开发者问题收集

Google 地图地点自动完成 - 未捕获的类型错误:无法读取未定义的属性“getPlace”

2016-05-14
6111
setAutocomplete() {
    this.originPlaceId = null;
    this.destinationPlaceId = null;
    this.travelMode = google.maps.TravelMode.WALKING;
    this.directionsDisplay.setMap(this.map);

    this.setMapControls(this.map);

    this.setupClickListener('changemode-walking', google.maps.TravelMode.WALKING);
    this.setupClickListener('changemode-transit', google.maps.TravelMode.TRANSIT);
    this.setupClickListener('changemode-driving', google.maps.TravelMode.DRIVING);

    console.log(this.originInput);
    this.originAutocomplete = new google.maps.places.Autocomplete(this.originInput);
    this.originAutocomplete.bindTo('bounds', this.map);
    console.log(this.originAutocomplete);
    this.originAutocomplete.addListener('place_changed', function() {
        console.log(this.originAutocomplete);
        var place = this.originAutocomplete.getPlace();
        console.log("here", place);
        if (!place.geometry) {
            window.alert("Autocomplete's returned place contains no geometry");
            return;
        }
        this.expandViewportToFitPlace(this.map, place);

        // If the place has a geometry, store its place ID and route if we have
        // the other place ID
        this.originPlaceId = place.place_id;
        this.route(this.directionsService, this.directionsDisplay);
    });

    this.destinationAutocomplete = new google.maps.places.Autocomplete(this.destinationPlaceInput);
    this.destinationAutocomplete.bindTo('bounds',this.map);
    this.destinationAutocomplete.addListener('place_changed', function() {
        var place = this.destinationAutocomplete.getPlace();
        if (!place.geometry) {
            window.alert("Autocomplete's returned place contains no geometry");
            return;
        }
        this.expandViewportToFitPlace(this.map, place);

        // If the place has a geometry, store its place ID and route if we have
        // the other place ID
        this.destinationPlaceId = place.place_id;
        this.route(this.directionsService, this.directionsDisplay);
        //this.getNearbyPlaces(this.destinationPlaceId, 5000);
    });
};
setMapControls(map) {
    this.originInput = document.getElementById('origin-input');
    this.destinationPlaceInput = document.getElementById('destination-input');
    this.modes = document.getElementById('mode-selector');

    map.controls[google.maps.ControlPosition.TOP_LEFT].push(this.originInput);
    map.controls[google.maps.ControlPosition.TOP_LEFT].push(this.destinationPlaceInput);
    map.controls[google.maps.ControlPosition.TOP_LEFT].push(this.modes);
};
<input id="origin-input" class="controls" type="text" force-selection="true" placeholder="Enter an origin location">
<input id="destination-input" class="controls" type="text" force-selection="true" placeholder="Enter a destination location">
<div id="mode-selector" class="controls">
    <input type="radio" name="type" id="changemode-walking" checked="checked">
    <label for="changemode-walking">Walking</label>
    <input type="radio" name="type" id="changemode-transit">
    <label for="changemode-transit">Transit</label>
    <input type="radio" name="type" id="changemode-driving">
    <label for="changemode-driving">Driving</label>
</div>
<div id="directionsList"></div>
<div id="map_canvas"></div>

我有这些函数,它们应该能从输入字段(originInput 和 destinationPlaceInput)为我提供从 Google 地图地点到 B 的路线。

选择输入后,控制台中出现此错误:

Uncaught TypeError: Cannot read property 'getPlace' of undefined

此错误在“place_changed”事件触发后引发。

2个回答

place_changed 回调中,关键字 this 指向已触发事件的对象。

因此您可以简单地使用

var place = this.getPlace();

而不是

var place = this.destinationAutocomplete.getPlace();
Dr.Molle
2016-05-14

如何保留控制器的上下文/ this

tldr:

创建一个返回具有上下文的函数的函数:

this.searchBox.addListener('places_changed', ((that) => () => this.placesChanged(that))(this));

解释

正如 Dr.Molle 指出的那样: this 指向触发事件的对象,即您想要在其上添加事件侦听器的元素。

addListener 采用函数声明。要保留对控制器的 this 的访问权限,您还可以创建一个闭包,将控制器的 this 传递到函数中,如下所示:

this.searchBox.addListener('places_changed', ((that) => () => this.placesChanged(that))(this));

在这里我定义了一个函数,它接受一个名为 that 的参数,并在执行时返回一个包含 this 的函数。它是一个闭包,因为内部函数的作用域保留了对外部函数作用域中 that 变量的引用(以及可以传递给 this.placesChanged 的其他变量)。

现在,如果发出事件 places_changed ,则运行函数声明。我仍然能够在 this.placesChanged 函数内更改 that 变量的属性。这是可能的,因为对象是通过引用传递的(而原始类型是通过值传递的)。

Brampage
2019-07-11