MainActivity.java

package com.nishant.mathsample;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.text.Editable;
import android.text.TextWatcher;
import android.widget.EditText;
import android.widget.LinearLayout;

import com.nishant.math.MathView;

import butterknife.BindView;
import butterknife.ButterKnife;

public class MainActivity extends AppCompatActivity {

  @BindView(R.id.activity_main)
  LinearLayout linearLayout;

  @BindView(R.id.math_view)
  MathView mathView;

  @BindView(R.id.input_view)
  EditText inputView;

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

    inputView.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) {
        mathView.setText(inputView.getText().toString());
      }
    });
  }


}