如何在传单地图中仅添加一个标记

问题描述

我要在用户点击时在地图上添加标记.
问题是我只需要一个标记，但是现在单击地图时会添加新的标记.
我正在尝试将其删除，但没有任何反应:

I am adding marker on map on user click.
Problem is that I want only one marker but now whenever I click on map new marker is added.
I am trying to remove it but nothing happens:

var marker;
    map.on('click', function (e) {
        map.removeLayer(marker)

        marker = new L.Marker(e.latlng, { draggable: true });
        marker.bindPopup("<strong>" + e.latlng + "</strong>").addTo(map);

        marker.on('dragend', markerDrag);
    });

推荐答案

可以使用.once代替使用.on捕获和处理事件.这样，事件将仅被捕获一次，并且处理程序将在此之后解除绑定.

Instead of using .on to capture and handle the event, you could use .once. That way the event will be only captured once and the handler will unbind itself after that.

map.on('click', function () {
    console.log('I fire every click');
});

map.once('click', function () {
    console.log('I fire only once');
});

如果您需要自己解除绑定处理程序，则可以使用.off.检查事件方法的引用: http://leafletjs.com/reference.html#events

If you're ever need to unbind a handler yourself you can use .off. Check the reference for event methods: http://leafletjs.com/reference.html#events

关于为什么上面的代码无法正常工作的原因，请首先单击以删除标记:map.removeLayer(marker)，但是变量marker不包含L.Marker实例，因此地图无法去掉它.您应该先检查是否已定义它，然后再删除它:

As to why your code above isn't working, on first click you're trying remove the marker: map.removeLayer(marker), but the variable marker doesn't contain a L.Marker instance so the map is unable to remove it. You should check if it's defined first and only then remove it:

var marker;
map.on('click', function (e) {
    if (marker) { // check
        map.removeLayer(marker); // remove
    }
    marker = new L.Marker(e.latlng); // set
});

这是有关Plunker的一个工作示例: =预览

Here's a working example on Plunker: http://plnkr.co/edit/iEcivecU7HGajQqDWzVH?p=preview

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