Open a New Activity and Pass Variables to It

<?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"
    tools:context="com.example.application.exampleapp.MainActivity">

    <EditText
        android:id="@+id/edittext1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginEnd="16dp" />

    <EditText
        android:id="@+id/edittext2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/edittext1"
        android:layout_marginStart="16dp"
        android:layout_marginEnd="16dp"
        android:inputType="number" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:text="Activity 1"
        android:textSize="30sp" />

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/textView3"
        android:layout_centerHorizontal="true"
        android:text="open activity 2" />

</RelativeLayout>

<?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"
    tools:context="com.example.application.exampleapp.Activity2">

    <TextView
        android:id="@+id/textview1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginEnd="16dp" />

    <TextView
        android:id="@+id/textview2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_below="@id/textview1"
        android:layout_marginStart="16dp"
        android:layout_marginEnd="16dp" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:text="Activity 2"
        android:textSize="30sp" />

</RelativeLayout>

package com.example.application.exampleapp;

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

public class MainActivity extends AppCompatActivity {
    public static final String EXTRA_TEXT = "com.example.application.example.EXTRA_TEXT";
    public static final String EXTRA_NUMBER = "com.example.application.example.EXTRA_NUMBER";

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

        Button button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                openActivity2();
            }
        });
    }

    public void openActivity2() {
        EditText editText1 = (EditText) findViewById(R.id.edittext1);
        String text = editText1.getText().toString();

        EditText editText2 = (EditText) findViewById(R.id.edittext2);
        int number = Integer.parseInt(editText2.getText().toString());

        Intent intent = new Intent(this, Activity2.class);
        intent.putExtra(EXTRA_TEXT, text);
        intent.putExtra(EXTRA_NUMBER, number);
        startActivity(intent);
    }
}

package com.example.application.exampleapp;

import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;

public class Activity2 extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_2);

        Intent intent = getIntent();
        String text = intent.getStringExtra(MainActivity.EXTRA_TEXT);
        int number = intent.getIntExtra(MainActivity.EXTRA_NUMBER, 0);

        TextView textView1 = (TextView) findViewById(R.id.textview1);
        TextView textView2 = (TextView) findViewById(R.id.textview2);

        textView1.setText(text);
        textView2.setText("" + number);
    }
}

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.application.exampleapp">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".Activity2"
            android:parentActivityName=".MainActivity"></activity>
    </application>

</manifest>