1

我正在尝试在 gwt-platform 项目中使用 gwt-graphics。

当我尝试注册一个圆圈的 ClickHandler 时，我遇到了一个异常：我可以将 ClickHandler 添加到视图中的圆圈，但是如何在演示者中添加？

看法：

import org.vaadin.gwtgraphics.client.DrawingArea;
import org.vaadin.gwtgraphics.client.shape.Circle;

import com.gwtplatform.mvp.client.ViewImpl;
import com.google.gwt.event.dom.client.ClickEvent;
import com.google.gwt.event.dom.client.ClickHandler;
import com.google.gwt.event.dom.client.HasClickHandlers;
import com.google.gwt.user.client.Window;
import com.google.gwt.user.client.ui.Button;
import com.google.gwt.user.client.ui.HasValue;
import com.google.gwt.user.client.ui.HTMLPanel;
import com.google.gwt.user.client.ui.Label;
import com.google.gwt.user.client.ui.TextBox;
import com.google.gwt.user.client.ui.Widget;
import com.google.inject.Inject;
import com.google.gwt.user.client.ui.AbsolutePanel;
import com.google.gwt.user.client.ui.Image;
import com.google.gwt.user.client.ui.PushButton;

public class MainPageView extends ViewImpl implements MainPagePresenter.MyView {

    private static String html = "<h1>Web Application Starter Project</h1>\n"
            + "<table align=\"center\">\n"
            + "  <tr>\n"
            + "    <td colspan=\"2\" style=\"font-weight:bold;\">Please enter your name:</td>\n"
            + "  </tr>\n"
            + "  <tr>\n"
            + "    <td id=\"nameFieldContainer\"></td>\n"
            + "    <td id=\"sendButtonContainer\"></td>\n"
            + "  </tr>\n"
            + "  <tr>\n"
            + "    <td colspan=\"2\" style=\"color:red;\" id=\"errorLabelContainer\"></td>\n"
            + "  </tr>\n" + "</table>\n";
    private final HTMLPanel panel = new HTMLPanel(html);
    private final Label errorLabel;
    private final TextBox nameField;
    private final Button sendButton;
    private AbsolutePanel absolutePanel = new AbsolutePanel();
    Image image_1;
    Image image;
    DrawingArea d;
    Circle circle;

    @Inject
    public MainPageView() {

        sendButton = new Button("Send");
        nameField = new TextBox();
        nameField.setText("GWT User");
        errorLabel = new Label();

        // We can add style names to widgets
        sendButton.addStyleName("sendButton");

        // Add the nameField and sendButton to the RootPanel
        // Use RootPanel.get() to get the entire body element
        panel.add(nameField, "nameFieldContainer");
        panel.add(sendButton, "sendButtonContainer");

        d = new DrawingArea(500, 500);
        panel.add(absolutePanel);
        absolutePanel.setHeight("500px");

//      circle.addClickHandler(new ClickHandler() {
//          
//          @Override
//          public void onClick(ClickEvent event) {
//              Window.alert("image2");
//              
//          }
//      });
         image = new Image("ball1.png");
        absolutePanel.add(image, 59, 10);
        image.setSize("100px", "100px");

         image_1 = new Image("Hexagon.svg");
        absolutePanel.add(image_1, 115, 10);
        image_1.setSize("100px", "100px");

        absolutePanel.add(d, 100, 100);
//      
        Circle circle = new Circle(100, 100, 150);
        circle.setStrokeColor("red");
        d.add(circle);

        panel.add(errorLabel, "errorLabelContainer");
    }

    @Override
    public Widget asWidget() {
        return panel;
    }

    @Override
    public HasValue<String> getNameValue() {
        return nameField;
    }

    @Override
    public HasClickHandlers getSendClickHandlers() {
        return sendButton;
    }

    @Override
    public void resetAndFocus() {
        // Focus the cursor on the name field when the app loads
        nameField.setFocus(true);
        nameField.selectAll();
    }

    @Override
    public void setError(String errorText) {
        errorLabel.setText(errorText);
    }

//  @Override
//  public HasClickHandlers getImage1() {
//      return image;
//  }
//  
//  @Override
//  public HasClickHandlers getImage2() {
//      return image_1;
//      
//  }

    @Override
    public HasClickHandlers getCircle() {
        return circle;
    }


}

主持人：

package mybla.client.core;

import org.vaadin.gwtgraphics.client.shape.Circle;

import com.gwtplatform.mvp.client.Presenter;
import com.gwtplatform.mvp.client.View;
import com.gwtplatform.mvp.client.annotations.ProxyStandard;
import com.gwtplatform.mvp.client.annotations.NameToken;

import mybla.client.place.NameTokens;

import com.gwtplatform.mvp.client.proxy.ProxyPlace;
import com.google.inject.Inject;
import com.google.gwt.event.shared.EventBus;
import com.gwtplatform.mvp.client.proxy.RevealRootContentEvent;
import com.google.gwt.event.dom.client.ClickEvent;
import com.google.gwt.event.dom.client.ClickHandler;
import com.google.gwt.event.dom.client.HasClickHandlers;
import com.google.gwt.user.client.Window;
import com.google.gwt.user.client.ui.HasValue;
import com.gwtplatform.mvp.client.proxy.PlaceManager;
import com.gwtplatform.mvp.client.proxy.PlaceRequest;

import mybla.shared.FieldVerifier;

public class MainPagePresenter extends
        Presenter<MainPagePresenter.MyView, MainPagePresenter.MyProxy> {

    public interface MyView extends View {

        HasValue<String> getNameValue();

        HasClickHandlers getSendClickHandlers();

        void resetAndFocus();

        void setError(String errorText);

        HasClickHandlers getCircle();

//      HasClickHandlers getImage2();
//
//      HasClickHandlers getImage1();




    }

    @ProxyStandard
    @NameToken(NameTokens.main)
    public interface MyProxy extends ProxyPlace<MainPagePresenter> {
    }

    private final PlaceManager placeManager;

    @Inject
    public MainPagePresenter(final EventBus eventBus, final MyView view,
            final MyProxy proxy, final PlaceManager placeManager) {
        super(eventBus, view, proxy);

        this.placeManager = placeManager;
    }

    @Override
    protected void revealInParent() {
        RevealRootContentEvent.fire(this, this);
    }

    @Override
    protected void onBind() {
        super.onBind();
        registerHandler(getView().getSendClickHandlers().addClickHandler(
                new ClickHandler() {
                    @Override
                    public void onClick(ClickEvent event) {
                        sendNameToServer();
                    }
                }));
//      registerHandler(getView().getImage1().addClickHandler(new ClickHandler() {
//          
//          @Override
//          public void onClick(ClickEvent event) {
//              Window.alert("image1");
//              
//          }
//      }));

        registerHandler(getView().getCircle().addClickHandler(new ClickHandler() {

            @Override
            public void onClick(ClickEvent event) {
                Window.alert("image2");

            }
        }));
    }

    @Override
    protected void onReset() {
        super.onReset();
        getView().resetAndFocus();
    }

    /**
     * Send the name from the nameField to the server and wait for a response.
     */
    private void sendNameToServer() {
        // First, we validate the input.
        getView().setError("");
        String textToServer = getView().getNameValue().getValue();
        if (!FieldVerifier.isValidName(textToServer)) {
            getView().setError("Please enter at least four characters");
            return;
        }

        // Then, we transmit it to the ResponsePresenter, which will do the server call
        placeManager.revealPlace(new PlaceRequest(NameTokens.response).with(
                ResponsePresenter.textToServerParam, textToServer));
    }
}
4

2 回答 2

0

在您的演示者中：

getView().getCircle().addClickHandler(new ClickHandler() {
    @Override
    public void onClick(ClickEvent event)
    {
        Window.alert("image2");
    }
});

这将使用 presenter.view 中设置的 getter 方法来访问 View 本身中的圆圈。

于 2013-10-16T10:42:04.727 回答
0

看起来您在 View 的构造函数中实例化的圆圈是一个局部变量，而不是您的 getCircle() 方法返回的类范围变量。此外，用于添加 onclick 处理程序的注释掉的代码位于实例化局部变量的代码之前。

你有：

...

// circle.addClickHandler(new ClickHandler() {
//     
//   @Override
//   public void onClick(ClickEvent event) {
//     Window.alert("image2");
//   }
// });

...

Circle circle = new Circle(100, 100, 150);
circle.setStrokeColor("red");
d.add(circle);

将其更改为：

...

circle = new Circle(100, 100, 150);  // This now references the class-scope variable, rather than creating a new local variable.
circle.setStrokeColor("red");
d.add(circle);

circle.addClickHandler(new ClickHandler() {  // This will no longer throw a null-pointer exception.

  @Override
  public void onClick(ClickEvent event) {
    Window.alert("image2");
  }
});
于 2015-03-02T19:25:38.700 回答