ここでチュートリアルから始めて、ビューの描画コードを追加しました（画面全体をカバーしています）。world.step（、）を呼び出していても、シーンは静的で動的ではないように見えます。シーンを動的にするにはどうすればよいですか？私の描画は正しい実装ですか、それとも（jBox2d関数を使用して）より良い方法がありますか？
private class PhysicsView extends View {
Paint mPaint;
public PhysicsView(Context context) {
super(context);
mPaint = new Paint();
mPaint.setColor(Color.BLUE);
mPaint.setStyle(Style.FILL_AND_STROKE);
}
@Override
public void onDraw(Canvas canvas) {
super.onDraw(canvas);
synchronized (canvas) {
Body[] b = mWorld.bodies;
for (int i = 0; i < b.length; i++) {
if (b[i] != null) {
Float mass = b[i].getMass();
Vec2 v = b[i].getPosition();
canvas.drawCircle(v.x, v.y, 15, mPaint);
}
}
Paint p2 = new Paint(mPaint);
p2.setColor(Color.GREEN);
Vec2 base = mWorld.groundBody.getPosition();
canvas.drawRect(new RectF((float) base.x - 25.0f,
(float) base.y - 10.0f, (float) base.x + 25.0f,
(float) base.y + 10.0f), p2);
canvas.drawLine(0.0f, 0.0f,
mWorld.world.getWorldAABB().upperBound.x, mWorld.world
.getWorldAABB().upperBound.y, p2);
}
}
}
public class PhysicsWorld {
public int targetFPS = 40;
public int timeStep = (1000 / targetFPS);
public int iterations = 5;
public Body[] bodies = new Body[50];
public Body groundBody;
private int count = 0;
private AABB worldAABB;
public World world;
private BodyDef groundBodyDef;
private PolygonDef groundShapeDef;
private Vec2 screenDimensions;
public void create(Vec2 dimens) {
screenDimensions = dimens;
worldAABB = new AABB();
worldAABB.lowerBound.set(new Vec2((float) -1*dimens.x, (float) -1*dimens.y));
worldAABB.upperBound.set(new Vec2((float) dimens.x, (float) dimens.y));
Vec2 gravity = new Vec2((float) 0.0, (float) 0.0);
boolean doSleep = true;
world = new World(worldAABB, gravity, doSleep);
groundBodyDef = new BodyDef();
groundBodyDef.position.set(new Vec2((float) dimens.x/2, (float) dimens.y - 10.0f));
groundBody = world.createBody(groundBodyDef);
groundBody.m_mass = 200.0f;
groundShapeDef = new PolygonDef();
groundShapeDef.setAsBox((float) 50.0, (float) 10.0);
groundShapeDef.density = 1.0f;
groundShapeDef.friction = 0.3f;
groundBody.createShape(groundShapeDef);
}
public void addBall() {
float x = (float) Math.random() * screenDimensions.x;
float y = (float) Math.random() * screenDimensions.y;
BodyDef bodyDef = new BodyDef();
bodyDef.position.set(new Vec2((float) x, (float) y));
bodyDef.massData.mass = 20.0f;
bodies[count] = world.createBody(bodyDef);
bodies[count].m_type = Body.e_dynamicType;
bodies[count].m_linearVelocity = new Vec2(1.0f, 2.0f);
CircleDef circle = new CircleDef();
circle.radius = (float) 1.8;
circle.density = (float) 1.0;
circle.type = ShapeType.CIRCLE_SHAPE;
bodies[count].createShape(circle);
count++;
}
public void update() {
world.step(timeStep, iterations);
}
public void changeGravity(Vec2 gravity) {
world.setGravity(gravity);
}
}