binding - Android: Two-way databinding -

i trying 2 way databinding on android application. have set application bind data ui don't know how can update data model when edittext text changed.

i think of creating extended edittext override focus , textchanged can detect text changed , focus validation. how can know data object dealing with.

i tried using app:addtextchangelistener passing function return textwatcher in layout.xml received nullpointerexception.

does know how two-way databinding on android?

you can implement ontextchangemethod in data object

 public void ontextchanged(charsequence newtext, int start, int before, int count) {      setstringfield(newtext.tostring());  } 

and add

<edittext         ...         android:ontextchanged="@{data.ontextchanged}" /> 

so, data updated every time text changed. in addition, if display yourfield on ui should observablefield.

public class data {     private observablefield<string> stringfield = new observablefield<>();      public void setstringfield(string changingtext) {         stringfield.set(changingtext);     }      public observablefield<string> getstringfield() {         return stringfield;     }      public void ontextchanged(charsequence newtext, int start, int before, int count) {         setstringfield(newtext.tostring());     } } 

all layout looks this:

<layout xmlns:android="http://schemas.android.com/apk/res/android">      <data>         <variable             name="data"             type="your.package.data" />     </data>      <linearlayout         android:layout_width="match_parent"         android:layout_height="match_parent"         android:orientation="vertical">          <edittext             android:id="@+id/username"             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:ontextchanged="@{data.ontextchanged}" />           <textview             android:layout_width="wrap_content"             android:layout_height="wrap_content"             android:text="@{data.stringfield}" />     </linearlayout> </layout>