画布在移动网络上获取触摸位置

   function getMouse(e) {
     var element = canvas, offsetX = 0, offsetY = 0;
     if (element.offsetParent) {
       do {
         offsetX += element.offsetLeft;
         offsetY += element.offsetTop;
       } while ((element = element.offsetParent));
     }
     mx = (e.pageX - offsetX) - LINE_WIDTH;
     my =( e.pageY - offsetY )- LINE_WIDTH;
   }
   function mouseDown(e){
     getMouse(e);
     clear(fctx);
     var l = lines.length;
     for (var i = l-1; i >= 0; i--) {
       draw(fctx,lines[i]);
       var imageData = fctx.getImageData(mx, my, 1, 1);
       if (imageData.data[3] > 0) {
         selectedObject = lines[i];
         isDrag = true;
         canvas.onmousemove = drag;
         clear(fctx);
       }
     }
   }
   function mouseUp(){
     isDrag = false;
   }
   canvas.onmousedown = mouseDown;
   canvas.onmouseup = mouseUp;
   canvas.addEventListener('touchstart', mouseDown, false);
   canvas.addEventListener('touchend', mouseUp, false);

从触摸事件生成鼠标事件

好吧，在这里看到这个问题有一段时间了，没有人会给出答案，我会给出一个。

与鼠标事件不同的触摸事件涉及与UI的许多接触点。为了适应这种情况，触摸事件提供了一系列触摸点。由于鼠标不能同时位于两个位置，因此为了获得最佳的用户体验，这两种交互方法应该单独处理。OP，因为你没有问检测设备是触摸还是鼠标驱动，我把它留给了另一个人来问。

同时处理

鼠标和触摸事件可以共存。在没有鼠标或触摸事件的设备上添加侦听器不是问题。缺少的输入接口根本不会生成任何事件。这使得为您的页面实现透明解决方案变得容易。

这取决于您喜欢哪个接口，以及在硬件不可用时模拟该接口。在这种情况下，我将从创建的任何触摸事件中模拟鼠标。

以编程方式创建事件

该代码使用MouseEvent对象来创建和调度事件。它使用简单，并且事件与真实的鼠标事件无法区分。有关MouseEvents的详细描述，请转到MDN MouseEvent

最基本的

创建鼠标点击事件并将其发送到文档

  var event = new MouseEvent( "click", {'view': window, 'bubbles': true,'cancelable': true});
  document.dispatchEvent(event);

您还可以将事件分派到各个元素。

  document.getElementById("someButton").dispatchEvent(event);

要监听事件，它与监听实际鼠标是一样的。

  document.getElementById("someButton").addEventListener(function(event){
        // your code
  ));

MouseEvent函数中的第二个参数用于添加有关事件的额外信息。例如，假设clientX和clientY是鼠标的位置，或者which或buttons是为其按下的按钮。

如果你看过mouseEvent，你就会知道它有很多特性。因此，在鼠标事件中发送的内容将取决于事件侦听器使用的内容。

触摸事件

触摸事件类似于鼠标。有touchstart、touchmove和touchend。它们的不同之处在于，它们提供了一系列位置，每个接触点一个项目。不确定最大值是多少，但对于这个答案，我们只对一个感兴趣。有关详细信息，请参阅MDN touchEvent。

我们需要做的是，对于只涉及一个接触点的触摸事件，我们希望在同一位置生成相应的鼠标事件。如果触摸事件返回多个接触点，我们无法知道它们的预期焦点在哪个，因此我们将忽略它们。

function touchEventHandler(event){
    if (event.touches.length > 1){  // Ignor multi touch events
        return;
    }
}

所以现在我们知道触摸是一个单一的接触，我们可以根据触摸事件中的信息创建鼠标事件。

最基本的

touch = event.changedTouches[0]; // get the position information
if(type === "touchmove"){        
    mouseEventType = "mousemove";   // get the name of the mouse event
                                    // this touch will emulate   
}else
if(type === "touchstart"){  
    mouseEventType = "mousedown";     // mouse event to create
}else
if(type === "touchend"){ 
    mouseEventType = "mouseup";     // ignore mouse up if click only
}
var mouseEvent = new MouseEvent( // create event
    mouseEventType,   // type of event
    {
        'view': event.target.ownerDocument.defaultView,
        'bubbles': true,
        'cancelable': true,
        'screenX':touch.screenX,  // get the touch coords 
        'screenY':touch.screenY,  // and add them to the 
        'clientX':touch.clientX,  // mouse event
        'clientY':touch.clientY,
});
// send it to the same target as the touch event contact point.
touch.target.dispatchEvent(mouseEvent);

现在，当用户只在一个位置触摸设备时，鼠标侦听器将接收mousedown、mousemove、mouseup事件。

错过点击

到目前为止一切都很好，但缺少一个鼠标事件，这也是必需的。"onClick"我不确定是否存在模棱两可的触摸事件，就像我看到的一个练习一样，我们必须有足够的信息来决定一组触摸事件是否可以被视为点击。

这将取决于开始和结束触摸事件之间的距离，超过几个像素以及拖动。这也将取决于时间长短。（虽然与鼠标不同）我发现人们倾向于点击，而鼠标可以被按住，而不是在释放时确认，或者拖动以取消，这不是人们使用触摸界面的方式。

因此，我记录了touchStart事件发生的时间。CCD_ 13及其起始位置。然后在touchEnd事件中，我找到了它移动的距离和此后的时间。如果它们都在我设置的限制之下，我还会生成一个鼠标点击事件和鼠标向上事件。

因此，这是将触摸事件转换为鼠标事件的基本方法。

某些代码

下面是一个名为mouseTouch的API，它可以实现我刚才解释的功能。它涵盖了简单绘图应用程序中所需的最基本的鼠标交互。

//                                _______               _     
//                               |__   __|             | |    
//    _ __ ___   ___  _   _ ___  ___| | ___  _   _  ___| |__  
//   | '_ ` _ ' / _ '| | | / __|/ _ ' |/ _ '| | | |/ __| '_ ' 
//   | | | | | | (_) | |_| '__ '  __/ | (_) | |_| | (__| | | |
//   |_| |_| |_|'___/ '__,_|___/'___|_|'___/ '__,_|'___|_| |_|
//                                                            
//    
// Demonstration of a simple mouse emulation API using touch events.
// Using touch to simulate a mouse.
// Keeping it clean with touchMouse the only pubic reference.
// See Usage instructions at bottom.
var touchMouse = (function(){
    "use strict";
    var timeStart, touchStart, mouseTouch, listeningElement, hypot;

    mouseTouch = {};  // the public object 
    // public properties.
    mouseTouch.clickRadius = 3; // if touch start and end within 3 pixels then may be a click
    mouseTouch.clickTime = 200; // if touch start and end in under this time in ms then may be a click
    mouseTouch.generateClick = true; // if true simulates onClick event
                                     // if false only generate mousedown, mousemove, and mouseup
    mouseTouch.clickOnly = false; // if true on generate click events
    mouseTouch.status = "Started."; // just for debugging

    // ES6 new math function
    // not sure the extent of support for Math.hypot so hav simple poly fill
    if(typeof Math.hypot === 'function'){
        hypot = Math.hypot;
    }else{
        hypot = function(x,y){  // Untested 
            return Math.sqrt(Math.pow(x,2)+Math.pow(y,2));
        };
    }
    // Use the new API and MouseEvent object
    function triggerMouseEvemt(type,fromTouch,fromEvent){
      var mouseEvent = new MouseEvent(
          type, 
          {
              'view': fromEvent.target.ownerDocument.defaultView,
              'bubbles': true,
              'cancelable': true,
                'screenX':fromTouch.screenX,
                'screenY':fromTouch.screenY,
                'clientX':fromTouch.clientX,
                'clientY':fromTouch.clientY,
                'offsetX':fromTouch.clientX, // this is for old Chrome 
                'offsetY':fromTouch.clientY,
                'ctrlKey':fromEvent.ctrlKey,
                'altKey':fromEvent.altKey,
                'shiftKey':fromEvent.shiftKey,
                'metaKey':fromEvent.metaKey,
                'button':0,
                'buttons':1,
          });
        // to do.
        // dispatch returns cancelled you will have to 
        // add code here if needed
        fromTouch.target.dispatchEvent(mouseEvent);
    }
    // touch listener. Listens to Touch start, move and end.
    // dispatches mouse events as needed. Also sends a click event
    // if click falls within supplied thresholds and conditions
    function emulateMouse(event) {
        var type, time, touch, isClick, mouseEventType, x, y, dx, dy, dist;
        event.preventDefault();  // stop any default happenings interfering
        type = event.type ;  // the type.
        // ignore multi touch input
        if (event.touches.length > 1){
            if(touchStart !== undefined){ // don't leave the mouse down
                triggerMouseEvent("mouseup",event.changedTouches[0],event);
            }
            touchStart = undefined;
            return;
        }
        mouseEventType = "";
        isClick = false;  // default no click
        // check for each event type I have the most numorus move event first, Good practice to always think about the efficancy for conditional coding.
        if(type === "touchmove" && !mouseTouch.clickOnly){        // touchMove
            touch = event.changedTouches[0];
            mouseEventType = "mousemove";      // not much to do just move the mouse
        }else
        if(type === "touchstart"){  
            touch = touchStart = event.changedTouches[0]; // save the touch start for dist check
            timeStart = event.timeStamp; // save the start time
            mouseEventType = !mouseTouch.clickOnly?"mousedown":"";     // mouse event to create
        }else
        if(type === "touchend"){  // end check time and distance
            touch =  event.changedTouches[0];
            mouseEventType = !mouseTouch.clickOnly?"mouseup":"";     // ignore mouse up if click only
            // if click generator active
            if(touchStart !== undefined && mouseTouch.generateClick){
                time = event.timeStamp - timeStart;  // how long since touch start
                // if time is right
                if(time < mouseTouch.clickTime){
                    // get the distance from the start touch
                    dx = touchStart.clientX-touch.clientX;
                    dy = touchStart.clientY-touch.clientY;
                    dist = hypot(dx,dy);
                    if(dist < mouseTouch.clickRadius){
                        isClick = true;
                    }
                }
            }
        }
        // send mouse basic events if any
        if(mouseEventType !== ""){
            // send the event
            triggerMouseEvent(mouseEventType,touch,event);
        }
        // if a click also generates a mouse click event
        if(isClick){
            // generate mouse click
            triggerMouseEvent("click",touch,event);
        }
    }
    // remove events
    function removeTouchEvents(){
        listeningElement.removeEventListener("touchstart", emulateMouse);
        listeningElement.removeEventListener("touchend", emulateMouse);
        listeningElement.removeEventListener("touchmove", emulateMouse);
        listeningElement = undefined;  
    }
    // start  adds listeners and makes it all happen.
    // element is optional and will default to document.
    // or will Listen to element.
    function startTouchEvents(element){
        if(listeningElement !== undefined){ // untested
            // throws to stop cut and past useage of this example code.
            // Overwriting the listeningElement can result in a memory leak.
            // You can remove this condition block and it will work
            // BUT IT IS NOT RECOGMENDED
            throw new ReferanceError("touchMouse says!!!! API limits functionality to one element.");
        }
        if(element === undefined){
            element = document;
        }
        listeningElement = element;
        listeningElement.addEventListener("touchstart", emulateMouse);
        listeningElement.addEventListener("touchend", emulateMouse);
        listeningElement.addEventListener("touchmove", emulateMouse);
    }
    // add the start event to public object.
    mouseTouch.start = startTouchEvents;
    // stops event listeners and remove them from the DOM 
    mouseTouch.stop = removeTouchEvents;
    return mouseTouch;
})(); 





// How to use
touchMouse.start(); // done using defaults will emulate mouse on the entier page 
// For one element and only clicks
// HTML
<input value="touch click me" id="touchButton" type="button"></input>
// Script
var el = document.getElementById("touchButton");
if(el !== null){
    touchMouse.clickOnly = true;
    touchMouse.start(el);
}
// For drawing on a canvas
<canvas id="touchCanvas"></canvas> 
// script
var el = document.getElementById("touchButton");
if(el !== null){
    touchMouse.generateClick = false; // no mouse clicks please
    touchMouse.start(el);
}
// For switching elements call stop then call start on the new element
// warning touchMouse retained a reference to the element you
// pass it with start. Dereferencing touchMouse will not delete it.
// Once you have called start you must call stop in order to delete it.
// API
//---------------------------------------------------------------
// To dereference call the stop method if you have called start . Then dereference touchMouse
// Example
touchMouse.stop();
touchMouse = undefined;

// Methods.
//---------------------------------------------------------------
// touchMouse.start(element); // element optional. Element is the element to attach listeners to.
                              // Calling start a second time without calling stop will
                              // throw a reference error. This is to stop memory leaks.
                              // YOU Have been warned...
// touchMouse.stop();          // removes listeners and dereferences any DOM objects held
//---------------------------------------------------------------
// Properties
// mouseTouch.clickRadius = 3; // Number. Default 3. If touch start and end within 3 pixels then may be a click
// mouseTouch.clickTime = 200; // Number. Default 200. If touch start and end in under this time in ms then may be a click
// mouseTouch.generateClick;   // Boolean. Default true. If true simulates onClick event
//                                    // if false only generate mousedown, mousemove, and mouseup
// mouseTouch.clickOnly;      // Boolean.  Default false. If true only generate click events Default false
// mouseTouch.status;         // String. Just for debugging kinda pointless really. 

希望这能帮助您编写代码。