ตัวอย่างโค้ดสำหรับการเปลี่ยนหน้า Activity

activity_do_something.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:gravity="center"
    android:orientation="vertical"
    tools:context="com.akexorcist.myapplication.DoSomethingActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Do Something Activity"
        android:textSize="20sp" />

    <Button
        android:id="@+id/btn_back"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="30dp"
        android:text="Back" />

</LinearLayout>

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
    android:gravity="center"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.akexorcist.myapplication.MainActivity">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Main Activity"
        android:textSize="20sp" />

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="30dp"
        android:orientation="horizontal">

        <Button
            android:id="@+id/btn_next"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Next" />

        <Button
            android:id="@+id/btn_close"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Close" />
    </LinearLayout>
</LinearLayout>

DoSomethingActivity.java

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

public class DoSomethingActivity extends AppCompatActivity implements View.OnClickListener {

    private Button btnBack;

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

        btnBack = (Button) findViewById(R.id.btn_back);
        btnBack.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        if (view == btnBack) {
            backToPrevActivity();
        }
    }

    private void backToPrevActivity() {
        finish();
    }
}

MainActivity.java

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

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private Button btnNext;
    private Button btnClose;

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

        btnNext = (Button) findViewById(R.id.btn_next);
        btnClose = (Button) findViewById(R.id.btn_close);

        btnNext.setOnClickListener(this);
        btnClose.setOnClickListener(this);
    }

    @Override
    public void onClick(View view) {
        // When Click Button Next
        if (view == btnNext) {
            nextActivity();
        } else if (view == btnClose) {
            closeThisActivity();
        }
    }

    private void nextActivity() {
        Intent intent = new Intent(this, DoSomethingActivity.class);
        startActivity(intent);
    }

    private void closeThisActivity() {
        finish();
    }
}