Ok I had the same problem working with webviews, I realized that WebViewClient can't load "blob URLs" as Chrome Desktop client does. I solved it using Javascript Interfaces. You can do this by following the steps below and it works fine with minSdkVersion: 17. First, transform the Blob URL data in Base64 string using JS. Second, send this string to a Java Class and finally convert it in an available format, in this case I converted it in a ".pdf" file.
Before continue you can download the source code here :). The app is developed in Kotlin and Java. If you find any error, please let me know and I will fix it:
https://github.com/JaegerCodes/AmazingAndroidWebview
First things first. You have to setup your webview. In my case I'm loading the webpages in a fragment:
public class WebviewFragment extends Fragment {
WebView browser;
...
// invoke this method after set your WebViewClient and ChromeClient
private void browserSettings() {
browser.getSettings().setJavaScriptEnabled(true);
browser.setDownloadListener(new DownloadListener() {
@Override
public void onDownloadStart(String url, String userAgent, String contentDisposition, String mimeType, long contentLength) {
browser.loadUrl(JavaScriptInterface.getBase64StringFromBlobUrl(url));
}
});
browser.getSettings().setAppCachePath(getActivity().getApplicationContext().getCacheDir().getAbsolutePath());
browser.getSettings().setCacheMode(WebSettings.LOAD_DEFAULT);
browser.getSettings().setDatabaseEnabled(true);
browser.getSettings().setDomStorageEnabled(true);
browser.getSettings().setUseWideViewPort(true);
browser.getSettings().setLoadWithOverviewMode(true);
browser.addJavascriptInterface(new JavaScriptInterface(getContext()), "Android");
browser.getSettings().setPluginState(PluginState.ON);
}
}
Finally, create a JavaScriptInterface class. This class contains the script that is going to be executed in our webpage.
public class JavaScriptInterface {
private Context context;
public JavaScriptInterface(Context context) {
this.context = context;
}
@JavascriptInterface
public void getBase64FromBlobData(String base64Data) throws IOException {
convertBase64StringToPdfAndStoreIt(base64Data);
}
public static String getBase64StringFromBlobUrl(String blobUrl) {
if(blobUrl.startsWith("blob")){
return "javascript: var xhr = new XMLHttpRequest();" +
"xhr.open('GET', '"+ blobUrl +"', true);" +
"xhr.setRequestHeader('Content-type','application/pdf');" +
"xhr.responseType = 'blob';" +
"xhr.onload = function(e) {" +
" if (this.status == 200) {" +
" var blobPdf = this.response;" +
" var reader = new FileReader();" +
" reader.readAsDataURL(blobPdf);" +
" reader.onloadend = function() {" +
" base64data = reader.result;" +
" Android.getBase64FromBlobData(base64data);" +
" }" +
" }" +
"};" +
"xhr.send();";
}
return "javascript: console.log('It is not a Blob URL');";
}
private void convertBase64StringToPdfAndStoreIt(String base64PDf) throws IOException {
final int notificationId = 1;
String currentDateTime = DateFormat.getDateTimeInstance().format(new Date());
final File dwldsPath = new File(Environment.getExternalStoragePublicDirectory(
Environment.DIRECTORY_DOWNLOADS) + "/YourFileName_" + currentDateTime + "_.pdf");
byte[] pdfAsBytes = Base64.decode(base64PDf.replaceFirst("^data:application/pdf;base64,", ""), 0);
FileOutputStream os;
os = new FileOutputStream(dwldsPath, false);
os.write(pdfAsBytes);
os.flush();
if (dwldsPath.exists()) {
Intent intent = new Intent();
intent.setAction(android.content.Intent.ACTION_VIEW);
Uri apkURI = FileProvider.getUriForFile(context,context.getApplicationContext().getPackageName() + ".provider", dwldsPath);
intent.setDataAndType(apkURI, MimeTypeMap.getSingleton().getMimeTypeFromExtension("pdf"));
intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
PendingIntent pendingIntent = PendingIntent.getActivity(context,1, intent, PendingIntent.FLAG_CANCEL_CURRENT | PendingIntent.FLAG_IMMUTABLE);
String CHANNEL_ID = "MYCHANNEL";
final NotificationManager notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
NotificationChannel notificationChannel= new NotificationChannel(CHANNEL_ID,"name", NotificationManager.IMPORTANCE_LOW);
Notification notification = new Notification.Builder(context,CHANNEL_ID)
.setContentText("You have got something new!")
.setContentTitle("File downloaded")
.setContentIntent(pendingIntent)
.setChannelId(CHANNEL_ID)
.setSmallIcon(android.R.drawable.sym_action_chat)
.build();
if (notificationManager != null) {
notificationManager.createNotificationChannel(notificationChannel);
notificationManager.notify(notificationId, notification);
}
} else {
NotificationCompat.Builder b = new NotificationCompat.Builder(context, CHANNEL_ID)
.setDefaults(NotificationCompat.DEFAULT_ALL)
.setWhen(System.currentTimeMillis())
.setSmallIcon(android.R.drawable.sym_action_chat)
//.setContentIntent(pendingIntent)
.setContentTitle("MY TITLE")
.setContentText("MY TEXT CONTENT");
if (notificationManager != null) {
notificationManager.notify(notificationId, b.build());
Handler h = new Handler();
long delayInMilliseconds = 1000;
h.postDelayed(new Runnable() {
public void run() {
notificationManager.cancel(notificationId);
}
}, delayInMilliseconds);
}
}
}
Toast.makeText(context, "PDF FILE DOWNLOADED!", Toast.LENGTH_SHORT).show();
}
}
EXTRA: If you want to share these downloaded files with other Apps create an xml file in: ..\res\xml\provider_paths.xml
<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
<external-path name="external_files" path="."/>
</paths>
Finally add this provider to your AndroidManifest.xml file
<application ...>
<provider
android:name="androidx.core.content.FileProvider"
android:authorities="${applicationId}.provider"
android:exported="false"
android:grantUriPermissions="true">
<meta-data
android:name="android.support.FILE_PROVIDER_PATHS"
android:resource="@xml/provider_paths"/>
</provider>
<!-- some code below ->
Another approach is by using "Chrome Custom Tabs"
Java:
CustomTabsIntent.Builder builder = new CustomTabsIntent.Builder();
CustomTabsIntent customTabsIntent = builder.build();
customTabsIntent.launchUrl(context, Uri.parse("https://stackoverflow.com"));
Kotlin:
val url = "https://stackoverflow.com/"
val builder = CustomTabsIntent.Builder()
val customTabsIntent = builder.build()
customTabsIntent.launchUrl(this, Uri.parse(url))
Sources:
https://mcmap.net/q/587272/-how-to-read-the-data-in-a-blob-in-webview-on-android-duplicate
https://mcmap.net/q/66099/-how-to-get-a-file-or-blob-from-an-object-url
https://mcmap.net/q/576812/-how-to-convert-base64-to-pdf
https://developer.android.com/training/secure-file-sharing/setup-sharing
