获得自己程序的版本

private String mVersion;        public String longVersion() {            if (mVersion == null) {                PackageManager pm = getPackageManager();                PackageInfo pi;                try {                    pi = pm.getPackageInfo(getPackageName(), 0);                    mVersion = pi.versionName;                } catch (NameNotFoundException e) {                    mVersion = ""; // failed, ignored                }            }            return mVersion;        }        public String shortVersion() {            String v = longVersion();            v = v.substring(0, v.lastIndexOf('.'));            return v;        }