Implement TextWatcher to EditText

This example implement TextWatcher, attach to EditText with addTextChangedListener(). Its methods will be called when the text is changed.

Implement TextWatcher to EditText

package com.example.androidedittext;

import android.os.Bundle;
import android.app.Activity;
import android.text.Editable;
import android.text.TextWatcher;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends Activity {
 
 TextView promptAfter, promptBefore, promptOn;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  
  promptAfter = (TextView)findViewById(R.id.promptAfter);
  promptBefore = (TextView)findViewById(R.id.promptBefore);
  promptOn = (TextView)findViewById(R.id.promptOn);
  
  EditText input = (EditText)findViewById(R.id.input);
  input.addTextChangedListener(textWatcher);
 }

 TextWatcher textWatcher = new TextWatcher(){

  @Override
  public void afterTextChanged(Editable s) {
   promptAfter.setText(s.toString());
  }

  @Override
  public void beforeTextChanged(CharSequence s, 
    int start, int count, int after) {
   promptBefore.setText(s + "\n" + 
    start + " / " + count + " / " + after);
  }

  @Override
  public void onTextChanged(CharSequence s, 
    int start, int before, int count) {
   promptOn.setText(s + "\n" 
    + start + " / " + before + " / " + count);
  }
  
 };

}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="android-coding.blogspot.com" />

    <EditText
        android:id="@+id/input"
     android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textSize="28sp" />
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textStyle="italic"
        android:text="afterTextChanged(Editable s)" />
    <TextView
        android:id="@+id/promptAfter"
     android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textStyle="bold" />
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textStyle="italic"
        android:text="beforeTextChanged(CharSequence s, int start, int count, int after)" />
    <TextView
        android:id="@+id/promptBefore"
     android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textStyle="bold" />
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textStyle="italic"
        android:text="onTextChanged(CharSequence s, int start, int before, int count)" />
    <TextView
        android:id="@+id/promptOn"
     android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:textStyle="bold" />
 
</LinearLayout>