問題描述

誰能告訴我我做錯了什么?我可以使用常規面板進行拖放操作，但現在嘗試使用表格，但無法對其進行整理.我對 Points 和 DropTargets 感到困惑.不要介意添加"按鈕.我覺得我需要先處理 DnD.

Can someone show me what I'm doing wrong? I was able to get drag and drop working with a regular panel but now trying with a table and I can't sort it out. I'm getting confused with the Points and DropTargets. Dont mind the "Add" button. I feel like I need to deal with the DnD first.

public class Table extends JFrame implements ActionListener {

    private JTable table;
    private JScrollPane scroll;
    private JButton add;
    private JFileChooser choose;
    private JMenuBar menubar;
    private JMenu menu;
    private JMenuItem file;
    private DefaultTableModel tm = new DefaultTableModel(new String[] { "File",
            "File Type", "Size", "Status" }, 2);

    public Table() {

        // String column [] = {"Filename ","File Type", "Size", "Status" };
        /*
         * Object[][] data = { {"File1", ".jpg","32 MB", "Not Processed"},
         * {"File2", ".txt"," 5 Kb", "Not Processed"}, {"File3", ".doc","3 Kb",
         * "Not Processed"},
         * };
         */

        table = new JTable();
        table.setModel(tm);
        table.setFillsViewportHeight(true);
        table.setPreferredSize(new Dimension(500, 300));

        scroll = new JScrollPane(table);

        table.setDropTarget(new DropTarget() {
            @Override
            public synchronized void drop(DropTargetDropEvent dtde) {

                Point point = dtde.getLocation();
                int column = table.columnAtPoint(point);
                int row = table.rowAtPoint(point);

                dtde.acceptDrop(DnDConstants.ACTION_COPY_OR_MOVE);
                Transferable t = dtde.getTransferable();
                List fileList = null;
                try {
                    fileList = (List) t
                            .getTransferData(DataFlavor.javaFileListFlavor);
                } catch (UnsupportedFlavorException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                File f = (File) fileList.get(0);
                table.setValueAt(f.getAbsolutePath(), row, column);
                table.setValueAt(f.length(), row, column + 1);
                super.drop(dtde);
            }
        });
        scroll.setDropTarget(new DropTarget() {
            @Override
            public synchronized void drop(DropTargetDropEvent dtde) {
                Point point = dtde.getLocation();
                int column = table.columnAtPoint(point);
                int row = table.rowAtPoint(point);

                dtde.acceptDrop(DnDConstants.ACTION_COPY_OR_MOVE);
                Transferable t = dtde.getTransferable();
                List fileList = null;
                try {
                    fileList = (List) t
                            .getTransferData(DataFlavor.javaFileListFlavor);
                } catch (UnsupportedFlavorException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                File f = (File) fileList.get(0);
                table.setValueAt(f.getAbsolutePath(), row, column);
                table.setValueAt(f.length(), row, column + 1);
                // handle drop outside current table (e.g. add row)
                super.drop(dtde);
            }
        });

        add(scroll, BorderLayout.CENTER);

        menubar = new JMenuBar();
        menu = new JMenu("File");
        file = new JMenuItem("file");
        menu.add(file);
        // menubar.add(menu);
        add(menu, BorderLayout.NORTH);

        ImageIcon icon = new ImageIcon("lock_icon.png");

        add = new JButton("Add", icon);
        add.addActionListener(this);

        JFileChooser choose = new JFileChooser();
        choose.addActionListener(this);
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        JButton clicked = (JButton) e.getSource();

        int returnValue = 0;

        if (clicked == add) {
            choose = new JFileChooser();
            choose.showOpenDialog(null);

            if (returnValue == JFileChooser.APPROVE_OPTION) {
                File file = choose.getSelectedFile();
                file.getAbsolutePath();

            }

        }

    }

    public static void main(String[] args) {
        javax.swing.SwingUtilities.invokeLater(new Runnable() {
            public void run() {

                Table t = new Table();

                t.setDefaultCloseOperation(EXIT_ON_CLOSE);
                t.pack();
                t.setSize(600, 200);
                t.setVisible(true);
                t.setTitle("ZipLock");
                t.setIconImage(null);

            }
        });

    }

}

推薦答案

我個人會放棄滾動窗格上的放置目標，這會給你帶來很多問題.

I personally would ditch the drop target on the scroll pane, it's going to cause you to many problems.

你的 drop 方法有點古怪...

Your drop method is a little queezy...

這是個壞主意……

List fileList = null;
try {
    fileList = (List) t
        .getTransferData(DataFlavor.javaFileListFlavor);
} catch (UnsupportedFlavorException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
} catch (IOException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}
File f = (File) fileList.get(0);
table.setValueAt(f.getAbsolutePath(), row, column);
table.setValueAt(f.length(), row, column + 1);

基本上，您嘗試從可轉移文件中提取文件列表，無論操作成功與否，您都嘗試使用它?！您根本沒有驗證返回的值...

Basically, you try and extract the file list from the transferable, and regardless of the success of the operation, you try and use it ?! You do no validation of the returned value at all...

您的放置代碼通常并不真正關心放置發生在哪一列，因為您已經有名稱和大小列，所以我實際上完全忽略了這一點.

Your drop code generally doesn't really care about what column the drop occurred on, as you have name and size columns already, so I'd actually ignore that altogether.

至于行，現在你有兩個選擇.當用戶沒有放在現有行上時，您要么添加新行，要么拒絕嘗試.

As for the row, now you have two choices. Either you add a new row when the user doesn't drop on an existing one or you reject the attempt.

(或拒絕不調用現有行的拖動)

(Or reject drags that don't call over an existing row)

要在用戶拖動時拒絕操作，你需要重寫 dragOver 方法...

To reject the operation while the user is dragging, you need to override the dragOver method...

@Override
public synchronized void dragOver(DropTargetDragEvent dtde) {
    Point point = dtde.getLocation();
    int row = table.rowAtPoint(point);
    if (row < 0) {
        dtde.rejectDrag();
        table.clearSelection();
    } else {
        dtde.acceptDrag(DnDConstants.ACTION_COPY_OR_MOVE);
        table.setRowSelectionInterval(row, row);
    }
}

現在，我在這里有點聰明(而且不是聰明的方式).基本上，如果用戶拖過一行，我會突出顯示它.這使得下降的去向更加明顯.

Now, I'm been a little smart here (and not in the clever way). Basically, if the user has dragged over a row, I've highlighted it. This makes it a little more obvious where the drop is going.

在你的 drop 方法中，我還會做一些額外的檢查......

In your drop method, I would also make some additional checks...

@Override
public synchronized void drop(DropTargetDropEvent dtde) {    
    Point point = dtde.getLocation();
    int row = table.rowAtPoint(point);
    if (row >= 0) {
        if (dtde.isDataFlavorSupported(DataFlavor.javaFileListFlavor)) {
            dtde.acceptDrop(DnDConstants.ACTION_COPY_OR_MOVE);
            Transferable t = dtde.getTransferable();
            List fileList = null;
            try {
                fileList = (List) t.getTransferData(DataFlavor.javaFileListFlavor);
                if (fileList.size() > 0) {
                    table.clearSelection();
                    Point point = dtde.getLocation();
                    int row = table.rowAtPoint(point);
                    DefaultTableModel model = (DefaultTableModel) table.getModel();
                    model.setValueAt(f.getAbsolutePath(), row, 0);
                    model.setValueAt(f.length(), row, 2);
                }
            } catch (UnsupportedFlavorException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        } else {
            dtde.rejectDrop();
        }
    } else {
        dtde.rejectDrop();
    }
}

接受 Drag 的表外"

這個過程相對來說是一樣的，除了現在我們可以拋棄那些原本會導致我們拒絕拖放的條件(顯然)

Accept Drag's "outside" of the table

The process is relativly the same, except now we can throw away the conditions that would have otherwise caused us to reject the drag/drop (obviously)

@Override
public synchronized void dragOver(DropTargetDragEvent dtde) {
    Point point = dtde.getLocation();
    int row = table.rowAtPoint(point);
    if (row < 0) {
        table.clearSelection();
    } else {
        table.setRowSelectionInterval(row, row);
    }
    dtde.acceptDrag(DnDConstants.ACTION_COPY_OR_MOVE);
}

還有drop方法

@Override
public synchronized void drop(DropTargetDropEvent dtde) {    
    if (dtde.isDataFlavorSupported(DataFlavor.javaFileListFlavor)) {
        dtde.acceptDrop(DnDConstants.ACTION_COPY_OR_MOVE);
        Transferable t = dtde.getTransferable();
        List fileList = null;
        try {
            fileList = (List) t.getTransferData(DataFlavor.javaFileListFlavor);
            if (fileList.size() > 0) {
                table.clearSelection();
                Point point = dtde.getLocation();
                int row = table.rowAtPoint(point);
                DefaultTableModel model = (DefaultTableModel) table.getModel();
                for (Object value : fileList) {
                    if (value instanceof File) {
                        File f = (File) value;
                        if (row < 0) {
                            System.out.println("addRow");
                            model.addRow(new Object[]{f.getAbsolutePath(), "", f.length(), "", ""});
                        } else {
                            System.out.println("insertRow " + row);
                            model.insertRow(row, new Object[]{f.getAbsolutePath(), "", f.length(), "", ""});
                            row++;
                        }
                    }
                }
            }
        } catch (UnsupportedFlavorException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    } else {
        dtde.rejectDrop();
    }
}

注意.這將在放置點插入行，將所有現有行向下推，或者如果沒有放在現有行上，則將它們添加到末尾...

Note. This will insert rows at the drop point, push all the existing rows down OR if not dropped on an existing row, will add them to the end...

測試代碼

這是我用來測試代碼的完整運行示例...

This a full running example I used to test the code...

public class DropTable {

    public static void main(String[] args) {
        new DropTable();
    }

    public DropTable() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JFrame frame = new JFrame();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                frame.add(new DropPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }

        });
    }

    public class DropPane extends JPanel {

        private JTable table;
        private JScrollPane scroll;
        private DefaultTableModel tm = new DefaultTableModel(new String[]{"File", "File Type", "Size", "Status"}, 0);

        public DropPane() {
            table = new JTable();
            table.setShowGrid(true);
            table.setShowHorizontalLines(true);
            table.setShowVerticalLines(true);
            table.setGridColor(Color.GRAY);

            table.setModel(tm);
            table.setFillsViewportHeight(true);
            table.setPreferredSize(new Dimension(500, 300));

            scroll = new JScrollPane(table);

            table.setDropTarget(new DropTarget() {
                @Override
                public synchronized void dragOver(DropTargetDragEvent dtde) {
                    Point point = dtde.getLocation();
                    int row = table.rowAtPoint(point);
                    if (row < 0) {
                        table.clearSelection();
                    } else {
                        table.setRowSelectionInterval(row, row);
                    }
                    dtde.acceptDrag(DnDConstants.ACTION_COPY_OR_MOVE);
                }

                @Override
                public synchronized void drop(DropTargetDropEvent dtde) {
                    if (dtde.isDataFlavorSupported(DataFlavor.javaFileListFlavor)) {
                        dtde.acceptDrop(DnDConstants.ACTION_COPY_OR_MOVE);
                        Transferable t = dtde.getTransferable();
                        List fileList = null;
                        try {
                            fileList = (List) t.getTransferData(DataFlavor.javaFileListFlavor);
                            if (fileList.size() > 0) {
                                table.clearSelection();
                                Point point = dtde.getLocation();
                                int row = table.rowAtPoint(point);
                                DefaultTableModel model = (DefaultTableModel) table.getModel();
                                for (Object value : fileList) {
                                    if (value instanceof File) {
                                        File f = (File) value;
                                        if (row < 0) {
                                            model.addRow(new Object[]{f.getAbsolutePath(), "", f.length(), "", ""});
                                        } else {
                                            model.insertRow(row, new Object[]{f.getAbsolutePath(), "", f.length(), "", ""});
                                            row++;
                                        }
                                    }
                                }
                            }
                        } catch (UnsupportedFlavorException e) {
                            e.printStackTrace();
                        } catch (IOException e) {
                            e.printStackTrace();
                        }
                    } else {
                        dtde.rejectDrop();
                    }
                }

            });

            add(scroll, BorderLayout.CENTER);
        }
    }
}

這篇關于將文件從操作系統拖放到 JTable java的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！