Android TextWatcher Example

TextWatcher

Basically, a TextWatcher is used to keep watch on EditText while entering data into it. We can perform operation and keep watch on which characters are being entered or how many characters are being entered in the EditText.

For Ex. We can use TextWatcher to have checks on the password field that minimum number of characters are entered or not, or We can check the password Strength depending on number of characters entered in Password field .

TextWatcher class has 3 methods and we need override these methods to implement our own functionality.

1: public abstract void afterTextChanged (Editable s)

This method is called to notify you that, somewhere within s, the text has been changed. It is legitimate to make further changes to s from this callback, but be careful not to get yourself into an infinite loop, because any changes you make will cause this method to be called again recursively. (You are not told where the change took place because other afterTextChanged() methods may already have made other changes and invalidated the offsets. But if you need to know here, you can use setSpan(Object, int, int, int) in onTextChanged(CharSequence, int, int, int) to mark your place and then look up from here where the span ended up.

2: public abstract void beforeTextChanged (CharSequence s, int start, int count, int after)

This method is called to notify you that, within s, the count characters beginning at start are about to be replaced by new text with length after. It is an error to attempt to make changes to s from this callback.

3: public abstract void onTextChanged (CharSequence s, int start, int before, int count)

This method is called to notify you that, within s, the count characters beginning at start have just replaced old text that had length before. It is an error to attempt to make changes to s from this callback.

TextWatcher Example

In this post I have given an Example in which we have a password field of type EditText , in which user will  enter his password and we will show strength of password according to the number of characters entered by the user, we also show that maximum characters has been is entered when user enter 20 characters.

We have used following parameters to check Password Strength
        
Password Length            Password Strengthness
        1-5                                 Easy
        6-9                               Medium
      10-14                              Strong
      15-20                             Strongest

How to Attach TextWatcher to EditText

We create an Object of TextWatcher and override required methods

Declare the Objects

EditText editTextPassword;
 TextView textViewPasswordStrengthIndiactor;

inside onCreate()

editTextPassword.addTextChangedListener(mTextEditorWatcher);

Full Code :

main.xml

<LinearLayout
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:orientation="vertical"
            android:background="#E3FFC8"
            xmlns:android="http://schemas.android.com/apk/res/android">

            <TextView
                    android:id="@+id/textView1"
                    android:layout_marginTop="90dp"
                    android:textStyle="bold"
                    android:textColor="#520029"
                    android:layout_gravity="center_horizontal"
                    android:layout_width="wrap_content"
                 android:layout_height="wrap_content"
                 android:text="Text Watcher Demo"
                 android:textSize="30dp" />
    
   <!-- EditText to get the Password -->
               <EditText
                    android:layout_marginTop="40dp"
                    android:textSize="23dp"
                    android:id="@+id/editTextPassword"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:inputType="textPassword"
                   android:hint="Enter Your Password"
                   android:gravity="center_horizontal"
                   android:maxLength="20">
          
                   <requestFocus />
            </EditText>
   
          <LinearLayout
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            android:background="#B8FFB8">

            <TextView
                    android:id="@+id/textViewPassword"
                    android:textColor="#000099"
                    android:textSize="20dp"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="   Password Strength :  "
                    android:layout_gravity="center_vertical"/>

        <!--  TextView to show the Password Strength  -->
            <TextView
                    android:id="@+id/textViewPasswordStrength"
                    android:textColor="#005C00"
                    android:textStyle="bold"
                    android:textSize="23dp"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="Not Eneterd"
                    android:layout_gravity="center_vertical"/>
         </LinearLayout>
  </LinearLayout>

MainActivity.java

public class MainActivity extends Activity
{
                // Create Object of EditText and TextWatcher
                EditText editTextPassword;
                TextView textViewPasswordStrengthIndiactor;
                @Override
                protected void onCreate(Bundle savedInstanceState)
                {
                            super.onCreate(savedInstanceState);
                            setContentView(R.layout.main);
                           
                            // Get the Reference of EditText
                            editTextPassword=(EditText)findViewById(R.id.editTextPassword);
                            textViewPasswordStrengthIndiactor=(TextView)findViewById(R.id.textViewPasswordStrength);
                   
                            // Attach TextWatcher to EditText
                            editTextPassword.addTextChangedListener(mTextEditorWatcher);
                   
                }

   
                // EditTextWacther  Implementation
 
                private final TextWatcher  mTextEditorWatcher = new TextWatcher() {
                   
                    public void beforeTextChanged(CharSequence s, int start, int count, int after)
                    {
                                // When No Password Entered
                               textViewPasswordStrengthIndiactor.setText("Not Entered");
                    }

                    public void onTextChanged(CharSequence s, int start, int before, int count)
                    {
                       
                    }

                    public void afterTextChanged(Editable s)
                    {
                                 if(s.length()==0)
                                        textViewPasswordStrengthIndiactor.setText("Not Entered");
                                 else if(s.length()<6)
                                        textViewPasswordStrengthIndiactor.setText("EASY");
                                 else if(s.length()<10)
                                        textViewPasswordStrengthIndiactor.setText("MEDIUM");
                                 else if(s.length()<15)
                                        textViewPasswordStrengthIndiactor.setText("STRONG");
                                   else
                                        textViewPasswordStrengthIndiactor.setText("STRONGEST");
                       
                               if(s.length()==20)
                                   textViewPasswordStrengthIndiactor.setText("Password Max Length Reached");
                    }
            };

}

 


 

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