Layout di RelativeLayout

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_margin="@dimen/activity_horizontal_margin"
    tools:context=".MainActivity">

    <EditText
        android:id="@+id/edt_username"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_margin="@dimen/activity_vertical_margin"
        android:hint="@string/isikan_username"
        android:textSize="16sp" />

    <EditText
        android:id="@+id/edt_password"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/edt_username"
        android:layout_margin="@dimen/activity_vertical_margin"
        android:hint="@string/isikan_password"
        android:inputType="textPassword"
        android:textSize="16sp" />

    <Button
        android:id="@+id/btn_login"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/edt_password"
        android:layout_margin="@dimen/activity_vertical_margin"
        android:text="LOGIN"
        android:textAlignment="center"
        android:textSize="20sp" />
    
    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="LUPA KATA SANDI"
        android:textColor="@color/biruCustom"
        android:id="@+id/tv_lupa_sandi"
        android:textSize="12sp"
        android:textAlignment="center"
        android:layout_below="@id/btn_login"/>

</RelativeLayout>

MainActivity.java

package com.example.percobaanrelativelayout;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {
    Button btnLogin;

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

        btnLogin = findViewById(R.id.btn_login);

        btnLogin.setOnClickListener(this);

    }

    @Override
    public void onClick(View view) {
        if(view.getId()==R.id.btn_login){
            Toast.makeText(this,"Anda berhasil Login!",Toast.LENGTH_LONG).show();
        }
    }
}