Intercept and override HTTP requests from WebView

Question

I have a WebView in my application in which some site is opened  always the same  it is my own page   The site has some JS code that loads some images from the remote host  I want to intercept requests to such images  by URL pattern  and give back my own content  i e  another image   or leave request untouched depending on internal application logic  Is it possible to do that  EDIT  The current state of the question    WebView has the ability to set a WebViewClient  as noted by Axarydax   WebViewClient have two useful methods  shouldOverrideUrlLoading onLoadResource  shouldOverrideUrlLoading is able to intercept any URL loading  if loading is triggered by page interaction  i e  link on a page is clicked  WebView loadURL  quot  quot   isn t triggering this method   It is also able to cancel URL loading by returning false  This approach isn t usable  cause  it is not able to intercept loading of page resources  and images  what I need to intercept  is such a page resource   onLoadResource is triggering every time that page resource  and images  thx to Jessyjones  are loading  but there is no way to cancel that  That makes this method not suitable for my task also

User · Answer

This may helps    TargetApi Build VERSION CODES LOLLIPOP   Override public WebResourceResponse shouldInterceptRequest WebView view  WebResourceRequest request        String url   request getUrl   toString        WebResourceResponse response   super shouldInterceptRequest view  request          load native js     if  url    null  amp  amp  url contains INJECTION TOKEN   scheme define                 response   new WebResourceResponse                   text javascript                    utf-8                   loadJsInputStream url  JsCache getJsFilePath path     InputStream                 return response

User · Answer

You don t mention the API version  but since API 11 there s the method WebViewClient shouldInterceptRequest  Maybe this could help

User · Answer

It looks like API level 11 has support for what you need  See WebViewClient shouldInterceptRequest

User · Answer

Try this  I ve used it in a personal wiki-like app   webView setWebViewClient new WebViewClient          Override     public boolean shouldOverrideUrlLoading WebView view  String url            if  url startsWith  foo                        magic             return true                    return false

User · Answer

An ultimate solution would be to embed a simple http server listening on your  secret  port on loopback  Then you can substitute the matched image src URL with something like http   localhost 123     mypic jpg

User · Answer

As far as I know  shouldOverrideUrlLoading is not called for images but rather for hyperlinks    I think the appropriate method is    Override  public void onLoadResource WebView view  String url   This method is called for every resource  image  styleesheet  script  that s loaded by the webview  but since it s a void  I haven t found a way to change that url and replace it so that it loads a local resource

User · Answer

Here is my solution I use for my app   I have several asset folder with css   js   img anf font files   The application gets all filenames and looks if a file with this name is requested  If yes  it loads it from asset folder     get list of files of specific asset folder         private ArrayList listAssetFiles String path                 List myArrayList   new ArrayList                String    list              try                   list   getAssets   list path                   for String f1   list                       myArrayList add f1                                   catch  IOException e                    e printStackTrace                              return  ArrayList  myArrayList                       get mime type by url         public String getMimeType String url                String type   null              String extension   MimeTypeMap getFileExtensionFromUrl url               if  extension    null                    if  extension equals  js                          return  text javascript                                     else if  extension equals  woff                          return  application font-woff                                     else if  extension equals  woff2                          return  application font-woff2                                     else if  extension equals  ttf                          return  application x-font-ttf                                     else if  extension equals  eot                          return  application vnd ms-fontobject                                     else if  extension equals  svg                          return  image svg xml                                     type   MimeTypeMap getSingleton   getMimeTypeFromExtension extension                             return type                       return webresourceresponse         public WebResourceResponse loadFilesFromAssetFolder  String folder  String url                List myArrayList   listAssetFiles folder               for  Object str   myArrayList                    if  url contains  CharSequence  str                         try                           Log i TAG2   File     str                           Log i TAG2   MIME     getMimeType url                            return new WebResourceResponse getMimeType url    UTF-8   getAssets   open String valueOf folder       str                           catch  IOException e                            e printStackTrace                                                                      return null                        TargetApi Build VERSION CODES LOLLIPOP           SuppressLint  NewApi            Override         public WebResourceResponse shouldInterceptRequest final WebView view  String url                  Log i TAG2   SHOULD OVERRIDE INIT                  String url   webResourceRequest getUrl   toString                String extension   MimeTypeMap getFileExtensionFromUrl url                 I have some folders for files with the same extension             if  extension equals  css      extension equals  js      extension equals  img                      return loadFilesFromAssetFolder extension  url                               more possible extensions for font folder             if  extension equals  woff      extension equals  woff2      extension equals  ttf      extension equals  svg      extension equals  eot                      return loadFilesFromAssetFolder  font   url                              return null

[android] Intercept and override HTTP requests from WebView

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