应用源码之(滑轮关.zip

package com.pulleyj; import org.jbox2d.collision.AABB; import org.jbox2d.collision.PolygonDef; import org.jbox2d.common.Vec2; import org.jbox2d.dynamics.Body; import org.jbox2d.dynamics.BodyDef; import org.jbox2d.dynamics.World; import org.jbox2d.dynamics.joints.PulleyJoint; import org.jbox2d.dynamics.joints.PulleyJointDef; import android.content.Context; import android.graphics.Canvas; import android.graphics.Color; import android.graphics.Paint; import android.graphics.Paint.Style; import android.util.Log; import android.view.SurfaceHolder; import android.view.SurfaceView; import android.view.SurfaceHolder.Callback; public class MySurfaceView extends SurfaceView implements Callback, Runnable { private Thread th; private SurfaceHolder sfh; private Canvas canvas; private Paint paint; private boolean flag; // ----添加一个物理世界---->> final float RATE = 30; World world; AABB aabb; Vec2 gravity; float timeStep = 1f / 60f; int iterations = 10; // ------>>移动关节 Body body1, body2; float body1x = 40, body1y = 200, body1w = 80, body1h = 80, body2x = 120, body2y = 200, body2w = 80, body2h = 80; float anchor1x=100,anchor1y=45,anchor2x=200 ,anchor2y=45 ; public MySurfaceView(Context context) { super(context); this.setKeepScreenOn(true); sfh = this.getHolder(); sfh.addCallback(this); paint = new Paint(); paint.setAntiAlias(true); this.setFocusable(true); // --添加一个物理世界--->> aabb = new AABB(); gravity = new Vec2(0, 10); aabb.lowerBound.set(-100, -100); aabb.upperBound.set(100, 100); world = new World(aabb, gravity, true); // ----在物理世界中添加两个矩形Body body1 = createPolygon(body1x, body1y, body1w, body1h,1); body2 = createPolygon(body2x, body2y, body2w, body2h,2); // 设置滑轮关节 createPulleyJointDef(); } public void surfaceCreated(SurfaceHolder holder) { flag = true; th = new Thread(this); th.start(); } // 滑轮关节(让物体沿着 一个世界锚点进行滑轮) public PulleyJoint createPulleyJointDef() { //创建滑轮关节数据实例 PulleyJointDef pjd = new PulleyJointDef(); Vec2 ga1 = new Vec2(anchor1x/ RATE,anchor1y/ RATE); Vec2 ga2 = new Vec2(anchor2x/ RATE,anchor2y/ RATE); //初始化滑轮关节数据 //body，两个滑轮的锚点，两个body的锚点，比例系数 pjd.initialize(body1, body2, ga1, ga2, body1.getWorldCenter(), body2 .getWorldCenter(), 1f); PulleyJoint pj = (PulleyJoint) world.createJoint(pjd); return pj; } public Body createPolygon(float x, float y, float width, float height, float density) { PolygonDef pd = new PolygonDef(); pd.density = density; pd.friction = 0.8f; pd.restitution = 0.3f; pd.setAsBox(width / 2 / RATE, height / 2 / RATE); BodyDef bd = new BodyDef(); bd.position.set((x + width / 2) / RATE, (y + height / 2) / RATE); Body body = world.createBody(bd); bd.angle = (float) (15 * Math.PI / 180); body.m_userData = new MyRect(x, y, width, height); body.createShape(pd); body.setMassFromShapes(); return body; } public void myDraw() { try { canvas = sfh.lockCanvas(); if (canvas != null) { canvas.drawColor(Color.WHITE); Body body = world.getBodyList(); for (int i = 1; i < world.getBodyCount(); i++) { ((MyRect) body.m_userData).draw(canvas, paint); body = body.m_next; } canvas.drawCircle(anchor1x, anchor1y, 10, paint); canvas.drawCircle(anchor2x, anchor2y, 10, paint); canvas.drawLine(anchor1x, anchor1y, anchor2x, anchor2y, paint); canvas.drawLine(anchor1x, anchor1y, body1.getPosition().x*RATE, body1.getPosition().y*RATE, paint); canvas.drawLine(anchor2x, anchor2y, body2.getPosition().x*RATE, body2.getPosition().y*RATE, paint); } } catch (Exception e) { Log.e("Himi", "myDraw is Error!"); } finally { if (canvas != null) sfh.unlockCanvasAndPost(canvas); } } public void Logic() { world.step(timeStep, iterations); Body body = world.getBodyList(); paint.setStyle(Style.STROKE); for (int i = 1; i < world.getBodyCount(); i++) { MyRect mc = (MyRect) body.m_userData; mc.setX(body.getPosition().x * RATE - mc.w / 2); mc.setY(body.getPosition().y * RATE - mc.h / 2); mc.setAngle((float) (body.getAngle() * 180 / Math.PI)); body = body.m_next; } } public void run() { while (flag) { myDraw(); Logic(); try { Thread.sleep((long) timeStep * 1000); } catch (Exception ex) { Log.e("Himi", "Thread is Error!"); } } } public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) { } public void surfaceDestroyed(SurfaceHolder holder) { flag = false; } }