java - 和引擎物理的例子

因此，我正在研究AndEngine PhysicsExample代码。我想知道此方法（http://pastebin.com/Day2hciB）是什么意思：

private void addFace(final float pX, final float pY) {
        this.mFaceCount++;
        Debug.d("Faces: " + this.mFaceCount);

        final AnimatedSprite face;
        final Body body;

        if(this.mFaceCount % 4 == 0) {
            face = new AnimatedSprite(pX, pY, this.mBoxFaceTextureRegion, this.getVertexBufferObjectManager());
            body = PhysicsFactory.createBoxBody(this.mPhysicsWorld, face, BodyType.DynamicBody, FIXTURE_DEF);
        } else if (this.mFaceCount % 4 == 1) {
            face = new AnimatedSprite(pX, pY, this.mCircleFaceTextureRegion, this.getVertexBufferObjectManager());
            body = PhysicsFactory.createCircleBody(this.mPhysicsWorld, face, BodyType.DynamicBody, FIXTURE_DEF);
        } else if (this.mFaceCount % 4 == 2) {
            face = new AnimatedSprite(pX, pY, this.mTriangleFaceTextureRegion, this.getVertexBufferObjectManager());
            body = PhysicsExample.createTriangleBody(this.mPhysicsWorld, face, BodyType.DynamicBody, FIXTURE_DEF);
        } else {
            face = new AnimatedSprite(pX, pY, this.mHexagonFaceTextureRegion, this.getVertexBufferObjectManager());
            body = PhysicsExample.createHexagonBody(this.mPhysicsWorld, face, BodyType.DynamicBody, FIXTURE_DEF);
        }

        face.animate(200);

        this.mScene.attachChild(face);
        this.mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(face, body, true, true));
    }

最佳答案

private void addFace(final float pX, final float pY) {
            this.mFaceCount++;
            Debug.d("Faces: " + this.mFaceCount);

            final AnimatedSprite face;
            final Body body;

            if(this.mFaceCount % 4 == 0) {
                    face = new AnimatedSprite(pX, pY, this.mBoxFaceTextureRegion, this.getVertexBufferObjectManager());
                    body = PhysicsFactory.createBoxBody(this.mPhysicsWorld, face, BodyType.DynamicBody, FIXTURE_DEF);
            } else if (this.mFaceCount % 4 == 1) {
                    face = new AnimatedSprite(pX, pY, this.mCircleFaceTextureRegion, this.getVertexBufferObjectManager());
                    body = PhysicsFactory.createCircleBody(this.mPhysicsWorld, face, BodyType.DynamicBody, FIXTURE_DEF);
            } else if (this.mFaceCount % 4 == 2) {
                    face = new AnimatedSprite(pX, pY, this.mTriangleFaceTextureRegion, this.getVertexBufferObjectManager());
                    body = PhysicsExample.createTriangleBody(this.mPhysicsWorld, face, BodyType.DynamicBody, FIXTURE_DEF);
            } else {
                    face = new AnimatedSprite(pX, pY, this.mHexagonFaceTextureRegion, this.getVertexBufferObjectManager());
                    body = PhysicsExample.createHexagonBody(this.mPhysicsWorld, face, BodyType.DynamicBody, FIXTURE_DEF);
            }

            face.animate(200);

            this.mScene.attachChild(face);
            this.mPhysicsWorld.registerPhysicsConnector(new PhysicsConnector(face, body, true, true));
    }

该代码的作用是根据其形状将主体设置为精灵。每次添加面部时，mFaceCount自身都会加1。该行的作用：

if(this.mFaceCount % 4 == 0)

是检查以除以4的余数是否等于0（其他为1，2，3）。所有这一切都告诉它要添加到场景中的精灵。您会注意到，首先添加一个正方形，然后添加一个圆形，然后添加一个三角形，然后添加一个六边形。

真正的代码在这些行中：

face = new AnimatedSprite(pX, pY, this.mBoxFaceTextureRegion, this.getVertexBufferObjectManager());
                    body = PhysicsFactory.createBoxBody(this.mPhysicsWorld, face, BodyType.DynamicBody, FIXTURE_DEF);

这将创建一个名为face的精灵，并在其上附加一个盒子主体。下一个附加一个圆圈。现在您会注意到接下来的两个不同。他们说PhysicsExample.create而不是PhysicsFactory.create。 PhysicsExample是活动，因此他们正在PhysicsExample中而不是从PhysicsFactory中调用方法。 createTriangleBody实际上调用此方法（在代码中稍后介绍）：

private static Body createTriangleBody(final PhysicsWorld pPhysicsWorld, final IAreaShape pAreaShape, final BodyType pBodyType, final FixtureDef pFixtureDef) {
    /* Remember that the vertices are relative to the center-coordinates of the Shape. */
    final float halfWidth = pAreaShape.getWidthScaled() * 0.5f / PIXEL_TO_METER_RATIO_DEFAULT;
    final float halfHeight = pAreaShape.getHeightScaled() * 0.5f / PIXEL_TO_METER_RATIO_DEFAULT;

    final float top = -halfHeight;
    final float bottom = halfHeight;
    final float left = -halfHeight;
    final float centerX = 0;
    final float right = halfWidth;

    final Vector2[] vertices = {
            new Vector2(centerX, top),
            new Vector2(right, bottom),
            new Vector2(left, bottom)
    };

    return PhysicsFactory.createPolygonBody(pPhysicsWorld, pAreaShape, vertices, pBodyType, pFixtureDef);
}

这会在子画面周围创建一个三角形（不要问我如何。我不明白他在这里使用的数学方法，但是我精确地复制了它，并且适用于大致等边的三角形。整个顶点需要花费一些时间。而且我不要得到向量！）。 createHexagonMethod所做的只是六边形。我希望回答您的问题？让我知道是否遗漏了什么。