JavaFX2-ObservableList到TableView

Question

希望我能把问题弄得尽可能清楚。我正在使用JavaFX库为GUI开发一个小型java应用程序。我正在做一个POP连接，并将消息存储为ObservableList。为此，我使用javax.mail。我将这个observablelist传递给一个tableview，并通过以下方式将所需的值传递给TableColumns：

        fromColumn.setCellValueFactory(
            new PropertyValueFactory<Message,String>("from")
        );
        subjectColumn.setCellValueFactory(
            new PropertyValueFactory<Message,String>("subject")
        );
        dateColumn.setCellValueFactory(
            new PropertyValueFactory<Message,String>("sentDate")
        );

Subject和sentDate是完美的读入。但不幸的是，“from”将对象引用添加到TableColumn中，因为Message-Class中的From-Attribute是InternetAdress-Object，它的toString（）-方法不返回字符串，而可能返回引用。结果是FromColumn中显示的follwoing：

[Ljavax.mail.internet.InternetAddress;@3596cd38

有人知道解决方案吗？我如何获得上面提到的列中显示的InternetAdress的字符串值？

提前致谢

Answer 1

我认为您需要定义一个自定义单元格值工厂，以获得所需格式的地址信息，而不是使用PropertyValueFactory。

下面的示例是针对只读表的--如果表中的消息数据需要是可编辑的，那么解决方案将明显更加复杂。

fromColumn.setCellValueFactory(new Callback<CellDataFeatures<Message, String>, ObservableValue<String>>() {
    @Override public ObservableValue<String> call(CellDataFeatures<Message, String> m) {
        // m.getValue() returns the Message instance for a particular TableView row
        return new ReadOnlyObjectWrapper<String>(Arrays.toString(m.getValue().getFrom()));
    }
});

下面是一个可执行示例（加上示例数据文件），它演示了自定义单元格值工厂的使用。将示例数据文件放在与应用程序java程序相同的目录中，并确保构建系统将示例文件复制到构建输出目录，该目录包含应用程序的编译类文件。您将需要路径上的javamail jar文件来编译和运行应用程序。

import java.io.*;
import java.util.Arrays;
import java.util.logging.*;
import javafx.application.Application;
import javafx.beans.property.ReadOnlyObjectWrapper;
import javafx.beans.value.ObservableValue;
import javafx.collections.*;
import javafx.geometry.Insets;
import javafx.scene.Scene;
import javafx.scene.control.*;
import javafx.scene.control.TableColumn.CellDataFeatures;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.scene.layout.VBox;
import javafx.scene.text.Font;
import javafx.stage.Stage;
import javafx.util.Callback;
import javax.mail.*;
import javax.mail.internet.MimeMessage;

public class MailTableSample extends Application {
  private TableView<Message> table = new TableView<Message>();
  public static void main(String[] args) { launch(args);}

  @Override public void start(Stage stage) {
    stage.setTitle("Table View Sample");

    final Label label = new Label("Mail");
    label.setFont(new Font("Arial", 20));

    table.setEditable(false);

    TableColumn subjectColumn = new TableColumn("Subject");
    subjectColumn.setMinWidth(100);
    subjectColumn.setCellValueFactory(
      new PropertyValueFactory<Message, String>("subject")
    );

    TableColumn sentDate = new TableColumn("Sent");
    sentDate.setMinWidth(100);
    sentDate.setCellValueFactory(
      new PropertyValueFactory<Message, String>("sentDate")
    );

    TableColumn fromColumn = new TableColumn("From");
    fromColumn.setMinWidth(200);
    fromColumn.setCellValueFactory(new Callback<CellDataFeatures<Message, String>, ObservableValue<String>>() {
        @Override public ObservableValue<String> call(CellDataFeatures<Message, String> m) {
          try {
            // m.getValue() returns the Message instance for a particular TableView row
            return new ReadOnlyObjectWrapper<String>(Arrays.toString(m.getValue().getFrom()));
          } catch (MessagingException ex) {
            Logger.getLogger(MailTableSample.class.getName()).log(Level.SEVERE, null, ex);
            return null;
          }
        }
    });    

    table.setItems(fetchMessages());
    table.getColumns().addAll(fromColumn, subjectColumn, sentDate);
    table.setPrefSize(600, 200);

    final VBox vbox = new VBox();
    vbox.setSpacing(5);
    vbox.setPadding(new Insets(10));
    vbox.getChildren().addAll(label, table);

    stage.setScene(new Scene(vbox));
    stage.show();
  }

  private ObservableList<Message> fetchMessages() {
    ObservableList<Message> messages = FXCollections.observableArrayList();
    try {
      Session session = Session.getDefaultInstance(System.getProperties());
      for (int i = 0; i < 3; i++) {
        InputStream mboxStream = new BufferedInputStream(
          getClass().getResourceAsStream("msg_" + (i+1) + ".txt")
        );
        Message message = new MimeMessage(session, mboxStream);
        messages.add(message);
      }
    } catch (MessagingException ex) {
      Logger.getLogger(MailTableSample.class.getName()).log(Level.SEVERE, null, ex);
    }

    return messages;
  }
}

From [e-mail]  Tue Jul 23 19:39:23 2002
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From: Timo Sirainen <[e-mail]>
To: [e-mail]
Subject: [dovecot] first test mail
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X-UID: 1                                                  
Status: O

lets see if it works

From [e-mail]  Mon Jul 29 02:17:12 2002
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Date: Mon, 29 Jul 2002 02:17:11 +0300
From: John Smith <[e-mail]>
To: [e-mail]
Subject: [dovecot] Dovecot 0.93 released
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Status: O

First alpha quality release, everything critical is now implemented. From
now on it's mostly stabilization and optimization. Features that can't break
existing code could still be added, especially SSL and authentication stuff.

From [e-mail]  Wed Jul 31 22:48:41 2002
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Date: Wed, 31 Jul 2002 22:48:39 +0300
From: Timo Sirainen <[e-mail]>
To: [e-mail]
Subject: [dovecot] v0.95 released
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Status: O

v0.95 2002-07-31  Timo Sirainen <[e-mail]>

    + Initial SSL support using GNU TLS, tested with v0.5.1.
      TLS support is still missing.
    + Digest-MD5 authentication method
    + passwd-file authentication backend
    + Code cleanups
    - Found several bugs from mempool and ioloop code, now we should
      be stable? :)
    - A few corrections for long header field handling