After making some progress in my game, I was looking around for camera scrolling methods to use for my TDS game and found one that I thought would work well for it.
This is an example of what sort of scrolling I want: 
The creator of the document called it a target-focus camera (I do not know if there is an official name for it), and I was wondering how to create camera scrolling like that featured in the example and if anyone has examples that I can look at to see how it works and such.
Please note that there are quite a few things in here that will be removed due to not being needed. Most of them are the "is never used" stuff.
Player class.
import java.awt.*;
import javax.swing.*;
import java.awt.image.*;
import javax.imageio.*;
import java.io.*;
import java.awt.event.MouseEvent;
import java.lang.Math;
public class Player
{
// prototype of the mouse location information.
PointerInfo a = MouseInfo.getPointerInfo();
Point b = a.getLocation();
int mX = (int)b.getX();
int mY = (int)b.getY();
private int xPos, yPos, r;
int dist = 1;
//information on what part of the world the player is at.
private int secX,secY;
private int dx,dy;
//speed will depend on what ship Player is using and what items it has.
private int speed;
// private int xLoc, yLoc;
// private Sector location;
//prototype variables to dictate where the camera will center
int cX = (mX - xPos) * dist + xPos;
int cY = (mY - yPos) * dist + yPos;
private String userName;
private Ship ship;
// private Weapon weapon;
// private Engine engine;
private boolean left;
private boolean right;
private boolean up;
private boolean down;
// private boolean firing;
private Color color1;
private Color color2;
// Variable to use when finding the angle needed to turn.
private double angleToTurn;
double mx, my;
public Player(Ship s){
setShip(s);
// x = GameData.WIDTH / 2;
// y = GameData.HEIGHT / 2;
xPos = s.getX();
yPos = s.getY();
r = s.getR();
dx = 0;
dy = 0;
speed = 5;
color1 = Color.WHITE;
color2 = Color.RED;
// firing = false;
// firingTimer = System.nanoTime();
// firingDelay = 200;
// recovering = false;
// recoveryTimer = 0;
// score = 0;
}
public void setShip(Ship s){
ship = s;
}
// public int getXLoc(){return xLoc;}
// public int getYLoc(){return yLoc;}
// public Sector getLocation(){return location;}
public int getx() { return xPos; }
public int gety() {return yPos;}
public int getr() { return r; }
public void setLeft(boolean b) { left = b; }
public void setRight(boolean b) { right = b; }
public void setUp(boolean b) { up = b; }
public void setDown(boolean b) { down = b; }
//TODO Add controls for mouse based on what class of ship it is.
public void update() {
if(left) {
dx = -speed;
}
if(right) {
dx = speed;
}
if(up) {
dy = -speed;
}
if(down) {
dy = speed;
}
xPos += dx;
yPos += dy;
if(xPos < ship.getX2() ){
xPos = ship.getX2();
}
if(yPos < ship.getY2() ){
yPos = ship.getY2();
}
if(xPos > GameData.WIDTH - r){xPos = GameData.WIDTH - r;
}
if(yPos > GameData.HEIGHT - r){
yPos = GameData.HEIGHT - r;
}
dx = 0;
dy = 0;
// firing
/*
if(firing){long elapsed = (System.nanoTime() - firingTimer) / 1000000;
GamePanel.bullets.add(new Bullet(270, x, y));
if(elapsed > firingDelay) {
firingTimer = System.nanoTime();
}
}
*/
/*
if(recovering) {
long elapsed = (System.nanoTime() - recoveryTimer) / 1000000;
if(elapsed > 2000) {
recovering = false;
recoveryTimer = 0;
}
}
*/
}
public void draw(Graphics2D g) {
g.drawImage(ship.buff, xPos, yPos, null);
/*
g.setColor(color1);
g.fillOval(x - r, y - r, 2 * r, 2 * r);
g.setStroke(new BasicStroke(3));
g.setColor(color1.darker());
g.drawOval(x - r, y - r, 2 * r, 2 * r);
g.setStroke(new BasicStroke(1));
*/
}
public void moveToNextLoc(Sector m){}
//TODO add mouse rotation to the player (to start out with)
}
GameData
import javax.swing.JPanel;
import java.awt.*;
import java.awt.image.*;
import java.awt.event.*;
import java.util.*;
//import javax.swing.*;
//import javax.imageio.*;
//import java.io.*;
import java.awt.event.MouseEvent;
//import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
public class GameData extends JPanel implements Runnable, KeyListener, MouseMotionListener
{
// instance variables - replace the example below with your own
// MouseListener mouse = new MouseMotionListener();
Point playerPoint;
Point turretPoint;
public static int WIDTH = 400;
public static int HEIGHT = 400; // stuff here may change
public static int MINWIDTH = 0;
public static int MINHEIGHT = 0;
private int FPS = 30;
// private double averageFPS;
private Thread thread;
private boolean running;
private BufferedImage image;
private Graphics2D g;
public static Player userPlayer;
public static ArrayList<Bullet> bullets;
public static ArrayList<Text> texts;
// float angle = (float)(Math.atan2(userPlayer.gety() - mouse.y, userPlayer.getx() - mouse.x));
public GameData() {
super();
setPreferredSize(new Dimension(WIDTH, HEIGHT));
setFocusable(true);
requestFocus();
}
public void addNotify() {
super.addNotify();
if(thread == null) {
thread = new Thread(this);
thread.start();
}
addKeyListener(this);
}
public void run() {
this.requestFocus();
running = true;
image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
g = (Graphics2D) image.getGraphics();
g.setRenderingHint(
RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);
g.setRenderingHint(
RenderingHints.KEY_TEXT_ANTIALIASING,
RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
userPlayer = new Player(sampleShip);
//bullets = new ArrayList<Projectile>();
//enemies = new ArrayList<Enemy>();
//powerups = new ArrayList<PowerUp>();
//explosions = new ArrayList<Explosion>();
texts = new ArrayList<Text>();
long startTime;
long URDTimeMillis;
long waitTime;
long totalTime = 0;
int frameCount = 0;
int maxFrameCount = 30;
long targetTime = 1000 / FPS;
//hue = 0;
// GAME LOOP
while(running) {
startTime = System.nanoTime();
gameUpdate();
gameRender();
gameDraw();
URDTimeMillis = (System.nanoTime() - startTime) / 1000000;
waitTime = targetTime - URDTimeMillis;
try {
Thread.sleep(waitTime);
}
catch(Exception e) {
}
frameCount++;
if(frameCount == maxFrameCount) {
// averageFPS = 1000.0 / ((totalTime / frameCount) / 1000000);
frameCount = 0;
totalTime = 0;
}
}
g.setColor(new Color(0, 100, 255));
g.fillRect(0, 0, WIDTH, HEIGHT);
g.setColor(Color.WHITE);
g.setFont(new Font("Century Gothic", Font.PLAIN, 16));
String s = "G A M E O V E R";
int length = (int) g.getFontMetrics().getStringBounds(s, g).getWidth();
g.drawString(s, (WIDTH - length) / 2, HEIGHT / 2);
// s = "Final Score: " + userPlayer.getScore();
length = (int) g.getFontMetrics().getStringBounds(s, g).getWidth();
g.drawString(s, (WIDTH - length) / 2, HEIGHT / 2 + 30);
gameDraw();
}
private void gameUpdate() {
// new wave
// create enemies
/*
if(waveStart && enemies.size() == 0) {
createNewEnemies();
}
*/
// player update
userPlayer.update();
// bullet update
/*
for(int i = 0; i < bullets.size(); i++) {
boolean remove = bullets.get(i).update();
if(remove) {
bullets.remove(i);
i--;
}
}
*/
/*
// enemy update
for(int i = 0; i < enemies.size(); i++) {
enemies.get(i).update();
}
*/
// powerup update
/*
for(int i = 0; i < powerups.size(); i++) {
boolean remove = powerups.get(i).update();
if(remove) {
powerups.remove(i);
i--;
}
}
*/
/*
*
// explosion update
for(int i = 0; i < explosions.size(); i++) {
boolean remove = explosions.get(i).update();
if(remove) {
explosions.remove(i);
i--;
}
}
*/
// text update
for(int i = 0; i < texts.size(); i++) {
boolean remove = texts.get(i).update();
if(remove) {
texts.remove(i);
i--;
}
}
// bullet-enemy collision
/*
for(int i = 0; i < bullets.size(); i++) {
Bullet b = bullets.get(i);
double bx = b.getx();
double by = b.gety();
double br = b.getr();
for(int j = 0; j < enemies.size(); j++) {
Enemy e = enemies.get(j);
double ex = e.getx();
double ey = e.gety();
double er = e.getr();
double dx = bx - ex;
double dy = by - ey;
double dist = Math.sqrt(dx * dx + dy * dy);
if(dist < br + er) {
e.hit();
bullets.remove(i);
i--;
break;
}
}
}
*/
/*
// check dead enemies
for(int i = 0; i < enemies.size(); i++) {
if(enemies.get(i).isDead()) {
Enemy e = enemies.get(i);
// chance for powerup
double rand = Math.random();
if(rand < 0.001) powerups.add(new PowerUp(1, e.getx(), e.gety()));
else if(rand < 0.020) powerups.add(new PowerUp(3, e.getx(), e.gety()));
else if(rand < 0.120) powerups.add(new PowerUp(2, e.getx(), e.gety()));
else if(rand < 0.130) powerups.add(new PowerUp(4, e.getx(), e.gety()));
player.addScore(e.getType() + e.getRank());
enemies.remove(i);
i--;
e.explode();
explosions.add(new Explosion(e.getx(), e.gety(), e.getr(), e.getr() + 30));
}
}
*/
// check dead player
/*
if(userPlayer.isDead()) {
running = false;
}
*/
// player-enemy collision
/*
if(!player.isRecovering()) {
int px = player.getx();
int py = player.gety();
int pr = player.getr();
for(int i = 0; i < enemies.size(); i++) {
Enemy e = enemies.get(i);
double ex = e.getx();
double ey = e.gety();
double er = e.getr();
double dx = px - ex;
double dy = py - ey;
double dist = Math.sqrt(dx * dx + dy * dy);
if(dist < pr + er) {
player.loseLife();
}
}
}
*/
// player-powerup collision
/*
int px = player.getx();
int py = player.gety();
int pr = player.getr();
for(int i = 0; i < powerups.size(); i++) {
PowerUp p = powerups.get(i);
double x = p.getx();
double y = p.gety();
double r = p.getr();
double dx = px - x;
double dy = py - y;
double dist = Math.sqrt(dx * dx + dy * dy);
// collected powerup
if(dist < pr + r) {
int type = p.getType();
if(type == 1) {
player.gainLife();
texts.add(new Text(player.getx(), player.gety(), 2000, "Extra Life"));
}
if(type == 2) {
player.increasePower(1);
texts.add(new Text(player.getx(), player.gety(), 2000, "Power"));
}
if(type == 3) {
player.increasePower(2);
texts.add(new Text(player.getx(), player.gety(), 2000, "Double Power"));
}
if(type == 4) {
slowDownTimer = System.nanoTime();
for(int j = 0; j < enemies.size(); j++) {
enemies.get(j).setSlow(true);
}
texts.add(new Text(player.getx(), player.gety(), 2000, "Slow Down"));
}
powerups.remove(i);
i--;
}
}
*/
}
private void gameRender() {
// draw background
g.setColor(new Color(0, 100, 255));
g.fillRect(0, 0, WIDTH, HEIGHT);
// draw slowdown screen
// draw player
userPlayer.draw(g);
// draw bullet
/*
for(int i = 0; i < bullets.size(); i++) {
bullets.get(i).draw(g);
}
// draw enemy
for(int i = 0; i < enemies.size(); i++) {
enemies.get(i).draw(g);
}
// draw powerups
/*
for(int i = 0; i < powerups.size(); i++) {
powerups.get(i).draw(g);
}
*/
/*
// draw explosions
for(int i = 0; i < explosions.size(); i++) {
explosions.get(i).draw(g);
}
// draw text
for(int i = 0; i < texts.size(); i++) {
texts.get(i).draw(g);
}
// draw player lives
for(int i = 0; i < player.getLives(); i++) {
g.setColor(Color.WHITE);
g.fillOval(20 + (20 * i), 20, player.getr() * 2, player.getr() * 2);
g.setStroke(new BasicStroke(3));
g.setColor(Color.WHITE.darker());
g.drawOval(20 + (20 * i), 20, player.getr() * 2, player.getr() * 2);
g.setStroke(new BasicStroke(1));
}
// draw player power
g.setColor(Color.YELLOW);
g.fillRect(20, 40, player.getPower() * 8, 8);
g.setColor(Color.YELLOW.darker());
g.setStroke(new BasicStroke(2));
for(int i = 0; i < player.getRequiredPower(); i++) {
g.drawRect(20 + 8 * i, 40, 8, 8);
}
g.setStroke(new BasicStroke(1));
// draw player score
g.setColor(Color.WHITE);
g.setFont(new Font("Century Gothic", Font.PLAIN, 14));
g.drawString("Score: " + player.getScore(), WIDTH - 100, 30);
*/
}
private void gameDraw() {
Graphics g2 = this.getGraphics();
g2.drawImage(image, 0, 0, null);
g2.dispose();
// adapter.render(g);
}
public void keyTyped(KeyEvent key) {}
public void keyPressed(KeyEvent key) {
int keyCode = key.getKeyCode();
if(keyCode == KeyEvent.VK_LEFT) {
userPlayer.setLeft(true);
}
if(keyCode == KeyEvent.VK_RIGHT) {
userPlayer.setRight(true);
}
if(keyCode == KeyEvent.VK_UP) {
userPlayer.setUp(true);
}
if(keyCode == KeyEvent.VK_DOWN) {
userPlayer.setDown(true);
}
/*
if(keyCode == KeyEvent.VK_Z) {
userPlayer.setFiring(true);
}
*/
}
public void keyReleased(KeyEvent key) {
int keyCode = key.getKeyCode();
if(keyCode == KeyEvent.VK_LEFT) {
userPlayer.setLeft(false);
}
if(keyCode == KeyEvent.VK_RIGHT) {
userPlayer.setRight(false);
}
if(keyCode == KeyEvent.VK_UP) {
userPlayer.setUp(false);
}
if(keyCode == KeyEvent.VK_DOWN) {
userPlayer.setDown(false);
}
/*
if(keyCode == KeyEvent.VK_Z) {
userPlayer.setFiring(false);
}
*/
}
// for mouse. MOUSE PROGRESS FTW!
public void mouseClicked(MouseEvent e) {
}
public void mouseExited(MouseEvent e) {
}
public void mouseEntered(MouseEvent e) {
}
public void mousePressed(MouseEvent e) {
playerPoint = e.getPoint();
float angle = (float)(Math.atan2(userPlayer.gety() - playerPoint.y, userPlayer.getx() - playerPoint.x));
int x = e.getX();
int y = e.getY();
}
public void mouseReleased(MouseEvent e) {
playerPoint = null;
}
public void mouseMoved(MouseEvent e) {
int x = e.getX();
int y = e.getY();
float angle = (float)(Math.atan2(userPlayer.gety() - playerPoint.y, userPlayer.getx() - playerPoint.x));
// ^^^ p used to be mouse so watch out on that.
}
public void mouseDragged(MouseEvent e) {
turretPoint = e.getPoint();
float angle = (float)(Math.atan2(userPlayer.gety() - turretPoint.y, userPlayer.getx() - turretPoint.x));
}
Ship sampleShip = new Ship(83,83,83,0,0,false,"C:\\Users\\Kenny\\Desktop\\ProjectProto\\ProtoGame\\Proto\\Images\\Ships\\ATN_FIGHTER_LOWRES.PNG");
//TODO: have file directory change to allow other devices to be able to get the files.
}
Camera.
import java.awt.*;
public class Camera{
private int x,y;
private Player player;
private int xPos, yPos;
MapSector sec;
GameData data;
public int xmax = sec.XSIZE;
public int ymax = sec.YSIZE;
public int dist = 1;
// prototype of the mouse location information.
private PointerInfo a;
private Point b;
private int mX,mY,cX,cY;
private int dirX
public int xView;
public int yView;
//Location of the center of an Image
private int iX, iY;
public Camera(int x, int y, Player player, int xPos,int yPos){
this.x = x;
this.y = y;
this.player = player;
xPos = player.getx();
yPos = player.gety();
xView = data.WIDTH;
yView = data.HEIGHT;
iX = player.ship.img.getCenterX();
iY = player.ship.img.getCenterY();
}
public int getX(){return x;}
public int getY(){return y;}
public void setX(int x){this.x = x;}
public void setY(int y){this.y = y;}
public void updateCamera(){
a = MouseInfo.getPointerInfo();
b = a.getLocation();
mX = (int)b.getX();
mY = (int)b.getY();
cX = (mX - xPos) * dist + xPos;
cY = (mY - yPos) * dist + yPos;
}
public void defaultCamera(){
cX = iX;
cY = iY;
}
