Working with Edittext, Textview and Button

Screenshots :

activity_main.xml :

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent"

tools:context="com.chantisandroid.buttonexample.MainActivity">

<Button

    android:layout_width="wrap_content"

    android:layout_height="wrap_content"

    android:text="clickme"

    android:id="@+id/button_click"

    android:layout_below="@+id/editText_enter"

    android:layout_centerHorizontal="true"

    android:layout_marginTop="74dp" />

    <EditText

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:id="@+id/editText_enter"

        android:layout_marginTop="66dp"

        android:layout_alignParentTop="true"

        android:layout_alignParentRight="true"

        android:layout_alignParentEnd="true"

        android:layout_marginLeft="10dp"

        android:layout_marginRight="10dp"

        android:hint="enter text here" />

    <TextView

        android:layout_width="wrap_content"

        android:layout_height="wrap_content"

        android:textAppearance="?android:attr/textAppearanceLarge"

        android:id="@+id/textView_result"

        android:layout_below="@+id/button_click"

        android:layout_centerHorizontal="true"

        android:layout_marginTop="102dp" />

</RelativeLayout>

MainActivity.java :

package com.chantisandroid.buttonexample;

import android.support.v7.app.AppCompatActivity;

import android.os.Bundle;

import android.view.View;

import android.widget.Button;

import android.widget.EditText;

import android.widget.TextView;

import android.widget.Toast;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    Button click;

    EditText enter;

    TextView results;

    String str;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        enter = (EditText)findViewById(R.id.editText_enter);

        results = (TextView)findViewById(R.id.textView_result);

        click = (Button)findViewById(R.id.button_click);

        click.setOnClickListener(this);

    }

    @Override

    public void onClick(View view) {

        str = enter.getText().toString().trim();

        results.setText(str);

    }

}