Overview
The Obstacle class represents an obstacle (asteroid/pig) in the Space Birds game. Obstacles move downward from the top of the screen and can be destroyed by the player’s bullets. Each obstacle has a collision rectangle that is smaller than its visual size to provide fairer collision detection for the player.
Constructor
Creates a new obstacle instance with the specified properties.
public Obstacle(Texture texture, float x, float y, float width, float height, float speed)
The graphical texture of the obstacle
Initial horizontal position in pixels
Initial vertical position in pixels (should be above the screen)
Visual width of the obstacle in pixels
Visual height of the obstacle in pixels
Movement speed in pixels per frame (positive value moves downward)
Example
Texture obstacleTexture = new Texture("images/obstacle.png");
float x = MathUtils.random(0, Gdx.graphics.getWidth() - 64);
float y = Gdx.graphics.getHeight() + 10; // Start above screen
Obstacle obstacle = new Obstacle(obstacleTexture, x, y, 64, 64, 3.0f);
Fields
| Field | Type | Description |
|---|
x | float | Current horizontal position |
y | float | Current vertical position |
width | float | Visual width of the obstacle |
height | float | Visual height of the obstacle |
speed | float | Movement speed in pixels per frame |
texture | Texture | Graphical texture for rendering |
bounds | Rectangle | Collision rectangle (smaller than visual size for fair gameplay) |
active | boolean | Whether the obstacle is active and should be processed |
Methods
render
Draws the obstacle to the screen if it is active.
public void render(SpriteBatch batch)
The SpriteBatch where the obstacle texture will be rendered
for (Obstacle obstacle : obstacles) {
obstacle.render(batch);
}
update
Updates the obstacle’s position. The obstacle moves downward according to its speed, and the collision bounds are updated accordingly.
Example:
for (int i = obstacles.size - 1; i >= 0; i--) {
Obstacle obstacle = obstacles.get(i);
obstacle.update();
if (obstacle.isOutOfScreen()) {
obstacles.removeIndex(i);
}
}
isOutOfScreen
Checks if the obstacle has exited the screen or has been destroyed.
public boolean isOutOfScreen()
boolean - true if the obstacle is below the screen or has been destroyed, false otherwise
Example:
if (obstacle.isOutOfScreen()) {
obstacles.remove(obstacle);
}
destroy
Marks the obstacle as destroyed. A destroyed obstacle will not be rendered or updated.
Example:
if (bullet.getBounds().overlaps(obstacle.getBounds())) {
obstacle.destroy();
bullet.setActive(false);
score += 10;
}
isActive
Checks if the obstacle is active (not destroyed).
public boolean isActive()
boolean - true if the obstacle is active, false if it has been destroyed
Example:
if (obstacle.isActive()) {
// Check for collisions
}
getBounds
Returns the collision rectangle of the obstacle. The collision bounds are smaller than the visual size (reduced by 25% on each side) to provide fairer collision detection.
public Rectangle getBounds()
Rectangle - The collision bounds (smaller than visual size)
Example:
for (Obstacle obstacle : obstacles) {
if (player.getBounds().overlaps(obstacle.getBounds())) {
// Handle player collision
gameOver();
}
for (Bullet bullet : bullets) {
if (bullet.getBounds().overlaps(obstacle.getBounds())) {
obstacle.destroy();
bullet.setActive(false);
score += 10;
}
}
}
Complete Usage Example
public class ObstacleManager {
private Array<Obstacle> obstacles;
private Texture obstacleTexture;
private float spawnTimer;
private float spawnInterval;
public ObstacleManager() {
obstacles = new Array<>();
obstacleTexture = new Texture("images/obstacle.png");
spawnTimer = 0;
spawnInterval = 2.0f; // Spawn every 2 seconds
}
public void update(float deltaTime) {
// Update spawn timer
spawnTimer += deltaTime;
if (spawnTimer >= spawnInterval) {
spawnObstacle();
spawnTimer = 0;
}
// Update all obstacles
for (int i = obstacles.size - 1; i >= 0; i--) {
Obstacle obstacle = obstacles.get(i);
obstacle.update();
// Remove obstacles that are off screen
if (obstacle.isOutOfScreen()) {
obstacles.removeIndex(i);
}
}
}
private void spawnObstacle() {
float width = 64;
float x = MathUtils.random(0, Gdx.graphics.getWidth() - width);
float y = Gdx.graphics.getHeight() + 10;
float speed = MathUtils.random(2.0f, 5.0f);
Obstacle obstacle = new Obstacle(obstacleTexture, x, y, width, width, speed);
obstacles.add(obstacle);
}
public void checkCollisions(Player player, Array<Bullet> bullets) {
for (Obstacle obstacle : obstacles) {
if (!obstacle.isActive()) continue;
// Check player collision
if (player.getBounds().overlaps(obstacle.getBounds())) {
// Handle game over
return;
}
// Check bullet collisions
for (Bullet bullet : bullets) {
if (bullet.isActive() &&
bullet.getBounds().overlaps(obstacle.getBounds())) {
obstacle.destroy();
bullet.setActive(false);
break;
}
}
}
}
public void render(SpriteBatch batch) {
for (Obstacle obstacle : obstacles) {
obstacle.render(batch);
}
}
public void dispose() {
obstacleTexture.dispose();
obstacles.clear();
}
public Array<Obstacle> getObstacles() {
return obstacles;
}
}
Collision Bounds
The obstacle’s collision rectangle is intentionally smaller than its visual size to provide fairer gameplay:
- Visual size: The full
width and height specified in the constructor
- Collision size: Reduced by 25% on each side (12.5% from each edge)
- Collision offset: Positioned at
(x + width/8, y + height/8)
This means if an obstacle has a visual size of 64x64 pixels, its collision rectangle will be 48x48 pixels, centered within the visual representation.
Notes
- Obstacles move downward (speed is subtracted from y position)
- The collision bounds automatically update when the obstacle moves
- Obstacles should be spawned above the screen (y > screen height) to appear smoothly
- Use
isOutOfScreen() to clean up obstacles that have passed the bottom of the screen
- Unlike bullets, obstacle textures are typically shared and should be disposed by the manager, not individual obstacles