如何在android WebView中开启长按动作下载图片？

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

<WebView
    android:id="@+id/webView"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

WebView webView = findViewById(R.id.webView);
webView.setWebViewClient(new WebViewClient());
webView.setWebChromeClient(new WebChromeClient());

webView.setWebViewClient(new WebViewClient() {
    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url) {
        if (url.endsWith(".jpg") || url.endsWith(".png") || url.endsWith(".gif")) {
            DownloadManager.Request request = new DownloadManager.Request(Uri.parse(url));
            request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
            request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, "image.jpg");
            DownloadManager downloadManager = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);
            downloadManager.enqueue(request);
            return true;
        }
        return false;
    }
});

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