First, you should add below code in your HTML file

<input type="button" value="Say hello" onClick="showAndroidCamera()" />

<script type="text/javascript">
    function showAndroidCamera() {
        Android.openCamera();
    }
</script>

After creating one class in the Android side

class WebAppInterface(private val mContext: Context) {

    /** Show a toast from the web page  */
    @JavascriptInterface
    fun openCamera() {
        //This method called when user clicks on webview button.
        Toast.makeText(mContext, open Camera, Toast.LENGTH_SHORT).show()
    }
}

and add WebAppInterface handler to you webview

webView.addJavascriptInterface(WebAppInterface(this), "Android")

For Example

public class MainActivity extends AppCompatActivity {

    private WebView webView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        this.getSupportActionBar().hide();

        webView = findViewById(R.id.webView);
        webView.setWebViewClient(new WebViewClient());
        webView.loadUrl("https://apps.url/loja/index.php");

        WebSettings webSettings = webView.getSettings();
        webSettings.setJavaScriptEnabled(true);
      webView.addJavascriptInterface(WebAppInterface(this), "Android")


    }
}
class WebAppInterface(private val mContext: Context) {

    /** Show a toast from the web page  */
    @JavascriptInterface
    fun openCamera() {
        //This method called when user clicks on webview button.
        Toast.makeText(mContext, open Camera, Toast.LENGTH_SHORT).show()
    }
}

For more information please : Android Webview

I am creating a webview, to load an external website.

On this site I have a form with an input file. Clicking it should open the cell phone’s camera, but it doesn’t happen.

It looks like the webview has some blocking. How to fix this?

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns_android="http://schemas.android.com/apk/res/android"
    package="br.com.app...">

    <uses-permission android_name="android.permission.INTERNET"/>
    <uses-permission android_name="android.permission.CAMERA" />
    <uses-permission android_name="android.permission.READ_EXTERNAL_STORAGE"/>
    <uses-permission android_name="android.permission.WRITE_EXTERNAL_STORAGE"/>

    <application
        android_allowBackup="true"
        android_icon="@mipmap/ic_launcher"
        android_label="@string/app_name"
        android_roundIcon="@mipmap/ic_launcher_round"
        android_supportsRtl="true"
        android_theme="@style/AppTheme">
        <activity android_name=".MainActivity">
            <intent-filter>
                <action android_name="android.intent.action.MAIN" />

                <category android_name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

MainActivity.java

package br.com.app...;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;

public class MainActivity extends AppCompatActivity {

    private WebView webView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        this.getSupportActionBar().hide();

        webView = findViewById(R.id.webView);
        webView.setWebViewClient(new WebViewClient());
        webView.loadUrl("https://apps.url/loja/index.php");

        WebSettings webSettings = webView.getSettings();
        webSettings.setJavaScriptEnabled(true);
    }
}