GWT / Java - 关于示例代码的一些基本 UI 问题

Question

我正在查看 gwt 提供的示例 gwt 代码，并在修改它时 - 我有两个问题。我们对我来说不是特别清楚的事情（代码发布在下面 - 有点长：抱歉）

1) 弹出对话框一开始似乎没有设置为“隐藏”，即使它已组装，但在单击按钮之前它实际上并没有显示 - 这是为什么呢？ （例如，我没有看到任何 dialogBox.Hide() 调用

2) 在创建一个类似的对话框时，基本上是通过复制代码，我面临着调用对话框之间的问题 - 内容仍然存在，所以如果我用对话框上的按钮隐藏框，下一个它被调用的时间 - 新内容只是附加在它上面......我做错了什么？

非常感谢！

public void onModuleLoad() {
        final Button sendButton = new Button("Send");
        final TextBox nameField = new TextBox();
        nameField.setText("GWT User");
        final Label 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
        RootPanel.get("nameFieldContainer").add(nameField);
        RootPanel.get("sendButtonContainer").add(sendButton);
        RootPanel.get("errorLabelContainer").add(errorLabel);

        // Focus the cursor on the name field when the app loads
        nameField.setFocus(true);
        nameField.selectAll();

        // Create the popup dialog box
        final DialogBox dialogBox = new DialogBox();
        dialogBox.setText("Remote Procedure Call");
        dialogBox.setAnimationEnabled(true);
        final Button closeButton = new Button("Close");
        // We can set the id of a widget by accessing its Element
        closeButton.getElement().setId("closeButton");
        final Label textToServerLabel = new Label();
        final HTML serverResponseLabel = new HTML();
        VerticalPanel dialogVPanel = new VerticalPanel();
        dialogVPanel.addStyleName("dialogVPanel");
        dialogVPanel.add(new HTML("<b>Sending name to the server:</b>"));
        dialogVPanel.add(textToServerLabel);
        dialogVPanel.add(new HTML("<br><b>Server replies:</b>"));
        dialogVPanel.add(serverResponseLabel);
        dialogVPanel.setHorizontalAlignment(VerticalPanel.ALIGN_RIGHT);
        dialogVPanel.add(closeButton);
        dialogBox.setWidget(dialogVPanel);

        // Add a handler to close the DialogBox
        closeButton.addClickHandler(new ClickHandler() {
            public void onClick(ClickEvent event) {
                dialogBox.hide();
                sendButton.setEnabled(true);
                sendButton.setFocus(true);
            }
        });

        // Create a handler for the sendButton and nameField
        class MyHandler implements ClickHandler, KeyUpHandler {
            /**
             * Fired when the user clicks on the sendButton.
             */
            public void onClick(ClickEvent event) {
                sendNameToServer();
            }

            /**
             * Fired when the user types in the nameField.
             */
            public void onKeyUp(KeyUpEvent event) {
                if (event.getNativeKeyCode() == KeyCodes.KEY_ENTER) {
                    sendNameToServer();
                }
            }

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

                // Then, we send the input to the server.
                sendButton.setEnabled(false);
                textToServerLabel.setText(textToServer);
                serverResponseLabel.setText("");
                greetingService.greetServer(textToServer,
                        new AsyncCallback<String>() {
                            public void onFailure(Throwable caught) {
                                // Show the RPC error message to the user
                                dialogBox
                                        .setText("Remote Procedure Call - Failure");
                                serverResponseLabel
                                        .addStyleName("serverResponseLabelError");
                                serverResponseLabel.setHTML(SERVER_ERROR);
                                dialogBox.center();
                                closeButton.setFocus(true);
                            }

                            public void onSuccess(String result) {
                                dialogBox.setText("Remote Procedure Call");
                                serverResponseLabel
                                        .removeStyleName("serverResponseLabelError");
                                serverResponseLabel.setHTML(result);
                                dialogBox.center();
                                closeButton.setFocus(true);
                            }
                        });
            }
        }

        // Add a handler to send the name to the server
        MyHandler handler = new MyHandler();
        sendButton.addClickHandler(handler);
        nameField.addKeyUpHandler(handler);
    }

Answer 1

默认情况下不显示 DialogBox - 您必须通过 show() 或 center() 显式显示它。

关于第二部分 - 您提供的源代码是导致问题的原因吗？乍一看似乎并非如此。您描述的问题似乎可能是由于尝试将内容添加到dialogVPanel（即保存DialogBox 的内容）而没有先clear()ing 造成的。