求安卓大神解答！！~~~？？

[hexiong1987]

someView.setOnLongClickListener(new View.OnLongClickListener() {
// Called when the user long-clicks on someView
public boolean onLongClick(View view) {
if (mActionMode != null) {
return false;
}

// Start the CAB using the ActionMode.Callback defined above
mActionMode = getActivity().startActionMode(mActionModeCallback);
view.setSelected(true);
return true;
}
});



为什么要判断mActionMode != null) 谢谢！
本人是菜鸟~