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"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="#006600">
<LinearLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_weight="1"
    android:orientation="horizontal"
    tools:context="com.example.android.scorekeeper.MainActivity">
    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:orientation="vertical"
        android:layout_weight="1"
        android:paddingLeft="10dp"
        android:paddingRight="10dp">
    <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:text="Team A"
            android:textStyle="bold"
            android:textSize="13sp"
            android:textAlignment="center"
            android:textColor="@android:color/darker_gray"
            android:paddingBottom="10dp"
            android:paddingTop="10dp"/>
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:id="@+id/teamA_points"
            android:textColor="#FFFFFF"
            android:text="0"
            android:textSize="50sp"
            android:paddingBottom="10dp"/>

        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            android:paddingBottom="10dp">
            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:textStyle="bold"
                android:textColor="@android:color/darker_gray"
                android:text="Fouls: "/>
            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/teamA_fouls"
                android:textColor="#FFFFFF"
                android:text="0"/>
        </LinearLayout>

        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="+1 Point"
            android:layout_gravity="center"
            android:onClick="increaseTeamAPoints"/>
        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="+1 Foul"
            android:layout_gravity="center"
            android:onClick="increaseTeamAFouls"/>
    </LinearLayout>
    <View
        android:layout_width="1dp"
        android:layout_height="300dp"
        android:background="@android:color/white"/>

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:orientation="vertical"
        android:layout_weight="1"
        android:paddingLeft="10dp"
        android:paddingRight="10dp">
        <TextView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:text="Team B"
            android:textAlignment="center"
            android:textStyle="bold"
            android:textSize="13sp"
            android:textColor="@android:color/darker_gray"
            android:paddingBottom="10dp"
            android:paddingTop="10dp"/>
        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:id="@+id/teamB_points"
            android:textColor="#FFFFFF"
            android:text="0"
            android:textSize="50sp"
            android:paddingBottom="10dp"/>

        <LinearLayout
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:orientation="horizontal"
            android:paddingBottom="10dp">
        <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:textStyle="bold"
                android:textColor="@android:color/darker_gray"
                android:text="Fouls: "/>+
            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:id="@+id/teamB_fouls"
                android:textColor="#FFFFFF"
                android:text="0"/>
        </LinearLayout>
        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="+1 Point"
            android:layout_gravity="center"
            android:onClick="increaseTeamBPoints"/>
        <Button
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:text="+1 Foul"
            android:onClick="increaseTeamBFouls"/>
    </LinearLayout>
</LinearLayout>
    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Reset scores"
        android:onClick="resetScores"/>
</LinearLayout>

MainActivity.java

package com.example.android.scorekeeper;

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

public class MainActivity extends AppCompatActivity {

    int teamAPoints = 0;
    int teamBPoints = 0;
    int teamAFouls = 0;
    int teamBFouls = 0;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    public void displayTeamAPoints() {
        TextView textView = (TextView) findViewById(R.id.teamA_points);
        textView.setText(String.valueOf(teamAPoints));
    }

    public void displayTeamBPoints() {
        TextView textView = (TextView) findViewById(R.id.teamB_points);
        textView.setText(String.valueOf(teamBPoints));
    }

    public void displayTeamAFouls() {
        TextView textView = (TextView) findViewById(R.id.teamA_fouls);
        textView.setText(String.valueOf(teamAFouls));
    }

    public void displayTeamBFouls() {
        TextView textView = (TextView) findViewById(R.id.teamB_fouls);
        textView.setText(String.valueOf(teamBFouls));
    }

    public void increaseTeamAPoints(View v) {
        teamAPoints +=1;
        displayTeamAPoints();
    }

    public void increaseTeamBPoints(View v) {
        teamBPoints +=1;
        displayTeamBPoints();
    }

    public void increaseTeamAFouls(View v) {
        teamAFouls +=1;
        displayTeamAFouls();
    }

    public void increaseTeamBFouls(View v) {
        teamBFouls +=1;
        displayTeamBFouls();
    }

    public void resetScores(View v) {
        teamBFouls = 0;
        displayTeamBFouls();
        teamAFouls = 0;
        displayTeamAFouls();
        teamBPoints = 0;
        displayTeamBPoints();
        teamAPoints = 0;
        displayTeamAPoints();
    }
}