胶合位置服务需要很长时间才能显示坐标

Question

我尝试了以下代码，它正在运行，但是在启动应用程序后首次单击按钮，单击按钮时坐标显示正确的消息，但是对于下次单击，消息很长时间不幸显示消息。

我的代码如下：

button.setOnAction(e->{
        PositionService positionService = Services.get(PositionService.class).orElseThrow(() -> new RuntimeException("PositionService not available."));
        positionService.positionProperty().addListener((obs, ov, nv) -> MobileApplication.getInstance().showMessage("Latest known GPS coordinates from device: " + nv.getLatitude() + ", " + nv.getLongitude()));
    });

提前致谢。

Answer 1

假设您有一个使用您的IDE的Gluon插件创建的单个视图项目，并且您已将所需的location服务和权限添加到Android清单中：

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>

例如，您可以在BasicView中执行：

public BasicView(String name) {
    super(name);

    Label label = new Label("GPS is not active");

    Button button = new Button("Active GPS");
    button.setGraphic(new Icon(MaterialDesignIcon.LOCATION_ON));

    button.setOnAction(e -> {
        Services.get(PositionService.class).ifPresent(service -> {
            // if there is GPS service, disable button to avoid adding more
            // listeners
            button.setDisable(true);
            label.setText("Waiting for GPS signal");

            service.positionProperty().addListener((obs, ov, nv) -> 
                label.setText("Latest known GPS coordinates:\n" + nv.getLatitude() + ", " + nv.getLongitude()));
        });
    });

    VBox controls = new VBox(15.0, label, button);
    controls.setAlignment(Pos.CENTER);

    setCenter(controls);
}

或者您可以在创建视图时初始化服务，而无需激活它：

public BasicView(String name) {
    super(name);

    Label label = new Label("GPS is not active");

    Services.get(PositionService.class).ifPresent(service -> {
            label.setText("Waiting for GPS signal");

            service.positionProperty().addListener((obs, ov, nv) -> 
                label.setText("Latest known GPS coordinates:\n" + nv.getLatitude() + ", " + nv.getLongitude()));
        });

}

无论哪种方式，您都可以将应用部署到Android / iOS设备并进行测试。

修改

或者，如果您想要包含一个按钮，那么您可以根据需要随时点击它。

public BasicView(String name) {
    super(name);

    Label label = new Label("GPS is not active");

    Button button = new Button("Get GPS coordinates");
    button.setGraphic(new Icon(MaterialDesignIcon.LOCATION_ON));
    button.setDisable(true);

    Services.get(PositionService.class).ifPresent(service -> {
        label.setText("Waiting for GPS signal");

        service.positionProperty().addListener((obs, ov, nv) -> {
            label.setText("Latest known GPS coordinates:\n" + nv.getLatitude() + ", " + nv.getLongitude());
        });

        // enable button and add listener to retrieve coordinates
        button.setDisable(false); 
        button.setOnAction(e -> {
            Position position = service.getPosition();
            MobileApplication.getInstance().showMessage("Latest known GPS coordinates from device:\n" + 
                    position.getLatitude() + ", " + position.getLongitude());
        });
    });

    VBox controls = new VBox(15.0, label, button);
    controls.setAlignment(Pos.CENTER);

    setCenter(controls);
}

请注意，点击该按钮时，您应使用service.getPosition()。