Andriod UI automator test: check box click doesn't work

I'am writing test script using Andriod UI automator.

What I expect to do is click checkbox on webview, but it doesn't work.

When i checked the function click( ), it returns false.

The UIObject is exactly checkbox object, when i checked the function getclassName(). (I checked the element resourceId through uiautomatorviewer)

Other elements such as button returns true when i called method click

I Have no idea what problem is. Plz help me!!