如何檢測谷歌地圖標記圖像無法加載提供默認圖像？

Question

按照Google Maps API中的示例代碼（為簡潔起見截斷），如何檢查標記圖像無法加載並使用其他/默認圖像？

var image = {
  url: 'https://broken.url.com/no-such-image.png',
  size: new google.maps.Size(20, 32),
  origin: new google.maps.Point(0, 0),
  anchor: new google.maps.Point(0, 32)
};

var marker = new google.maps.Marker({
  position: {lat: -33.890542, lng: 151.274856},
  map: map,
  icon: image,
  title: 'Marker demo',
  zIndex: 1
});

Answer 1

您可以嘗試使用javascript加載圖像。 如果可以加載（觸發onload事件），則添加帶圖像的標記，否則（觸發onerror事件）回退到其他東西（例如默認標記沒有圖像）：

var image = new Image();
var image_url = "https://broken.url.com/no-such-image.png";
image.onload = function () {
   console.info("Image loaded, adding marker with image !");
   var marker = new google.maps.Marker({
        position: {lat: -33.890542, lng: 151.274856},
        map: map,
        icon: {
             url: image_url,
             size: new google.maps.Size(20, 32),
             origin: new google.maps.Point(0, 0),
             anchor: new google.maps.Point(0, 32)
        },
        title: 'Marker demo',
        zIndex: 1
   });
}
image.onerror = function () {
   console.error("Cannot load image, adding marker without image");
   var marker = new google.maps.Marker({
      position: {lat: -33.890542, lng: 151.274856},
      map: map,
      title: 'Marker demo',
      zIndex: 1
   });
}
image.src = image_url;