為什么只顯示出一個12呢???
countdown.js
var WINDOW_WIDTH = 1024;
var WINDOW_HEIGHT = 768;
var RADIUS = 8;
var MARGIN_TOP = 60;
var MARGIN_LEFT = 30;
window.onload = function(){
? ? var canvas = document.getElementById('canvas');
? ? var context = canvas.getContext("2d");
? ? canvas.width = WINDOW_WIDTH;
? ? canvas.height = WINDOW_HEIGHT;
? ? render( context );
};
function render( cxt ){
? ? var hours = 12;
? ? var minutes = 34;
? ? var seconds = 56;
? ? renderDigit( MARGIN_LEFT , MARGIN_TOP , parseInt(hours/10) , cxt );
? ? renderDigit( MARGIN_LEFT + 15*(RADIUS+1) , MARGIN_TOP , parseInt(hours%10) , cxt );
? ? renderDigit( MARGIN_LEFT + 30*(RADIUS + 1) , MARGIN_TOP , 10 , cxt );
? ? renderDigit( MARGIN_LEFT + 39*(RADIUS+1) , MARGIN_TOP , parseInt(minutes/10) , cxt);
? ? renderDigit( MARGIN_LEFT + 54*(RADIUS+1) , MARGIN_TOP , parseInt(minutes%10) , cxt);
? ? renderDigit( MARGIN_LEFT + 69*(RADIUS+1) , MARGIN_TOP , 10 , cxt);
? ? renderDigit( MARGIN_LEFT + 78*(RADIUS+1) , MARGIN_TOP , parseInt(seconds/10) , cxt);
? ? renderDigit( MARGIN_LEFT + 93*(RADIUS+1) , MARGIN_TOP , parseInt(seconds%10) , cxt);
}
function renderDigit( x , y , num , cxt ){
? ? cxt.fillStyle = "rgb(0,102,153)";
? ? for( var i = 0 ; i < digit[num].length ; i ++ )
? ? ? ? for(var j = 0 ; j < digit[num][i].length ; j ++ )
? ? ? ? ? ? if( digit[num][i][j] == 1 ){
? ? ? ? ? ? ? ? cxt.beginPath();
? ? ? ? ? ? ? ? cxt.arc( x+j*2*(RADIUS+1)+(RADIUS+1) , y+i*2*(RADIUS+1)+(RADIUS+1) , RADIUS , 0 , 2*Math.PI );
? ? ? ? ? ? ? ? cxt.closePath();
? ? ? ? ? ? ? ? cxt.fill();
? ? ? ? ? ? }
}
2017-10-08
要這么改:
2017-09-30
瀏覽器報錯了,顯示Uncaught TypeError: Cannot read property 'getContext' of null
2017-09-30
因為context = null 是空的