I have an app with a previously-existing, web-based registration process that I am trying to use inside a WebView. I need to add some style tags to the html in order to hide some elements for better displaying the content inside my app. I can get it to work on initial load, but I cannot figure out how to do it from one page to the next inside the WebView. Here is what I have working:
On initial load of the site, I am getting the raw html and appending "<style>MY STYLES HERE</style>" to the string before calling
wv.loadDataWithBaseURL(url, rawHtml, null, "UTF-8", url);
This works perfectly, but if a user clicks a link on the page and it loads another page into the WebView, then this code does not get called and the style tag is lost.
I assume I need to override "shouldOverrideUrlLoading" in the WebViewClient, but I don't know how to intercept the html from here. I thought I would try something like:
#Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
String rawHtml = getRawHtml(url) + "<style>...</style>";
wv.loadDataWithBaseURL(url, rawHtml, null, "UTF-8", url);
}
But this obviously sends it into an endless loop of intercepting the load to start a new load.
I have also tried overriding onPageFinished and doing:
wv.loadUrl("javascript:(function() { ... })()");
which works, except that it waits until the entire page is loaded before executing. This causes the page to appear loaded with all of the UI elements in tact, and then all of the ones I am trying to hide suddenly disappear. My ultimate goal is to enhance the look and feel of the site on a mobile device, so this is not an option.
Is there something else I can do in "shouldOverrideUrlLoading" to inject style tags? Or if not, what else can I try?
I've run into this problem, and depending on the number of redirects, etc, we have not been able to make the injected JavaScript available all the time.
At minimum, you should use the wv.loadUrl("javascript:(function() { ... })()"); approach, but call it in both onPageStarted() and onPageFinished().
Depending on the complexity of your pages, you might need to inject the JavaScript in onLoadResource() as well.
Related
I have a hybrid application where I have a WebView which is implementing the shouldOverrideUrlLoading method (both the deprecated and the newest version). This should take over control before loading any external links or certain links within my domain. Without going into specifics, the code looks roughtly like this:
private WebView mWebView;
mWebView.setWebViewClient(new myWebViewClient() {
#Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
if(url.isExternal() || url.contains("#specialCase")) {
// Do actions
return true;
}
return super.shouldOverrideUrlLoading(view, url);
}
});
I have noticed that all external links work properly, however shouldOverrideUrlLoading is not being called at all when the link is within my domain, so there is no way for me to detect those cases where I want to take over control.
The android documentation states
Give the host application a chance to take over the control when a new
url is about to be loaded in the current WebView.
Does that new mean different domain? Is there anything I am missing or doing wrong? Any ideas on how to detect the user has clicked a link pointing to the same domain?
Thank you in advance.
Finally found the reason why shouldOverrideUrlLoading was never been called.
Apparently the method is only called when the actual loading is about to start. Our web application is a single-page application, hence even though the URL changes, no new page is loaded and shouldOverrideUrlLoading is not called.
I have an app that heavily uses the Android WebView to display my custom HTML content. The latest Android update (4.4/Kit-Kat/SDK-19) featured a redesigned WebView.
One of my users with a Nexus 5 reported a problem where some links cause the app to crash. I ran in the 4.4 emulator and debug into my WebViewClient's shouldOverrideUrlLoading() method. On all previously tested Android versions (2.2-4.3) the url String passed into the method had my custom url with "/" characters in it. In 4.4 the exact same link now has "\" characters in their place.
This doesn't make any sense to me. I load the HTML exactly the same, so somehow the new WebView converted all my slashes into backslashes.
Why does the new WebView do this?
Changes in URL handling are a known issue. Please see the migration guide for more detail.
The behaviour in this particular case will depend on what your base URL's scheme is, from what you're describing I'm guessing your base URL's scheme is "http(s)://" in which case the Chromium WebView performs URL normalization.
You might want to consider using the URI class to handle the discrepancy between the Classic and Chromium WebViews in this case.
I did more debugging and discovered I actually have the question reversed. Turns out the older versions of WebView did conversions of the URL, not the new one.
I load HTML with a format similar to this into a WebView:
link
I use the double back slashes as delimiters and parse the data later when the link is clicked. In older versions of WebView it converted my double backslash characters into forward slashes. It had been so long since I was in that code, I forgot I adjusted my code to use forward slashes rather than the backslashes in the original HTML.
The new version of WebView leaves my custom URL intact, giving me the exact same string as my original HTML. So turns out the old WebView is the problem not the new one.
The new WebView applies additional restrictions when requesting resources and resolving links that use a custom URL scheme. For example, if you implement callbacks such as shouldOverrideUrlLoading() or shouldInterceptRequest(), then WebView invokes them only for valid URLs.
If you are using a custom URL scheme or a base URL and notice that your app is receiving fewer calls to these callbacks or failing to load resources on Android 4.4, ensure that the requests specify valid URLs that conform to RFC 3986.
For example, the new WebView may not call your shouldOverrideUrlLoading() method for links like this:
Show Profile
The result of the user clicking such a link can vary:
If you loaded the page by calling loadData() or loadDataWithBaseURL() with an invalid or null base URL, then you will not receive the shouldOverrideUrlLoading() callback for this type of link on the page.
Note: When you use loadDataWithBaseURL() and the base URL is invalid or set null, all links in the content you are loading must be absolute.
If you loaded the page by calling loadUrl() or provided a valid base URL with loadDataWithBaseURL(), then you will receive the shouldOverrideUrlLoading() callback for this type of link on the page, but the URL you receive will be absolute, relative to the current page. For example, the URL you receive will be "http://www.example.com/showProfile" instead of just "showProfile".
Instead of using a simple string in a link as shown above, you can use a custom scheme such as the following:
Show Profile
You can then handle this URL in your shouldOverrideUrlLoading() method like this:
// The URL scheme should be non-hierarchical (no trailing slashes)
private static final String APP_SCHEME = "example-app:";
#Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
if (url.startsWith(APP_SCHEME)) {
urlData = URLDecoder.decode(url.substring(APP_SCHEME.length()), "UTF-8");
respondToData(urlData);
return true;
}
return false;
}
If you can't alter the HTML then you may be able to use loadDataWithBaseURL() and set a base URL consisting of a custom scheme and a valid host, such as "example-app:///". For example:
webView.loadDataWithBaseURL("example-app://example.co.uk/", HTML_DATA,
null, "UTF-8", null);
The valid host name should conform to RFC 3986 and it's important to include the trailing slash at the end, otherwise, any requests from the loaded page may be dropped.
to avoid webview below 4.4 convert backslash to forward slash, I just escape my url, then in Java code, use URI.decode to get the real url.That works for me.
There is a rather specific webpage loaded into WebView which URL is like http://www.site.com/mob/ (basically a mobile-optimized web page). This webpage display 25 articles only and on the bottom is a button "More articles".
When a user presses it, I catch URL http://www.site.com/Web/MobHomeItems.aspx?page=N (where N is 2, 3, 4...) and after that another 25 items have been loaded on the same screen.
Now, when I click on some article and go to article details, and later return to the page via the Back key, the WebView forgets how many articles have been loaded and simply loads the default page with 25 displayed articles. Imagine how frustrating this would be to a user if he came to 100th article.
I tried overriding many methods in WebClient and in WebChromeClient, but so far I have been unable to load N number of pages loaded via "More Articles" button. For example, I first thought this would help, but it did not.
#Override
public void onLoadResource(WebView view, String url) {
//http://www.site.com/Web/MobHomeItems.aspx?page=2
if (url.contains("?page=")) {
//save this URL for later and on return from
// article details, pass it to LoadResource()
super.onLoadResource(view, url);
}
Then I tried similar approach with other method - basically remembering how many pages have been loaded on the main page, and then on return from article details, simply tell webview to load this URL.
Can anyone help me? How to append loaded pages to the main page? Should I use JavaScript here maybe?
PS. Loading mentioned URL http://www.site.com/Web/MobHomeItems.aspx?page=N does not help as it loads this concrete page into the WebView only, and it does not append this Nth page to the main page.
EDIT
As #Raghunandan asked, I do not have problems loading back to 1st page (?page=1). This is default when user presses Back button on article details. I want to load to the page where a user was before pressing article details. If he was on ?page=100, I want to load back to that page e.g. I want to have 25x100 articles open. Again, default is always "open 25 articles or ?page=1 or http://www.site.com".
Override the method shouldOverrideUrlLoading of WebViewClient.
like this:
public boolean shouldOverrideUrlLoading (WebView view, String url) {
if (url is kind of article detail) {
WebView newOne = new WebView(); // create a new Webview for displaying the details.
view.setVisibility(View.INVISIBLE); // hiding current page (article list)
return true; // To tell the WebView we have process this url.
}
return false;
}
The user click one link of article's detail.
shouldOverriderUrlLoading would be triggered.
We created one new WebView to open the url.
Hiding current page
The user reading artical
The user click back key, close the newOne WebView then make the
previous WebView visible.The article list will show up immediately and remained the old statement
.
There is a another way to do this.
The WebSettings has a private method "setPageCacheCapacity" , the default value is 0 , you could enlarge it (may be 5).
You can access this method by using reflection of java.
The method can enable WebView to cache more than one document. In the other word. when user press the back key, the WebView will go back to the older document.
I have a WebView where I am loading a javascript that loads some content. That content is an html with an iframe.
It seems any click within iframe is not triggering calls to WebViewClient#shouldOverrideUrlLoading(WebView view, String url); The webview has set both WebViewClient and WebChromeClient.
A work-around I can see of is to call getSettings().setSupportMultipleWindows(true) on the WebView and then within onCreateWindow(WebView view, boolean isDialog, boolean isUserGesture, Message resultMsg) assume the call was made within iframe and use some inserted javascript in order to get the iframe data. But that seems ugly to me.
So, the question: how do you detect a click within iframe loaded within the webview?
Thanks!
I think I have found what is the problem: I broke the Same Origin Policy. A colleague that is doing web development pointed me in the right direction.
The whole document (containing the iFrame) has a different origin (combination of scheme, host name and port number) than containing iframe. As long as those frames (containing document and inner iframe) have different origins, they cannot communicate. That's why I am not getting calls to shouldOverrideUrlLoading.
EDIT: It seems there is a way to overpass above security policy, but that comes with accepted security risk: Add the following header in the response that contains the iframe: "Access-Control-Allow-Origin:*"
I am working on an android project right now and have a question about how to do callbacks in different webviews. I used JSInterface for my project too. Here I have 2 webviews. One has an index page, anther is a overlay(still a html page though.) What I want to do is if any user clicks on some links on the overlay, it should fire a callback function which is written in the java file where the index page was connected to through JSInterface. It might sound confusing, but I have draw something to help make it clear!
Thanks!
You can use a custom URL scheme like myurl://function for your functionality links. Then write an event handler for the WebView's shouldOverrideUrlLoading event in which you decide how to process the URL: either instruct the webview to load it, or do some custom action.
#Override
public boolean shouldOverrideUrlLoading(WebView view, String url)
{
if (url.startsWith("myurl://"))
{
// Parse further to extract function and do custom action
}
else
{
// Load the page via the webview
view.loadUrl(url);
}
return true;
}
I used startsWith to check the URL for this quick and dirty example, but you should consider using android.net.Uri.parse for parsing URLs.
This should allow you to call the Java function foo() without having to go through the first WebView.
If you want to go through the first webview, then you can call a function on the JSInterface like this (where webView1 is the first WebView retrieved through findViewById):
webView1.loadUrl("javascript:myjsinterface.myjsfunc();")