Question

我有一个基于动画的画布，在鼠标悬停时为雨滴设置动画，动画在鼠标移动时停止。我有提交的文本框应该在画布上显示文本。但是当我再次移出和鼠标悬停时，此文本消失。我知道画布在鼠标悬停时重绘，但我无法确定如何使文本保持原样。谢谢！

我已根据此处提供的解决方案调整了代码=＆gt; Random images falling like rain in canvas (Javascript)

的Javascript

var ctx;
var imgBg;
var imgDrops;
var x = 0;
var y = 0;
var noOfDrops = 7;
var fallingDrops = [];
var intV;

imgBg = new Image();
imgBg.src = "image.jpg";
var canvas = document.getElementById('canvasRegn');
ctx = canvas.getContext('2d');
ctx.drawImage(imgBg,0,0,600,450); //Background

function draw() {
    ctx.drawImage(imgBg, 0, 0,600,450); //Background

    for (var i=0; i< noOfDrops; i++)
    {
    ctx.drawImage (fallingDrops[i].image, fallingDrops[i].x, fallingDrops[i].y); //The rain drop

    fallingDrops[i].y += fallingDrops[i].speed;
    fallingDrops[i+4].x += fallingDrops[i].speed-1;//Set the falling speed
    if (fallingDrops[i].y > 450) {  //Repeat the raindrop when it falls out of view
    fallingDrops[i].y = -120; //Account for the image size
    fallingDrops[i].x = Math.random() * 600;    //Make it appear randomly along the width    
    }

    }
}

function setup() {

    intV = setInterval(function(){draw()}, 36);
    for (var i = 0; i < noOfDrops; i++) {
        var fallingDr = new Object();
        fallingDr["image"] =  new Image();
        fallingDr.image.src = "Rain.svg";       
        fallingDr["x"] = Math.random() * 600;
        fallingDr["y"] = Math.random() * 5;
        fallingDr["speed"] = 3 + Math.random() * 5;
        fallingDrops.push(fallingDr);

        }
}
function start(){
setup();
}

function stop(){
    clearInterval(intV);
}

function clicked(){
    var x=document.getElementById("form_val");
    ctx.clearRect(0,0,600,400);
    ctx.font="36px Verdana";
    ctx.fillStyle="yellow";
    ctx.strokeStyle="green";
    ctx.lineWidth=2;
    ctx.strokeText(x.value,200,200);
    ctx.fillText(x.value,200,200);
}

HTML

<canvas id="canvasRegn" width="600" height="450"style="margin:10px;" onmouseover="start()" onmouseout="stop()">
</canvas>
<br>
<input type="text" name="fname" size="50" id="form_val">
<button id="submit" onclick="clicked()">Submit</button>

Answer 1

每次重绘画布时都需要重新绘制文本框，我会亲自重命名“clicked（）”并从“draw（）”内部调用它（在drop之前或之后，取决于你是否希望它出现上面或下面）

您还必须从“clicked（）”中删除ctx.clearRect（），否则它将覆盖下雨（如果您将其置于顶部）

然后你需要编辑它的调用方式，clicked（）函数可以设置一个在draw函数中检查的布尔变量（如果为true，则绘制文本框）

伪代码示例：

var text = false
draw(){
    drawRain()
    if(text == true){drawText()}
}
clicked(){
    text = true
}

然后，如果您希望文本框可编辑，则可以在drawText（）中使用变量而不是固定值。

在drawText（）之外

fontVar = "36px Verdana";
fillColour = "yellow";
strokeColour = "green";

在drawText（）

中

ctx.font=fontVar;
ctx.fillStyle=fillColour;
ctx.strokeStyle=strokeColour;

Answer 2

这个问题的答案在于铺设两个画布层。第一个Canvas图层将具有背景图像和动画效果。它上面的第二层将绘制文本。注意：感谢@DBS寻找解决方案。

<强>的JavaScript ：

script type="text/javascript">
var ctx;
var ctx2
var imgBg;
var imgDrops;
var x = 0;
var y = 0;
var noOfDrops = 20;
var fallingDrops = [];
var intV;
fontVar ="36px Verdana";
fillColour="yellow";
strokeColour="green";

imgBg = new Image();
imgBg.src = "image.jpg";
var canvas = document.getElementById('myCanvas');
ctx = canvas.getContext('2d');
ctx.drawImage(imgBg,0,0,600,400); //Background

var canvas2 = document.getElementById('drawText');
ctx2 = canvas2.getContext('2d');

function drawing(){
ctx.drawImage(imgBg,0,0,600,400); //Background
}

function draw() {
    ctx.drawImage(imgBg, 0, 0,600,400); //Background    
    for (var i=0; i< noOfDrops; i++)
    {

    ctx.drawImage (fallingDrops[i].image, fallingDrops[i].x, fallingDrops[i].y,35,35); //The rain drop

    fallingDrops[i].y += fallingDrops[i].speed;
    fallingDrops[i+7].x += fallingDrops[i].speed-1;//Set the falling speed
    if (fallingDrops[i].y > 400) {  //Repeat the raindrop when it falls out of view
        fallingDrops[i].y = -120; //Account for the image size
        fallingDrops[i].x = Math.random() * 600;    //Make it appear randomly along the width    
        }
    }       
}


function setup() {

    intV = setInterval(function(){draw()}, 36);
    for (var i = 0; i < noOfDrops; i++) {
        var fallingDr = new Object();
        fallingDr["image"] =  new Image();
        fallingDr.image.src = "Rain.svg";       
        fallingDr["x"] = Math.random() * 600;
        fallingDr["y"] = Math.random() * 5;
        fallingDr["speed"] = 3 + Math.random() * 5;
        fallingDrops.push(fallingDr);

        }
}
function start(){
setup();
}

function stop(){
    clearInterval(intV);
}

function clicked(){
    z=document.getElementById("form_val");
    ctx2.clearRect(0,0,600,400);
    ctx2.font=fontVar;
    ctx2.fillStyle=fillColour;
    ctx2.strokeStyle=strokeColour;
    ctx2.lineWidth=2;
    ctx2.strokeText(z.value,200,200);
    ctx2.fillText(z.value,200,200);
}

</script>

<强> HTML

<div class="wrapper">
<canvas id="myCanvas" width="600" height="400" style="margin:1px;"></canvas>
<canvas id="drawText" width="600" height="400" onmouseover="start()" onmouseout="stop()</canvas>
</div>
<br>
Greeting Message: <input type="text" name="fname" size="50" id="form_val">
<button id="submit" onclick="clicked()">Add this message</button>
</div>

<强> CSS

How can I stack two same-sized canvas on top of each other?

HTML5画布上的文本和动画

2 个答案: