Handler 容易引起内存泄露，这是大家都知道的，所以你应该会在适当的时候调用 removeCallbacks()
Handler removeCallbacks 安全性分析
Author: linroid
Permalink: http://linroid.com/2015/01/22/2015-01-22-handler-removecallbacks-safety/
License: Copyright (c) 2019 CC-BY-NC-4.0 LICENSE
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