我不了解在 Box2d/AndEngine 中设置角速度的大小。我有这个：
最终浮点 omegaFactor = (float) 1.0; ballBody.setAngularVelocity((float) ( (Math.PI) * omegaFactor) );
omegaFactor > 0 时，身体向一个方向旋转。如果我将 omegaFactor 更改为 -1.0，身体会朝相反的方向旋转，这很好。但是，改变大小没有效果。例如，值 1111.0 表现出与 1.0 相同的行为。请注意，body 是 DynamicBody。我需要做什么来影响旋转速度？这是整个测试代码：
package example.bouncingball;
import java.io.IOException;
import java.io.InputStream;
import org.andengine.engine.camera.Camera;
import org.andengine.engine.options.EngineOptions;
import org.andengine.engine.options.ScreenOrientation;
import org.andengine.engine.options.resolutionpolicy.RatioResolutionPolicy;
import org.andengine.entity.primitive.Rectangle;
import org.andengine.entity.scene.Scene;
import org.andengine.entity.sprite.Sprite;
import org.andengine.extension.physics.box2d.PhysicsConnector;
import org.andengine.extension.physics.box2d.PhysicsFactory;
import org.andengine.extension.physics.box2d.PhysicsWorld;
import org.andengine.input.sensor.acceleration.AccelerationData;
import org.andengine.input.sensor.acceleration.IAccelerationListener;
import org.andengine.opengl.texture.ITexture;
import org.andengine.opengl.texture.atlas.bitmap.BitmapTextureAtlasTextureRegionFactory;
import org.andengine.opengl.texture.bitmap.BitmapTexture;
import org.andengine.opengl.texture.region.TextureRegion;
import org.andengine.opengl.texture.region.TextureRegionFactory;
import org.andengine.opengl.vbo.VertexBufferObjectManager;
import org.andengine.ui.activity.SimpleBaseGameActivity;
import org.andengine.util.adt.io.in.IInputStreamOpener;
import org.andengine.util.debug.Debug;
import android.hardware.SensorManager;
import com.badlogic.gdx.math.Vector2;
import com.badlogic.gdx.physics.box2d.Body;
import com.badlogic.gdx.physics.box2d.BodyDef.BodyType;
import com.badlogic.gdx.physics.box2d.FixtureDef;
/**
* Demonstrate some physics
* Image file: assets/gfx/ball.png 128x128
*
*/
public class MainActivity extends SimpleBaseGameActivity implements IAccelerationListener {
// ===========================================================
// Fields
// ===========================================================
private Scene scene;
private PhysicsWorld mPhysicsWorld;
private TextureRegion mBallTextureRegion;
private Sprite mBallSprite;
private final int LEFT_EDGE = 0;
private final int CAMERA_WIDTH = 720; // right of screen
private final int TOP_OF_SCREEN = 0;
private final int CAMERA_HEIGHT = 480; // bottom of screen
public EngineOptions onCreateEngineOptions() {
final Camera camera = new Camera(0, 0, CAMERA_WIDTH, CAMERA_HEIGHT);
final EngineOptions engineOptions = new EngineOptions(true, ScreenOrientation.LANDSCAPE_FIXED, new RatioResolutionPolicy(CAMERA_WIDTH, CAMERA_HEIGHT), camera);
return engineOptions;
}
@Override
protected void onCreateResources() {
try {
BitmapTextureAtlasTextureRegionFactory.setAssetBasePath("gfx/");
setBallTexture();
}
catch (Exception exception) {
System.out.println ("MainActivity.onCreateResources(): " + exception);
Debug.d("MainActivity.onCreateResources(): " + exception);
}
}
@Override
protected Scene onCreateScene() {
scene = new Scene();
final VertexBufferObjectManager vertexBufferObjectManager = this.getVertexBufferObjectManager();
// physics world
this.mPhysicsWorld = new PhysicsWorld(new Vector2(0, SensorManager.GRAVITY_EARTH), false);
final Rectangle ground = new Rectangle(0, CAMERA_HEIGHT - 2, CAMERA_WIDTH, 2, vertexBufferObjectManager);
//final Rectangle roof = new Rectangle(0, 0, CAMERA_WIDTH, 2, vertexBufferObjectManager); // roof at top of screen
// y < 0 so as to lift the roof to start the ball off-screen
final Rectangle roof = new Rectangle(0, -200, CAMERA_WIDTH, 2, vertexBufferObjectManager);
final Rectangle left = new Rectangle(0, 0, 2, CAMERA_HEIGHT, vertexBufferObjectManager);
final Rectangle right = new Rectangle(CAMERA_WIDTH - 2, 0, 2, CAMERA_HEIGHT, vertexBufferObjectManager);
final FixtureDef wallFixtureDef = PhysicsFactory.createFixtureDef(0, 0.5f, 0.5f);
PhysicsFactory.createBoxBody(this.mPhysicsWorld, ground, BodyType.StaticBody, wallFixtureDef);
PhysicsFactory.createBoxBody(this.mPhysicsWorld, roof, BodyType.StaticBody, wallFixtureDef);
PhysicsFactory.createBoxBody(this.mPhysicsWorld, left, BodyType.StaticBody, wallFixtureDef);
PhysicsFactory.createBoxBody(this.mPhysicsWorld, right, BodyType.StaticBody, wallFixtureDef);
scene.attachChild(ground);
scene.attachChild(roof);
scene.attachChild(left);
scene.attachChild(right);
scene.registerUpdateHandler(this.mPhysicsWorld);
// end physics world
// if we use body.Transform() then x,y do not matter here
// except that it appears to flash at the x,y defined here before the transform
// so set it to the same
final int startX = CAMERA_WIDTH - 160;
mBallSprite = new Sprite( startX,
TOP_OF_SCREEN - 100, // off screen
this.mBallTextureRegion,
getVertexBufferObjectManager());
final Sprite ballFace = new Sprite( startX, TOP_OF_SCREEN - 100, this.mBallTextureRegion, this.getVertexBufferObjectManager());
// increasing elasticity makes the ball more 'bouncy'
// if friction is 0, it doesn't roll on the floor, it just spins in one spot
// if friction is < 0, the ball disappears when it hits the floor, or wall presumably
final FixtureDef BALL_FIXTURE_DEF = PhysicsFactory.createFixtureDef(
1, // density
0.5f, // elasticity
0.5f); // friction
final Body ballBody = PhysicsFactory.createCircleBody(this.mPhysicsWorld, ballFace, BodyType.DynamicBody, BALL_FIXTURE_DEF);
// Angular velocity - omega of the object is the change of angle with respect to time
// Angular velocity is measured in radians per second
// omegaFactor: 2.0: 2 revolutions per second, clockwise
// -0.5: 1/2 revolution per second, counterclockwise
final float omegaFactor = (float) 1.0;
ballBody.setAngularVelocity((float) ( (Math.PI) * omegaFactor) );
this.mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(mBallSprite, ballBody, true, true));
scene.attachChild(mBallSprite);
return scene;
}
private void setBallTexture() throws IOException {
ITexture texture = new BitmapTexture(this.getTextureManager(), new IInputStreamOpener() {
@Override
public InputStream open() throws IOException {
return getAssets().open("gfx/ball.png");
}
});
texture.load();
this.mBallTextureRegion = TextureRegionFactory.extractFromTexture(texture);
}
// IAccelerationListener interface
@Override
public void onAccelerationAccuracyChanged(final AccelerationData pAccelerationData) {
}
@Override
public void onAccelerationChanged(final AccelerationData pAccelerationData) {
}
// end IAccelerationListener interface
}