Javascript 如何让这个HTML5画布绘制应用程序同时适用于触摸和鼠标事件？

以下是我尝试执行的操作的源代码：

Javascript:

    window.addEventListener('load', function () {
    // get the canvas element and its context
    var canvas = document.getElementById('sketchpad');
    var context = canvas.getContext('2d');

    // create a drawer which tracks touch movements
    var drawer = {
        isDrawing: false,
        touchstart: function (coors) {
            context.beginPath();
            context.moveTo(coors.x, coors.y);
            this.isDrawing = true;
        },
        touchmove: function (coors) {
            if (this.isDrawing) {
                context.lineTo(coors.x, coors.y);
                context.stroke();
            }
        },
        touchend: function (coors) {
            if (this.isDrawing) {
                this.touchmove(coors);
                this.isDrawing = false;
            }
        }
    };
    // create a function to pass touch events and coordinates to drawer
    function draw(event) {
        // get the touch coordinates
        var coors = {
            x: event.targetTouches[0].pageX,
            y: event.targetTouches[0].pageY
        };
        // pass the coordinates to the appropriate handler
        drawer[event.type](coors);
    }

    // attach the touchstart, touchmove, touchend event listeners.
    canvas.addEventListener('touchstart', draw, false);
    canvas.addEventListener('touchmove', draw, false);
    canvas.addEventListener('touchend', draw, false);

    // prevent elastic scrolling
    document.body.addEventListener('touchmove', function (event) {
        event.preventDefault();
    }, false); // end body.onTouchMove

}, false); // end window.onLoad

HTML:

我尝试为鼠标下/上/移动添加事件侦听器，但这些似乎不起作用

或者，如果有人对在计算机和平板电脑上运行的开源画布绘制应用程序有任何建议，我宁愿使用它

到目前为止，唯一引人注目的是，不幸的是，它不能在android平板电脑上运行（至少是我尝试过的那些）

我添加了一种在触摸设备中运行时进行检测的方法，以及一个将鼠标事件映射到触摸事件的开关

还请注意，当touchend发生时，我们需要使用

event.changedtouchs

来正确获取

coors

window.addEventListener('load', function () {
// get the canvas element and its context
var canvas = document.getElementById('sketchpad');
var context = canvas.getContext('2d');

// create a drawer which tracks touch movements
var drawer = {
    isDrawing: false,
    touchstart: function (coors) {
        context.beginPath();
        context.moveTo(coors.x, coors.y);
        this.isDrawing = true;
    },
    touchmove: function (coors) {
        if (this.isDrawing) {
            context.lineTo(coors.x, coors.y);
            context.stroke();
        }
    },
    touchend: function (coors) {
        if (this.isDrawing) {
            this.touchmove(coors);
            this.isDrawing = false;
        }
    }
};
// create a function to pass touch events and coordinates to drawer
function draw(event) { 
    var type = null;
    // map mouse events to touch events
    switch(event.type){
        case "mousedown":
                event.touches = [];
                event.touches[0] = { 
                    pageX: event.pageX,
                    pageY: event.pageY
                };
                type = "touchstart";                  
        break;
        case "mousemove":                
                event.touches = [];
                event.touches[0] = { 
                    pageX: event.pageX,
                    pageY: event.pageY
                };
                type = "touchmove";                
        break;
        case "mouseup":                
                event.touches = [];
                event.touches[0] = { 
                    pageX: event.pageX,
                    pageY: event.pageY
                };
                type = "touchend";
        break;
    }        

    // touchend clear the touches[0], so we need to use changedTouches[0]
    var coors;
    if(event.type === "touchend") {
        coors = {
            x: event.changedTouches[0].pageX,
            y: event.changedTouches[0].pageY
        };
    }
    else {
        // get the touch coordinates
        coors = {
            x: event.touches[0].pageX,
            y: event.touches[0].pageY
        };
    }
    type = type || event.type
    // pass the coordinates to the appropriate handler
    drawer[type](coors);
}

// detect touch capabilities
var touchAvailable = ('createTouch' in document) || ('ontouchstart' in window);

// attach the touchstart, touchmove, touchend event listeners.
if(touchAvailable){
    canvas.addEventListener('touchstart', draw, false);
    canvas.addEventListener('touchmove', draw, false);
    canvas.addEventListener('touchend', draw, false);        
}    
// attach the mousedown, mousemove, mouseup event listeners.
else {
    canvas.addEventListener('mousedown', draw, false);
    canvas.addEventListener('mousemove', draw, false);
    canvas.addEventListener('mouseup', draw, false);
}

// prevent elastic scrolling
document.body.addEventListener('touchmove', function (event) {
    event.preventDefault();
}, false); // end body.onTouchMove

}, false); // end window.onLoad

---

令人惊叹的！太棒了！我没有想过用这种方式检测触摸事件——我以前只是尝试在触摸事件之外添加鼠标事件。

body {
    margin:0;
    padding:0;
    font-family:Arial;
}
#container {
    position:relative;
}
#sketchpad {
    border: 1px solid #000;
}

window.addEventListener('load', function () {
// get the canvas element and its context
var canvas = document.getElementById('sketchpad');
var context = canvas.getContext('2d');

// create a drawer which tracks touch movements
var drawer = {
    isDrawing: false,
    touchstart: function (coors) {
        context.beginPath();
        context.moveTo(coors.x, coors.y);
        this.isDrawing = true;
    },
    touchmove: function (coors) {
        if (this.isDrawing) {
            context.lineTo(coors.x, coors.y);
            context.stroke();
        }
    },
    touchend: function (coors) {
        if (this.isDrawing) {
            this.touchmove(coors);
            this.isDrawing = false;
        }
    }
};
// create a function to pass touch events and coordinates to drawer
function draw(event) { 
    var type = null;
    // map mouse events to touch events
    switch(event.type){
        case "mousedown":
                event.touches = [];
                event.touches[0] = { 
                    pageX: event.pageX,
                    pageY: event.pageY
                };
                type = "touchstart";                  
        break;
        case "mousemove":                
                event.touches = [];
                event.touches[0] = { 
                    pageX: event.pageX,
                    pageY: event.pageY
                };
                type = "touchmove";                
        break;
        case "mouseup":                
                event.touches = [];
                event.touches[0] = { 
                    pageX: event.pageX,
                    pageY: event.pageY
                };
                type = "touchend";
        break;
    }        

    // touchend clear the touches[0], so we need to use changedTouches[0]
    var coors;
    if(event.type === "touchend") {
        coors = {
            x: event.changedTouches[0].pageX,
            y: event.changedTouches[0].pageY
        };
    }
    else {
        // get the touch coordinates
        coors = {
            x: event.touches[0].pageX,
            y: event.touches[0].pageY
        };
    }
    type = type || event.type
    // pass the coordinates to the appropriate handler
    drawer[type](coors);
}

// detect touch capabilities
var touchAvailable = ('createTouch' in document) || ('ontouchstart' in window);

// attach the touchstart, touchmove, touchend event listeners.
if(touchAvailable){
    canvas.addEventListener('touchstart', draw, false);
    canvas.addEventListener('touchmove', draw, false);
    canvas.addEventListener('touchend', draw, false);        
}    
// attach the mousedown, mousemove, mouseup event listeners.
else {
    canvas.addEventListener('mousedown', draw, false);
    canvas.addEventListener('mousemove', draw, false);
    canvas.addEventListener('mouseup', draw, false);
}

// prevent elastic scrolling
document.body.addEventListener('touchmove', function (event) {
    event.preventDefault();
}, false); // end body.onTouchMove

}, false); // end window.onLoad