Android Studio EditText with TextWatcher

Syntax

The syntax for implementing EditText with TextWatcher in Android Studio is as follows:

EditText editText = findViewById(R.id.editText);
editText.addTextChangedListener(new TextWatcher() {
    @Override
    public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {
        // This method is called to notify the listener that the text is about to be changed
    }

    @Override
    public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {
        // This method is called to notify the listener that the text has been changed
    }

    @Override
    public void afterTextChanged(Editable editable) {
        // This method is called to notify the listener that the text has been changed and the editing is complete
    }
});

Example

Let's take a look at a simple example of EditText with TextWatcher

public class MainActivity extends AppCompatActivity {

    EditText editText;
    TextView textView;

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

        editText = findViewById(R.id.editText);
        textView = findViewById(R.id.textView);

        editText.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {
                
            }

            @Override
            public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {
                textView.setText(charSequence);
            }

            @Override
            public void afterTextChanged(Editable editable) {

            }
        });
    }
}

Output

The output of the above example would look like this:

Explanation

EditText with TextWatcher is a powerful tool that allows us to listen to changes made to an EditText in real time. By adding a TextWatcher to an EditText, we can listen to changes made to the EditText and update any views or data as needed. In the example above, we added a TextWatcher to an EditText and updated a TextView with the text entered into the EditText.

Use

EditText with TextWatcher is useful in scenarios where we need to update views or data in real time as the user types into an EditText.

Some common use cases for EditText with TextWatcher are:

• Validating user input in real time
• Auto-formatting text as the user types
• Filtering a list or RecyclerView based on user input

Important Points

• BeforeTextChanged() method is called when the text is about to be changed.
• OnTextChanged() method is called when the text has been changed.
• AfterTextChanged() method is called when the text has been changed and the editing is complete.
• Avoid doing heavy processing in the TextWatcher methods, as it can affect the performance.

Summary

EditText with TextWatcher is a powerful tool that allows us to listen to changes made to an EditText in real time. It is useful in scenarios where we need to update views or data in real time as the user types into an EditText. By adding a TextWatcher to an EditText, we can listen to changes made to the EditText and update any views or data as needed.