html5弹跳球示例代码_HTML5教程-查字典教程网

<html>

<head>

//box

var box_x=0;

var box_y=0;

var box_width=300;

var box_height=300;

//注意:定位球采用球的中心

var ball_x=10;

var ball_y=10;

var ball_radius=10;

var ball_vx=5;

var ball_vy=3;

var box_bound_left=box_x+ball_radius;

var box_bound_right=box_x+box_width-ball_radius;

var box_bound_top=box_y+ball_radius;

var box_bound_bottom=box_y+box_height-ball_radius;

//ball

//context

var ctx;

function init()

{

ctx=document.getElementById('canvas').getContext('2d');

ctx.lineWidth=ball_radius;

ctx.fill;

move_ball();

setInterval(move_ball,100);//note

}

function move_ball()

{

ctx.clearRect(box_x,box_y,box_width,box_height);

move_and_check();

ctx.beginPath();

ctx.arc(ball_x,ball_y,ball_radius,0,Math.PI*2,true);

ctx.fill();

ctx.strokeRect(box_x,box_y,box_width,box_height);

}

function move_and_check()

{

var cur_ball_x=ball_x+ball_vx;

var cur_ball_y=ball_y+ball_vy;

if(cur_ball_x<box_bound_left)

{

ball_vx=-ball_vx;

cur_ball_x=box_bound_left;

}

if(cur_ball_x>box_bound_right)

{

ball_vx=-ball_vx;

cur_ball_x=box_bound_right;

}

if(cur_ball_y<box_bound_top)

{

ball_vy=-ball_vy;

cur_ball_y=box_bound_top;

}

if(cur_ball_y>box_bound_bottom)

{

ball_vy=-ball_vy;

cur_ball_y=box_bound_bottom;

}

ball_x=cur_ball_x;

ball_y=cur_ball_y;

}

</script>

</head>

</body>

</html>