Polymer 2.0中的纸张工具栏

Question

When I install paper-toolbar when using Polymer 2.0 I always get this in the PolymerCLI

Unable to find a suitable version for polymer, please choose one by typing one of the numbers below:
1) polymer#^1.2.0 which resolved to 1.8.1 and is required by paper-toolbar#1.1.7
2) polymer#^1.1.0 which resolved to 1.8.1 and is required by iron-flex-layout#1.3.2
3) polymer#^1.0.0 which resolved to 1.8.1 and is required by paper-styles#1.2.0
4) polymer#^2.0.0-rc.2 which resolved to 2.0.0-rc.2 and is required by Pokedex
5) polymer#^2.0.0-rc.1 which resolved to 2.0.0-rc.2 and is required by iron-component-page#9bcd9558d7

Prefix the choice with ! to persist it to bower.json


? Answer

Answer 1

这是因为在安装某些Polymer Element时必须指定版本：

bower install --save PolymerElements/paper-button#2.0-preview