Android: after loading data many times in webview appear white page - android

when I load some data in web view many times that white page appears ...just scroll it the data is return back..Am notice this issues on android 4.x ...I test it in android 2.3.3 webview work fine
what I can do to prevent this issues ?

I am facing a similar issue and finally solved but I am not sure why. Things that make it work was:
1)
When I finish with a WebView onDestroy of activity/fragment I have:
#Override
protected void onDestroy() {
super.onDestroy();
if (isFinishing()) {
if (myWebView != null) {
myWebView.destroy();
myWebView = null;
}
}
}
2)
I render the code via myWebView .loadDataWithBaseURL("file:///android_asset/", html_sourse, "text/html", "UTF-8", null); instead of myWebView.loadData(Uri.encode(html_sourse), "text/html", "utf-8");. When I am using the second line with an embedded css stylish inside html code page does not appear, changing to the first one (loadDataWithBaseURL) and adding to the html code a css from asset folder page appeared. I cannot understand why but works for me!
3) (optional)
Sometimes it is helpful to use clears if you do not care about keeping history:
myWebView.clearHistory();
myWebView.clearCache(true);

Related

Jellybean/ICS Android HTTP Post Method + WebView.RestoreState

I'm using the API 17 emulator to test a page containing a web view.
The webview first loads a page using the GET method.
Then the user submits the web form using HTTP POST method which causes a second page to load.
At this point if I rotate the screen I receive the "Webpage not available" error seen below. This only occurs if the page was loaded using the POST method. Note: I'm trying to restore the webview's state using webview.restoreState (see code below). Is there any way to tell Android to re-post the form data and reload the page instead of displaying this error message?!
I can't reproduce this same issue on KitKat, Lollipop, or Gingerbread... I can only reproduce this issue on Jellybean and Ice Cream Sandwich so far...
I've also confirmed this is an issue on an actual Nexus 7 device running Jellybean, so it's not an emulator-only problem.
Note: I'm not particularly interesting in using something like android:configChanges="orientation|keyboardHidden". As I understand it, this might solve my rotation issues, but the problem may still resurface if the activity state needs to be restored for other reasons.
Screenshots:
Step #1: Load the WebView Normally
Step #2: Submit the Form (uses HTTP Post Method)
Step #3: Rotate the screen to trigger webview.restoreState - error occurs
Code:
Here is some sample code to go along with my question. The code is in Mono C# but should be very nearly identical to Java.
public class MainActivity : Activity
{
WebView webview;
protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
webview = new WebView(this);
SetContentView(webview);
if (bundle == null)
webview.LoadUrl("http://2-dot-npwc-services.appspot.com/test-post.jsp");
else
webview.RestoreState(bundle);
}
protected override void OnSaveInstanceState(Bundle bundle)
{
base.OnSaveInstanceState(bundle);
webview.SaveState(bundle);
}
}
The sample HTML page that is performing the POST method looks like this:
<html>
<form action="test-post.jsp" method="post">
<input type="text" name="test" value="test"/>
<input type="submit"/>
</form>
<p>You entered: <%=request.getParameter("test")%></p>
</html>
The browser it's doing good (although it's a pain for us), you have 2 ways:
1- Keeping the webView instance and restoring the state, adding like you said android:configChanges="orientation|keyboardHidden"
2- Or reloading the post petition again.
I take the first one and if i get some error, i will go back to the last page. Doing static content, so on rotation no network or a new petition it's needed on each rotation, which if not, on server side will be a pain too.
To achieve the "if error go back" you need to set a Custom WebClient and override this method
webview.setWebViewClient(new WebViewClient() {
#Override
public void onReceivedError(WebView webView, int errorCode, String description, String failingUrl) {
if ( webView.canGoBack() ) {
Toast.makeText(MainActivity.this, R.string.error_web, Toast.LENGTH_SHORT).show();
webView.goBack();
}
}
});
You can filter by errorCode to go back when you want, in some kind of error you can go back on other do other thing. I dont' know which error raises this POST request or if you want more filter on other situations, so i'm sure you can do a fine grain filter using it.
Edit: You have here the possible error codes
WebViewClient Error Codes
I hope this helps.

WebView gets stuck on Read-only Empty TEXTAREA on Samsung Galaxy S3 (Android 4.1.1)

I observed that the Android Webview gets stuck when I try to tap into and focus on a TEXTAREA that is read-only and empty. The keyboard comes up and of course doesn't input anything into the TEXTAREA, but after that the WebView is stuck.
I can only force dismiss the keyboard using the "BACK" key but no other actions are performed. Can't do anything except restart the whole application.
<textarea rows="3" id="abcd" readonly="readonly" name="abcd"></textarea>
I keep getting this Verbose Message in the LOGCAT console against webview.
singleCursorHandlerTouchEVent ~getEditableSupport FASLE
This happens only on the Samsung S3 device running Android 4.1.1 and works perfectly on Samsung Nexus S (Android 4.1.2) and 4.1.2 Android emulator.
Other solutions proposed in these links did not work
Phonegap TouchEvent
Phonegap button does not fire due to "singleCursorHandlerTouchEvent -getEditableSupport FASLE"
This issue can be reproduced easily with this Standalone Webview example
public class TestWebViewTextStylesActivity extends Activity {
WebView mWebView = null;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
String data = "<html><body>" +
"<textarea rows='3' id='abcd' readonly='readonly' name='abcd'></textarea>" +
"</body></html>";
mWebView = new WebView(this);
setContentView(mWebView);
// Set some HTML
mWebView.loadDataWithBaseURL("file:///android_asset/", data, "text/html", "UTF-8", null);
}
}
I found the solution after spending half a day looking at various alternatives.
The solution was very simple which was to introduce a space between the TEXTAREA html tags.
<textarea rows="3" id="abcd" readonly="readonly" name="abcd"> </textarea>
_____________________________________________________________||___________
________________________________________________INSERTED___SPACE ___HERE__
And I've also observed that setting the .innerText attribute to BLANK string via JS also causes the TEXTAREA to cause Webview Freeze.
That space is also required without which the browser assumes all the HTML followed by the TEXTAREA also belongs inside the TEXTAREA. So correct way is to give a single space and then complete the TEXTAREA (</TEXTAREA>)
For Writable TEXTAREA HTML elements you can't have this empty space or this gets prefixed with the value that's inputted by the user. So I had to write a JS method that will empty out the value that I had to inject before setting it to the WebView.
function clearOffTextArea(textAreaId) {
var x = document.getElementById(textAreaId);
var isReadOnly = false;
if (x.hasAttribute('readOnly')) {
isReadOnly = x.readOnly;
}
if (isReadOnly == false) {
if (customMethodToTrimString(x.innerText) == '') {
x.innerText = '';
}
}
}

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.

Google search links in the webview of my app opening of a blank page ..!

The webview with google search result links loaded in my android app, when I clicked on the links, it is opening up a blank screen.
I think, it is something to do with onmousedown event attached with every href links in the result page.
will be very thankful if I am provided with a way to handle this and make webview to actually openup the link that I am clicking on.
Here's another solution. After Google finishes loading the blank page you load the WebView with the previous page (which is the actual result) using the WebView's tag or a member variable. Like this:
#Override
public void onPageFinished(WebView view, String url)
{
System.out.println("onPageFinished: " + url);
if ("about:blank".equals(url) && view.getTag() != null)
{
view.loadUrl(view.getTag().toString());
}
else
{
view.setTag(url);
}
}
Here's my LogCat:
I/System.out(13182): onPageFinished: http://www.google.com/#hl=en&sugexp=les%3B&gs_rn=1&gs_ri=tablet-gws&cp=2&gs_id=9&xhr=t&q=amazon...
I/System.out(13182): onPageFinished: http://www.amazon.com/
I/System.out(13182): onPageFinished: about:blank
I/System.out(13182): onPageFinished: http://www.amazon.com/
I'm having the same problem. I get the "about:blank" page when I click on Google search results in a WebView in my Asus Transformer TF700 running 4.1.1. It doesn't happen in my Acer A100 tablet or other phones.
I noticed the result links work when I switch from Tablet to Classic version at the bottom of main Google Search Page.
https://www.google.com/?nota=1
If you remove the ?nota=1 in the above URL you won't see the Tablet option in your PC. In your tablet however the default google.com URL displays the Tablet option at the bottom.
If you use nota=1 in your search results page the links will work. Like this:
http://www.google.com/search?nota=1&q=amazon
I know this is not perfect. We'd like the default Google search results page's links to work. Google is doing something funky on the Tablet version which Asus Transformer doesn't seem to like!
I will post an update when I figure out what is causing this. Oh! the fun with Android :)
I wanted to add this as a comment to Stan Texan's answer, but I don't have enough rep points...
I'm testing on an older tablet (LG Optimus Tab/DoCoMo L-06c/T-Mobile G-Slate/Rogers LG V909) running Honeycomb (3.1) and my WebView is running into the same problem on Google's website.
Google's own browser works just fine when navigating to www.google.com, but when I use that url in a WebView in my app, the links are all "about:blank". 0_o
Therefore, if the user wants to go to Google's search page, I rewrite the url as follows:
//get the url from the user..
inUrl = urlAddressEditText.getText().toString();
// make sure it's properly formatted...
...
// then add the "/?nota=1&" if it's a Google domain.
String outUrl = inUrl.replaceFirst("(www\\.google\\..*/?)(\\??)", "$1/?nota=1&");
webView.loadView(outUrl);
So far this works, but I haven't tested it out for every scenario.
I had a look at your Vuwize app. Instead of embedding www.google.com directly into a WebView, you seem to have your own search form, run a Google search, and then render the result page yourself. This could explain your problem because result links in search results from Google is not straight href links to original pages. To understand more about your problem, it's necessary to see what exactly you're doing and how you run Google search from your server side.
If you just embed www.google.com in a WebView directly like this:
setContentView(R.layout.main);
mWebView = (WebView) findViewById(R.id.webview);
mWebView.getSettings().setJavaScriptEnabled(true);
mWebView.loadUrl("http://www.google.com");
mWebView.setWebViewClient(new HelloWebViewClient());
Users can enter search directly into Google and get result pages, where links are all clickable in the same WebView.
Here's another solution to handle blank pages caused in Jelly Bean. I found 2 URLs that cause blank pages. Override loadUrl(String) and not load them at all.
#Override
public void loadUrl(String url)
{
if (url != null && !(url.startsWith("file:///android_asset") || "about:blank".equals(url)))
{
super.loadUrl(url);
}
}

WebView does not display loaded Html on some phones

I have a WebView in one of my Activities where I want to load a Html page. The page contains jquery-mobile and some html. So I do the following in my Activity :
mWebView=(WebView) findViewById(R.id.MyWebView);
mWebView.getSettings().setJavaScriptEnabled(true);
mWebView.setWebViewClient(new WebViewClient(){
[...]
});
mWebView.loadUrl("http://www.mymobilepage.html");
The problem is that the page gets loaded and displayed on the emulator, and on a HTC Desire, but when I try to load it on a LG Optimus One nothing gets displayed. The events onPageStarted and onPageFinished both get fired in my WebViewClient but just a blank page is displayed, and also I don't have any errors in my LogCat.
Thanks in advance.
When onPageFinished is called, the page may not be completely rendered. The documentation states:
Notify the host application that a page has finished loading. This method is called only for main frame. When onPageFinished() is called, the rendering picture may not be updated yet. To get the notification for the new Picture, use onNewPicture(WebView, Picture).
However, note that onNewPicture is documented as deprecated and obsolete. I ask about a replacement/alternative here.
This should be a comment, but since there is a bit of code on it I've added as response.
Try changing default background to transparent and alerting as soon as the page is loaded, just to be sure that at least the html is being interpreted:
mWebView = (WebView) this.findViewById(R.id.webview);
mWebView.setBackgroundColor(0);
mWebView.getSettings().setJavaScriptEnabled(true);
mWebView.getSettings().setJavaScriptCanOpenWindowsAutomatically(false);
mWebView.setWebViewClient(new WebViewClient(){
#Override
public void onPageFinished(WebView view, String url)
{
super.onPageFinished(view, url);
view.loadUrl("javascript:(function() { alert('hello'); })()");
} });
and when loading the webpage:
mWebView.clearView();
mWebView.loadUrl("http://yourmobilepage.something/");
and let us know if something happened.
Try this:
webView.post(new Runnable() {
#Override
public void run() {
// Your code here...
}
});
Have you checked your html/js code with different versions on the emulator? Newer Android versions have newer versions of WebKit, that might be the problem.
I would also check if you have LogCat set to show Error messages only, or Debug+Info+Warning+Error messages. According to this, the javascript errors should show up as Debug messages.
I had a similar issue to this, I found that calling clearview and then reload seemed to clear it up -- as in:
mWebView.clearView();
mWebView.loadUrl("http://yourmobilepage.something/");
mWebView.reload();

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