Develop Reference

Get an image src from a webview in android

I am trying to get the src of a captcha image found in a webview but when i type the below code the output says:
Uncaught TypeError: Cannot read property 'src' of null
and another question if i get the image src how can i put the image in an image view?
any help will be really appreciated
here is my code so far:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
wv = (WebView) findViewById(R.id.wv) ;
mImgCaptcha = (ImageView) findViewById(R.id.imgCaptcha);
done = (Button) findViewById(R.id.done);
contentView = (TextView) findViewById(R.id.textView);
username = (EditText) findViewById(R.id.editText);
password = (EditText) findViewById(R.id.password);
code = (EditText) findViewById(R.id.code);
WebSettings webSettings = wv.getSettings();
webSettings.setJavaScriptEnabled(true);
wv.getSettings().setDomStorageEnabled(true);
wv.loadUrl("https://noor.moe.gov.sa/NOOR/Login.aspx");
wv.loadUrl("javascript:var a = document.getElementById('imgCaptcha').src;");
System.out.println(wv.getUrl());
done.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
wv.loadUrl("javascript:var x = document.getElementById('tbPublic').value = '" + username.getText().toString() + "';");
wv.loadUrl("javascript:var x = document.getElementById('tbPrivate').value = '" + password.getText().toString() + "';");
wv.loadUrl("javascript:var x = document.getElementById('tbCaptcha').value = '" + code.getText().toString() + "';");
try {
Thread.sleep(2000);
wv.loadUrl("javascript:(function(){" +
"l=document.getElementById('btnLogin');" +
"e=document.createEvent('HTMLEvents');" +
"e.initEvent('click',true,true);" +
" l.dispatchEvent(e);" +
"})()");
} catch (InterruptedException e) {
e.printStackTrace();
}

It's because the page is not loaded yet when you are trying to query the DOM. You need to query the DOM when you can be sure that the page has loaded.
We need to set the WebViewClient for the webview and then listen to onPageFinished event. The code might look something like this:
webView.setWebViewClient(new WebViewClient(){
#Override
public void onPageFinished(WebView view, String url) {
super.onPageFinished(view, url);
// you can now query the DOM.
webView.loadUrl("javascript:var a = document.getElementById('imgCaptcha').src;");
}
});
Further reading: https://developer.android.com/reference/android/webkit/WebViewClient#onPageFinished(android.webkit.WebView,%2520java.lang.String)

Android webview href not support in html page

I want to load to a about.html page inside asset folder by clicking a button in index.html inside android webview.
Here's the code:
Button:
About
Java:
WebView browser = (WebView) findViewById(webview);
browser.getSettings().setJavaScriptEnabled(true);
browser.setWebChromeClient(new WebChromeClient());
browser.loadUrl("file:///android_asset/www/index.html");
browser.setWebViewClient(new WebViewClient() {
#Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {
view.loadUrl(url);
return false;
}
});
But the problem is when i click on button it doesn't load about.html but if I add a javascript function with below code it works.. but i want to use href.
Code:
<button onclick="about()">About</button>
<script>
function about() {
location.href = "about.html";
}
</script>
How do I solve it?

write an interface for TagHandler and in your fromHtml method check for the tag and handle it by loading the page
https://developer.android.com/reference/android/text/Html.html

try this code:
private void loadWebView(WebView webView,String htmlString)
{
try {
final String mimeType = "text/html";
final String encoding = "UTF-8";
WebViewClient yourWebClient = new WebViewClient()
{
#Override
public boolean shouldOverrideUrlLoading(WebView view, String url)
{
// This line we let me load only pages inside Webpage
if ( url.contains("") == true )
// Load new URL Don't override URL Link
return false;
// Return true to override url loading (In this case do nothing).
return true;
}
};
// Get Web view
webView.getSettings().setJavaScriptEnabled(true);
webView.getSettings().setSupportZoom(true);
webView.getSettings().setBuiltInZoomControls(true);
webView.setWebViewClient(yourWebClient);
// Load URL
webView.loadDataWithBaseURL("", htmlString, mimeType, encoding, "");
} catch (Exception e) {
e.printStackTrace();
}
}
use it as:
loadWebView(browser, "file:///android_asset/www/index.html") //pass url

WebView code generating Uncaught TypeError and Uncaught ReferenceError errors on Android 4.4.2 (API 19) emulator

I'm having a problem with my code when running on a Android 4.4.2 KitKat (API 19) emulator...
When I emulate my project on a Android 4.3 (API 18) emulator, it works normally and creates the mathematical expressions with MathJax:
Image of emulator
But when I use a Android 4.4.2 emulator, the app don't work correctly:
Image of emulator
Here is the code of my project:
package com.testes.testesapp;
import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
import android.view.View;
import android.webkit.WebView;
import android.widget.Button;
import android.widget.EditText;
public class MainActivity extends Activity implements View.OnClickListener {
private int exampleIndex = 0;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
WebView webView = (WebView) findViewById(R.id.webview);
webView.getSettings().setJavaScriptEnabled(true);
//webView.getSettings().setBuiltInZoomControls(true);
webView.loadDataWithBaseURL("http://test", "<script type='text/x-mathjax-config'>"
+ "MathJax.Hub.Config({ "
+ "showMathMenu: false, "
+ "jax: ['input/TeX','output/HTML-CSS'], " // output/SVG
+ "extensions: ['tex2jax.js','toMathML.js'], "
+ "TeX: { extensions: ['AMSmath.js','AMSsymbols.js',"
+ "'noErrors.js','noUndefined.js'] }, "
// + "'SVG' : { blacker: 30, "
// + "styles: { path: { 'shape-rendering': 'crispEdges' } } } "
+ "});</script>"
+ "<script type='text/javascript' "
+ "src='file:///android_asset/MathJax/MathJax.js'"
+ "></script>"
+ "<span id='math'></span>","text/html","utf-8","");
EditText edit = (EditText) findViewById(R.id.edit);
edit.setBackgroundColor(Color.LTGRAY);
edit.setTextColor(Color.BLACK);
edit.setText("");
Button btnShow = (Button) findViewById(R.id.btnShow);
btnShow.setOnClickListener(this);
Button btnClear = (Button) findViewById(R.id.btnClear);
btnClear.setOnClickListener(this);
Button btnExample = (Button) findViewById(R.id.btnExample);
btnExample.setOnClickListener(this);
}
private String doubleEscapeTeX(String s) {
String t="";
for (int i=0; i < s.length(); i++) {
if (s.charAt(i) == '\'') t += '\\';
if (s.charAt(i) != '\n') t += s.charAt(i);
if (s.charAt(i) == '\\') t += "\\";
}
return t;
}
private String getExample(int index) {
return getResources().getStringArray(R.array.tex_examples)[index];
}
public void onClick(View v) {
if (v == findViewById(R.id.btnShow)) {
WebView webView = (WebView) findViewById(R.id.webview);
EditText edit = (EditText) findViewById(R.id.edit);
webView.loadUrl("javascript:document.getElementById('math').innerHTML='\\\\["
+ doubleEscapeTeX(edit.getText().toString()) + "\\\\]';");
webView.loadUrl("javascript:MathJax.Hub.Queue(['Typeset',MathJax.Hub]);");
}
else if (v == findViewById(R.id.btnClear)) {
WebView webView = (WebView) findViewById(R.id.webview);
EditText edit = (EditText) findViewById(R.id.edit);
edit.setText("");
webView.loadUrl("javascript:document.getElementById('math').innerHTML='';");
}
else if (v == findViewById(R.id.btnExample)) {
WebView webView = (WebView) findViewById(R.id.webview);
EditText edit = (EditText) findViewById(R.id.edit);
edit.setText(getExample(exampleIndex++));
if (exampleIndex > getResources().getStringArray(R.array.tex_examples).length - 1)
exampleIndex=0;
webView.loadUrl("javascript:document.getElementById('math').innerHTML='\\\\["
+ doubleEscapeTeX(edit.getText().toString()) + "\\\\]';");
webView.loadUrl("javascript:MathJax.Hub.Queue(['Typeset',MathJax.Hub]);");
}
}
}
When I press the "Example" or the "Show" button, LogCat emits the errors:
I/chromium(1254): [INFO:CONSOLE(1)] "Uncaught TypeError: Cannot set property 'innerHTML' of null", source: http://test/ (1)
I/chromium(1254): [INFO:CONSOLE(1)] "Uncaught ReferenceError: MathJax is not defined", source: http://test/ (1)
I have no idea how to fix this problem, and would like somebody's help to solve this. Thanks.

I got this problem too.
Here is my solution:
change your base URL from "http://test" to "http://test/"
change this code webView.loadUrl(..) to webView.evaluateJavascript(..);. Especially for code where we want to load innerHTML. Don't forget to add anotation #TargetApi(Build.VERSION_CODES.KITKAT) because it's only for Android 4.4 and above
never put webView.loadWithBaseUrl(..) in the same process with webView.loadUrl(..). Because If webView.loadUrl(..) was loaded before webView.loadWithBaseUrl(..) finished, it will raise error as OP stated above.
For number 3, your codes is already conform with this (because in your codes, webView.loadUrl(..) execution was already separated with webView.loadWithBaseUrl(..) by using OnClick event. So, don't pay attention to it.
But if your apps need to load them at one event, consider to separate them by using this code:
`
private void initiateWebView(){
webViewEquationDisplay.setWebViewClient(new WebViewClient() {
#Override
public void onPageFinished(WebView view, String url) {
super.onPageFinished(view, url);
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT){
loadUrlKitKat(equationSymbolFinal+equationToBeDisplayedFinal);
}
else{
webViewEquationDisplay.loadUrl("javascript:document.getElementById('math').innerHTML='<font color=\"yellow\">`"+equationToBeDisplayedFinal+"`</font>';");
}
webViewEquationDisplay.loadUrl("javascript:MathJax.Hub.Queue(['Typeset',MathJax.Hub]);");
}
});
final String mathJaxOfflineUrl = "file:///android_asset/MathJax/MathJax.js";
webViewEquationDisplay.loadDataWithBaseURL("http://bar/", "<script type='text/x-mathjax-config'>"
+"MathJax.Hub.Config({ "
+"showMathMenu: false, "
+"jax: ['input/AsciiMath','output/HTML-CSS'], "
+"extensions: ['asciimath2jax.js'], "
+"AsciiMath: { fixphi: true, useMathMLspacing: true, displaystyle: false, decimalsign: \".\" }, "
+"});</script>"
+"<script type='text/javascript' "
+"src='"+mathJaxOfflineUrl+"'"
+"></script><span id='math'></span>","text/html","utf-8","");
}
#TargetApi(Build.VERSION_CODES.KITKAT)
private void loadUrlKitKat(String param){
webViewEquationDisplay.evaluateJavascript("javascript:document.getElementById('math').innerHTML='<font color=\"#97FD97\">`"+param+"`</font>';",null);
}
`
good luck

I had the same problem when I moved different javascript functions out of the main page to an separate .js file. For some reason, Android can't find externally-loaded JavaScript webview functions from Java - only the ones in the main page. Once I moved the function back from the JS file, it immediately started working.
Try making a "proxy" function like this directly inside the main HTML:
function proxy() {
call_some_other_function_from_JS_file();
}
This worked for me. I'm sure there must be a way to get find these functions, because I didn't have this problem on iOS. Someone please comment if you know a better way.

webview.evaluateJavascript("javascript:document.getElementById('math').innerHTML='"+doubleEscapeTeX(questn)+"';",null);
webview.loadUrl("javascript:MathJax.Hub.Queue(['Typeset',MathJax.Hub]);");
This is the sollution for api 19 or above

inject js file to webview

I need to inject some javaScript files into loading page.
my code:
#Override
public void doUpdateVisitedHistory(WebView view, String url, boolean isReload) {
super.doUpdateVisitedHistory(view, url, isReload); //To change body of overridden methods use File | Settings | File Templates
mWebView.loadUrl("javascript:(function(){var script = document.createElement('script');script.setAttribute('src', 'file:///android_asset/jquery.js'); script.setAttribute('type', 'text/javascript'); document.body.appendChild(script)})();");
mWebView.loadUrl("javascript:(function(){var script = document.createElement('script');script.setAttribute('src', 'file:///android_asset/rangy-core.js'); script.setAttribute('type', 'text/javascript'); document.body.appendChild(script)})();");
mWebView.loadUrl("javascript:(function(){var script = document.createElement('script');script.setAttribute('src', 'file:///android_asset/rangy-serializer.js'); script.setAttribute('type', 'text/javascript'); document.body.appendChild(script)})();");
mWebView.loadUrl("javascript:(function(){var script = document.createElement('script');script.setAttribute('src', 'file:///android_asset/android.selection.js'); script.setAttribute('type', 'text/javascript'); document.body.appendChild(script)})();");// .
}
but it's not work =(
Change code to
mWebView.loadUrl("javascript:function loadScript(url, callback)" +
"{" +
" var head = document.getElementsByTagName('head')[0];" +
" var script = document.createElement('script');" +
" script.type = 'text/javascript';" +
" script.src = url;" +
" script.onreadystatechange = callback;" +
" script.onload = callback;" +
" head.appendChild(script);" +
"}");
mWebView.loadUrl("javascript:loadScript('file:///android_asset/jquery.js','callback')");
mWebView.loadUrl("javascript:loadScript('file:///android_asset/rangy-core.js','callback')");
mWebView.loadUrl("javascript:loadScript('file:///android_asset/rangy-serializer.js','callback')");
mWebView.loadUrl("javascript:loadScript('file:///android_asset/android.selection.js','callback')");
Now I have Error : 06-11 10:24:15.432: ERROR/Web Console(7962): Not allowed to load local resource: file:///android_asset/jquery.js at null:0

You can use js method to load js file and pass url as a parameter from java
Here is the full working example
[Activity.java]
public class MainActivity extends Activity {
WebView mWebView;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mWebView = (WebView) findViewById(R.id.webview);
WebSettings webSettings = mWebView.getSettings();
webSettings.setJavaScriptEnabled(true);
mWebView.addJavascriptInterface(new JavaScriptInterface(), "jsinterface");
mWebView.loadUrl("file:///android_asset/sq.html");
}
final class JavaScriptInterface {
JavaScriptInterface() {
}
#JavascriptInterface
public void windowLoaded() {
mWebView.loadUrl("javascript:loadScript('test.js', 'testing')");
Log.i("browser", "browser loaded");
}
}
}
[sq.html]
<html>
<head>
<script>
onload = function () {
window.jsinterface.windowLoaded();
}
//JS
function loadScript(url, callback)
{
console.log("loading script " + url);
// adding the script tag to the head as suggested before
var head = document.getElementsByTagName('head')[0];
var script = document.createElement('script');
script.type = 'text/javascript';
script.src = url;
// then bind the event to the callback function
// there are several events for cross browser compatibility
//script.onreadystatechange = callback;
script.onload = callback;
// fire the loading
head.appendChild(script);
}
</script>
</head>
<body>replace this
</body>
</html>
[test.js] inside assets folder
document.body.innerHTML = "<p>testing</p>";
on successful execution webview will show testing by loading test.js dynamically.

Here is how i ended up doing it. I used the Content:// protocol and set up a contentprovider to handle returning a file descriptor to the system
Here is my fileContentProvider:
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import org.apache.commons.io.IOUtils;
import android.content.ContentProvider;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.ParcelFileDescriptor;
import android.util.Log;
public class FileContentProvider extends ContentProvider {
#Override
public ParcelFileDescriptor openFile(Uri uri, String mode) {
Log.d("FileContentProvider","fetching: " + uri);
ParcelFileDescriptor parcel = null;
String fileNameRequested = uri.getLastPathSegment();
String[] name=fileNameRequested.split("\\.");
String prefix=name[0];
String suffix=name[1];
// String path = getContext().getFilesDir().getAbsolutePath() + "/" + uri.getPath();
//String path=file:///android_asset/"+Consts.FILE_JAVASCRIPT+"
/*check if this is a javascript file*/
if(suffix.equalsIgnoreCase("js")){
InputStream is = null;
try {
is = getContext().getAssets().open("www/"+Consts.FILE_JAVASCRIPT);
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
File file = stream2file(is,prefix,suffix);
try {
parcel = ParcelFileDescriptor.open(file, ParcelFileDescriptor.MODE_READ_ONLY);
} catch (FileNotFoundException e) {
Log.e("FileContentProvider", "uri " + uri.toString(), e);
}
}
return parcel;
}
/*converts an inputstream to a temp file*/
public File stream2file (InputStream in,String prefix,String suffix) {
File tempFile = null;
try {
tempFile = File.createTempFile(prefix, suffix);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
tempFile.deleteOnExit();
FileOutputStream out = null;
try {
out = new FileOutputStream(tempFile);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
try {
IOUtils.copy(in, out);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return tempFile;
}
#Override
public boolean onCreate() {
return true;
}
#Override
public int delete(Uri uri, String s, String[] as) {
throw new UnsupportedOperationException("Not supported by this provider");
}
#Override
public String getType(Uri uri) {
throw new UnsupportedOperationException("Not supported by this provider");
}
#Override
public Uri insert(Uri uri, ContentValues contentvalues) {
throw new UnsupportedOperationException("Not supported by this provider");
}
#Override
public Cursor query(Uri uri, String[] as, String s, String[] as1, String s1) {
throw new UnsupportedOperationException("Not supported by this provider");
}
#Override
public int update(Uri uri, ContentValues contentvalues, String s, String[] as) {
throw new UnsupportedOperationException("Not supported by this provider");
}
}
in the manifest i defined the provider:
<provider android:name="com.example.mypackage.FileContentProvider"
android:authorities="com.example.fileprovider"
/>
Here is the javascript o inject into the webview:
webView.loadUrl("javascript:(function() { "
+ "var script=document.createElement('script'); "
+ " script.setAttribute('type','text/javascript'); "
+ " script.setAttribute('src', 'content://com.example.fileprovider/myjavascriptfile.js'); "
/* + " script.onload = function(){ "
+ " test(); "
+ " }; "
*/ + "document.body.appendChild(script); "
+ "})();");
and here is the myjavascriptfile.js (as an example):
function changeBackground(color) {
document.body.style.backgroundColor = color;
}

You don't really need the content provider. Instead of
mWebView.loadUrl("file:///android_asset/sq.html");
you can use the following to load the original html file. Then the script will be able to upload test.js from the assets directory
mWebView.loadDataWithBaseURL("file:///android_asset/", data,
"text/html", null, null);

Android, getting html content in my app

I need to get some properties of an html page which is loaded in a webview.
Something similar to what is here: stringByEvaluatingJavascriptFromString (iOS method, what is Android equivalent?)
So I have a JavaScriptInterface:
class MyJavaScriptInterface {
#android.webkit.JavascriptInterface
public void jsCallback(String jsResult) {
// your code...
Log.d("Debug", jsResult);
}
}
ant then here is the JS I use to get the string I need:
webView.addJavascriptInterface(new MyJavaScriptInterface(), "HTMLOUT");
webView.loadUrl("javascript:( "
+ "function () { "
+ "var htmltag = document.getElementsByTagName(\"html\");"
+ "var dataStr = htmltag[0].getAttribute(\"some-data-property-i-need\"); "
+ "console.log(window.HTMLOUT);"
+ "window.HTMLOUT.jsCallback(dataStr); } ) ()");
now in the console I see this traces:
06-02 01:14:06.409: V/CallNative fired:(26789): objc://domReady
06-02 01:14:06.464: I/Web Console(26789): undefined at null:1
06-02 01:14:06.480: E/Web Console(26789): Uncaught TypeError: Cannot call method 'jsCallback' of undefined at null:1
and I have no idea why "window.HTMLOUT" is undefined.
Please note that it was working at a point and then I modified a bit the JS part but I still cannot figure it out what could be the problem.

JS code can be executed after the whole page is loaded, have a try at this way:
webView.setWebViewClient(new WebViewClient() {
#Override
public void onPageFinished(WebView view, String url) {
super.onPageFinished(view, url);
// Call JS code here
}
});
webView.loadDataWithBaseURL(null, "<html></html>", "text/html", "UTF-8", "");
If previous method does not work, please have a try at HTMLOUT.jsCallback(dataStr) instead of window.HTMLOUT.jsCallback(dataStr).