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我正在使用此代码在画布上绘制图像并且它成功在画布上绘制图像现在我想在画布上移动图像为此我编写代码我检查是否按下键盘的右键我将增加 x如果按下左键，图像的坐标我将减少 x 坐标，但图像不会在画布上移动

player = new Image();
player.src = "game_character.png";
context.drawImage(player,player.x * wallDim + wallDim ,player.y * wallDim + wallDim ,50,50);

如何在画布上移动图像

 var handleInput = function(event, keyState) {
        switch(event.which) {
              case 37: { // Left Arrow
                    keyDown.arrowLeft = keyState;
                    break;
              }
              case 38: { // Up Arrow
                    keyDown.arrowUp = keyState;
                    break;
              }
              case 39: { // Right Arrow
                    keyDown.arrowRight = keyState;
                    break;
              }
              case 40: { // Down Arrow
                    keyDown.arrowDown = keyState;
                    break;
              }
        }
  }

  /**
  * physics
  *
  * This function contains the basic logic for the maze.
  */
  var physics = function() {
       console.log("physics ");
       console.log("first condition "+keyDown.arrowRight +player.x+1);
        if(keyDown.arrowLeft && player.x-1 >= 0 && map[player.y][player.x-1] != 1) {
              player.x--;
              redraw = true;
        }

        if(keyDown.arrowUp && player.y-1 >= 0 && map[player.y-1][player.x] != 1) {
              player.y--;
              redraw = true;
        }

        if(keyDown.arrowRight && player.x+1 < map[0].length && map[player.y][player.x+1] != 1) {
              console.log("arrow right");
              player.x++;
              redraw = true;
        }

        if(keyDown.arrowDown && player.y+1 < map.length && map[player.y+1][player.x] != 1) {
              player.y++;
              redraw = true;
        }
        if(keyDown.arrowRight && player.x+1 >= map[0].length)
        {
            player.x++;
            document.getElementById("canvas_div").style.display="none";
            document.getElementById("end_screen_div").style.display="block";
            //alert("completed");
        }
  }

  /**
  * draw
  *
  * This function simply draws the current state of the game.
  */
  var draw = function() {

        // Don't redraw if nothing has changed
        if(!redraw)
              return;

        context.clearRect(0, 0, cols, rows);
        context.beginPath();

        // Draw the maze
        for(var a = 0; a < rows; a++) {
              for(var b = 0; b < cols; b++) {
                    switch(map[a][b]) {
                          case C.EMPTY: context.fillStyle = colors.empty; break;
                          case C.WALL: context.fillStyle = colors.wall; break;
                    }

                        context.fillRect(b * wallDim, a * wallDim, wallDim, wallDim); // x, y, width, height
              }
        }

        // Draw the player
     /* context.fillStyle = colors.player;
        context.arc(
              player.x * wallDim + wallDim / 2, // x position
              player.y * wallDim + wallDim / 2, // y position
              wallDim / 2, // Radius
              0, // Starting angle
              Math.PI * 2, // Ending angle
              true // antiClockwise
        );*/


    player = new Image();
    player.src = "game_character.png";

    context.drawImage(player,player.x * wallDim + wallDim ,player.y * wallDim + wallDim ,50,50);

    var firstplayer=new Image();
    firstplayer.src="top_character01.png";

    context.drawImage(firstplayer,680,0,60,60);

    var secondplayer= new Image();
    secondplayer.src="top_character02.png";

    context.drawImage(secondplayer,750,0,60,60);

    context.fill();
    context.closePath();

        redraw = false;
  }
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2 回答 2

0

在您的 draw 方法中，您每次都重新初始化播放器：

player = new Image();
player.src = "game_character.png";

因此，您删除了由事件处理程序修改的 player.x。

您应该只在绘图函数之外初始化播放器一次。您可以像这样移动初始化：

var player = new Image();
player.src = "game_character.png";
var draw = function() {

绝对不需要player.src = "game_character.png";在绘图函数内部调用。

作为一般规则，在处理动画时，尽量从绘图函数中删除所有可以删除的内容，这应该尽可能快。

于 2012-07-05T13:08:10.660 回答
0

每次都需要重新绘制画布。像这样的东西：

function init()
{
    canvas = document.getElementById("canvas");
    context = canvas.getContext("2d");

    x = canvas.width / 2; //align to centre of the screen
    y = canvas.height / 2; //same as above

    speed = 5; //speed for the player to move at

    width = 50; //width of the player
    height = 50; //height of the player

    playerimage = new Image();
    playerimage.src = "path/to/image/for/player"; //path to the image to use for the player

    canvas.addEventListener("keypress", update);
}

function update(event)
{
    if (event.keyCode == 38)
    {
        y -= speed; //going up
    }
    if (event.keyCode == 40)
    {
        y += speed; //going down
    }
    if (event.keyCode == 37)
    {
        x -= speed; //going left
    }
    if (event.keyCode == 39)
    {
        x += speed; //going right
    }
    render();
}

function render()
{
    context.clearRect(0, 0, canvas.width, canvas.height);
    context.drawImage(playerimage, x, y, width, height);
}

我还没有测试过，所以我不知道它是否有效，并且可能会出现一些错误。它应该工作！如果不出意外，它将（希望）让您了解一种可以进行此操作的方法...

于 2012-07-05T13:16:40.360 回答