愤怒的小鸟－物理世界Box2d（2）－点击添加精灵，画线

// 如何实现愤怒的小鸟里面手一拉就会出现两根随着小鸟动的线条

//  在场景实例化init内 画上两根线，并将其隐藏
    auto line_1 = DrawNode::create();
    auto line_2 = DrawNode::create();
    this->addChild(line_1);
    this->addChild(line_2);
    line_1->setVisible(false);
    line_2->setVisible(false);
    line_1->setTag(10001);
    line_2->setTag(10002);
    // 添加事件的监听，以完成在点击的时候能出现一个小鸟，并且小鸟和线条会随着鼠标的移动而移动
    // 并且在点击结束的瞬间给 精灵小鸟 一个力 ，让它能够飞出去
    auto listener = EventListenerTouchOneByOne::create();
    listener->onTouchBegan = CC_CALLBACK_2(HelloWorld::onTouchBegan, this);
    listener->onTouchMoved = CC_CALLBACK_2(HelloWorld::onTouchMoved, this);
    listener->onTouchEnded = CC_CALLBACK_2(HelloWorld::onTouchEnded, this);
    _eventDispatcher->addEventListenerWithSceneGraphPriority(listener, this);

bool HelloWorld::onTouchBegan(Touch* t,Event* e){
    
    bird_Index++;
//    CCLOG("map: x=%f , y=%f", t->getLocation().x,t->getLocation().y);
//    addNewPigAtLocation(t->getLocation().x, t->getLocation().y);
    
    // 点击添加小鸟
    auto bird = Sprite::create("bird1.png");
    this->addChild(bird);
    bird->setTag(1000+bird_Index);
    CCLOG("index = %d",1000+bird_Index);
    bird->setPosition(t->getLocation());
    
    return true;
}

void HelloWorld::onTouchMoved(Touch* t,Event* e){
    // 点击让小鸟跟着移动
    auto now_Bird = this->getChildByTag(1000+bird_Index);
    now_Bird->setPosition(t->getLocation());
    
    auto l1 = (DrawNode*)this->getChildByTag(10001);
    auto l2 = (DrawNode*)this->getChildByTag(10002);
    // 这里必须擦掉之前画的线
    l1->clear();
    l2->clear();
    l1->drawSegment(Vec2(140,120), t->getLocation(),4,Color4F(Color3B::BLACK));
    l2->drawSegment(Vec2(160,120), t->getLocation(),4,Color4F(Color3B::BLACK));
    l1->setVisible(true);
    l2->setVisible(true);
    
}

void HelloWorld::onTouchEnded(Touch* t,Event* e){
    // 松手时小鸟飞出去  body:静态动态，位置
    b2BodyDef bird_Def;
    bird_Def.type = b2_dynamicBody;
    bird_Def.position.Set(t->getLocation().x/32.0f,t->getLocation().y/32.0f);
    b2Body* bird_Body = World->CreateBody(&bird_Def);
    
    //  物体形状   polygonshape    circleshape
    b2CircleShape body_Shape;
    body_Shape.m_radius = 22/32.0f;
    
    //  物体属性   fixture：形状也要添加（圆形），密度，摩擦力，反弹力。
    b2FixtureDef bird_Fixture;
    bird_Fixture.shape = &body_Shape;
    bird_Fixture.density = 1.0f;
    bird_Fixture.restitution = 0.4;
    bird_Fixture.friction = 1.0f;
    bird_Body->CreateFixture(&bird_Fixture);
    bird_Body->SetSleepingAllowed(true);
    
    CCLOG("index_check = %d",1000+bird_Index);
    auto now_bird = this->getChildByTag(1000+bird_Index);
    bird_Body->SetUserData(now_bird);
    
    //  从这里看的出来  把b2vec2 似乎都是加速的定义，这里还是x。y  跟重力没什么区别
    b2Vec2 force = b2Vec2(150-t->getLocation().x,120-t->getLocation().y);
    //  而这里是 apply ，并不是顺手写的 set ，毕竟是加给它的加速度么 f=ma
    bird_Body->ApplyLinearImpulse(force,bird_Body->GetPosition(),true);
    
    auto l1 = this->getChildByTag(10001);
    auto l2 = this->getChildByTag(10002);
    l1->setVisible(false);
    l2->setVisible(false);
}