st;
        }
    }