我正在尝试将拖放添加到单元小部件。更具体地说，我想拖放ClickableTextCell，但是它们没有特定的方法，甚至没有.addDomHandler，所以我不能只创建像.addDomHandler(new DragStartHandler() { ... }这样的东西
有人可以提供一些有关如何分离DnD细胞的帮助，最好是使用纯GWT吗？
最佳答案
我不知道如何用GWT实现DnD，但是我知道如何实现CnC(Clic'n Clic)，这可能会让您感兴趣。 DnD很酷，很有趣，很漂亮，但我认为有时候它们不是很方便。例如，如果您有一个需要滚动的大屏幕，并且想要从上到下DnD一个项目，那么握住鼠标并不是那么方便...但这只是一种个人感觉...
无论如何，我建议您使用ListDataProvider和简单事件来移动项目:第一个clic选择源项目，第二个clic选择目标。知道来源和目的地后，就可以移动项目了。
它对我来说效果很好...如果您添加一些样式以突出显示源和目标，那就非常好了。
例子:
这是主要的类:
import java.util.ArrayList;
import com.google.gwt.event.dom.client.ClickEvent;
import com.google.gwt.event.dom.client.ClickHandler;
import com.google.gwt.user.cellview.client.CellList;
import com.google.gwt.user.client.ui.DialogBox;
import com.google.gwt.user.client.ui.FlowPanel;
import com.google.gwt.user.client.ui.FocusPanel;
import com.google.gwt.user.client.ui.Grid;
import com.google.gwt.user.client.ui.Label;
import com.google.gwt.view.client.ListDataProvider;
import com.google.gwt.view.client.SelectionChangeEvent;
import com.google.gwt.view.client.SingleSelectionModel;
public class Clic_Clic {
private static final Integer LEFT = 0;
private static final Integer CENTER = 1;
private static final Integer RIGHT = 2;
private ClicClicSelectionModel<Item> selectionModel = new ClicClicSelectionModel<Item>();
ListDataProvider<Item> leftLDP = new ListDataProvider<Item>();
ListDataProvider<Item> centerLDP = new ListDataProvider<Item>();
ListDataProvider<Item> rightLDP = new ListDataProvider<Item>();
FocusPanel left = new FocusPanel(), center = new FocusPanel(), right = new FocusPanel();
Item selected = null;
public Clic_Clic() {
// --- Builds the GUI
DialogBox clic_clic = buildGUI();
clic_clic.center();
clic_clic.show();
// --- Initializes data
configureSelectionManagement();
initCellLists();
configureAddAndRemove();
// --- Fills the left LDP
leftLDP.getList().add(new Item("Fraternité", LEFT));
leftLDP.refresh();
// --- Fills the center LDP
centerLDP.getList().add(new Item("Egalité", LEFT));
centerLDP.refresh();
// --- Fills the right LDP
rightLDP.getList().add(new Item("Liberté", RIGHT));
rightLDP.refresh();
}
private DialogBox buildGUI() {
DialogBox db = new DialogBox();
db.setText("A simple example for Clic 'n Clic");
db.setSize("300px", "200px");
db.setGlassEnabled(true);
db.setModal(true);
FlowPanel fp = buildContent();
db.add(fp);
return db;
}
private FlowPanel buildContent() {
Grid g = new Grid(1, 3);
g.setSize("300px", "200px");
g.setWidget(0, 0, left);
left.setSize("100px", "100px");
left.getElement().getStyle().setBackgroundColor("blue");
g.setWidget(0, 1, center);
center.setSize("100px", "100px");
g.setWidget(0, 2, right);
right.setSize("100px", "100px");
right.getElement().getStyle().setBackgroundColor("red");
FlowPanel fp = new FlowPanel();
fp.setSize("300px", "200px");
fp.add(new Label("Do you know the correct order ?"));
fp.add(g);
return fp;
}
private void initCellLists() {
// --- Associates the left panel with the leftLDP ListDataProvider
CellList<Item> cellListLeft = new CellList<Item>(new MyCell());
cellListLeft.setSelectionModel(selectionModel);
left.add(cellListLeft);
leftLDP = new ListDataProvider<Item>(new ArrayList<Item>());
leftLDP.addDataDisplay(cellListLeft);
// --- Associates the center panel with the centerLDP ListDataProvider
CellList<Item> cellListCenter = new CellList<Item>(new MyCell());
cellListCenter.setSelectionModel(selectionModel);
center.add(cellListCenter);
centerLDP = new ListDataProvider<Item>(new ArrayList<Item>());
centerLDP.addDataDisplay(cellListCenter);
// --- Associates the right panel with the rightLDP ListDataProvider
CellList<Item> cellListRight = new CellList<Item>(new MyCell());
cellListRight.setSelectionModel(selectionModel);
right.add(cellListRight);
rightLDP = new ListDataProvider<Item>(new ArrayList<Item>());
rightLDP.addDataDisplay(cellListRight);
}
private void configureAddAndRemove() {
// --- If the user clic on the left
left.addClickHandler(new ClickHandler() {
@Override
public void onClick(ClickEvent event) {
if (selected != null) {
// --- If the selected item comes from the right
if (selected.getContainerIndex() == RIGHT) {
rightLDP.getList().remove(selected);
rightLDP.refresh();
selected.setContainerIndex(LEFT);
leftLDP.getList().add(selected);
leftLDP.refresh();
selected = null;
}
// --- If the selected item comes from the center
if (selected.getContainerIndex() == CENTER) {
centerLDP.getList().remove(selected);
centerLDP.refresh();
selected.setContainerIndex(LEFT);
leftLDP.getList().add(selected);
leftLDP.refresh();
selected = null;
}
}
}
});
// --- If the user clic on the center
center.addClickHandler(new ClickHandler() {
@Override
public void onClick(ClickEvent event) {
if (selected != null) {
// --- If the selected item comes from the right
if (selected.getContainerIndex() == RIGHT) {
rightLDP.getList().remove(selected);
rightLDP.refresh();
selected.setContainerIndex(CENTER);
centerLDP.getList().add(selected);
centerLDP.refresh();
selected = null;
}
// --- If the selected item comes from the left
if (selected.getContainerIndex() == LEFT) {
leftLDP.getList().remove(selected);
leftLDP.refresh();
selected.setContainerIndex(CENTER);
centerLDP.getList().add(selected);
centerLDP.refresh();
selected = null;
}
}
}
});
// --- If the user clic on the right
right.addClickHandler(new ClickHandler() {
@Override
public void onClick(ClickEvent event) {
// --- If the selected item comes from the left
if (selected.getContainerIndex() == LEFT) {
leftLDP.getList().remove(selected);
leftLDP.refresh();
selected.setContainerIndex(RIGHT);
rightLDP.getList().add(selected);
rightLDP.refresh();
selected = null;
}
// --- If the selected item comes from the center
if (selected.getContainerIndex() == CENTER) {
centerLDP.getList().remove(selected);
centerLDP.refresh();
selected.setContainerIndex(RIGHT);
rightLDP.getList().add(selected);
rightLDP.refresh();
selected = null;
}
}
});
}
@SuppressWarnings("hiding")
class ClicClicSelectionModel<Item> extends SingleSelectionModel<Item> {
@Override
public void setSelected(Item object, boolean selected) {
if (getSelectedObject() != null && getSelectedObject().equals(object)) {
super.setSelected(object, !selected);
} else {
super.setSelected(object, selected);
}
};
}
private void configureSelectionManagement() {
selectionModel.addSelectionChangeHandler(new SelectionChangeEvent.Handler() {
@Override
public void onSelectionChange(SelectionChangeEvent event) {
Item selected = selectionModel.getSelectedObject();
updateSelected(selected);
}
});
}
private void updateSelected(Item item) {
// --- If no item has been selected, update the selected item
if (selected == null) {
selected = item;
}
}
}
您还需要以下一个:
public class Item {
private String label;
private Integer containerIndex;
public Item(String l, Integer id) {
this.label = l;
this.containerIndex = id;
}
public String getLabel() {
return label;
}
public void setLabel(String label) {
this.label = label;
}
public Integer getContainerIndex() {
return containerIndex;
}
public void setContainerIndex(Integer containerIndex) {
this.containerIndex = containerIndex;
}
}
最后，这个:
import com.google.gwt.cell.client.AbstractCell;
import com.google.gwt.safehtml.shared.SafeHtml;
import com.google.gwt.safehtml.shared.SafeHtmlBuilder;
import com.google.gwt.safehtml.shared.SafeHtmlUtils;
public class MyCell extends AbstractCell<Item> {
@Override
public void render(com.google.gwt.cell.client.Cell.Context context, Item value, SafeHtmlBuilder sb) {
if (value != null) {
// --- If the value comes from the user, we escape it to avoid XSS
// attacks.
SafeHtml safeValue = SafeHtmlUtils.fromString(value.getLabel());
sb.append(safeValue);
}
}
}
干得好。
下次，我将尝试举一个有趣的例子:)
希望能帮助到你。