javascript - Canvas 中的多次碰撞

Question

我正在尝试制作解锁我的游戏。我有一系列对象，并且发生了边界碰撞。但现在我陷入了物体之间的碰撞。我对数组中的对象进行了循环，但它停止在最后一个对象上。每次与所选对象一起移动时，如何对每个对象进行碰撞检查？完整代码在这里:http://foxfcb.sweb.cz/我是编程新手，所以请耐心等待。

canvas.addEventListener('mousemove', function (e) {

    ...

        var shapes = myState.shapes;
        var l = shapes.length;

        for (var i = 0; i < l; i++) {

            var shape = myState.shapes[i];
            var selection = myState.selection;

            // collision between objects
            if (selection.x < (shape.x + shape.w) && (selection.x + selection.w) > shape.x &&
                selection.y < (shape.y + shape.h) && (selection.y + selection.h) > shape.y) {
                myState.valid = true; //stop
            }
            // boundaries collision
            else if (myState.selection.x < 0 || myState.selection.y < 0 || myState.selection.x + myState.selection.w > 600 || myState.selection.y + myState.selection.h > 600) {
                myState.valid = true; //stop
            }

            else {
                myState.valid = false;  //moving

            }
        }

    }

Answer 1

当您检查其他对象时，您正在重置valid 标志。

这是您的碰撞检测函数。请注意，我在循环之前设置了一次 state = false，如果发生冲突，我将退出循环，因为没有必要检测其他冲突，因为标志是 true 或false。如果您检测到碰撞，则将除最后一个对象之外的所有对象上的标志设置回 false。

var textCollision = function(){
    var shapes, l, shape, selection, i;
    shapes = myState.shapes;
    l = shapes.length;
    myState.valid = false; // assume no collision 
    for (i = 0; i < l; i++) {
        shape = myState.shapes[i];
        selection = myState.selection;
        if (selection.x < (shape.x + shape.w) && (selection.x + selection.w) > shape.x &&
            selection.y < (shape.y + shape.h) && (selection.y + selection.h) > shape.y) {
            myState.valid = true; //stop
            // there is no point testing any others as it will make no dif
            break; // step out of the for loop.
        }
        // boundaries collision
        else if (myState.selection.x < 0 || myState.selection.y < 0 || myState.selection.x + myState.selection.w > 600 || myState.selection.y + myState.selection.h > 600) {
            myState.valid = true; //stop
            // there is no point testing any others as it will make no dif
            break; // step out of the for loop.
        }
    }

}

中断。

Break 是 JavaScript 保留标记，用于跳出循环和切换。

for循环

for(i = 0; i < 10; i++){
    if(i === 2){
        break;  // exit the loop at 2
    }
}

While循环

while(i < 10){
    if(i === 2){
        break; // exit out of the while loop
    }
}

在 do{ }While() 循环上也执行相同的操作。

Break仅退出当前循环；

for(j = 0; j < 10; j++){  // j loop
    for(i = 0; i < 10; i++){ // i loop
        if(i === 2){
            break;  // exit the i loop at 2
        }
    }
    // the break moves execution to the first line after the loop it is in 
    // the j loop continues as normal
}

Break 也用于 switch 语句

function num(i){
    switch(i){
    case 1:
       console.log("one");
       // no break token so execution continues inside the switch
    case 2:
       console.log("two");
    }
}
num(1); // outputs "one" "two"

为了防止这种情况，请使用break

function num(i){
    switch(i){
    case 1:
       console.log("one");
       break;  // break out of the switch

    case 2:
       console.log("two");
       // no point having a break here as it is at the end anyways
    }
    // break moves execution to here
}
num(1); // outputs "one"