Learn how to create ddTextChangedListener, create setOnSeekBarChangeListener, and manage and edit GUI using Java Activity in android studio.
Please refer to Lecture 6 PPT slides
Created By Mohammed Falah.

package com.example.user.myapplication;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.RadioButton;
import android.widget.SeekBar;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

        EditText et1;
        TextView tv1;
        RadioButton rb1,rb2;
        Button btn;
        SeekBar sb;

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

        et1=(EditText)findViewById(R.id.et1);
        tv1=(TextView)findViewById(R.id.textView);
        rb1=(RadioButton)findViewById(R.id.rb1);
        rb2=(RadioButton)findViewById(R.id.rb2);
        btn=(Button)findViewById(R.id.btn1);
        sb=(SeekBar)findViewById(R.id.seekBar);
        rb1.setChecked(true);
        sb.setMax(100);
        sb.setProgress(50);
        et1.addTextChangedListener(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) {
                tv1.setText(et1.getText().toString());

            }
        });
        sb.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
                tv1.setTextSize(progress);
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {

            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {

            }
        });
        btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(rb1.isChecked()){
                    rb1.setChecked(false);
                    rb2.setChecked(true);
                } else  if(rb2.isChecked()){
                    rb1.setChecked(true);
                    rb2.setChecked(false);}
            }
        });

    }
}