android on Text Change Listener

In Kotlin simply use KTX extension function: (It uses TextWatcher)

yourEditText.doOnTextChanged { text, start, count, after -> 
        // action which will be invoked when the text is changing
    }

import core-KTX:

implementation "androidx.core:core-ktx:1.2.0"

If you are using Kotlin for Android development then you can add TextChangedListener() using this code:

myTextField.addTextChangedListener(object : TextWatcher{
        override fun afterTextChanged(s: Editable?) {}

        override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) {}

        override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {}
    })

var filenameText = findViewById(R.id.filename) as EditText
filenameText.addTextChangedListener(object : TextWatcher {
    override fun afterTextChanged(s: Editable?) {
        filename = filenameText.text.toString()
        Log.i("FileName: ", filename)
    }
    
    override fun beforeTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {}
    override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) {}
})

I wrote my own extension for this, very helpful for me. (Kotlin)

You can write only like that :

editText.customAfterTextChanged { editable -> 
    //You have accessed the editable object. 
}

My extension :

fun EditText.customAfterTextChanged(action: (Editable?)-> Unit){
    this.addTextChangedListener(object : TextWatcher {
       override fun beforeTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {}
       override fun onTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {}
       override fun afterTextChanged(editable: Editable?) {
        action(editable)
    }
})}

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) {
                if (noteid != -1) {
                    MainActivity.notes.set(noteid, String.valueOf(charSequence));
                    MainActivity.arrayAdapter.notifyDataSetChanged();
                }
            }
            @Override
            public void afterTextChanged(Editable editable) {

            }
        });

in this code noteid is basically arguments taken back which is being putted into the indent or passed through the indent.

  Intent intent = getIntent();
         noteid = intent.getIntExtra("noteid", -1);

the code on the downside is basically the extra code ,if you want to understand more clearly.

how to make the menu or insert the menu in our code , 
    create the  menu folder this the folder created by going into the raw
    ->rightclick->
    directory->name the folder as you wish->
    then click on the directory formed->
    then click on new file and then name for file as you wish ie the folder name file
    and now type the 2 lines code in it and see the magic.

new activity code named as NoteEditor.java for editing purpose,my app is basicley the note app.

package com.example.elavi.notes;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.widget.EditText;
import android.widget.Toast;

import static android.media.CamcorderProfile.get;
public class NoteEditorActivity extends AppCompatActivity {
    EditText editText;
    int noteid;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_note_editor);
        editText = findViewById(R.id.editText);
        Intent intent = getIntent();
         noteid = intent.getIntExtra("noteid", -1);
        if (noteid != -1) {
            String text = MainActivity.notes.get(noteid);
            editText.setText(text);

           Toast.makeText(getApplicationContext(),"The arraylist content is"+MainActivity.notes.get(noteid),Toast.LENGTH_SHORT).show();
        }
        else
        {
            Toast.makeText(getApplicationContext(),"Here we go",Toast.LENGTH_SHORT).show();
            MainActivity.notes.add("");
            noteid=MainActivity.notes.size()-1;
        }
        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) {
                if (noteid != -1) {
                    MainActivity.notes.set(noteid, String.valueOf(charSequence));
                    MainActivity.arrayAdapter.notifyDataSetChanged();
                }
            }
            @Override
            public void afterTextChanged(Editable editable) {

            }
        });
    }
}

We can remove the TextWatcher for a field just before editing its text then add it back after editing the text.

Declare Text Watchers for both field1 and field2 as separate variables to give them a name: e.g. for field1

private TextWatcher Field_1_Watcher = new TextWatcher() {
    @Override
    public void beforeTextChanged(CharSequence s, int start, int count, int after) {
    }

    @Override
    public void afterTextChanged(Editable s) {
    }

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

    }

};

then add the watcher using its name: field1.addTextChangedListener(Field_1_Watcher) for field1, and field2.addTextChangedListener(Field_2_Watcher) for field2

Before changing the field2 text remove the TextWatcher: field2.removeTextChangedListener(Field_2_Watcher) change the text: field2.setText("")

then add the TextWatcher back: field2.addTextChangedListener(Field_2_Watcher)

Do the same for the other field

Another solution that may help someone. There are 2 EditText which change instead of each other after editing. By default, it led to cyclicity.

use variable:

Boolean uahEdited = false;
Boolean usdEdited = false;

add TextWatcher

uahEdit = findViewById(R.id.uahEdit);
usdEdit = findViewById(R.id.usdEdit);

uahEdit.addTextChangedListener(new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {
            if (!usdEdited) {
                uahEdited = true;
            }
        }

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            String tmp = uahEdit.getText().toString();

            if(!tmp.isEmpty() && uahEdited) {
                uah = Double.valueOf(tmp);
                usd = uah / 27;
                usdEdit.setText(String.valueOf(usd));
            } else if (tmp.isEmpty()) {
                usdEdit.getText().clear();
            }
        }

        @Override
        public void afterTextChanged(Editable s) {
            uahEdited = false;
        }
    });

usdEdit.addTextChangedListener(new TextWatcher() {
        @Override
        public void beforeTextChanged(CharSequence s, int start, int count, int after) {
            if (!uahEdited) {
                usdEdited = true;
            }
        }

        @Override
        public void onTextChanged(CharSequence s, int start, int before, int count) {
            String tmp = usdEdit.getText().toString();

            if (!tmp.isEmpty() && usdEdited) {
                usd = Double.valueOf(tmp);
                uah = usd * 27;
                uahEdit.setText(String.valueOf(uah));
            } else if (tmp.isEmpty()) {
                uahEdit.getText().clear();
            }
        }

        @Override
        public void afterTextChanged(Editable s) {
            usdEdited = false;
        }
    });

Don't criticize too much. I am a novice developer

etSearch.addTextChangedListener(object : TextWatcher {
     override fun beforeTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
          TODO("Not yet implemented")
     }

     override fun onTextChanged(p0: CharSequence?, p1: Int, p2: Int, p3: Int) {
          TODO("Not yet implemented")
     }

     override fun afterTextChanged(p0: Editable?) {
          TODO("Not yet implemented")
     }
})

Add background dynamically in onCreate method:

getWindow().setBackgroundDrawableResource(R.drawable.background);

also remove background from XML.