How to read the data in a Blob in WebView on Android?

Question

I have a server that creates an object blob on the browser and I want to download this within WebView in an Android app. I tried redirecting the request to the browser instance as well as using the download manager to do this, but neither of them seems to work (Even though if I open up the same page in Chrome, the download operation works there).

I tried the following code,it throws error:

Android.content.ActivityNotFoundException: No Activity found to handle Intent { act=android.intent.action.VIEW dat=blob:https%3A//111.111.111.111%3A8080/40b63131-63b1-4fa4-9451-c6297bbd111a"

Edit

Android.content.ActivityNotFoundException: No Activity found to handle Intent { act=android.intent.action.VIEW dat=blob:http://digitalinsensu.com/0f0d6127-a0f1-44c3-af85-72f648258d6d

Code:

mWebView.setDownloadListener(new DownloadListener() {
public void onDownloadStart(String url, String userAgent,String contentDisposition, String mimetype,long contentLength) {
    Intent i = new Intent(Intent.ACTION_VIEW);
    i.setData(Uri.parse(url));
    startActivity(i);
}
});

and this throws java.lang.IllegalArgumentException: Can only download HTTP/HTTPS URIs error:

mWebView.setDownloadListener(new DownloadListener() {
    public void onDownloadStart(String url, String userAgent,String contentDisposition, String mimetype,long contentLength) {
        DownloadManager.Request request = new DownloadManager.Request(Uri.parse(url));
        request.allowScanningByMediaScanner();
        request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
        request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, "download");
        DownloadManager dm = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);
        dm.enqueue(request);

    }
});

How should I be downloading the blob? Any help would be appreciated.

Why would you use a webview to download an object? It won't know how to parse anything but a webpage. Use DownloadManager instead. — Gabe Sechan, Feb 15 '16 at 02:39
@GabeSechan I load a url in my webview that does a bunch of things and creates a blob, and I want to download that to the device. — Alice Van Der Land, Feb 15 '16 at 02:43
@DougStevenson I understand that the code does not work because it tries to operate on a blob saved on the browser rather than an HTTP address, but I have not been able to find how to download a blob in Android. — Alice Van Der Land, Feb 15 '16 at 02:46
@GulizTuncay If the url string is just "blob:" I don't think there's anything you can do with that to get to the data you want. — Doug Stevenson, Feb 15 '16 at 02:55
Definitely seems like your url isn't right. It needs to be a fully qualified url — Gabe Sechan, Feb 15 '16 at 03:01
@DougStevenson I just did not copy paste the whole url in there. — Alice Van Der Land, Feb 15 '16 at 03:07
@GabeSechan Yes, seems like those methods only work with proper URLs and not blobs. I couldn't figure out how to access the blob from java though. — Alice Van Der Land, Feb 15 '16 at 03:14
There's got to be a url starting with http or https to access the data. blob: is not a protocol to transfer data with. — Gabe Sechan, Feb 15 '16 at 03:23
It looks like there is an encoded url in the blob url. Is that what you're trying to download? — Doug Stevenson, Feb 15 '16 at 06:34
@DougStevenson We are expecting the same behavior as Android Native `Browser`.i.e File Downloads perfectly in browser. — , Dec 23 '16 at 10:07

score 0 · Answer 1 · answered Dec 23 '16 at 10:55

0

You need to intercept the callback for handling url clicks like this:

webView.setWebViewClient(new WebViewClient() {
    @Override
    public void onPageStarted(WebView view, String url, Bitmap favicon) {
        super.onPageStarted(view, url, favicon);
        shouldOverrideUrlLoading(view, Uri.parse(url));
    }

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    @Override
    public boolean shouldOverrideUrlLoading(WebView view, WebResourceRequest request) {
        return shouldOverrideUrlLoading(view, request.getUrl());
    }

    // legacy callback
    @Override
    public boolean shouldOverrideUrlLoading(WebView view, String url) {
        if(Build.VERSION.SDK_INT < Build.VERSION_CODES.LOLLIPOP) {
            return shouldOverrideUrlLoading(view, Uri.parse(url));
        }
        return super.shouldOverrideUrlLoading(view, url);
    }

    private boolean shouldOverrideUrlLoading(final WebView view, final Uri request) {
        if(request.getScheme().equals("blob")) {
            // do your special handling for blob urls here
            return true;
        }
    }
});

In shouldOverrideUrlLoading() you can do your special handling.

answered Dec 23 '16 at 10:55

rekire

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Which type of *special handling* please specify? bdw `shouldOverrideUrlLoading()` is not called at all :-( – Dec 23 '16 at 11:04
What do you want to do with that url? – rekire Dec 23 '16 at 13:07
try this special handling: `webView.loadUrl(request.toString().substring(5));` – rekire Dec 23 '16 at 13:28
2

How should the correct http address look like? I mean there is **no** official *blob* protocol. – rekire Dec 23 '16 at 13:38
1

shouldOverrideUrlLoading() isn't triggered at all for this download (tested with Webview 66) – Alexey Ozerov May 11 '18 at 12:56
@AlexeyOzerov did you override all overloads like in my example code? That is working fine for me. – rekire May 11 '18 at 18:18
Yes, none of the overridden shouldOverrideUrlLoading() methods is triggered with SDK 23 and SDK 24 Webview 66 using this test https://jsfiddle.net/3khffu41/ – Alexey Ozerov May 13 '18 at 14:06

How to read the data in a Blob in WebView on Android?

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