tdebindings/qtjava/javalib/tutorial/t11/CannonField.java

import org.kde.qt.*;

public class CannonField extends QWidget {
	private int ang;
	private int f;

	private int timerCount;
	private QTimer autoShootTimer;
	private float shoot_ang;
	private float shoot_f;
	private final QRect barrelRect = new QRect(33, -4, 15, 8);
	
	public CannonField(QWidget parent, String name) {
		super(parent, name);
		ang = 45;
		f = 0;
		timerCount = 0;
		autoShootTimer = new QTimer(this, "movement handler");
		connect(autoShootTimer, SIGNAL("timeout()"),
						this, SLOT("moveShot()"));
		shoot_ang = 0;
		shoot_f = 0;
		
		setPalette(new QPalette(new QColor(250, 250, 200)));
	}

	public int angle() {
		return ang;
	}

	public void setAngle(int degrees) {
		if (degrees < 5)
			degrees = 5;
		if (degrees > 70)
			degrees = 70;
		if (ang == degrees)
			return;
		ang = degrees;
		repaint();
		emit("angleChanged", ang);
	}

	public int force() {
		return f;
	}

	public void setForce(int newton) {
		if (newton < 0)
			newton = 0;
		if (f == newton)
			return;
		f = newton;
		emit("forceChanged", f);
	}

	public void shoot() {
		if (autoShootTimer.isActive())
			return;
		timerCount = 0;
		shoot_ang = ang;
		shoot_f = f;
		autoShootTimer.start(50);
	}

	public void moveShot() {
		QRegion r = new QRegion(shotRect());
		timerCount++;

		QRect shotR = shotRect();

		if (shotR.x() > width() || shotR.y() > height())
			autoShootTimer.stop();
		else
			r = r.unite(new QRegion(shotR));
		repaint(r);
	}

	public void paintEvent(QPaintEvent e) {
		QRect updateR = e.rect();
		QPainter p = new QPainter(this);

		if (updateR.intersects(cannonRect()))
			paintCannon(p);
		if (autoShootTimer.isActive() && updateR.intersects(shotRect()))
		paintShot(p);
	}

	private void paintShot(QPainter p) {
		p.setBrush(black());
		p.setPen(NoPen);
		p.drawRect(shotRect());
	}

	private void paintCannon(QPainter p) {
		QRect cr = cannonRect();
		QPixmap pix = new QPixmap(cr.size());
		pix.fill(new QColor(250, 250, 200));

		QPainter tmp = new QPainter(pix);
		tmp.setBrush(blue());
		tmp.setPen(NoPen);

		tmp.translate(0, pix.height() - 1);
		tmp.drawPie(new QRect(-35,-35, 70, 70), 0, 90*16);
		tmp.rotate(-ang);
		tmp.drawRect(barrelRect);
		tmp.end();

		p.drawPixmap(cr.topLeft(), pix);
	}

	private QRect cannonRect() {
		QRect r = new QRect(0, 0, 50, 50);
		r.moveBottomLeft(rect().bottomLeft());
		return r;
	}
	
	private QRect shotRect() {
		final double gravity = 4;

		double time      = timerCount / 4.0;
		double velocity  = shoot_f;
		double radians   = shoot_ang*3.14159265/180;

		double velx      = velocity*Math.cos(radians);
		double vely      = velocity*Math.sin(radians);
		double x0        = (barrelRect.right() + 5)*Math.cos(radians);
		double y0        = (barrelRect.right() + 5)*Math.sin(radians);
		double x         = x0 + velx*time;
		double y         = y0 + vely*time - 0.5*gravity*time*time;

		QRect r = new QRect(0, 0, 6, 6);
		r.moveCenter(new QPoint((int) x, height() - 1 - (int) y));
		return r;
}

	public QSizePolicy sizePolicy() {
		return new QSizePolicy(QSizePolicy.Expanding, QSizePolicy.Expanding);
	}
}