PackageInfo 新增 firstInstallTime 和 lastUpdateTime 可以查看一个软件的安装和上次更新时间，这比直接获取APK路径查看文件时间更可靠，对于付费的私有路径未root的机型无权限获取的。

 

    /**

     * The time at which the app was first installed.  Units are as

     * per System#currentTimeMillis()}.

     */

    public long firstInstallTime;

    /**

     * The time at which the app was last updated.  Units are as

     * per System#currentTimeMillis()}.

     */

    public long lastUpdateTime;