google-app-engine - 在 GWT/Java 的 SuggestBox 中建议地址

Question

我想定义一个SuggestBox，它的行为类似于Google Maps 中的搜索栏。 :当您开始键入时，会出现以键入的字母开头的真实地址。

我想，我需要使用 Geocoder.getLocations(String address, LocationCallback callback) method ，但我不知道如何将它与 oracle 连接，建议框需要 oracle 来产生它的建议。

请问如何将 getLocations 方法与 SuggestOracle 连接起来？

Answer 1

我通过实现 SuggestBox 的子类解决了这个问题，它有自己的 SuggestOracle。 AddressOracle 作为 Google map 服务的包装器处理，Google Maps API for GWT 中的类 Geocoder 为其提供抽象。

所以这是我的解决方案:

首先，我们为带有 Google map 建议的 SuggestBox 实现小部件

public class GoogleMapsSuggestBox extends SuggestBox {
    public GoogleMapsSuggestBox() {
        super(new AddressOracle());
    }
}

然后我们实现 SuggestOracle，它包装了 Geocoder 异步方法抽象:

class AddressOracle extends SuggestOracle {

    // this instance is needed, to call the getLocations-Service
    private final Geocoder geocoder;


    public AddressOracle() {
        geocoder = new Geocoder();
    }

    @Override
    public void requestSuggestions(final Request request,
            final Callback callback) {
        // this is the string, the user has typed so far
        String addressQuery = request.getQuery();
        // look up for suggestions, only if at least 2 letters have been typed
        if (addressQuery.length() > 2) {    
            geocoder.getLocations(addressQuery, new LocationCallback() {

                @Override
                public void onFailure(int statusCode) {
                    // do nothing
                }

                @Override
                public void onSuccess(JsArray<Placemark> places) {
                    // create an oracle response from the places, found by the
                    // getLocations-Service
                    Collection<Suggestion> result = new LinkedList<Suggestion>();
                    for (int i = 0; i < places.length(); i++) {
                        String address = places.get(i).getAddress();
                        AddressSuggestion newSuggestion = new AddressSuggestion(
                                address);
                        result.add(newSuggestion);
                    }
                    Response response = new Response(result);
                    callback.onSuggestionsReady(request, response);
                }

            });

        } else {
            Response response = new Response(
                    Collections.<Suggestion> emptyList());
            callback.onSuggestionsReady(request, response);
        }

    }
}

这是 oracle 建议的一个特殊类，它只表示一个带有传递地址的字符串。

class AddressSuggestion implements SuggestOracle.Suggestion, Serializable {

    private static final long serialVersionUID = 1L;

    String address;

    public AddressSuggestion(String address) {
        this.address = address;
    }

    @Override
    public String getDisplayString() {
        return this.address;
    }

    @Override
    public String getReplacementString() {
        return this.address;
    }
}

现在，您可以通过在 EntryPoint 类的 onModuleLoad() 方法中编写以下行，将新的小部件绑定(bind)到您的网页中:

RootPanel.get("hm-map").add(new GoogleMapsSuggestBox());