How to use the TextWatcher class in Android

Question

Can anyone tell me how to mask the substring in EditText or how to change EditText substring input to password type or replace by another character like this 123xxxxxxxxx3455   String contents   et1 getText   toString     et1 setText contents replace substring 0  contents length  -2          Please  tell me how I can use the TextWatcher method in Android

User · Answer

For Kotlin use KTX extension function   It uses TextWatcher as previous answers   yourEditText doOnTextChanged   text  start  count  after - gt              action which will be invoked when the text is changing          import core-KTX   implementation  androidx core core-ktx 1 2 0

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For use of the TextWatcher     et1 addTextChangedListener new TextWatcher          Override     public void onTextChanged CharSequence s  int start  int before  int count                TODO Auto-generated method stub             Override     public void beforeTextChanged CharSequence s  int start  int count  int after                TODO Auto-generated method stub             Override     public void afterTextChanged Editable s                TODO Auto-generated method stub

User · Answer

Create custom TextWatcher subclass   public class CustomWatcher implements TextWatcher        private boolean mWasEdited   false        Override     public void beforeTextChanged CharSequence s  int start  int count  int after                 Override     public void onTextChanged CharSequence s  int start  int before  int count                 Override     public void afterTextChanged Editable s             if  mWasEdited                mWasEdited   false              return                        get entered value  if required          String enteredValue    s toString             String newValue    new value               don t get trap into infinite loop         mWasEdited   true             just replace entered value with whatever you want         s replace 0  s length    newValue              Set listener for your EditText   mTargetEditText addTextChangedListener new CustomWatcher

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The TextWatcher interface has 3 callbacks methods which are all called in the following order when a change occurred to the text  beforeTextChanged CharSequence s  int start  int count  int after    Called before the changes have been applied to the text  The s parameter is the text before any change is applied  The start parameter is the position of the beginning of the changed part in the text  The count parameter is the length of the changed part in the s sequence since the start position  And the after parameter is the length of the new sequence which will replace the part of the s sequence from start to start count  You must not change the text in the TextView from this method  by using myTextView setText String newText     onTextChanged CharSequence s  int start  int before  int count     Similar to the beforeTextChanged method but called after the text changes  The s parameter is the text after changes have been applied  The start parameter is the same as in the beforeTextChanged method  The count parameter is the after parameter in the beforeTextChanged method  And the before parameter is the count parameter in the beforeTextChanged method  You must not change the text in the TextView from this method  by using myTextView setText String newText     afterTextChanged Editable s    You can change the text in the TextView from this method      Warning  When you change the text in the TextView  the TextWatcher will be triggered again  starting an infinite loop  You should then add like a boolean  ignore property which prevent the infinite loop  Exemple   new TextWatcher             boolean  ignore   false     indicates if the change was made by the TextWatcher itself            Override         public void afterTextChanged Editable s                if   ignore                  return                ignore   true     prevent infinite loop                Change your text here                 myTextView setText myNewText                ignore   false     release  so the TextWatcher start to listen again                        Other methods       Summary    A ready to use class  TextViewListener Personally  I made my custom text listener  which gives me the 4 parts in separate strings  which is  for me  much more intuitive to use            Text view listener which splits the update text event in four parts        lt ul gt            lt li gt The text placed  lt b gt before lt  b gt  the updated part  lt  li gt            lt li gt The  lt b gt old lt  b gt  text in the updated part  lt  li gt            lt li gt The  lt b gt new lt  b gt  text in the updated part  lt  li gt            lt li gt The text placed  lt b gt after lt  b gt  the updated part  lt  li gt        lt  ul gt       Created by Jeremy B             public abstract class TextViewListener implements TextWatcher                  Unchanged sequence which is placed before the updated sequence              private String  before                    Updated sequence before the update              private String  old                    Updated sequence after the update              private String  new                    Unchanged sequence which is placed after the updated sequence              private String  after                    Indicates when changes are made from within the listener  should be omitted              private boolean  ignore   false          Override     public void beforeTextChanged CharSequence sequence  int start  int count  int after             before   sequence subSequence 0 start  toString             old   sequence subSequence start  start count  toString             after   sequence subSequence start count  sequence length    toString                  Override     public void onTextChanged CharSequence sequence  int start  int before  int count             new   sequence subSequence start  start count  toString                  Override     public void afterTextChanged Editable sequence            if   ignore              return             onTextChanged  before   old   new   after                           Triggered method when the text in the text view has changed          lt br  gt         You can apply changes to the text view from this method        with the condition to call   link  startUpdates    before any update         and to call   link  endUpdates    after them                 param before Unchanged part of the text placed before the updated part          param old Old updated part of the text          param aNew New updated part of the text          param after Unchanged part of the text placed after the updated part              protected abstract void onTextChanged String before  String old  String aNew  String after                     Call this method when you start to update the text view  so it stops listening to it and then prevent an infinite loop          see  endUpdates               protected void startUpdates             ignore   true                          Call this method when you finished to update the text view in order to restart to listen to it          see  startUpdates               protected void endUpdates             ignore   false             Example  myEditText addTextChangedListener new TextViewListener              Override         protected void onTextChanged String before  String old  String aNew  String after                  intuitive use of parameters            String completeOldText   before   old   after             String completeNewText   before   aNew   after                            update TextView             startUpdates       to prevent infinite loop              myEditText setText myNewText               endUpdates

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Using TextWatcher in Android  Here is a sample code  Try using addTextChangedListener method of TextView  addTextChangedListener new TextWatcher              BigDecimal previousValue          BigDecimal currentValue            Override         public void onTextChanged CharSequence s  int start  int before  int                 count                if  isFirstTimeChange                    return                            if  s toString   length    gt  0                    try                       currentValue   new BigDecimal s toString   replace          replace                               catch  Exception e                        currentValue   new BigDecimal 0                                                       Override         public void beforeTextChanged CharSequence s  int start  int count                  int after                if  isFirstTimeChange                    return                            if  s toString   length    gt  0                    try                       previousValue   new BigDecimal s toString   replace          replace                               catch  Exception e                        previousValue   new BigDecimal 0                                                       Override         public void afterTextChanged Editable editable                if  isFirstTimeChange                    isFirstTimeChange   false                  return                            if  currentValue    null  amp  amp  previousValue    null                    if   currentValue compareTo previousValue   gt  0                           setBackgroundResource R color devises overview color green                       setBackgroundColor flashOnColor                     else if   currentValue compareTo previousValue   lt  0                           setBackgroundResource R color devises overview color red                        setBackgroundColor flashOffColor                     else                         setBackgroundColor textColor                                     handler removeCallbacks runnable                   handler postDelayed runnable  1000

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Supplemental answer Here is a visual supplement to the other answers  My fuller answer with the code and explanations is here   Red  text about to be deleted  replaced  Green  text that was just added  replacing the old red text

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public class Test extends AppCompatActivity        EditText firstEditText      EditText secondEditText        Override     protected void onCreate  Nullable Bundle savedInstanceState            super onCreate savedInstanceState           setContentView R layout test           firstEditText    EditText findViewById R id firstEditText           secondEditText    EditText findViewById R id secondEditText            firstEditText addTextChangedListener new EditTextListener                 private class EditTextListener implements TextWatcher             Override         public void beforeTextChanged CharSequence s  int start  int count  int after                         Override         public void onTextChanged CharSequence s  int start  int before  int count                secondEditText setText firstEditText getText                         Override         public void afterTextChanged Editable s

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if you implement with dialog edittext  use like this   its same with use to other edittext   dialog getInputEditText   addTextChangedListener new TextWatcher          Override     public void beforeTextChanged CharSequence charSequence  int start  int before  int count                Override     public void onTextChanged CharSequence charSequence  int start  int before  int count            if  start lt 2                   dialog getActionButton DialogAction POSITIVE  setEnabled false                else                  double size    Double parseDouble charSequence toString                     if  size  gt  0 000001  amp  amp  size  lt  0 999999                       dialog getActionButton DialogAction POSITIVE  setEnabled true                    else                      ToastHelper show HistoryActivity this   Size must between 0 1 - 0 9                        dialog getActionButton DialogAction POSITIVE  setEnabled false                                                Override     public void afterTextChanged Editable editable

User · Answer

A little bigger perspective of the solution    Override     public View onCreateView LayoutInflater inflater  ViewGroup container  Bundle savedInstanceState            View v   inflater inflate R layout yourlayout  container  false           View tv   v findViewById R id et1             TextView  tv  addTextChangedListener new TextWatcher                  Override             public void onTextChanged CharSequence s  int start  int before  int count                     SpannableString contentText   new SpannableString   TextView  tv  getText                      String contents   Html toHtml contentText  toString                                Override             public void beforeTextChanged CharSequence s  int start  int count  int after                        TODO Auto-generated method stub                             Override             public void afterTextChanged Editable s                        TODO Auto-generated method stub                                   return v          This works for me  doing it my first time

[android] How to use the TextWatcher class in Android?

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