Source

import java.io.File;

import android.app.Activity;
import android.app.DownloadManager;
import android.content.Context;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.view.Menu;
import android.webkit.MimeTypeMap;
import android.webkit.WebChromeClient;
import android.webkit.WebSettings;
import android.webkit.WebSettings.PluginState;
import android.webkit.WebView;
import android.webkit.WebViewClient;

public class MainActivity extends Activity {

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

        WebView webview = new WebView(this);
        webview.setWebChromeClient(new WebChromeClient());
        WebViewClient client = new ChildBrowserClient();
        webview.setWebViewClient(client);
        WebSettings settings = webview.getSettings();
        settings.setJavaScriptEnabled(true);
        webview.setInitialScale(1);
        webview.getSettings().setUseWideViewPort(true);
        settings.setJavaScriptCanOpenWindowsAutomatically(false);
        settings.setBuiltInZoomControls(true);
        settings.setPluginState(PluginState.ON);
        settings.setDomStorageEnabled(true);
        webview.loadUrl("https://www.youtube.com/");
        webview.setId(5);
        webview.setInitialScale(0);
        webview.requestFocus();
        webview.requestFocusFromTouch();
        setContentView(webview);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }
    public class ChildBrowserClient extends WebViewClient
    {
        @Override
        public boolean shouldOverrideUrlLoading(WebView view, String url) {

boolean value = true;
String extension = MimeTypeMap.getFileExtensionFromUrl(url);
if (extension != null) {
MimeTypeMap mime = MimeTypeMap.getSingleton();
String mimeType = mime.getMimeTypeFromExtension(extension);
if (mimeType != null) {
if (mimeType.toLowerCase().contains("video")
|| extension.toLowerCase().contains("mov")
|| extension.toLowerCase().contains("mp3")) {
DownloadManager mdDownloadManager = (DownloadManager) MainActivity.this
.getSystemService(Context.DOWNLOAD_SERVICE);
DownloadManager.Request request = new DownloadManager.Request(
Uri.parse(url));
File destinationFile = new File(
Environment.getExternalStorageDirectory(),
getFileName(url));
request.setDescription("Downloading via Your app name..");
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
request.setDestinationUri(Uri.fromFile(destinationFile));
mdDownloadManager.enqueue(request);
value = false;
}
}
if (value) {
view.loadUrl(url);
}
}
return value;
        }
    }
    public String getFileName(String url) {
        String filenameWithoutExtension = "";
        filenameWithoutExtension = String.valueOf(System.currentTimeMillis()
 + ".mp4");
        return filenameWithoutExtension;
}
}