我要求在画布绘图中输入控件/下拉列表。这就像我想从画布中获取用户的一些输入。在我的画布上有一些盒子，每个盒子可以拖放，一旦它在某个地方掉落然后我们的用户我修改它们（通过输入或从下拉列表中选择它来提供一些输入）。到目前为止，我能够绘制盒子并使可拖动和可拖动，这里是相同的JS小提琴 -
http://jsfiddle.net/akki166786/wa52f9pm/
<script type="text/javascript">
window.onload = function(){
draw();
}
</script>
<body style="margin: 0;padding:0;clear:both; cursor: pointer">
<canvas id="canvas" tabindex="1" style="float:left" ></canvas>
<div id="plainEnglish" tabindex="2" style="float: left;"></div>
</body>
<script>
var c = document.getElementById("canvas");
var ctx = c.getContext("2d");
c.width = 600;
c.height = 300;
//My mouse coordinates
var x,y;
c.addEventListener("mousedown",down);
c.addEventListener("mousemove",move);
c.addEventListener("mouseup",up);
var r = 0;
function counter() {
r++;
console.log(r);
}
//I'll save my boxes in this array
var myBoxes = new Array();
// Those boxes which I have moved to droppable area of the canvas.
var myDroppedBoxes = new Array();
//This function describes what a box is.
//Each created box gets its own values
function box(x,y,w,h,rgb,text) {
this.x = x,
this.y = y;
this.xS = x; //saving x
this.yS = y; //saving y
this.w = w;
this.h = h;
this.rgb = rgb;
this.text = text;
//to determine if the box is being draged
this.draging = false;
this.isBeingDragged = false;
}
//Let's make some boxes!!
myBoxes[0] = new box(20,20,75,20,"#6AA121","First");
myBoxes[1] = new box(20,50,75,20,"#6AA121", "Second");
myBoxes[2] = new box(20,80,75,20,"#6AA121","third");
//here we draw everything
function draw() {
ctx.clearRect(0,0,c.width,c.height);
//Dropable area
ctx.fillStyle="red";
ctx.fillRect(c.width/2,0,c.width,c.height);
//Boxes!
for (var i = 0; i<myBoxes.length; i++) {
var b = myBoxes[i];
if (b.draging) { //box on the move
//Also draw it on the original spot
ctx.fillStyle=b.rgb;
ctx.fillRect(b.xS,b.yS,b.w,b.h);
ctx.strokeRect(b.xS,b.yS,b.w,b.h);
ctx.font = "14px Arial";
ctx.strokeText(b.text, b.xS + 5 , b.yS + 15);
}
ctx.fillStyle=b.rgb;
ctx.fillRect(b.x,b.y,b.w,b.h);
ctx.strokeRect(b.x,b.y,b.w,b.h);
ctx.font = "14px Arial";
ctx.strokeText(b.text, b.x + 5 , b.y + 15);
}
for(var i = 0; i< myDroppedBoxes.length; i++) {
var b = myDroppedBoxes[i];
ctx.fillStyle=b.rgb;
ctx.fillRect(b.x,b.y,b.w,b.h);
ctx.strokeRect(b.x,b.y,b.w,b.h);
ctx.font = "14px Arial";
ctx.strokeText(b.text, b.x + 5 , b.y + 15);
}
}
function down(event) {
event = event || window.event;
x = event.pageX - c.offsetLeft,
y = event.pageY - c.offsetTop;
for (var i = 0; i<myBoxes.length; i++) {
var b = myBoxes[i];
if (x>b.xS && x<b.xS+b.w && y>b.yS && y<b.yS+b.h) {
myBoxes[i].draging = true;
myBoxes[i].isBeingDragged = true;
}
}
for (var i = 0; i<myDroppedBoxes.length; i++) {
var b = myDroppedBoxes[i];
if (x>b.x && x<b.x + b.w && y>b.y && y<b.y + b.h) {
b.draging = true;
b.isBeingDragged = true;
}
}
draw();
}
function move(event) {
event = event || window.event;
x = event.pageX - c.offsetLeft,
y = event.pageY - c.offsetTop;
for (var i = 0; i<myBoxes.length; i++) {
var b = myBoxes[i];
if (b.draging && b.isBeingDragged) {
myBoxes[i].x = x;
myBoxes[i].y = y;
if (b.x>c.width/2) {
var length = myDroppedBoxes.length ;
myDroppedBoxes[length] = new box(x,y,b.w,b.h,b.rgb,b.text);
myDroppedBoxes[length].draging = true;
myDroppedBoxes[length].isBeingDragged = true;
b.x = b.xS;
b.y = b.yS;
b.isBeingDragged = false;
}
}
}
for (var i = 0; i<myDroppedBoxes.length; i++) {
var b = myDroppedBoxes[i];
if (b.draging && b.isBeingDragged) {
b.x = x;
b.y = y;
}
}
draw();
}
function up(event) {
event = event || window.event;
x = event.pageX - c.offsetLeft,
y = event.pageY - c.offsetTop;
for (var i = 0; i< myBoxes.length; i++) {
var b = myBoxes[i];
if (b.draging && b.isBeingDragged) {
//Let's see if the rectangle is inside the dropable area
if (b.x < c.width/2) {
myBoxes[i].x = b.xS;
myBoxes[i].y = b.yS;
myBoxes[i].draging = false;
b.isBeingDragged = false;
}
}
}
for (var i = 0; i< myDroppedBoxes.length; i++) {
var b = myDroppedBoxes[i];
if ( b.isBeingDragged) {
//Let's see if the rectangle is inside the dropable area
if (b.x>c.width/2) {
b.x = x;
b.y = y;
clubLegos(b);
plainTextMaker();
b.isBeingDragged = false;
}
else {
//No it's not, sending it back to its original spot
myDroppedBoxes.splice(i,1);
}
}
}
draw();
}
function clubLegos(b) {
// this loop is for checking that the box is lying near to which other box.
for(var j = 0; j < myDroppedBoxes.length; j++) {
var z = myDroppedBoxes[j];
if(!z.isBeingDragged) {
if(((x > z.x) && (x < (z.x + z.w))) && ((y > (z.y - 15)) && (y < (z.y + z.h + 10)))) {
b.x = z.x;
if( (y - z.y) >= 0) {
b.y = (z.y + z.h);
console.log("inside if " + y + " " + z.y);
}
else {
console.log("inside else " + y + " " + z.y);
b.y = (z.y - z.h);
}
}
}
}
}
function plainTextMaker() {
plainEnglishDiv = document.getElementById("plainEnglish");
plainEnglishDiv.innerHTML = "<h3>Here I am generating some plain text based on each drag and drop</h3>";
}
</script>
</html>
目前有三个可拖动的盒子，我想把控件放在里面。当它们被丢弃到某处时，那些输入控件也应该在那个框内。
我不知道如何将控件放在画布中，我知道DOM元素不能进入画布。所以我必须通过绘制它们来创建输入控件或下拉列表的一瞥，但是如何？
提前致谢。
答案 0 :(得分：1)
简单地说画布是一个可编辑的图像，你可以自己创建一切。但这需要为每个元素编写所有动画。就像当您单击其中一个输入框（与拖动相同）时，一条线开始闪烁，表示您可以键入，此行应在您键入/删除时重新定位。如果你想要下拉，你应该编写崩溃/打开功能，蓝色选择值等...
因此，如果你的元素有点类似于基本的表单元素，那么我会选择更具DOM的解决方案。例如，彼此相邻的2个div，1个空，1个填充表单元素。当用户将元素拖动到空div时，您可以使用javascript将副本添加到其DOM中。 （如果你把div放在当前画布上，你可以重复使用很多代码）