modelsim simulator problem. Help me. Thanks

Hi, All,
I meet a question when I use modelsim.
The question is:
After I finished a simulation, I can see signals in the dataflow and waveform windows. Then I save a .wlf file.
Then I closed the modelsim tools. Then I reopen the modelsim again. Then I only open the .wfl file without running others. I can only see signals in waveform windows. I can't see ang signals in dataflow windows yet.And I drag signal from other windows to dataflow windows. It is still nothing. Before I close modelsim, I can see the signals in dataflow windows. But after I close modelsim and reopne modelsim, I can't see anything in dataflow windows.
The tools shows me "Error: Active logfile is not in simulation mode"
Could you give me some suggestion?
Thanks a lot.

请说中文，除非你是外国人；就是你是外国人，在特定的情况下，也请和我说中文。

.wlf 实际上是一个 脚本文件
当你再次打开modelsim时，需要重新点击work lib里得相应模块。弹出 sim窗口，把鼠标点下 想要观测得模块，这是右边得信号列表会列出该模块得所有信号。一般情况下，你想观察这些信号时，需要把他们add to wave。
不过介于你上次已经保存了响应得 wlf文件，只用在default 波形窗口，打开该文件就行了，点restart ，然后 就可以重新 run