錯誤彈窗如圖：

Installation failed with message Failed to finalize session: INSTALL_FAILED_TEST_ONLY:installPackageLI.

It is possible that this issue is resolved by uninstalling an existing version of the apk if it is present, and then re-installing.

WARNING: Uninstalling will remove the application data!

Do you want to uninstall the existing application?

1.Clean Project之後再試，如果還不行就在模擬器上面解除安裝該app。

2解決方法：

1、開啟選單File——Settings——Build,Execution,Deployment——Instant Run

2、不選中Enable Instant Run to hot swap code/resource changes on deploy(default enabled)

3、依次點選Apply——OK，重新執行程式，大功告成。 

我使用第一種方式，完美的解決了我自己的問題。