在一个循环中处理多个 JavaFX 应用程序启动

Question

我的代码目前通过 IMAP (imaps) 和 javamail 读取我的 Gmail 收件箱，一旦找到带有 zip/xap 附件的电子邮件，它就会显示一个阶段（窗口）询问是否下载文件，是或否。

一旦我做出选择，我希望舞台关闭，然后返回到循环中调用的位置。我的问题出现是因为您不能多次启动应用程序，所以我读到here 我应该在start 方法中写Platform.setImplicitExit(false);，然后使用primartyStage.hide()（？），然后使用Platform.runLater(() -> primaryStage.show()); 之类的东西稍后我需要再次显示舞台。

现在出现的问题是命令流开始于 Mail.java 的 doit() 方法，该方法循环通过我的收件箱，launch(args) 出现在方法内的 for loop 中。这意味着launch(args) 然后调用start 设置场景并展示舞台。因为有一个Controller.java 和fxml 关联，所以Controller 类有一个用于舞台按钮的事件处理程序，一旦start 显示舞台，它就会“拦截”流。因此，当我单击“是”或“否”时，它会隐藏舞台，然后只是 挂在那里。 好像它无法返回到 start 方法以从发生启动（args）的地方继续循环。如何在必要时正确隐藏/显示舞台，无论单击是还是否，都允许循环继续。

这是 Mail.java 和 Controller.java 的代码。非常感谢！

Mail.java

 [Other variables set here]
    public static int launchCount = 0;@FXML public Text subjectHolder;

    public static ReceiveMailImap obj = new ReceiveMailImap();

    public static void main(String[] args) throws IOException,        MessagingException {
        ReceiveMailImap.doit();
    }

    @Override
    public void start(Stage primaryStage) throws Exception {
        loader = new FXMLLoader(getClass().getResource("prompts.fxml"));
        root = loader.load();
        controller = loader.getController();
        controller.setPrimaryStage(primaryStage);
        scene = new Scene(root, 450, 250);
        controller.setPrimaryScene(scene);
        scene.getStylesheets().add("styleMain.css");
        Platform.setImplicitExit(false);
        primaryStage.setTitle("Download this file?");
        primaryStage.initStyle(StageStyle.UNDECORATED);
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void doit() throws MessagingException, IOException {
        Folder inbox = null;
        Store store = null;

        try {
            Properties props = System.getProperties();
            Session session = Session.getDefaultInstance(props, null);
            store = session.getStore("imaps");
            store.connect("imap.gmail.com", "myAccount@gmail.com", "Password");
            inbox = store.getFolder("Inbox");
            inbox.open(Folder.READ_WRITE);
            Message[] messages = inbox.getMessages();
            FetchProfile fp = new FetchProfile();
            fp.add(FetchProfile.Item.ENVELOPE);
            fp.add(UIDFolder.FetchProfileItem.FLAGS);
            fp.add(UIDFolder.FetchProfileItem.CONTENT_INFO);
            fp.add("X-mailer");

            inbox.fetch(messages, fp);
            int doc = 0;
            int maxDocs = 400;
            for (int i = messages.length - 1; i >= 0; i--) {
                Message message = messages[i];
                if (doc < maxDocs) {
                    doc++;
                    message.getSubject();

                    if (!hasAttachments(message)) {
                        continue;
                    }
                    String from = "Sender Unknown";
                    if (message.getReplyTo().length >= 1) {
                        from = message.getReplyTo()[0].toString();
                    } else if (message.getFrom().length >= 1) {
                        from = message.getFrom()[0].toString();
                    }
                    subject = message.getSubject();
                    if (from.contains("myAccount@gmail.com")) {
                        saveAttachment(message.getContent());
                        message.setFlag(Flags.Flag.SEEN, true);
                    }
                }
            }
        } finally {
            if (inbox != null) {
                inbox.close(true);
            }
            if (store != null) {
                store.close();
            }
        }
    }

    public static boolean hasAttachments(Message msg) throws MessagingException, IOException {
        if (msg.isMimeType("multipart/mixed")) {
            Multipart mp = (Multipart) msg.getContent();
            if (mp.getCount() > 1) return true;
        }
        return false;
    }

    public static void saveAttachment(Object content)
    throws IOException, MessagingException {
        out = null; in = null;
        try {
            if (content instanceof Multipart) {
                Multipart multi = ((Multipart) content);
                parts = multi.getCount();
                for (int j = 0; j < parts; ++j) {
                    part = (MimeBodyPart) multi.getBodyPart(j);
                    if (part.getContent() instanceof Multipart) {
                        // part-within-a-part, do some recursion...
                        saveAttachment(part.getContent());
                    } else {
                        int allow = 0;
                        if (part.isMimeType("application/x-silverlight-app")) {
                            extension = "xap";
                            allow = 1;
                        } else {
                            extension = "zip";
                            allow = 1;
                        }
                        if (allow == 1) {
                            if (launchCount == 0) {
                                launch(args);
                                launchCount++;
                            } else {
                                Platform.runLater(() -> primaryStage.show());
                            }
                        } else {
                            continue;
                        }
                    }
                }
            }

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if ( in != null) { in .close();
            }
            if (out != null) {
                out.flush();
                out.close();
            }
        }
    }

    public static File createFolder(String subject) {
        JFileChooser fr = new JFileChooser();
        FileSystemView myDocs = fr.getFileSystemView();
        String myDocuments = myDocs.getDefaultDirectory().toString();
        dir = new File(myDocuments + "\\" + subject);
        savePathNoExtension = dir.toString();
        dir.mkdir();
        System.out.println("Just created: " + dir);
        return dir;
    }

}

Controller.java

public class Controller implements Initializable {

    @FXML
    private Text subjectHolder;
    public Button yesButton, noButton;
    public ReceiveMailImap subject;

    @Override
    public void initialize(URL url, ResourceBundle rb) {
        subject= new ReceiveMailImap();
        subjectHolder.setText(subject.returnSubject());
    }
    public Stage primaryStage;
    public Scene scene;

    @FXML
    ComboBox<String> fieldCombo;

    public void setPrimaryStage(Stage stage) {
        this.primaryStage = stage;
    }

    public void setPrimaryScene(Scene scene) {
        this.scene = scene;
    }

    public String buttonPressed(ActionEvent e) throws IOException, MessagingException {
        Object source = e.getSource();
        if(source==yesButton){
            System.out.println("How to tell Mail.java that user clicked Yes?");
            return "POSITIVE";}
        else{subject.dlOrNot("no");
            System.out.println("How to tell Mail.java that user clicked No?");
            primaryStage.hide();
            return "NEGATIVE";}
    }

}

Answer 1

您发布的代码存在很多问题，但让我尝试解决您提出的问题。

代码挂起的原因是Application.launch(...)

在应用程序退出之前不会返回

一般来说，您在这里有点误解了 JavaFX 应用程序的整个生命周期。您应该将start(...) 方法视为与“传统”Java 应用程序中的main(...) 方法等效。唯一需要注意的是start(...)是在FX应用线程上执行的，所以如果你需要执行任何阻塞代码，你需要把它放在后台线程中。

为方便起见，start(...) 方法传递了一个Stage 实例，因为最常见的做法是创建一个场景图并将其显示在舞台上。不过，您没有义务使用此阶段，您可以忽略它，并在需要时创建自己的阶段。

我认为您基本上可以按如下方式构建您的代码（但说实话，我很难理解您在做什么）：

public class Mail extends Application {

    @Override
    public void start(Stage ignored) throws Exception {

        Platform.setImplicitExit(false);

        Message[] messages = /* retrieve messages */ ;
        for (Message message : messages) {
            if ( /* need to display window */) {
                showMessage(message);
            }
        }
    }

    private void showMessage(Message message) {
        FXMLLoader loader = new FXMLLoader(getClass().getResource("prompts.fxml"));
        Parent root = loader.load();

        Controller controller = loader.getController();
        Scene scene = new Scene(root, 450, 250);
        stage.setScene(scene);
        stage.initStyle(StageStyle.UNDECORATED);
        stage.setTitle(...);

        // showAndWait will block execution until the window is hidden, so 
        // you can query which button was pressed afterwards:

        stage.showAndWait();

        if (controller.wasYesPressed()) {
            // ...
        }
    }

    // for IDEs that don't support directly launching a JavaFX Application:
    public static void main(String[] args) { 
        launch(args);
    }
}

显然，您决定是否显示窗口的逻辑更复杂，但这将为您提供基本结构。

要检查按下了哪个按钮，请如上所述使用showAndWait，然后在您的控制器中执行

public class Controller {

    @FXML
    private Button yesButton ;

    private boolean yesButtonPressed = false ;

    public boolean wasYesPressed() {
        return yesButtonPressed ;
    }

    // use different handlers for different buttons:
    @FXML
    private void yesButtonPressed() {
        yesButtonPressed = true ;
        closeWindow();
    }

    @FXML
    private void noButtonPressed() {
        yesButtonPressed = false ; // not really needed, but makes things clearer
        closeWindow();
    }

    private void closeWindow() {
        // can use any @FXML-injected node here:
        yesButton.getScene().getWindow().hide();
    }
}