获取应用程序版本号

public String getVersionName() {
        String versionName = "";
        PackageManager packageManager = getPackageManager();
        try {
            PackageInfo packageInfo = packageManager.getPackageInfo("com.example.picdemo", 0);
            versionName=packageInfo.versionName;
        } catch (NameNotFoundException e) {
            e.printStackTrace();
        }
        return versionName;
    }