Test edildi cihazin indirme yöneticisini açarak indirme sağlıyor

kodunuzu güncelledim ve bir kaç ayar ekledim

AndroidManifest eklecenek

<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

activity_main.xml eklenecek

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">
    <WebView
        android:id="@+id/web_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</LinearLayout>

MainActivity

public class MainActivity extends AppCompatActivity {

WebView webView;
String url = "https://bilhos.com.tr/ ";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);


//İndirme dosyalarını kaydetmek için Çalışma Zamanı Harici depolama izni
if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.M) {
if (checkSelfPermission(Manifest.permission.WRITE_EXTERNAL_STORAGE)
== PackageManager.PERMISSION_DENIED) {
Log.d("permission", "permission denied to WRITE_EXTERNAL_STORAGE - requesting it");
String[] permissions = {Manifest.permission.WRITE_EXTERNAL_STORAGE};
requestPermissions(permissions, 1);
}
}


webView = findViewById(R.id.web_view);
webView.setWebViewClient(new WebViewClient());
webView.getSettings().setLoadsImagesAutomatically(true);
webView.getSettings().setJavaScriptEnabled(true);
webView.setScrollBarStyle(View.SCROLLBARS_INSIDE_OVERLAY);
webView.loadUrl(url);

//handle downloading
webView.setDownloadListener(new DownloadListener()
{
@Override
public void onDownloadStart(String url, String userAgent,
String contentDisposition, String mimeType,
long contentLength) {
DownloadManager.Request request = new DownloadManager.Request(
Uri.parse(url));
request.setMimeType(mimeType);
String cookies = CookieManager.getInstance().getCookie(url);
request.addRequestHeader("cookie", cookies);
request.addRequestHeader("User-Agent", userAgent);
request.setDescription("Downloading File...");
request.setTitle(URLUtil.guessFileName(url, contentDisposition, mimeType));
request.allowScanningByMediaScanner();
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
request.setDestinationInExternalPublicDir(
Environment.DIRECTORY_DOWNLOADS, URLUtil.guessFileName(
url, contentDisposition, mimeType));
DownloadManager dm = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);
dm.enqueue(request);
Toast.makeText(getApplicationContext(), "Dosya indiriliyor ", Toast.LENGTH_LONG).show();
}});

}

}