Question

目前我正在研究鱼类动画。我的鱼精灵是动画的，能够在画布上自由移动。其次，我想添加食物来喂养画布上的鱼。但是目前我被卡住了，当它在画布上画画时，无法让鱼儿游向食物。

以下是我的鱼精灵随机移动的方式：

Fish.prototype.changeDirection = function () {
    var me = this;
    var speedXSign = Math.random() < 0.5 ? 1 : -1;
    var speedYSign = Math.random() < 0.5 ? 1 : -1;
    this.speedX = speedXSign * (1 + Math.random() * 1.6);
    this.speedY = speedYSign * (1 + Math.random() * 1.6);
    var time = 1000 + 2000*Math.random();
    setTimeout(function() {me.changeDirection()}, time);
};

Fish.prototype.move = function () {
    this.animIndex++;
    if ( this.animIndex == animFrames.length) this.animIndex = 0;

    this.xPos += this.speedX;
    if ((this.xPos + this.frameWidth * this.frameScale / 1.8) >= canvas.width && this.speedX > 0 || 
    (this.xPos - this.frameWidth * this.frameScale / 1.8) <= 0 && this.speedX <= 0) {
        this.speedX = -this.speedX;
    }

    this.yPos += this.speedY;
    if ((this.yPos + this.frameHeight * this.frameScale / 1.8) >= canvas.height && this.speedY > 0 || 
    (this.yPos - this.frameHeight * this.frameScale / 1.8) <= 0 && this.speedY <= 0) {
        this.speedY = -this.speedY;
    }
};

现在，当我在画布上点击时，食物将会出现，并与X和Y偏移一起出现。

function addFood(foodArray){
    var iiimage = new Image();
    iiimage.src = 'Images/redFood.png';
    for(var m = 0 ; m<foodArray.length;m++){
        var x = foodArray[m].x;
        var y = foodArray[m].y;
        context.drawImage(iiimage,x,y,50,50);
    }
}

function getMousePos(canvas, evt) {
        var rect = canvas.getBoundingClientRect();
        return {
          x: evt.clientX - rect.left,
          y: evt.clientY - rect.top
        };
}

canvas.onmousedown = function(e){
    foodX = getMousePos(canvas,e).x;
    foodY = getMousePos(canvas,e).y;
    food = {x:foodX,y:foodY};
    foodArray.push(food);
    console.log('('+foodX+','+foodY+')');
    console.log(food);
    console.log(foodArray.length);
}

是否有可能让鱼精灵改变它的方向到最近的食物，然后在鱼精灵与食物接触后再回到它的随机运动。

这是我的小提琴：http://jsfiddle.net/Bernard_9/bV4r6/

Answer 1

这是我更新的fiddle，现在我将解释我所做的更改。

添加食物宽度和高度的变量：

...
var foodArray = [];
var foodWidth = 50;
var foodHeight = 50;
var food;
...

更新绘图功能以使用这些变量：

function addFood(foodArray) {
  ...
    var x = foodArray[m].x;
    var y = foodArray[m].y;
    context.drawImage(iiimage, x, y, foodWidth, foodHeight);
  ...
}

添加功能以找到最近的食物：

Fish.prototype.closestFood = function () {
var closestFoodIndex = -1;
var shortestDistance = Infinity;
for (var i = 0; i < foodArray.length; i++) {
        var distance = Math.max(Math.abs(this.xPos - foodArray[i].x), Math.abs(this.yPos - foodArray[i].y));
        if (distance < shortestDistance) {
            shortestDistance = distance;
            closestFoodIndex = i;
        }
    }
    return closestFoodIndex;
};

添加功能以改变对食物的指示：

Fish.prototype.chaseFood = function(index) {
    if (this.xPos > foodArray[index].x + foodWidth) {
        this.speedX = -1 * Math.abs(this.speedX);
    } else if (this.xPos < foodArray[index].x) {
        this.speedX = Math.abs(this.speedX);
    }
    if (this.yPos > foodArray[index].y + foodHeight) {
        this.speedY = -1 * Math.abs(this.speedY);
    } else if (this.yPos < foodArray[index].y) {
        this.speedY = Math.abs(this.speedY);
    }
};

添加变量以跟踪鱼在追逐食物的时间：

function Fish(xPos, yPos, speedX, speedY, imgFish, frameWidth, frameHeight) {
    ...
    this.chasingFood = false;
    ...
}

添加一种功能，可以吃鱼下的任何食物：

Fish.prototype.eatFood = function() {
    var foodX, foodY;
    var halfWidth = this.frameWidth * this.frameScale / 2;
    var halfHeight = this.frameHeight * this.frameScale / 2;
    // Loop backward because we are removing elements.
    for (var i = foodArray.length-1; i >= 0; i--) {
        foodX = foodArray[i].x + foodWidth / 2;
        foodY = foodArray[i].y + foodHeight / 2;
        if (foodX > this.xPos - halfWidth &&
            foodX < this.xPos + halfWidth &&
            foodY > this.yPos - halfHeight&&
            foodY < this.yPos + halfHeight)
        {
            foodArray.splice(i, 1);
        }
    }
};

更新移动功能，吃食物，寻找食物并追逐它：

Fish.prototype.move = function () {
    ...
    this.eatFood();

    var closestFoodIndex = this.closestFood();
    if (closestFoodIndex >= 0) {
        this.chasingFood = true;
        this.chaseFood(closestFoodIndex);
    } else {
        this.chaseingFood = false;
    }
    ...
};

更新改变方向功能，仅在不追逐食物时改变方向：

Fish.prototype.changeDirection = function () {
    var me = this;
    if (!this.chasingFood) {
        var speedXSign = Math.random() < 0.5 ? 1 : -1;
        var speedYSign = Math.random() < 0.5 ? 1 : -1;
        this.speedX = speedXSign * (1 + Math.random() * 1.6);
        this.speedY = speedYSign * (1 + Math.random() * 1.6);
    }
    var time = 1000 + 2000 * Math.random();
    setTimeout(function () {
        me.changeDirection();
    }, time);
};

这只会使鱼改变x和y方向，而不是速度。可以修改chaseFood功能以使它们加速，或者可以直接进食（尽管这可能会使动画看起来很奇怪）。

如果您需要有关任何新代码的更多说明，请发表评论。

将精灵图像移动到选定位置

1 个答案: