(Android)find.view.by.id , setOnClicklistener,Toast

package com.example.my01_helloworld;

import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {

Button btnCall,btnNew;
EditText etPhoneNum;

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

etPhoneNum = findViewById(R.id.etPhoneNum);
btnCall = findViewById(R.id.btnCall);
btnCall.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String phoneNum = "tel:"+etPhoneNum.getText().toString();

Intent intent = new Intent(Intent.ACTION_DIAL,Uri.parse(phoneNum));
startActivity(intent);
}
});

btnNew = findViewById(R.id.btnNew);
btnNew.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(getApplicationContext(),Sub1Activity.class);
startActivity(intent);
}
});

}

public void btn1Clicked(View view){
Toast.makeText(this, "버튼1클릭!!!", Toast.LENGTH_SHORT).show();
}

public void btn2Clicked(View view){
Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse("https://m.naver.com"));
startActivity(intent);
}
}