在研究了如何使用Label DnD 后，我遇到了使用此解決方案的問題： public class LayerItem extends JLabel { int x = 0, y = 0; public LayerItem(String text) { this.setText(text); this.addMouseMotionListener(new MouseAdapter(){ @Override public void mouseDragged(MouseEvent evt){ lblMouseDragged(evt); } }); } protected void lblMouseDragged(MouseEvent evt){ this.x = evt.getX(); this.y = evt.getY(); }}當(dāng)用戶單擊并按住 JLabel 時，X 和 Y 會隨著鼠標移動而被記錄下來。但是，我不知道如何知道單擊何時停止（即，用戶到達他的目標 JPanel）然后將文本移入其中。允許 JPanels 接收放置操作的唯一參考是執(zhí)行以下操作：new JPanel().setDropTarget(getDropTarget());但是，我無法再次找到有關(guān)通過 JLabel 作為坐標（絕對布局）放置目標的任何參考。
1 回答
慕斯王
TA貢獻1864條經(jīng)驗 獲得超2個贊
在查看@ MadProgrammer發(fā)布的幾個示例后，我想出了一個擴展 JPanel 和 JLabel 的解決方案。這是 JLabel 類：
public class LayerItem extends JLabel {
public LayerItem(String text) {
this.setText(text);
this.setTransferHandler(new ValueExportTransferHandler(text));
this.addMouseMotionListener(new MouseAdapter() {
@Override
public void mouseDragged(MouseEvent e) {
JLabel lbl = (JLabel) e.getSource();
TransferHandler handle = lbl.getTransferHandler();
handle.exportAsDrag(lbl, e, TransferHandler.COPY);
}
});
}
protected static class ValueExportTransferHandler extends TransferHandler {
public static final DataFlavor SUPPORTED_DATE_FLAVOR = DataFlavor.stringFlavor;
private String value;
public ValueExportTransferHandler(String value) {
this.value = value;
}
public String getValue() {
return value;
}
@Override
public int getSourceActions(JComponent c) {
return DnDConstants.ACTION_COPY_OR_MOVE;
}
@Override
protected Transferable createTransferable(JComponent c) {
Transferable t = new StringSelection(getValue());
return t;
}
@Override
protected void exportDone(JComponent source, Transferable data, int action) {
super.exportDone(source, data, action);
// Clean up and remove the LayerItem that was moved
((LayerItem) source).setVisible(false);
((LayerItem) source).getParent().remove((LayerItem) source);
}
}
}
這是 JPanel 的類：
public class LayerContainer extends JPanel {
public LayerContainer() {
this.setTransferHandler(new ValueImportTransferHandler());
this.setLayout(new GridBagLayout()); // Optional layout
this.setBorder(new CompoundBorder(new LineBorder(Color.DARK_GRAY), new EmptyBorder(20, 20, 20, 20))); // Optional border
}
protected static class ValueImportTransferHandler extends TransferHandler {
public static final DataFlavor SUPPORTED_DATE_FLAVOR = DataFlavor.stringFlavor;
public ValueImportTransferHandler() {
}
@Override
public boolean canImport(TransferHandler.TransferSupport support) {
return support.isDataFlavorSupported(SUPPORTED_DATE_FLAVOR);
}
@Override
public boolean importData(TransferHandler.TransferSupport support) {
boolean accept = false;
if (canImport(support)) {
try {
Transferable t = support.getTransferable();
Object value = t.getTransferData(SUPPORTED_DATE_FLAVOR);
if (value instanceof String) { // Ensure no errors
// TODO: here you can create your own handler
// ie: ((LayerContainer) component).getHandler()....
Component component = support.getComponent();
LayerItem j = new LayerItem((String) value);
((LayerContainer) component).add(j); // Add a new drag JLabel
accept = true;
}
} catch (Exception exp) {
exp.printStackTrace();
}
}
return accept;
}
}
}
這是一個如何使用它的示例（從一個 JPanel 拖到另一個并再次返回）：
JPanel left_panel = new LayerContainer();
panel_1.setBounds(28, 47, 129, 97);
add(panel_1);
LayerContainer right_panel = new LayerContainer();
layerContainer.setBounds(203, 47, 129, 97);
add(layerContainer);
JLabel lblToDrag = new LayerItem("Drag Me");
GridBagConstraints gbc_lblToDrag = new GridBagConstraints();
gbc_lblDragMe.gridx = 0;
gbc_lblDragMe.gridy = 0;
panel_right.add(lblToDrag, gbc_lblToDrag);
為了將來使用，我將創(chuàng)建一個onTransfer()方法并創(chuàng)建我自己LayerContainerHandler()的run()方法來覆蓋一個方法，因此每次將標簽移動到不同的容器時，它都會執(zhí)行單獨的操作。
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