In Java usually validate with some specific characters, we should use Regular Expressions. Same way in Android, here we use Patterns. More info about the Patterns: Click here In android EditText, we can use custom input filter to perform this. This is for maximum input digits before and after decimal pointer. CustomInputFilter.Java public class CustomInputFilter implements InputFilter {     int maxDigitsBeforeDecimalPoint;     int maxDigitsAfterDecimalPoint;     public CustomInputFilter(int maxDigitsBeforeDecimalPoint, int maxDigitsAfterDecimalPoint) {         this.maxDigitsBeforeDecimalPoint = maxDigitsBeforeDecimalPoint;         this.maxDigitsAfterDecimalPoint = maxDigitsAfterDecimalPoint;     }     @Override     public CharSequence filter(CharSequence source, int start, int end, Spanned dest, int dstart, int dend) {         StringBuilder builder = new StringBuilder(dest);         builder.replace(dstart, dend, source                 .subSequence(start, end).toStr

To enable back button should be not close the application and web pages navigation only,     @Override     public boolean onKeyDown(int keyCode, KeyEvent event) {         if (keyCode == KeyEvent.KEYCODE_BACK) {                webview.goBack();             return true;         }         return super.onKeyDown(keyCode, event);     } Webview settings:         WebSettings webSetting = sWebview.getSettings();         webSetting.setJavaScriptEnabled(true);         webSetting.setDisplayZoomControls(false);         //Set whether the DOM storage API is enabled.         webSetting.setDomStorageEnabled(true);         sWebview.setWebChromeClient(new WebChromeClient());         sWebview.setWebViewClient(new MyWebViewClient()); To interact between Java and Javascript: WebAppInterface.Java import android.app.Activity; import android.util.Log; import android.webkit.JavascriptInterface; import android.webkit.WebView; public class WebAppInterface {     Activity activity

Have a great day. Set the permission in Manifest.xml <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"/> <uses-permission android:name="android.permission.INTERNET" /> Then just use below code:  public String getLocalIpAddress() {         String firstIP = "192.168.0.1";         ArrayList<String> ipList = new ArrayList<String>();         try {             for (Enumeration<NetworkInterface> en = NetworkInterface.getNetworkInterfaces(); en.hasMoreElements(); ) {                 NetworkInterface intf = en.nextElement();                 for (Enumeration<InetAddress> enumIpAddr = intf.getInetAddresses(); enumIpAddr.hasMoreElements(); ) {                     InetAddress inetAddress = enumIpAddr.nextElement();                     if (!inetAddress.isLoopbackAddress()) {                         Log.d(TAG, inetAddress.getHostAddress().toString());                         ipList.add(inetAdd