Inject Multiple JavaScript to Multuple Page of WebView Android -

say, set webview example.com clicked on page , load example.com/about. in webview i've injected javascript modify html on example.com, , worked, , problem is, how inject javascript modify example.com/about. mean how inject multiple javascript multiple page of webview?

public class mainactivity extends appcompatactivity {      webview mwebview;      private int getscale() {         display display = ((windowmanager) getsystemservice(context.window_service)).getdefaultdisplay();         int width = display.getwidth();         double val = new double(width) / new double(100);         val = val * 100d;         return val.intvalue();     }      @override     protected void oncreate(bundle savedinstancestate) {         this.requestwindowfeature(window.feature_no_title);         getwindow().setflags(windowmanager.layoutparams.flag_fullscreen, windowmanager.layoutparams.flag_fullscreen);         super.oncreate(savedinstancestate);         setcontentview(r.layout.activity_main);         mwebview = (webview) findviewbyid(r.id.activity_main_webview);         // enable javascript         websettings websettings = mwebview.getsettings();         mwebview.setwebviewclient(new webviewclient());         websettings.setjavascriptenabled(true);         websettings.setallowuniversalaccessfromfileurls(true);         mwebview.setwebviewclient(new webviewclient());         mwebview.setwebviewclient(new webviewclient() {             @override             public void onpagefinished(webview view, string url) {                 // inject css when page done loading                 injectcss();                 mwebview.loadurl("javascript:var greeting = function (name) {\n" +                         "    console.log(\"great see you,\" + \" \" + name);\n" +                         "};");                 super.onpagefinished(view, url);                 //inject js edit html                 injectscriptfile(view, "script.js"); // see below ...                  // test if script loaded                 view.loadurl("javascript:settimeout(test(), 500)");             }              private void injectscriptfile(webview view, string scriptfile) {                 inputstream input;                 try {                     input = getassets().open(scriptfile);                     byte[] buffer = new byte[input.available()];                     input.read(buffer);                     input.close();                      // string-ify script byte-array using base64 encoding !!!                     string encoded = base64.encodetostring(buffer, base64.no_wrap);                     view.loadurl("javascript:(function() {" +                             "var parent = document.getelementsbytagname('head').item(0);" +                             "var script = document.createelement('script');" +                             "script.type = 'text/javascript';" +                             // tell browser base64-decode string script !!!                             "script.innerhtml = window.atob('" + encoded + "');" +                             "parent.appendchild(script)" +                             "})()");                 } catch (ioexception e) {                     // todo auto-generated catch block                     e.printstacktrace();                 }             }              @override             public boolean shouldoverrideurlloading(webview view, string url) {                 view.loadurl(url);                 return false;             }         });         mwebview.loadurl("example.com");         mwebview.getsettings().setbuiltinzoomcontrols(true);         mwebview.getsettings().setdisplayzoomcontrols(false);     }      private void injectcss() {         try {             inputstream inputstream = getassets().open("style.css");             byte[] buffer = new byte[inputstream.available()];             inputstream.read(buffer);             inputstream.close();             string encoded = base64.encodetostring(buffer, base64.no_wrap);             mwebview.loadurl("javascript:(function() {" +                     "var parent = document.getelementsbytagname('head').item(0);" +                     "var style = document.createelement('style');" +                     "style.type = 'text/css';" +                     // tell browser base64-decode string script !!!                     "style.innerhtml = window.atob('" + encoded + "');" +                     "parent.appendchild(style)" +                     "})()");         } catch (exception e) {             e.printstacktrace();         }     }      @override     protected void onsaveinstancestate(bundle outstate) {         super.onsaveinstancestate(outstate);         mwebview.savestate(outstate);     }      @override     protected void onrestoreinstancestate(bundle savedinstancestate) {         super.onrestoreinstancestate(savedinstancestate);         mwebview.restorestate(savedinstancestate);     }      @override     public boolean oncreateoptionsmenu(menu menu) {         super.oncreateoptionsmenu(menu); // add menu items, second value id, use in oncreateoptionsmenu         menu.add(0, 1, 0, "back");         menu.add(0, 2, 0, "refresh");         menu.add(0, 3, 0, "forward");         getmenuinflater().inflate(r.menu.menu_main, menu);         return true; // end of menu configuration     }      @override     public boolean onoptionsitemselected(menuitem item) {         switch (item.getitemid()) {              case 3: //if id equals 3 , go forward                 mwebview.cangoforward();                 item.seticon(r.drawable.forward);                 return true;         }         return super.onoptionsitemselected(item);     }      @override     public boolean onkeydown(int keycode, keyevent event) { // enables browsing previous pages hardware button         if ((keycode == keyevent.keycode_back) && mwebview.cangoback()) { // check if key event key , if there's history             mwebview.goback();             return true;         }   // if wasn't key or there's no web page history, bubble default         // system behavior (probably exit activity)         return super.onkeydown(keycode, event);     } }