Simple Solution:
Add this line in your manifest:
android:usesCleartextTraffic="true"
because I have faced the same issue with my php page for json api.
It should look like this:
<!-- begin snippet: js hide: false console: true babel: false -->
<!-- language: lang-html -->
<?xml version="1.0" encoding="utf-8"?>
<manifest ...>
<uses-permission android:name="android.permission.INTERNET" />
<application
...
android:usesCleartextTraffic="true"
...>
...
</application>
</manifest>
<!-- end snippet -->
Let's hope it works.
According to [Network security configuration][1] -
> Starting with Android 9.0 (API level 28), cleartext support is
> disabled by default.
Also have a look at - https://koz.io/android-m-and-the-war-on-cleartext-traffic/
**Option 1 -**
Create file res/xml/network_security_config.xml -
<?xml version="1.0" encoding="utf-8"?>
<network-security-config>
<domain-config cleartextTrafficPermitted="true">
<domain includeSubdomains="true">Your URL(ex: 127.0.0.1)</domain>
</domain-config>
</network-security-config>
AndroidManifest.xml -
<?xml version="1.0" encoding="utf-8"?>
<manifest ...>
<uses-permission android:name="android.permission.INTERNET" />
<application
...
android:networkSecurityConfig="@xml/network_security_config"
...>
...
</application>
</manifest>
**Option 2 -**
AndroidManifest.xml -
<?xml version="1.0" encoding="utf-8"?>
<manifest ...>
<uses-permission android:name="android.permission.INTERNET" />
<application
...
android:usesCleartextTraffic="true"
...>
...
</application>
</manifest>
Also as [@david.s' answer][2] pointed out `android:targetSandboxVersion` can be a problem too -
According to [Manifest Docs][3] -
> `android:targetSandboxVersion`
>
> The target sandbox for this app to use. The higher the sandbox version
> number, the higher the level of security. Its default value is 1; you
> can also set it to 2. Setting this attribute to 2 switches the app to
> a different SELinux sandbox. The following restrictions apply to a
> level 2 sandbox:
>
> - The default value of `usesCleartextTraffic` in the Network Security Config is false.
> - Uid sharing is not permitted.
**So Option 3 -**
If you have `android:targetSandboxVersion` in `<manifest>` then reduce it to `1`
AndroidManifest.xml -
<?xml version="1.0" encoding="utf-8"?>
<manifest android:targetSandboxVersion="1">
<uses-permission android:name="android.permission.INTERNET" />
...
</manifest>
[1]: https://developer.android.com/training/articles/security-config#CleartextTrafficPermitted
[2]: https://stackoverflow.com/a/45955297/7599300
[3]: https://developer.android.com/guide/topics/manifest/manifest-element#targetSandboxVersion
