小弟学习Box2D遇到了一个问题，求大神解答

[Tofun_]

小弟这两天学习box2d遇到了一个问题，问题如图。。。我让三角形从手机屏幕上下落，然后碰到矩形后弹起。。。。但是手机上我绘制的三角形还没碰到矩形，就已经弹起了。。。。
部分代码如下：
//三角形在手机屏幕中的坐标，宽高，单位“像素”
private float p_x=200, p_y=5, p_w=90, p_h=60;
//比例尺
private final float RATE = 30;
//设置三角形的顶点
private float[] vertex = {-1.5f, -1, 1.5f, -1, 0, 1};
//物理世界中绘制三角形的函数
private Body createPolygon(float[] vertex, float x, float y, float width, float height, boolean isStatic) {
PolygonDef polygonDef = new PolygonDef();
if (isStatic) {
polygonDef.density = 0;
} else {
polygonDef.density = 1;
}
polygonDef.friction = 0.5f;
polygonDef.restitution = 0.5f;
polygonDef.addVertex(new Vec2(vertex[0], vertex[1]));
polygonDef.addVertex(new Vec2(vertex[2], vertex[3]));
polygonDef.addVertex(new Vec2(vertex[4], vertex[5]));
BodyDef bodyDef = new BodyDef();
bodyDef.position.set((x + width / 2) / RATE, (y + height / 2) / RATE);
Body body = world.createBody(bodyDef);
body.createShape(polygonDef);
body.setMassFromShapes();
return body;
}
//在手机屏幕上绘制三角形的函数
private void mydraw(){
...
canvas.drawLine(p_x,p_y,p_x+p_w,p_y,paint);
canvas.drawLine(p_x+p_w,p_y,p_x+p_w/2,p_y+p_h,paint);
canvas.drawLine(p_x+p_w/2,p_y+p_h,p_x,p_y,paint);
...
}