嗨，我正在尝试在我的 react-native 项目上运行“yarn android”。并且遇到了以下错误：

yarn android v0.27.5
$ react-native-scripts android
10:37:45 AM: Starting packager...
10:39:34 AM: Starting Android...
10:39:37 AM: Packager started!

To view your app with live reloading, point the Expo app to this QR code.
You'll find the QR scanner on the Projects tab of the app.

    <QR CODE>                                                  

Or enter this address in the Expo app's search bar:

  exp://172.19.29.31:19000

Your phone will need to be on the same local network as this computer.
For links to install the Expo app, please visit https://expo.io.


    Logs from serving your app will appear here. Press Ctrl+C at any time to stop.

Error running adb: Error running app. Error: Activity not started, unable to resolve Intent { act=android.intent.action.VIEW dat=exp://172.19.29.31:19000 flg=0x10000000 }

(node:28009) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): TypeError: Cannot read property 'length' of null

我使用 create-react-native-app 生成器来设置我的应用程序，这是我的项目结构：

<username>$ls
App.js          app.json        gen         package.json
App.test.js     assets          my-app-key.keystore stylesheet.js
README.md       components      node_modules        yarn.lock 

我也尝试使用我的 expo 应用程序扫描二维码以在我的手机上运行我的应用程序，但它达到 100% 然后应用程序崩溃，或者它给出深蓝屏幕，其中错误为“未捕获错误”包装程序未在 http::19003 运行“（即使我扫描的端口是 http:19000）。

我刚刚也尝试运行“npm start”，然后运行“a”作为 android 选项，但收到消息： 11:40:20 AM：正在启动 Android...

Error running adb: Error running app. Error: Activity not started, unable to resolve Intent { act=android.intent.action.VIEW dat=exp://172.19.29.31:19000 flg=0x10000000 }


 › Press a to open Android device or emulator, or i to open iOS emulator.
 › Press q to display QR code.
 › Press r to restart packager, or R to restart packager and clear cache.
 › Press d to toggle development mode. (current mode: development)

(node:31496) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): TypeError: Cannot read property 'length' of null
11:43:30 AM: Running app on SM-T560NU in development mode

11:44:01 AM: [sane] Warning: Lost connection to watchman, reconnecting..

有人能帮我解决这个问题吗？