Android : How butterknife inject actionbar custome view?

I am using ButterKnife in my project and it's awesome.

I can inject the content view in my Activity by ButterKnife.inject(this), I'm also using custom view in my actionbar:

private void configActionbar() {
    ActionBar actionBar = getSupportActionBar();
    actionBar.setDisplayHomeAsUpEnabled(true);
    actionBar.setDisplayShowTitleEnabled(false);
    actionBar.setDisplayShowCustomEnabled(true);
    View actionbarView = LayoutInflater.from(this)
            .inflate(R.layout.actionbar_view, null);
    actionBar.setCustomView(actionbarView);
}

I want to bind onclick listener on the view included in the actionbar. The tradition way like following:

Button a = (Button)actionbarView.findViewById(R.id.btn);
a.setOnClickListener(xxxx) ;

Expected ButterKnife way:

@OnClick(R.id.btn)
public void btnClick(){....}

How to use ButterKnife way in my case?