Question

我正在尝试投射一个物体，并根据开始的触摸点和结束触点创建物体移动的角度和速度。到目前为止，我可以在拖动对象mySprite的同时跟踪触摸点。当物体被释放时，我也有静态重力。但是，我很难弄清楚如何将两者联系在一起。

我有一个函数onTouchEnd()，它可以检测对象何时被释放，并且是重力开始的地方。但是现在没有任何反应。

我缺少什么能够精确定位开始和结束触点，然后保存两者之间的对象轨迹角度？很抱歉这样的菜鸟。

编辑：使用localX，localY

更新代码

package  {
import flash.display.MovieClip;
import flash.events.*;
import flash.ui.Multitouch;
import flash.ui.MultitouchInputMode;
import flash.display.Sprite;

public class ThrowIt extends MovieClip{
    public var bg:Sprite = new Sprite();
    public var mySprite:Sprite = new Sprite(); 
    Multitouch.inputMode = MultitouchInputMode.TOUCH_POINT;
    public var startX:int;
    public var endX:int;
    public var startY:int;
    public var endY:int;
    public var angle:int;
    //public var speed:Number = 10; //this will change based on mouse speed
    public var moving:Number = 0;
    public var speedLimit:Number = 35;
    public var scale_x:Number = Math.cos(angle);
    public var scale_y:Number = Math.sin(angle);
    public var posY:Number = stage.y;
    public var goingUp:Boolean = false;
    public var goingDown:Boolean = false;
    //public var velocityX:Number = (speed*scale_x);
    //public var velocityY:Number = (speed*scale_y);

    public function ThrowIt() {
        mySprite.graphics.beginFill(0x336699); 
        mySprite.graphics.drawRect(0,0,40,40); 
        //addChild(bg);
        addChild(mySprite); 
        mySprite.addEventListener(TouchEvent.TOUCH_BEGIN, onTouchBegin); 
        mySprite.addEventListener(TouchEvent.TOUCH_END, onTouchEnd);
    }

    function onTouchBegin(e:TouchEvent) { 
        mySprite.startTouchDrag(e.touchPointID, false);

        /*TRACK THE START POINT OF THE DRAG HERE*/
        /*NEED THE X AND Y POSITION TO FIGURE OUT ANGLE AND VELOCITY OF OBJECT*/
        startX = e.localX;
        startY = e.localY;
        trace("the starting x is " + startX); 

    } 

    function onTouchEnd(e:TouchEvent) { 
        mySprite.stopTouchDrag(e.touchPointID); 
        /*TRACK THE END POINT OF THE DRAG HERE*/
        /*AGAIN, NEED BOTH THE X AND Y POSITION*/

        endY = e.localY;
        endX = e.localX;

        //angle = (endX - startX)*Math.PI(180);

        /*AFTER GETTING THE VELOCITY FIGURED OUT, THROW OBJECT*/
        if(!goingUp){
            goingUp = true;
            //moving = speedLimit*-1;
            moving = (startY - endY)*-1;
            moving += .2;
            mySprite.y += moving;
            mySprite.y = Math.min(mySprite.y, stage.stageHeight - 510); //min position of the object
            mySprite.y = Math.max(mySprite.y, 0); ///max position of the object
        }
        if(moving < 0){//if mySprite is still going up
            moving *= 1 - speedLimit/250;//decrease moving slightly
            if(moving > -speedLimit*.1){//if moving is small enough
                moving *= -1;//then begin to go down
            }
        }
        if(moving > 0 && moving <= speedLimit){//if mySprite is going down
            moving *= 1 + speedLimit/400;//increase the falling speed
        }
        mySprite.y += moving;
        //WHEN OBJECT GOES BELOW THE STAGE, DELETE IT AND STOP TRACKING EVENTS
        if(mySprite.y >= stage.stageHeight){
            removeChild(mySprite);
            mySprite.removeEventListener(TouchEvent.TOUCH_END, onTouchEnd);
            mySprite.removeEventListener(TouchEvent.TOUCH_BEGIN, onTouchBegin);

            trace("removed");
        }
    }


}

}

Answer 1

使用x值计算角度看起来很奇怪，试试这个：

angle = Math.atan( (startY - endY) / (startX - endX) );  // in rad

这将为您提供弧度角度。

为了计算速度，您必须在开始和结束触摸之间有一个时间变量。您可以使用getTimer()分别在函数beginTime和endTime中获取onTouchBegin和onTouchEnd。

之后你只需要用距离和时间来计算速度。

distance = Math.sqrt( ((startX - endX)*(startX - endX)) / ((startY - endY)*(startY - endY)) );
velocity = distance / (endTime-beginTime); // in pixel/ms

希望有所帮助;）

获取启动touchPoint并结束touchPoint以确定速度AS3

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