1：导入android studio project 时总会出现运行处一个红色叉号，这里可以点击选择叉号上面显示的Edit Configurations 查看右下角的错误警告信息。:
2：记录错误:
the apk for your currently selected variant(app-release-unsigned.apk)is not signed.Please specity a signing configuration for this variant(release)
3：解决方法：android studio左下角打开Build Variants，将release换为debug即可。