Question

本周末试图制作我的第一场比赛。我终于让我的矩形与我的地图同时出现了。我的矩形可以移动！但是当我单击按钮移动它时，地图就会消失。这是我需要制作某种游戏循环的地方，以便在每次点击按钮时更新地图或在其上设置计时器吗？或者我还有其他一些错误？谢谢大家！

   var canvas = <HTMLCanvasElement>document.getElementById('myCanvas');
var context = canvas.getContext("2d");
var img = new Image();
img.onload = function () {
    context.drawImage(img, 0, 0);
}
img.src = "";



var mapArray =
       ["############################",
        "#      #    #      o      ##",
        "#                          #",
        "#   ####   #####    ##     #",
        "##         #   #    ##     #",
        "###           ##     #     #",
        "#           ###      #     #",
        "#   ####          ###      #",
        "#   ##    #  o             #",
        "# o  #    #    o ###   ### #",
        "#    #    #                #",
        "############################"];

//need to add wall.scource =  and grass.source =
var wall = new Image();
var grass = new Image();
grass.src = "http://vignette2.wikia.nocookie.net/tibia/images/6/60/Grass_(Tile).gif/revision/latest?cb=20080817072800&path-prefix=en";
wall.src = "data:image/jpeg;base64,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";


var posX = 0;
var posY = 0;




//for loops set images at given coordinates according to position on mapArray
for (var y = 0; y < mapArray.length; y++) {
    for (var x = 0; x < mapArray[0].length; x++) {

        if (mapArray[y][x] == "") {
            context.drawImage(grass, (32 * x), (32 * y), 32, 32)//last two are size of image )
        }
        if (mapArray[y][x] == "#") {
            context.drawImage(wall, (32 * x), (32 * y), 32, 32)//last two are size of image )
        }
 }
}

context.rect(posX, posY, 32, 32)
context.stroke();//traces path, might not need this


//moves character
function move(e) {//next five lines are newly added. Final line of function is drawimage function that is new as well
    var ctx = canvas.getContext('2d');// create backing canvas
    var backCanvas = document.createElement('canvas');
    backCanvas.width = canvas.width;
    backCanvas.height = canvas.height;
    var backCtx = backCanvas.getContext('2d');

    //alert(e.keyCode);//gives feedback to what each keyCode is
    if (e.keyCode == 39) {
        posX += 5;
    }
    if (e.keyCode == 37) {
        posX -= 5;
    }
    if (e.keyCode == 40) {
        posY += 5;
    }
    if (e.keyCode == 38) {
        posY -= 5;

    }
    canvas.width = canvas.width;//clears the board after each move
    context.rect(posX, posY, 32, 32)
    context.stroke();
    ctx.drawImage(backCanvas, 0, 0);
}    
document.onkeydown = move;

Answer 1

是的，您的canvas.width = canvas.width;将清除画布，移动后您最终只能使用rect。也可以在移动函数中执行所有渲染代码，或者为地图创建一个备份画布，以便您可以在移动函数的顶部有效地渲染它，而无需每次都单步执行mapArray。在这里，他们使用备用画布：html5: copy a canvas to image and back

基于备份画布理念的代码：

var canvas = <HTMLCanvasElement>document.getElementById('myCanvas');
var context = canvas.getContext("2d");
var img = new Image();
img.onload = function () {
    context.drawImage(img, 0, 0);
}
img.src = "";



var mapArray =
       ["############################",
        "#      #    #      o      ##",
        "#                          #",
        "#   ####   #####    ##     #",
        "##         #   #    ##     #",
        "###           ##     #     #",
        "#           ###      #     #",
        "#   ####          ###      #",
        "#   ##    #  o             #",
        "# o  #    #    o ###   ### #",
        "#    #    #                #",
        "############################"];

//need to add wall.scource =  and grass.source =
var wall = new Image();
var grass = new Image();
grass.src = "http://vignette2.wikia.nocookie.net/tibia/images/6/60/Grass_(Tile).gif/revision/latest?cb=20080817072800&path-prefix=en";
wall.src = "data:image/jpeg;base64,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";


var posX = 0;
var posY = 0;




//for loops set images at given coordinates according to position on mapArray
for (var y = 0; y < mapArray.length; y++) {
    for (var x = 0; x < mapArray[0].length; x++) {

        if (mapArray[y][x] == "") {
            context.drawImage(grass, (32 * x), (32 * y), 32, 32)//last two are size of image )
        }
        if (mapArray[y][x] == "#") {
            context.drawImage(wall, (32 * x), (32 * y), 32, 32)//last two are size of image )
        }
 }
}

// Here you've rendered the static content and you want to save the state of the canvas in a backup at this point:

// create backing canvas
var backCanvas = document.createElement('canvas');
backCanvas.width = canvas.width;
backCanvas.height = canvas.height;
var backCtx = backCanvas.getContext('2d');

// save main canvas contents
backCtx.drawImage(canvas, 0,0);

context.rect(posX, posY, 32, 32)
context.stroke();//traces path, might not need this


//moves character
function move(e) {

    canvas.width = canvas.width;//clears the board after each move (not really necessary since we'll draw the backCanvas over it...)

    // Render the backup canvas here
    context.drawImage(backCanvas, 0,0);

    //alert(e.keyCode);//gives feedback to what each keyCode is
    if (e.keyCode == 39) {
        posX += 5;
    }
    if (e.keyCode == 37) {
        posX -= 5;
    }
    if (e.keyCode == 40) {
        posY += 5;
    }
    if (e.keyCode == 38) {
        posY -= 5;

    }
    context.rect(posX, posY, 32, 32)
    context.stroke();
}    
document.onkeydown = move;

Answer 2

jsFiddle：https://jsfiddle.net/j353agny/3/

var canvas = document.getElementById('myCanvas');
var context = canvas.getContext("2d");

var mapArray = ["############################",
    "#      #    #      o      ##",
    "#                          #",
    "#   ####   #####    ##     #",
    "##         #   #    ##     #",
    "###           ##     #     #",
    "#           ###      #     #",
    "#   ####          ###      #",
    "#   ##    #  o             #",
    "# o  #    #    o ###   ### #",
    "#    #    #                #",
    "############################"];

//need to add wall.scource =  and grass.source =
var wall = new Image();
var grass = new Image();
grass.src = "http://vignette2.wikia.nocookie.net/tibia/images/6/60/Grass_(Tile).gif/revision/latest?cb=20080817072800&path-prefix=en";
wall.src = "data:image/jpeg;base64,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";

// Player position

var posX = 0;
var posY = 0;

//moves character
function move(e) {

    //alert(e.keyCode);//gives feedback to what each keyCode is
    if (e.keyCode == 39) {
        posX += 5;
    }
    if (e.keyCode == 37) {
        posX -= 5;
    }
    if (e.keyCode == 40) {
        posY += 5;
    }
    if (e.keyCode == 38) {
        posY -= 5;

    }
}

document.onkeydown = move;

// every 3 miliseconds re-draw the stage with the player
setInterval(function () {
    console.log("REDRAW");
    // Clear the canvas and redraw
    context.fillStyle = "#FFF";
    context.fillRect(0,0,800,600);

    //for loops set images at given coordinates according to position on mapArray
    for (var y = 0; y < mapArray.length; y++) {
        for (var x = 0; x < mapArray[0].length; x++) {

            if (mapArray[y][x] == "") {
                context.drawImage(grass, (32 * x), (32 * y), 32, 32) //last two are size of image )
            }
            if (mapArray[y][x] == "#") {
                context.drawImage(wall, (32 * x), (32 * y), 32, 32) //last two are size of image )
            }
        }
    }
    context.fillStyle = "#00F";
    context.fillRect(posX, posY, 32, 32)
}, 3);

你可以做的只是使用一个每3毫秒运行一次的setInterval。基本上每3毫秒我就会画布重绘你的墙，然后重新绘制你的玩家。这将阻止你有任何奇怪的绘图问题。

P.S。您可以使用requestAnimationFrame代替setInterval来告诉您

为什么每次我的精灵移动时我的地图都会消失？

2 个答案: