How to Use the Textwatcher Class in Android

Common TextWatcher class

You can create a BaseFragment that will be extended by your fragments.

Therefore, you can manage your TextWatcher inside this BaseFragment and consequently the fragments which have this heritage, will receive your expected logic.

As in the following example:

BaseFragment.class

public abstract class BaseFragment extends Fragment implements TextWatcher {

    EditText editText;
    Button button;

    @Override
    public void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        //inflate your edit text
        ...

        //inflate your button
        ...

        editText.addTextChangedListener(this);

    }

    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
        //text watcher listener
    }

    @Override
    public void onTextChanged(CharSequence s, int start, int before, int count) {
        //text watcher listener
    }

    @Override
    public void afterTextChanged(Editable s) {
        //text watcher listener
    }
}

YourFragment.class

public class YourFragment extends BaseFragment {
   ...
}

How to add Text Watcher on multiple Edit text in android?

There is two ways you can do this.

First

TextWatcher textWatcher = new 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) {

        }

        @Override
        public void afterTextChanged(Editable s) {
              if (m_InputMobile.getText().hashCode() == s.hashCode()) {
                  checkFieldsForEmpty();
              }
              else if (m_InputPassword.getText().hashCode() == s.hashCode()) {
                  checkFieldsForEmpty();
              }
        }
    };

m_InputMobile = (EditText) findViewById(R.id.input_mobile);
m_InputMobile.addTextChangedListener(getmWatcher);
m_InputPassword = (EditText) findViewById(R.id.input_password);
m_InputPassword.addTextChangedListener(getmWatcher);

or make a custome TextWatcher class

Second

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    m_InputMobile = (EditText) findViewById(R.id.input_mobile);
    m_InputMobile.addTextChangedListener(new CustomTextWatcher(m_InputMobile));
    m_InputPassword = (EditText) findViewById(R.id.input_password);
    m_InputPassword.addTextChangedListener(new CustomTextWatcher(m_InputPassword));
}

private class CustomTextWatcher implements TextWatcher {
    private EditText mEditText;

    public CustomTextWatcher(EditText e) { 
        mEditText = e;
    }

   @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) {
       checkFieldsForEmpty();
   }
}

For more details visit this Question.

Happy Coding.

How to call TextWatcher from Class

Your editText is not 'aware' that it should call your class whenever something changes in it.

You should do it this way - your class should implement TextWatcher:

public class FormTextCosmetics implements TextWatcher {
    //Your code goes here
}

And then you use it like this -

etName.addTextChangedListener(new FormTextCosmetics());

Now the editText will call your class whenever something happens in it's text.

Accessing TextWatcher in another class - nullpointer exception

You need to pass your activity reference to another class to like below:

MainActivity code:

public class UnitConverter extends AppCompatActivity {
    public EditText input;
    .
    ......
    input = (EditText) findViewById(R.id.etInput);
    .........
    case Sample :
        new AnotherClass(UnitConverter.this);
}

AnotherClass code:

public class AnotherClass {
    public AnotherClass(UniteConverter ac) {
    ac.input.addTextChangedListener(new TextWatcher() {

        public void afterTextChanged(Editable s) {
        }

        public void beforeTextChanged(CharSequence s, int start,
                                  int count, int after) {
        }

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

How to use TextWatcher in android?

I think this piece of code will help you.....

EditText etSearchBar = (EditText)findViewById(Your_id);

    etSearchBar.addTextChangedListener(textwatcher);

    private TextWatcher textwatcher = new TextWatcher() {

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

            }

            @Override
            public void beforeTextChanged(CharSequence s, int start, int count,
                    int after) {


            }

            @Override
            public void afterTextChanged(Editable s) {

                //Do what ever you want here after you enter each text
            }
        };