鼠标拖动改变DIV等网页元素的大小的最佳实践

Posted 2020-09-26 追极

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1.初次实现

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
        <title>div change width by drag</title>
        <script src="../jQuery/jquery-1.8.3.min.js" type="text/javascript"></script>
    </head>

    <body>
        <h1>div change width by drag</h1>
        <div id="pos" style="color:red"></div>
        
        <div id="myDiv" style="border:2px solid red;width:300px;height:50px;margin-left: 100px;margin-top: 20px"></div>
    </body>
</html>

1.2 js代码

　　　　　　　　　 var eleLeft = $(\'#myDiv\').offset().left;
                var isMouseDown = false;
                var borderLen = 4; //左右边框
                
                $(\'#myDiv\').bind({
                    mousedown:function(e){
                        var ele = $(this);
                        var rightPos = eleLeft + ele.width() + borderLen;
                        if(rightPos-5 <= e.pageX && e.pageX <= rightPos){
                            isMouseDown = true;

                        }
                    },
            
                    mousemove:function(e){
                        var ele =  $(this);
                        var rightPos = eleLeft + ele.width() + borderLen;
                        $(\'#pos\').text("x:"+e.pageX + " eleLeft:"+eleLeft+" rightPos:"+rightPos);

                        if(rightPos-5 <= e.pageX && e.pageX <= rightPos){
                            ele.css(\'cursor\',\'e-resize\');
                        }else{
                            if(!isMouseDown){
                                ele.css(\'cursor\',\'auto\');
                            }
                        }
                        if(isMouseDown){
                            ele.width((e.pageX-eleLeft-borderLen)+\'px\');  //新鼠标位置-div距左-borderLen
                        }
                    },
                    mouseup:function(e){
                        isMouseDown = false;
                    }
                });

1.3 结果

只能往左拖动使div宽度变小，往右拖动没有用！原因往右拖动鼠标mousemove事件无法被div捕获了。拖动时也很难停下来！所以得改进。

2.再次改进

　　　　　　　　　　$(\'#myDiv\').bind({
                    mousedown:function(e){
                        var ele = $(this);
                        var rightPos = eleLeft + ele.width() + borderLen;
                        if(rightPos-5 <= e.pageX && e.pageX <= rightPos){
                            isMouseDown = true;
                        }
                    }
                });

                $(\'body\').bind({
                    mousemove:function(e){
                        var ele = $(\'#myDiv\');
                        var rightPos = eleLeft + ele.width() + borderLen;
                        $(\'#pos\').text("x:"+e.pageX + " eleLeft:"+eleLeft+" rightPos:"+rightPos);

                        if(rightPos-5 <= e.pageX && e.pageX <= rightPos){
                            ele.css(\'cursor\',\'e-resize\');
                        }else{
                            if(!isMouseDown){
                                ele.css(\'cursor\',\'auto\');
                            }
                        }
                        if(isMouseDown){
                            ele.width((e.pageX-eleLeft-borderLen)+\'px\');  
                        }
                    },
                    mouseup:function(e){
                        isMouseDown = false;
                    }
                });

这次解决了上述问题，可以往右拖，并且随时可以停下来了。到这里就完成了吗？NO!

当我引入一个其他div，并且阻止mouseup事件冒泡情况怎么样呢？答案是，拖动到这个其它div上放开鼠标后无法停止下来！

<div id="otherDiv" style="border: 2px solid blue;width: 200px;height: 200px;margin-left: 400px"></div>

　　　　　　　　　$(\'#otherDiv\').mouseup(function(e){
                    //e.preventDefault(); //阻止默认行为
                    e.stopPropagation(); //阻止事件冒泡(导致body捕获不到mouseup事件)
                });

3.完美解决

拖动停止可能受到其它元素的干扰，怎么解决？想到一些弹出层点击其它其它地方隐藏的功能，让我想到了，加一个遮罩层，让mouseup事件总是可以响应，不就搞定了嘛！

　　　　　　　　$(\'#myDiv\').bind({
                    mousedown:function(e){
                        var ele = $(this);
                        var rightPos = eleLeft + ele.width() + borderLen;
                        if(rightPos-5 <= e.pageX && e.pageX <= rightPos){
                            isMouseDown = true;

                            //创建遮罩层，防止mouseup事件被其它元素阻止冒泡，导致mouseup事件无法被body捕获，导致拖动不能停止
                            var bodyWidth = $(\'body\').width();
                            var bodyHeight = $(\'body\').height();
                            $(\'body\').append(\'<div id="mask" style="opacity:0.2;top:0px;left:0px;background-color:green;position:absolute;z-index:9999;width:\'+bodyWidth+\'px;height:\'+bodyHeight+\'px;"></div>\');
                        }
                    }
                });

                $(\'body\').bind({
                    mousemove:function(e){
                        var ele = $(\'#myDiv\');
                        var rightPos = eleLeft + ele.width() + borderLen;
                        $(\'#pos\').text("x:"+e.pageX + " eleLeft:"+eleLeft+" rightPos:"+rightPos);

                        if(rightPos-5 <= e.pageX && e.pageX <= rightPos){
                            ele.css(\'cursor\',\'e-resize\');
                        }else{
                            if(!isMouseDown){
                                ele.css(\'cursor\',\'auto\');
                            }
                        }
                        if(isMouseDown){
                            ele.width((e.pageX-eleLeft-borderLen)+\'px\'); 
                        }
                    },
                    mouseup:function(e){
                        isMouseDown = false;
                        $(\'#mask\').remove();
                    }
                });

                $(\'#otherDiv\').mouseup(function(e){
                    //e.preventDefault(); //阻止默认行为
                    e.stopPropagation(); //阻止事件冒泡(导致body捕获不到mouseup事件)
                });

4.完整代码和最终效果

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />

        <title>div change width by drag</title>

        <script src="../jQuery/jquery-1.8.3.min.js" type="text/javascript"></script>
        
        
    </head>

    <body>
        <h1>div change width by drag</h1>
        
        <div id="pos" style="color:red"></div>
        
        
        <div id="myDiv" style="border:2px solid red;width:300px;height:50px;margin-left: 100px;margin-top: 20px"></div>

        <div id="otherDiv" style="border: 2px solid blue;width: 200px;height: 200px;margin-left: 400px"></div>
    </body>
    

    <script type="text/javascript">
            $(document).ready(function(){
                var eleLeft = $(\'#myDiv\').offset().left;
                var isMouseDown = false;
                var borderLen = 4; //左右边框

                $(\'#myDiv\').bind({
                    mousedown:function(e){
                        var ele = $(this);
                        var rightPos = eleLeft + ele.width() + borderLen;
                        if(rightPos-5 <= e.pageX && e.pageX <= rightPos){
                            isMouseDown = true;

                            //创建遮罩层，防止mouseup事件被其它元素阻止冒泡，导致mouseup事件无法被body捕获，导致拖动不能停止
                            var bodyWidth = $(\'body\').width();
                            var bodyHeight = $(\'body\').height();
                            $(\'body\').append(\'<div id="mask" style="opacity:0.2;top:0px;left:0px;background-color:green;position:absolute;z-index:9999;width:\'+bodyWidth+\'px;height:\'+bodyHeight+\'px;"></div>\');
                        }
                    }
                });

                $(\'body\').bind({
                    mousemove:function(e){
                        var ele = $(\'#myDiv\');
                        var rightPos = eleLeft + ele.width() + borderLen;
                        $(\'#pos\').text("x:"+e.pageX + " eleLeft:"+eleLeft+" rightPos:"+rightPos);

                        if(rightPos-5 <= e.pageX && e.pageX <= rightPos){
                            ele.css(\'cursor\',\'e-resize\');
                        }else{
                            if(!isMouseDown){
                                ele.css(\'cursor\',\'auto\');
                            }
                        }
                        if(isMouseDown){
                            ele.width((e.pageX-eleLeft-borderLen)+\'px\'); 
                        }
                    },
                    mouseup:function(e){
                        isMouseDown = false;
                        $(\'#mask\').remove();
                    }
                });

                $(\'#otherDiv\').mouseup(function(e){
                    //e.preventDefault(); //阻止默认行为
                    e.stopPropagation(); //阻止事件冒泡(导致body捕获不到mouseup事件)
                });
            });
        </script>
</html>

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