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;
        }