JList中的拖放不起作用 [英] Drag and Drop in JList is not working
问题描述
所以我已经为我的应用程序编写了一个TransferHandler（沿着Oracle站点的例子），但是当我尝试移动数据时，它不会移动。它正在做的是将数据复制到索引（n-1，即如果我正在移动并且项目到n位置）索引n。可以请你检查什么是错误的，虽然我尝试过很多选项，但是没有一个可以为我工作。
So I have written a TransferHandler for my application (along the example from Oracle site) but when I am trying to move the data it is not moving. All it is doing is copying the data at index ( n-1 i.e if I am moving and item to n location) to index n. Could you please check what is wrong, though I have tried many options but none of them is working for me.
import javax.swing.TransferHandler;
import javax.swing.*;
import java.awt.datatransfer.*;
public class ListTransferHandler extends TransferHandler {
private int[] indices = null;
private int addIndex = -1; //Location where items were added
private int addCount = 0; //Number of items added.
public boolean canImport(TransferHandler.TransferSupport info) {
// Check for String flavor
if (!info.isDataFlavorSupported(DataFlavor.stringFlavor)) {
return false;
}
return true;
}
protected Transferable createTransferable(JComponent c) {
return new StringSelection(exportString(c));
}
public int getSourceActions(JComponent c) {
return TransferHandler.MOVE;
}
public boolean importData(TransferHandler.TransferSupport info) {
if (!info.isDrop()) {
return false;
}
JList list = (JList)info.getComponent();
DefaultListModel listModel = (DefaultListModel)list.getModel();
JList.DropLocation dl = (JList.DropLocation)info.getDropLocation();
int index = dl.getIndex();
boolean insert = dl.isInsert();
// Get the string that is being dropped.
Transferable t = info.getTransferable();
String data;
try {
data = (String)t.getTransferData(DataFlavor.stringFlavor);
}
catch (Exception e) { return false; }
// Perform the actual import.
if (insert) {
listModel.add(index, data);
} else {
listModel.set(index, data);
}
return true;
}
protected void exportDone(JComponent c, Transferable data, int action) {
cleanup(c, action == TransferHandler.MOVE);
}
//Bundle up the selected items in the list
//as a single string, for export.
protected String exportString(JComponent c) {
JList list = (JList)c;
indices = list.getSelectedIndices();
Object[] values = list.getSelectedValues();
StringBuffer buff = new StringBuffer();
for (int i = 0; i < values.length; i++) {
Object val = values[i];
buff.append(val == null ? "" : val.toString());
if (i != values.length - 1) {
buff.append("\n");
}
}
return buff.toString();
}
//Take the incoming string and wherever there is a
//newline, break it into a separate item in the list.
protected void importString(JComponent c, String str) {
JList target = (JList)c;
DefaultListModel listModel = (DefaultListModel)target.getModel();
int index = target.getSelectedIndex();
//Prevent the user from dropping data back on itself.
//For example, if the user is moving items #4,#5,#6 and #7 and
//attempts to insert the items after item #5, this would
//be problematic when removing the original items.
//So this is not allowed.
if (indices != null && index >= indices[0] - 1 &&
index <= indices[indices.length - 1]) {
indices = null;
return;
}
int max = listModel.getSize();
if (index < 0) {
index = max;
} else {
index++;
if (index > max) {
index = max;
}
}
addIndex = index;
String[] values = str.split("\n");
addCount = values.length;
for (int i = 0; i < values.length; i++) {
listModel.add(index++, values[i]);
}
}
//If the remove argument is true, the drop has been
//successful and it's time to remove the selected items
//from the list. If the remove argument is false, it
//was a Copy operation and the original list is left
//intact.
protected void cleanup(JComponent c, boolean remove) {
if (remove && indices != null) {
JList source = (JList)c;
DefaultListModel model = (DefaultListModel)source.getModel();
//If we are moving items around in the same list, we
//need to adjust the indices accordingly, since those
//after the insertion point have moved.
if (addCount > 0) {
for (int i = 0; i < indices.length; i++) {
if (indices[i] > addIndex) {
indices[i] += addCount;
}
}
}
for (int i = indices.length - 1; i >= 0; i--) {
model.remove(indices[i]);
}
}
indices = null;
addCount = 0;
addIndex = -1;
}
}
推荐答案
你导出成功完成后，需要从源中删除数据。
You need to "remove" the data from the source once the export has been completed successfully.
为了做到这一点，你需要覆盖 TransferHandler.exportDone 方法。
In order to do this, you need to override the TransferHandler.exportDone method.
protected void exportDone （JComponent来源，
可转移数据，
int action）
protected void exportDone(JComponent source, Transferable data, int action)
数据导出后调用。此方法应该删除
数据，如果该操作是MOVE，则转移该数据。
Invoked after data has been exported. This method should remove the data that was transferred if the action was MOVE.
由于MOVE不支持$ b $，因此实现此方法不执行任何操作b这个实现的操作（getSourceActions不包括
MOVE）。
This method is implemented to do nothing since MOVE is not a supported action of this implementation (getSourceActions does not include MOVE).
从那里你需要检查 action 键入，并确保目标组件已经接受了 MOVE ，而不仅仅是 COPY '编辑它，并从源列表中删除元素。
Basically, from there you need to check the action type and make sure the target component has accepted the MOVE and not simply COPY'ed it and remove the element from the source list.
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