自定义对象从嵌入式FX（JFXPanel）拖放到Swing

时间：2018-10-01 21:17:02

标签： java swing javafx drag-and-drop jfxpanel

此问题是对Custom object drag-and-drop from FX to Swing的后续问题。

我正在为使用JavaFX的某些图形用户界面的Swing应用程序开发插件。我们添加了拖放功能以改善用户体验。首先，我们为Stage使用了一个外部JavaFX窗口（Scene），现在我们想通过JFXPanel将其直接嵌入到Swing应用程序中。

现在，奇怪的是，无论是将完全相同的Scene加载到Stage还是JFXPanel中，对于拖放操作似乎都有很大的不同

当尝试将具有自定义MIME类型的某些自定义Java对象（序列化形式）从JavaFX应用程序拖到Swing应用程序中时，我已经遇到了一些问题。但是，以上提到的问题解决了我的问题。现在，在使用嵌入式JavaFX应用程序时，我遇到了一些新问题，因此我想问一问是否有人遇到类似问题或知道此方案的解决方案。

我已经编写了MVCE，它是一个简单的Java应用程序，其一侧是支持拖曳的JFXPanel，而另一侧是支持拖曳的JPanel 

public class MyApp {

    public static final DataFormat FORMAT = new DataFormat(
        // this works fine in a separate window
        //"JAVA_DATAFLAVOR:application/x-my-mime-type; class=java.lang.String",
        "application/x-my-mime-type; class=java.lang.String");

    public static final DataFlavor FLAVOR;

    static {
        try {
            FLAVOR = new DataFlavor("application/x-my-mime-type; class=java.lang.String");
        } catch (ClassNotFoundException ex) {
            throw new RuntimeException(ex);
        }
    }

    public static void main(String[] args) {
        new MyApp().run();
    }

    private void run() {
        JFrame frame = new JFrame();
        frame.setLayout(new GridLayout(1, 2));
        frame.add(buildFX());
        frame.add(buildSwing());
        frame.setSize(300, 300);
        frame.setVisible(true);
    }

    private JFXPanel buildFX() {
        BorderPane parent = new BorderPane();
        parent.setOnDragDetected(event -> {
            Dragboard dragboard = parent.startDragAndDrop(TransferMode.COPY);
            ClipboardContent content = new ClipboardContent();
            content.put(FORMAT, "Test");
            dragboard.setContent(content);
            event.consume();
        });
        JFXPanel panel = new JFXPanel();
        panel.setScene(new Scene(parent));
        return panel;
    }

    @SuppressWarnings("serial")
    private JPanel buildSwing() {
        JPanel panel = new JPanel();
        panel.setBackground(Color.ORANGE);
        panel.setTransferHandler(new TransferHandler() {

            @Override
            public boolean canImport(TransferSupport support) {
                return support.isDataFlavorSupported(FLAVOR);
            }

            @Override
            public boolean importData(TransferSupport support) {
                if (!canImport(support)) return false;
                try {
                    String data = (String) support.getTransferable().getTransferData(FLAVOR);
                    System.out.println(data);
                    return true;
                } catch (UnsupportedFlavorException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
                return false;
            }

        });
        return panel;
    }
}

根据另一个问题的答案，必须使用JAVA_DATAFLAVOR:中的前缀DataFormat，Swing才能正确处理MIME类型。但是，当在DataFormat中使用这样的JFXPanel（在示例中被禁用）时，似乎Java从FX应用程序中拖动时试图构造DataFlavor且无法解析MIME。加上前缀：

Exception in thread "AWT-EventQueue-0" java.lang.IllegalArgumentException: failed to parse:JAVA_DATAFLAVOR:application/x-my-mime-type; class=java.lang.String
    at java.awt.datatransfer.DataFlavor.<init>(Unknown Source)
    at javafx.embed.swing.SwingDnD$DnDTransferable.getTransferDataFlavors(SwingDnD.java:394)
    at sun.awt.datatransfer.DataTransferer.getFormatsForTransferable(Unknown Source)
    at sun.awt.dnd.SunDragSourceContextPeer.startDrag(Unknown Source)
    at java.awt.dnd.DragSource.startDrag(Unknown Source)
    at java.awt.dnd.DragSource.startDrag(Unknown Source)
    at java.awt.dnd.DragGestureEvent.startDrag(Unknown Source)
    at javafx.embed.swing.SwingDnD.startDrag(SwingDnD.java:280)
    at javafx.embed.swing.SwingDnD.lambda$null$66(SwingDnD.java:247)
    at java.awt.event.InvocationEvent.dispatch(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$500(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)

仅使用纯MIME类型，不带前缀，拖放操作有效，我什至可以收到正确的DataFlavor（java.awt.datatransfer.DataFlavor[mimetype=application/x-my-mime-type;representationclass=java.lang.String]），但删除的数据始终为{{ 1}}。从另一个问题中可以看出，使用第二种方法将两个分离的窗口一起使用，我什至无法收到null，但现在它可以在某种程度上达到这一极限。

1 个答案:

答案 0 :(得分：2)

对于转移的工作方式可能存在一些误解。

尝试直接以字符串形式检索传输数据可能适用于“文本/纯文本”或其他标准文本类型，并且如您所注意到的，对于自定义未注册类型的特殊情况，有些古怪之处。但是我认为进行自定义变通办法的努力是没有道理的。

由于您完全控制了自定义mime类型的内容结构以及同一应用程序中数据生产者和使用者的两端，因此我建议不要处理依赖于内部工具包实现的前缀或类映射。可能更好的方法是只定义您的MIME类型，而不必使用不相关的元数据和不正确的前缀（应该是这样）。

定义“ application / x-my-mime ”类型并正确解码数据就足够了。

样本1（序列化数据）

根据您的示例更正的以下内容，应将数据细化到Java 8中的Swing框架中。 

package jfxtest;

import java.awt.Color;
import java.awt.GridLayout;
import java.awt.datatransfer.DataFlavor;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.util.Collections;
import javafx.embed.swing.JFXPanel;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.input.DataFormat;
import javafx.scene.input.TransferMode;
import javafx.scene.layout.BorderPane;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.TransferHandler;
import javax.swing.TransferHandler.TransferSupport;

public class MyApp {

  final static String MY_MIME_TYPE = "application/x-my-mime";
  public static final DataFormat FORMAT = new DataFormat(MY_MIME_TYPE);
  public static final DataFlavor FLAVOR = new DataFlavor(MY_MIME_TYPE, "My Mime Type");

  private void startDrag(Node node) {
    node.startDragAndDrop(TransferMode.COPY).setContent(
        Collections.singletonMap(FORMAT, "Test"));
  }

  private boolean processData(TransferSupport support) {
    try (InputStream in = (InputStream) support.getTransferable().getTransferData(FLAVOR)) {
      Object transferred = new ObjectInputStream(in).readObject();
      System.out.println("transferred: " + transferred + " (" + transferred.getClass() + ")");
      return true;
    } catch (Exception e) {
      e.printStackTrace();
    }
    return false;
  }  

  public static void main(String[] args) {
    new MyApp().run();
  }

  private void run() {
    JFrame frame = new JFrame();
    frame.setLayout(new GridLayout(1, 2));
    frame.add(buildSwing());
    SwingUtilities.invokeLater(() -> {
      frame.add(buildFX());
    });
    frame.setSize(300, 300);
    frame.setVisible(true);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  }

  private JFXPanel buildFX() {
    BorderPane parent = new BorderPane();
    parent.setOnDragDetected(event -> {
      startDrag(parent);
      event.consume();
    });
    JFXPanel panel = new JFXPanel();
    panel.setScene(new Scene(parent));
    return panel;
  }


  private JPanel buildSwing() {
    JPanel panel = new JPanel();
    panel.setBackground(Color.ORANGE);
    panel.setTransferHandler(new TransferHandler() {
      private static final long serialVersionUID = 1L;

      @Override
      public boolean canImport(TransferSupport support) {
        return support.isDataFlavorSupported(FLAVOR);
      }

      @Override
      public boolean importData(TransferSupport support) {
        if (canImport(support)) {
          return processData(support);
        }
        return false;
      }

    });
    return panel;
  }

}

输出：transferred: Test (class java.lang.String)

这里的摘录是：

...

  final static String MY_MIME_TYPE = "application/x-my-mime";
  public static final DataFormat FORMAT = new DataFormat(MY_MIME_TYPE);
  public static final DataFlavor FLAVOR = new DataFlavor(MY_MIME_TYPE, "My Mime Type");

  private void startDrag(Node node) {
    node.startDragAndDrop(TransferMode.COPY).setContent(
        Collections.singletonMap(FORMAT, "Test"));    
  }

  private boolean processData(TransferSupport support) {
    try (InputStream in = (InputStream) support.getTransferable().getTransferData(FLAVOR)) {
      Object transferred = new ObjectInputStream(in).readObject();
      System.out.println("transferred: " + transferred + " (" + transferred.getClass() + ")");
      return true;
    } catch (Exception e) {
      e.printStackTrace();
    }
    return false;
  }

...

请注意，出于说明目的，数据检索非常简单，对于实际应用而言，可能希望添加更严格的流读取，处理错误等。

示例2（带有文字的自定义哑剧）

第一个示例传输一个序列化的对象（这通常是一件好事，很简单，因为您可以传输任何可序列化的东西，但是很难传输/接受（例如，第三者JSON））。在极少数情况下，当您希望为自定义MIME生成真实文本或其他任意内容而不是序列化的对象时，以下方法可以完成：

package jfxtest;

import java.awt.Color;
import java.awt.GridLayout;
import java.awt.datatransfer.DataFlavor;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.nio.charset.StandardCharsets;
import java.util.Collections;
import javafx.embed.swing.JFXPanel;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.input.DataFormat;
import javafx.scene.input.TransferMode;
import javafx.scene.layout.BorderPane;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.TransferHandler;
import javax.swing.TransferHandler.TransferSupport;

public class MyApp {

  final static String MY_MIME_TYPE = "application/x-my-mime";
  public static final DataFormat FORMAT = new DataFormat(MY_MIME_TYPE);
  public static final DataFlavor FLAVOR = new DataFlavor(MY_MIME_TYPE, "My Mime Type");

  private void startDrag(Node node) {
    node.startDragAndDrop(TransferMode.COPY).setContent(
        // put a ByteBuffer to transfer the content unaffected
        Collections.singletonMap(FORMAT, StandardCharsets.UTF_8.encode("Test")));
  }

  private boolean processData(TransferSupport support) {
    try (InputStream in = (InputStream) support.getTransferable().getTransferData(FLAVOR)) {
      byte[] textBytes = new byte[in.available()];
      in.read(textBytes);
      String transferred = new String(textBytes, StandardCharsets.UTF_8); 
      System.out.println("transferred text: " + transferred);
      return true;
    } catch (Exception e) {
      e.printStackTrace();
    }
    return false;
  }  

  public static void main(String[] args) {
    new MyApp().run();
  }

  private void run() {
    JFrame frame = new JFrame();
    frame.setLayout(new GridLayout(1, 2));
    frame.add(buildSwing());
    SwingUtilities.invokeLater(() -> {
      frame.add(buildFX());
    });
    frame.setSize(300, 300);
    frame.setVisible(true);
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
  }

  private JFXPanel buildFX() {
    BorderPane parent = new BorderPane();
    parent.setOnDragDetected(event -> {
      startDrag(parent);
      event.consume();
    });
    JFXPanel panel = new JFXPanel();
    panel.setScene(new Scene(parent));
    return panel;
  }


  private JPanel buildSwing() {
    JPanel panel = new JPanel();
    panel.setBackground(Color.ORANGE);
    panel.setTransferHandler(new TransferHandler() {
      private static final long serialVersionUID = 1L;

      @Override
      public boolean canImport(TransferSupport support) {
        return support.isDataFlavorSupported(FLAVOR);
      }

      @Override
      public boolean importData(TransferSupport support) {
        if (canImport(support)) {
          return processData(support);
        }
        return false;
      }

    });
    return panel;
  }

}

输出：transferred text: Test

这里的必不可少的部分是：

...

  private void startDrag(Node node) {
    node.startDragAndDrop(TransferMode.COPY).setContent(
        // put a ByteBuffer to transfer the content unaffected
        Collections.singletonMap(FORMAT, StandardCharsets.UTF_8.encode("Test")));
  }

  private boolean processData(TransferSupport support) {
    try (InputStream in = (InputStream) support.getTransferable().getTransferData(FLAVOR)) {
      byte[] textBytes = new byte[in.available()];
      in.read(textBytes);
      String transferred = new String(textBytes, StandardCharsets.UTF_8); 
      System.out.println("transferred text: " + transferred);
      return true;
    } catch (Exception e) {
      e.printStackTrace();
    }
    return false;
  }  

...

再一次说明一下，这里的流，错误等处理都是简单化的。

要注意的一件事是，还有一个预定义的“ application / x-java-serialized-object”（DataFlavor.javaSerializedObjectMimeType）用于更通用和更容易的反序列化。但是，长期的自定义MIME似乎更灵活，更易于处理。

相关问题
最新问题