基本上我想要实现的是将一些 div 拖到另一个容器 div 中。内部 div 到达容器 div 的边界时应该停止。我设法完成了大部分工作。但问题是,如果我缓慢而小心地拖动内部 div,它会停在它应该位于边缘的位置,但是如果我更快地拖动它,它有时会溢出边缘或在边缘之前停止。这里有什么问题?我应该怎么做才能解决这个问题?
function mouseMove(e) {
e.preventDefault();
console.log("mouse moving");
if(isMouseDown > 0 && currentElement) {
mouseX = e.clientX;
mouseY = e.clientY;
var diffX = mouseX - lastMouseX;
var diffY = mouseY - lastMouseY;
if(diffX + lastElementX + elementWidth < rightLimit && diffX + lastElementX > leftLimit) {
lastElementX += diffX;
lastMouseX = mouseX;
}
if(diffY + lastElementY + elementHeight < bottomLimit && diffY + lastElementY > topLimit) {
lastElementY += diffY;
lastMouseY = mouseY;
}
setCurrentElementPosition(lastElementX, lastElementY);
}
}
以上代码在鼠标移动事件改变内部 div 的位置时运行。
最佳答案
这是我的解决方案,我以前编写过视频游戏,您经常遇到这个问题。
您正在检查它是否会熄灭,但如果它熄灭则什么也不做!如果它到外面,你必须将它设置到边缘。
https://jsfiddle.net/7btv7oqy/3/
var lastElementX = 0; //last X position of element
var lastElementY = 0; //last Y position of element
var lastMouseX = 0; //last X position of mouse
var lastMouseY = 0;//last Y position of mouse
var mouseX = 0; //current mouse position X
var mouseY = 0; //current mouse position Y
var currentElement = null; //currently selected div
var elementWidth = 0;
var elementHeight = 0;
var container = null; //container div
var isMouseDown = 0; //if greater than zero, mouse is down
//limits of container div
var bottomLimit = 0;
var topLimit = 0;
var leftLimit = 0;
var rightLimit = 0;
function init() {
container = document.getElementsByClassName("container")[0];
topLimit = container.getBoundingClientRect().top;
bottomLimit = container.getBoundingClientRect().bottom;
leftLimit = container.getBoundingClientRect().left;
rightLimit = container.getBoundingClientRect().right;
document.addEventListener("mousedown", function mouseDown(e) {
e.preventDefault();
++isMouseDown;
document.addEventListener("mousemove", mouseMove);
setCurrentElement(getElementUnderMouse(e)); //set current element
currentElement.style.position = "absolute";
lastElementX = currentElement.getBoundingClientRect().left;
lastElementY = currentElement.getBoundingClientRect().top;
lastMouseX = e.clientX;
lastMouseY = e.clientY;
});
document.addEventListener("mouseup", function mouseUp(e) {
e.preventDefault();
--isMouseDown;
setCurrentElement(null);
document.removeEventListener("mousemove", mouseMove);
});
}
function mouseMove(e) {
e.preventDefault();
console.log("mouse moving");
// report(e);
if(isMouseDown > 0 && currentElement) {
mouseX = e.clientX;
mouseY = e.clientY;
var diffX = mouseX - lastMouseX;
var diffY = mouseY - lastMouseY;
if(diffX + lastElementX + elementWidth < rightLimit && diffX + lastElementX > leftLimit) {
lastElementX += diffX;
} else {
//without this, the location wouldn't update at all:
//check if it would go off the right edge, set to right edge
if (diffX + lastElementX + elementWidth >= rightLimit) {
lastElementX = rightLimit - elementWidth;
}
//check if it would go off the left edge, set to left edge
if(diffX + lastElementX <= leftLimit) {
lastElementX = leftLimit;
}
}
//this will always happen:
lastMouseX = mouseX;
if(diffY + lastElementY + elementHeight < bottomLimit && diffY + lastElementY > topLimit) {
lastElementY += diffY;
} else {
//without this, the location wouldn't update at all:
//check if it would go off the bottom edge, set to bottom edge
if(diffY + lastElementY + elementHeight >= bottomLimit) {
lastElementY = bottomLimit - elementHeight;
}
//check if it would go off the top edge, set to top edge
if(diffY + lastElementY <= topLimit) {
lastElementY = topLimit;
}
}
//this will always happen:
lastMouseY = mouseY;
setCurrentElementPosition(lastElementX, lastElementY);
}
}
function setCurrentElementPosition(left = null, top = null) {
if(currentElement) {
currentElement.style.top = top + 'px'
currentElement.style.left = left + 'px';
}
}
function setCurrentElement(element) {
currentElement = element;
if(element) {
elementWidth = currentElement.offsetWidth;
elementHeight = currentElement.offsetHeight;
} else {
elementWidth = 0;
elementHeight = 0;
}
}
function hasClass(element, cls) {
return ("" + element.className + "").indexOf("" + cls + "") > -1;
}
function getElementUnderMouse(e) {
var x = e.clientX;
var y = e.clientY;
return document.elementFromPoint(x, y);
}
function report(e) {
console.log("isMouseDown: " + isMouseDown);
console.log("mouseX: " + e.clientX);
console.log("mouseY: " + e.clientY);
console.log("currentElement: " + currentElement);
console.log("currentElement top: " + currentElement.getBoundingClientRect().top);
console.log("currentElement bottom: " + currentElement.getBoundingClientRect().bottom);
console.log("container top: " + container.getBoundingClientRect().top);
console.log("container bottom: " + container.getBoundingClientRect().bottom);
}
init();
编辑:不确定为什么它在右侧和底部缺少一个像素,您必须在这方面进行一些调查。尽管您使用了 offsetWidth
,但它似乎没有考虑到边框。祝你好运!
关于javascript - 使javascript动画流畅?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/41243987/