目前，GWT DataGrid标题在垂直滚动期间使用固定标题行执行此操作。有没有办法在整个（第一列）上实现相同的目标？
答案 0 :(得分：3)
我已经实现了ScrolledGrid，冻结了DataGrid中的第一列。您需要使用它而不是DataGrid才能使第一列被冻结。
import com.google.gwt.dom.client.*;
import com.google.gwt.event.dom.client.ScrollEvent;
import com.google.gwt.event.dom.client.ScrollHandler;
import com.google.gwt.user.cellview.client.DataGrid;
import com.google.gwt.user.client.ui.HeaderPanel;
import com.google.gwt.user.client.ui.ScrollPanel;
/**
*
* @author Yuri Plaksyuk
*/
public class ScrolledGrid extends DataGrid {
private final Text cssText;
private boolean addedClass = false;
private int currentScrollLeft = 0;
public ScrolledGrid() {
cssText = Document.get().createTextNode("");
StyleElement styleElement = Document.get().createStyleElement();
styleElement.setType("text/css");
styleElement.appendChild(cssText);
HeaderPanel headerPanel = (HeaderPanel) getWidget();
headerPanel.getElement().insertFirst(styleElement);
final ScrollPanel scrollPanel = (ScrollPanel) headerPanel.getContentWidget();
scrollPanel.addScrollHandler(new ScrollHandler() {
@Override
public void onScroll(ScrollEvent event) {
int scrollLeft = scrollPanel.getHorizontalScrollPosition();
if (scrollLeft != currentScrollLeft) {
StringBuilder css = new StringBuilder();
if (scrollLeft > 0) {
css.append(".ScrolledGrid-frozen {");
css.append("background-color: inherit;");
css.append("}");
css.append(".ScrolledGrid-frozen div {");
css.append("position: absolute;");
css.append("left: ").append(scrollLeft).append("px;");
css.append("width: ").append(getColumnWidth(getColumn(0))).append(";");
css.append("padding-left: 1.3em;");
css.append("padding-right: 0.5em;");
css.append("margin-top: -0.7em;");
css.append("white-space: nowrap;");
css.append("background-color: inherit;");
css.append("}");
}
else
css.append(".ScrolledGrid-frozen { }");
css.append("th.ScrolledGrid-frozen { background-color: white; }");
cssText.setData(css.toString());
if (!addedClass) {
NodeList<TableRowElement> rows;
TableRowElement row;
TableCellElement cell;
rows = getTableHeadElement().getRows();
for (int i = 0; i < rows.getLength(); ++i) {
row = rows.getItem(i);
cell = row.getCells().getItem(0);
cell.setInnerHTML("<div>" + cell.getInnerHTML() + "</div>");
cell.addClassName("ScrolledGrid-frozen");
}
rows = getTableBodyElement().getRows();
for (int i = 0; i < rows.getLength(); ++i) {
row = rows.getItem(i);
cell = row.getCells().getItem(0);
cell.addClassName("ScrolledGrid-frozen");
}
addedClass = true;
}
currentScrollLeft = scrollLeft;
}
}
});
}
}
不幸的是，有些CSS值是硬编码的。
答案 1 :(得分：0)
我采用Yuri的解决方案来实现以下目标：
它不会混淆列本身，而是在行级显示任意“冻结”信息。
import com.google.gwt.core.client.Scheduler;
import com.google.gwt.dom.client.*;
import com.google.gwt.event.dom.client.ScrollEvent;
import com.google.gwt.event.dom.client.ScrollHandler;
import com.google.gwt.user.cellview.client.DataGrid;
import com.google.gwt.user.cellview.client.DefaultCellTableBuilder;
import com.google.gwt.user.client.Timer;
import com.google.gwt.user.client.ui.HeaderPanel;
import com.google.gwt.user.client.ui.ScrollPanel;
/**
* @author Daniel Lintner
*
* A DataGrid extension with the ability to display some row-level-information
* when scrolling left (horizontal), hence important columns out of sight of the user.
*/
public class FrozenDataGrid extends DataGrid
{
//textnode getting updated dynamically when scolling horizontally
private Text cssText;
//the latest scroll-position
private int currentScrollLeft = 0;
//an object extracting String-info from your rowdata
private FrozenValueProvider valueProvider;
//inject basic styling into the document - once
//this is how the frozen row-info looks like
static
{
Text baseCss = Document.get().createTextNode("");
StyleElement styleElement = Document.get().createStyleElement();
styleElement.setType("text/css");
styleElement.appendChild(baseCss);
StringBuilder css = new StringBuilder();
css.append(".ScrolledGrid-base {");
css.append("position: absolute;");
css.append("background-color: gray;");
css.append("padding: .3em;");
css.append("padding-left: .5em;");
css.append("padding-right: .5em;");
css.append("border-radius: 3px 3px;");
css.append("transition: opacity 500ms;");
css.append("color: white;");
css.append("margin-top: 2px;");
css.append("white-space: nowrap;");
css.append("}");
baseCss.setData(css.toString());
Document.get().getBody().insertFirst(styleElement);
}
public FrozenDataGrid()
{
super();
init();
}
public FrozenDataGrid(int pageSize, DataGrid.Resources resources)
{
super(pageSize, resources);
init();
}
public void init()
{
//create a css textnode
cssText = Document.get().createTextNode("");
//create dynamic css Style
StyleElement styleElement = Document.get().createStyleElement();
styleElement.setType("text/css");
styleElement.appendChild(cssText);
//append the initial style condition
//todo the name of this style might be built dynamically per instance - if multiple grid-instances exist/not the use-case by now
StringBuilder css = new StringBuilder();
css.append(".ScrolledGrid-frozen {");
css.append("opacity:0;");
css.append("}");
cssText.setData(css.toString());
//set a custom CellTableBuilder in order to inject the info-div to the row
setTableBuilder(new DefaultCellTableBuilder(this)
{
@Override
public void buildRowImpl(final Object rowValue, final int absRowIndex)
{
//do what DefaultCellTableBuilder does
super.buildRowImpl(rowValue, absRowIndex);
//only do something if there is a valueProvider
if(valueProvider != null) {
//we do this deferred because this row has to created first in order to access it
Scheduler.get().scheduleDeferred(new Scheduler.ScheduledCommand()
{
@Override
public void execute()
{
createInfoDiv(getTableBodyElement().getRows().getItem(absRowIndex % getPageSize()), rowValue);
}
});
}
}
});
//fetch the ScrollPanel from the grid
HeaderPanel headerPanel = (HeaderPanel) getWidget();
headerPanel.getElement().insertFirst(styleElement);
final ScrollPanel scrollPanel = (ScrollPanel) headerPanel.getContentWidget();
//setup a timer handling the left-offset-css thing
//we use a timer to be able to cancel this operation -> e.g. continuous scroll
final Timer timer = new Timer(){
@Override
public void run() {
StringBuilder css = new StringBuilder();
//we need to left-offset the info-divs
if (scrollPanel.getHorizontalScrollPosition() > 100)
{
css.append(".ScrolledGrid-frozen {");
css.append("left: ").append(3 + scrollPanel.getHorizontalScrollPosition()).append("px;");
css.append("opacity: 1;");
css.append("}");
}
//we are close to the leftmost scroll position: info hidden
else
{
css.append(".ScrolledGrid-frozen {");
css.append("opacity:0;");
css.append("}");
}
cssText.setData(css.toString());
}
};
//track scrolling
scrollPanel.addScrollHandler(new ScrollHandler()
{
@Override
public void onScroll(ScrollEvent event)
{
//cancel previous actions to scroll events
if(timer.isRunning())
timer.cancel();
//actual horizontal scrollposition
int scrollLeft = scrollPanel.getHorizontalScrollPosition();
//a horizontal scroll takes places
if (scrollLeft != currentScrollLeft)
{
//first we hide the row-info
StringBuilder css = new StringBuilder();
css.append(".ScrolledGrid-frozen {");
css.append("opacity:0;");
css.append("}");
cssText.setData(css.toString());
//render left offset after a delay
timer.schedule(500);
//remember the current horizontal position
currentScrollLeft = scrollLeft;
}
}
});
}
private void createInfoDiv(TableRowElement row, Object value)
{
//create a div element and add value and style to it
DivElement div = Document.get().createDivElement();
div.setInnerText(valueProvider.getFrozenValue(value));
div.addClassName("ScrolledGrid-base");
div.addClassName("ScrolledGrid-frozen");
//we add it to the first child of the row, because added as child of the row directly
// confuses the CellTable with coordinating header positions
row.getFirstChildElement().insertFirst(div);
}
public void setFrozenValueProvider(FrozenValueProvider valueProvider) {
this.valueProvider = valueProvider;
}
public interface FrozenValueProvider<T>{
String getFrozenValue(T data);
}
}
希望这可以帮助开发人员解决这个很少且不能令人满意的问题。 并且......还有改进的余地。
干杯丹