Fabric.js - 如何爲畫布加載事件給出回調

Question

我從JSON對象加載畫布並調用toDataURL但我需要一個回調，它將在畫布加載後執行，因爲如果畫布上有圖像，toDataURL函數返回因爲在圖像加載之前調用了空白頁面。

canvas.loadFromJSON(json); 

// I need an event handler here which will be executed after canvas is loaded 

var dataURL = canvas.toDataURL(); 

Answer 1

您可以使用回叫loadFromJSON（URL，回調）

<pre> 
     canvas.loadFromJSON(url, function() { 
      //first render 
      canvas.renderAll.bind(canvas); 
      //before call to zoomOut(); 
      zoomOut(); 
     }); 



function zoomOut() { 
     var objects = canvas.getObjects(); 
     console.debug(objects); 
    ...... 
    }