Develop Reference

Android: Problems to display WebView for every url from the list

I have a standard task to display a ListView (UrlListView) with urls. When the user touches the row I open an activity (UrlViewActivity) with WebView.
Unfortunately, this trivial task brings many troubles for me in Android...
Standard approach:
UrlViewActivity has an *.xml file with a layout that contains WebView.
When the user touches any row inside UrlListView, I start this activity, set this layout as a content view, find my WebView by id and ask it to load an url. Yes, I also call inside my activity's onPause - mWebView.onPause() and inside onDestroy - mWebView.destroy();
Everything works pretty good until the user tries to open various urls rather often: opens an url, closes UrlViewActivity, opens another url and e t. c...usually after 15-25 such loads (every UrlViewActivity launch creates a new WebView) famous Android 4.4 bug occurs on Moto X and Nexus 5:
https://code.google.com/p/android/issues/detail?id=73632
so my app freezes inside nativeLockCanvas...
Then I tried another approach that some guys on StackOverFlow recommended:
Keeping WebView as a static object, create it only during the first startup and on every UrlViewActivity launch add this WebView and clear its state (and remove this WebView inside onStop() of course).
No freezing!!!
But there is a big problem to clear WebView's state on Android:
It's really hard to force a WebView correctly measure its height when loading a new url (WebView always tries to remember previous long page and doesn't want to decrease it height even when loading a very small page).
There are many advices to reset WebView's height like the following: How a change the content size of a webview in android?
But unfortunately clearView() is already deprecated and does nothing...The only working approach that I found is: calling mWebView.loadUrl("about:blank"); and inside overriden onPageFinished(WebView view, String url) method call mWebView.requestLayout();
That really works and pages become finally take correct height and scrolling works ok, but...it remembers blank page inside its history and shows it to user when he presses back button...
To resolve the problem of storing blank page in WebView's history I've tried to use clearHistory() method, but...if I call this method inside onPageFinished(WebView view, String url) right after my correct page was loaded guess what? WebView mystically forgets that it has just measured itself correctly (during first onPageFinished(WebView view, String url) call when "about:blank" page was loaded) and shows long scrolling even for a short pages...
Here is my code snippet:
enum WebViewStates {
WEB_VIEW_INITIALIZED, WEB_VIEW_RESET_DONE, WEB_VIEW_HISTORY_CLEARED
}
private ViewGroup mWebViewContainer;
private WebViewStates mWebViewState;
private void setupWebView() {
mScrollView.smoothScrollTo(0, 0);
mWebViewContainer.addView(mWebView);
mWebViewState = WebViewStates.WEB_VIEW_INITIALIZED;
mWebView.loadUrl("about:blank");
mWebView.setWebViewClient(new WebViewClient() {
#Override
public void onPageFinished(WebView view, String url) {
switch (mWebViewState) {
case WEB_VIEW_INITIALIZED:
mWebViewState = WebViewStates.WEB_VIEW_RESET_DONE;
mWebView.requestLayout();
mWebView.loadUrl(mPreviewUrl);
break;
case WEB_VIEW_RESET_DONE:
mWebViewState = WebViewStates.WEB_VIEW_HISTORY_CLEARED;
mWebView.clearHistory();
break;
case WEB_VIEW_HISTORY_CLEARED:
break;
}
super.onPageFinished(view, url);
}
});
}

Listen for URL fragment id change in WebView

It seems that the WebViewClient methods such as shouldInterceptRequest(), onPageStarted(), and shouldOverrideUrlLoading() only listen for URL changes that cause the WebView to load a new page. Is there a way to detect URL changes for fragment IDs, i.e. index.html#fragment_id, on a WebView?

I know that this is a really old question but i found out a solution that isn't available anywhere in Stack Overflow. jpetitto's answer works but it messes up javascript if we use hash change for routing or other such features.
I found out that by overriding the method doUpdateVisitedHistory in WebViewClient we can catch url's on hash change. Do see below snippet for example.
mWebView.setWebViewClient(new WebViewClient() {
#Override
public void doUpdateVisitedHistory(WebView view, String url, boolean isReload) {
super.doUpdateVisitedHistory(view, url, isReload);
// somecode to run on hash change.
}
}
Note: this method is fired on hash change and url change.

As mitvenkatesan described in his comment to the question, this can be achieved by overriding the window.onhashchange() event of the page inside the WebView.
It turns out that this solution has already been addressed in another question.

Button in a webview without Javascript

I have an android application that loads a webview from a server. I do not have the server code so I cannot change anything in Javascript. I want to figure out when a button is being clicked in a webview and what is the label in the button. I do not know the Id, I just want to get the label.
I tried searching for this but could not find an answer. I found solutions where you can work in the javascript but in my case I cannot.

This suggestion may help to find useful information that could lead to determination of your button label. Override shouldOverrideUrlLoading(), shouldInterceptRequest() and/or onLoadResource() for the WebViewClient so you can get at the URL of any redirects.
Example:
webview.setWebViewClient(new WebViewClient() {
public boolean shouldOverrideUrlLoading(WebView view, String url) {
// Try to learn something useful from the 'url' here.
// Continue as normal, loading the 'url' within this WebView.
view.loadUrl(url);
return false; // Allow the WebView to handle the request.
}
// Optional: Add similar for "shouldInterceptRequest()" and/or "onLoadResource()".
});
Note: Overriding shouldOverrideUrlLoading() as above is the standard way to keep redirects within the same WebView rather than redirecting to the default browser application.

You might really want to check this page:
Building Web Apps in WebView (Google API Guides)
Specifically, it seems that addJavascriptInterface might be what you are looking for:
addJavascriptInterface(Object object, String name)
It allows you to execute your Java code from javascript and, paired with the ability to insert code in a page, it's an incredibly powerful tool for granting you a high level of coupling between your Activity and your page.
I think that at this point you will already know what to do, but I'll sketch a possible course of action anyway:
create a javascript interface with the callbacks you want executed in your activity when a button is pressed
as soon as your page loads, install the code to call your javascript interface in each button (or link) by injection
Hope this helps

WebView disappears when I click on an embedded link

I've done alot of Googling on this and haven't found an answer. I have a webview as part of an overall layout with other controls. I use the webview to show formatted text (recipe descriptions with bold and italic fonts) and URLs. The URLs point to Youtube and are fully qualified (ie. http://www.youtube.com/watch?v=fyzyhuVgzRE). When I click on the link in my web view, the web view control itself disappears from the layout (leaving the rest of the controls on the page intact) and the default web browser does not launch.
It behaves as if I've set the visibility of the web view to GONE, but I do not manipulate the visibility of any of the controls on the layout.
One interesting clue in the LogCat output is an INFO level message from the OS:
MotionRecognitionManager .unregisterListener : / listener count = 0->0,
listener=android.webkit.ZoomManager$1#41ac2fc0
Any ideas what would cause this behavior?
EDIT
Here is how I setup the webview in the onCreate() method of the activity:
webView1 = (WebView)findViewById(R.id.webView1);
webView1.getSettings().setJavaScriptEnabled(true);
webView1.getSettings().setAllowFileAccess(true);
webView1.setWebViewClient(new MyWebViewClient());
And the MyWebViewClient class:
private class MyWebViewClient extends WebViewClient {
public boolean shouldOverrideUrlLoading(WebView view, String url) {
if (url != null && url.startsWith("http://")) {
view.getContext().startActivity(new Intent(Intent.ACTION_VIEW, Uri.parse(url)));
return true;
} else {
return false;
}
}
}
Oddly enough the shouldOverrideUrlLoading is never called.

Well, I'm a dope. It turns out that the double quotes in the href attribute of the anchor were doubled. My system integrates with a MySQL db over the web and I have to do alot of transformation of data between MySQL/PHP and Android/SQLite. During one of these transformations I double-escaped the quotes in the href. So what should have been:
Link Text
was instead rendered as:
Link Text
In the web view the resulting URL looked fine. It was underscored properly and looked like any other URL. It is odd though that simple doubling the quotes causes the behavior. I'll see if there is a known bug like this for Android. At the very least the WebView should through some kind of exception, not simply disappear from the screen.

I faced this type of behavior when webview tries to load content it cant handle. Intercept ref clicks using WebViewClient and send intent to open this ref in external application. Check this thread.

Limit WebView touch handling to links

Is it possible to capture touch events over a WebView in the activity that contains it, without loosing link functionality?
Consider a WebView showing a webpage with links. If the user taps on a link I would like the WebView to handle the touch event. If the user taps somewhere else I would like the activity to handle the touch event.
How can this be done?

Yes, it is.
(I can't elaborate more on this unless you are more specific on your question.)

If i understand your question correctly it'd seem difficult to interpret whether something is a link or not in the onTouchEvent() since all it knows about is X,Y coordinates (not html). However, off the top of my head it seems you could probably use the javascript binding piece in WebView to have javascript decide if the something is a link or not and act accordingly. Again, I haven't done this before nor tested it...just thinking out loud.

When initializing your WebView, try:
mWebView.setWebViewClient(new WebViewClientOverrider());
Then create a private class:
private class WebViewClientOverrider extends WebViewClient {
#Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
//TODO handle the link
return true;
}
}
Lastly, replace the TODO handle the link line with your own code for handling the link selection.

Or you can monitor the stack trace for:
android.webkit.CallbackProxy.uiOverrideUrlLoading()
See http://www.javapractices.com/topic/TopicAction.do?Id=78 for how to determine your stack trace from a throwable (created in an overriden WebView.loadUrl() method).