RandomText

//Manifest
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="a100dayschallege.inducesmile.com.randomtext">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        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=".Main2Activity"></activity>
    </application>

</manifest>

//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:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    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="a100dayschallege.inducesmile.com.randomtext.MainActivity">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Random Text"
        android:textAppearance="@style/Base.TextAppearance.AppCompat.Large"
        android:layout_centerHorizontal="true"
        android:paddingTop="100dp"
        android:textAlignment="center"
        android:textSize="30sp"
        android:textColor="#000000"
        android:layout_gravity="center"
        android:id="@+id/textview1"
 />

    <Button
        android:text="Activity A Button"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:textStyle="bold"
        android:layout_margin="20dp"
        android:background="@color/ButtonColor"
        android:layout_alignParentBottom="true"
        android:layout_marginBottom="40dp"
        android:id="@+id/button_a"

        android:onClick="ClickMe"
        />
</RelativeLayout>

//Mainactivity.Java
package a100dayschallege.inducesmile.com.randomtext;

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

import java.util.Random;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        Random random = new Random();
        Integer number = random.nextInt(50);
        TextView textView = (TextView)findViewById(R.id.textview1);
        String my_string = String.valueOf(number);
        textView.setText(my_string);


    }
    public void ClickMe(View view){

        Intent intent = new Intent(MainActivity.this,Main2Activity.class);
        startActivity(intent);
    }

}
//activitymain2.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:id="@+id/activity_main2"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    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="a100dayschallege.inducesmile.com.randomtext.Main2Activity">

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Random Text"
        android:textAppearance="@style/Base.TextAppearance.AppCompat.Large"
        android:layout_centerHorizontal="true"
        android:paddingTop="100dp"
        android:textAlignment="center"
        android:textSize="30sp"
        android:textColor="#000000"
        android:layout_gravity="center"
        android:id="@+id/textview2"
        />

    <Button
        android:text="Activity B Button"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:textStyle="bold"
        android:layout_margin="20dp"
        android:background="@color/ButtonColor"
        android:layout_alignParentBottom="true"
        android:layout_marginBottom="40dp"
        android:id="@+id/button_b"
        android:onClick="ClickMeNow"
        />

</RelativeLayout>

//Main2Activity.java

package a100dayschallege.inducesmile.com.randomtext;

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

import java.util.Random;

public class Main2Activity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);

        Random random = new Random();
        Integer number = random.nextInt(50);
        TextView textView = (TextView)findViewById(R.id.textview2);

        String my_string = String.valueOf(number);
        textView.setText(my_string);
    }
    public void ClickMeNow(View view){

        Intent intent = new Intent(Main2Activity.this,MainActivity.class);
        startActivity(intent);
    }
}