如何在JavaFX 9中查找TableView中可见行的索引 [英] How to find the indices of the visible rows in a TableView in JavaFX 9

问题描述

如何在JavaFX 9中获取TableView中可见行的索引？在JavaFX 8中，我可以执行以下操作：

How do I get the indices of the visible rows in a TableView in JavaFX 9? In JavaFX 8, I can do the following:

  // --- The offending imports in Java 9
  // import com.sun.javafx.scene.control.skin.TableViewSkin;
  // import com.sun.javafx.scene.control.skin.VirtualFlow;

  /**
   * This is a total hack. We need it as scrollTo jumps the selected
   * row to the top of the table. Jarring if the row is already 
   * visible. As a workaround, we only scroll if the row isn't already
   * visible
   *
   * @return A 2 element ray with the start and end index of visible rows
   */
  public int[] getVisibleRows() {
      TableView<?> tableView = getTableView();
      TableViewSkin<?> skin = (TableViewSkin<?>) tableView.getSkin();
      if (skin == null) return new int[] {0, 0};
      VirtualFlow<?> flow = (VirtualFlow<?>) skin.getChildren().get(1);
      int idxFirst;
      int idxLast;
      if (flow != null &&
              flow.getFirstVisibleCellWithinViewPort() != null &&
              flow.getLastVisibleCellWithinViewPort() != null) {
          idxFirst = flow.getFirstVisibleCellWithinViewPort().getIndex();
          if (idxFirst > tableView.getItems().size()) {
              idxFirst = tableView.getItems().size() - 1;
          }
          idxLast = flow.getLastVisibleCellWithinViewPort().getIndex();
          if (idxLast > tableView.getItems().size()) {
              idxLast = tableView.getItems().size() - 1;
          }
      }
      else {
          idxFirst = 0;
          idxLast = 0;
      }
      return new int[]{idxFirst, idxLast};
  }

在Java 9中，作为模块化的一部分，JDK团队隐藏了API不是公开的（例如所有以'com.sun'开头的包）如果我尝试在Java 9中编译它，我会收到以下错误：

In Java 9, as part of the modularization, the JDK team is hiding the API's that weren't meant to be public (e.g. all packages that start with 'com.sun') If I try to compile this in Java 9, I get errors of:

  [...] cannot find symbol
  [ERROR]   symbol:   class TableViewSkin
  [ERROR]   location: package com.sun.javafx.scene.control.skin

  [...] cannot find symbol
  [ERROR]   symbol:   class VirtualFlow
  [ERROR]   location: package com.sun.javafx.scene.control.skin

有没有官方的方法来获取TableView中的可见行？有关另一个的更好的解决方法吗？

Is there any official way to get the visible rows in a TableView? Any ideas on another, better workaround for this?

更新：基于@ user4712734解决方案的解决方案

TableViewExt<?> tableViewExt = new TableViewExt<>(tableView);

public int[] getVisibleRows() {
    return new int[]{ tableViewExt.getFirstVisibleIndex(), 
                      tableViewExt.getLastVisibleIndex()};
}

TableViewExt的代码

推荐答案

我遇到了同样的问题，因为我也是使用JavaFX 8特定的TableViewSkin / VirtualFlow代码，但现在使用此解决方法，在此问题的另一篇文章中包含了一些建议 - 请参阅 Tableview可见行

I had same issue as I was also using the JavaFX 8 specific TableViewSkin/VirtualFlow code, but now use this workaround which wraps up some of the suggestions in another post on this issue - see Tableview visible rows

此变通方法在Java8 / 9中运行和编译，不使用参考包com.sun.javafx。要使用该类，您需要在构造TableView和向其添加行之间创建TableViewExtra：

This workaround runs and compiles in Java8/9 and does not use reference package com.sun.javafx. To use the class you need to create a TableViewExtra between constructing your TableView and adding rows to it:

TableView<YourRowType> tableView = new TableView<YourRowType>();
TableViewExtra<YourRowType> tvX = new TableViewExtra(tableView);
// Add some rows etc

然后你可以打电话：

int firstVisRowIndex = tvX.getFirstVisibleIndex();
int lastVisRowIndex  = tvX.getLastVisibleIndex();
txV.scrollToSelection();

您可以看到我曾在评论中使用的旧com.sun.javafx依赖项：

You can see the old com.sun.javafx dependencies I once used in comments:

import java.util.LinkedHashSet;

//com.sun.javafx: START
//import com.sun.javafx.scene.control.skin.TableViewSkin;
//import com.sun.javafx.scene.control.skin.VirtualFlow;
//import javafx.beans.value.ChangeListener;
//import javafx.beans.value.ObservableValue;
//import javafx.scene.Node;
//import javafx.scene.control.IndexedCell;
//import javafx.scene.control.Skin;
// com.sun.javafx: END 

import javafx.collections.ObservableList;
import javafx.scene.control.TableRow;
import javafx.scene.control.TableView;
import javafx.util.Callback;

/**
 * Extra calls for TableView which would have been nice to see in JavaFx TableView
 */
public class TableViewExtra<T> // com.sun.javafx: implements ChangeListener<Skin<?>>
{
    private final TableView<T> tableView;

    // com.sun.javafx: private VirtualFlow<?> flow;

    LinkedHashSet<TableRow<T>> rows = new LinkedHashSet<>();
    private int firstIndex;
    private int lastIndex;

    public TableViewExtra(TableView<T> tableView)
    {
        this.tableView = tableView;

        // com.sun.javafx: tableView.skinProperty().addListener(this);

        // Callback to monitor row creation and to identify visible screen rows
        final Callback<TableView<T>, TableRow<T>> rf = tableView.getRowFactory();

        final Callback<TableView<T>, TableRow<T>> modifiedRowFactory = new Callback<TableView<T>, TableRow<T>>() {

            @Override
            public TableRow<T> call(TableView<T> param)
            {
                TableRow<T> r = rf != null ? rf.call(param) : new TableRow<T>();
                // Save row, this implementation relies on JaxaFX re-using TableRow efficiently
                rows.add(r);
                return r;
            }
        };
        tableView.setRowFactory(modifiedRowFactory);
    }

    // com.sun.javafx BEGIN
//    public void changed(ObservableValue<? extends Skin<?>> ov, Skin<?> t, Skin<?> t1)
//    {
//        if (t1 == null) {
//            return;
//        }
//
//        TableViewSkin<?> tvs = (TableViewSkin<?>) t1;
//        ObservableList<Node> kids = tvs.getChildren();
//
//        if (kids == null || kids.isEmpty() || kids.size() < 2) {
//            return;
//        }
//        flow = (VirtualFlow<?>) kids.get(1);
//    }
    // com.sun.javafx END

    /**
     * Changes the current view to ensure that one of the passed index positions
     * is visible on screen. The view is not changed if any of the passed index positions is already visible.
     * The table scroll position is moved so that the closest index to the current position is visible. 
     * @param indices Assumed to be in ascending order.
     * 
     */
    public void
    scrollToIndex(int ... indices)
    {
        int first = getFirstVisibleIndex();
        int last = getLastVisibleIndex();
        int where = first;

        boolean changeScrollPos = true;

        // No point moving current scroll position if one of the index items is visible already:
        if (first >= 0 && last >= first)
            for (int idx : indices)
            {
                if (first <= idx && idx <= last)
                {
                    changeScrollPos = false;
                    break;
                }
            }


        if (indices.length > 0 && changeScrollPos)
        {
            where = indices[0];
            if (first >= 0)
            {
                int x = closestTo(indices, first);
                int abs = Math.abs(x - first);
                if (abs < Math.abs(where - first))
                {
                    where = x;
                }
            }
            if (last >= 0)
            {
                int x = closestTo(indices, last);
                int abs = Math.abs(x - last);
                if (abs < Math.abs(where - last))
                {
                    where = x;
                }
            }
            tableView.scrollTo(where);
        }
    }

    private static int closestTo(int[] indices, int value)
    {
        int x    = indices[0];
        int diff = Math.abs(value - x);
        int newDiff = diff;
        for (int v : indices)
        {
            newDiff = Math.abs(value - v);
            if (newDiff < diff)
            {
                x    = v;
                diff = newDiff;
            }
        }
        return x;
    }

    private void recomputeVisibleIndexes()
    {
        firstIndex = -1;
        lastIndex = -1;

        // Work out which of the rows are visible
        double tblViewHeight = tableView.getHeight();
        double headerHeight = tableView.lookup(".column-header-background").getBoundsInLocal().getHeight();
        double viewPortHeight = tblViewHeight - headerHeight;
        for(TableRow<T> r : rows)
        {
            double minY = r.getBoundsInParent().getMinY();
            double maxY = r.getBoundsInParent().getMaxY();

            boolean hidden  = (maxY < 0) || (minY > viewPortHeight);
            // boolean fullyVisible = !hidden && (maxY <= viewPortHeight) && (minY >= 0);
            if (!hidden)
            {
                if (firstIndex < 0 || r.getIndex() < firstIndex)
                {
                    firstIndex = r.getIndex();
                }
                if (lastIndex < 0 || r.getIndex() > lastIndex)
                {
                    lastIndex = r.getIndex();
                }
            }
        }

    }
    /**
     * Find the first row in the tableView which is visible on the display
     * @return -1 if none visible or the index of the first visible row (wholly or fully)
     */
    public int getFirstVisibleIndex()
    {
        // com.sun.javafx: START
//        int jre8Index = -1;
//        if (flow != null)
//        {
//            IndexedCell<?> cell = flow.getFirstVisibleCell();
//            if (cell != null)
//            {
//                jre8Index = cell.getIndex();
//            }
//        }
        // com.sun.javafx: END

        recomputeVisibleIndexes();

        System.out.println("getFirstVisibleIndex "+firstIndex+" rows="+rows.size()/*com.sun.javafx:+" jre8Index="+jre8Index*/);
        return firstIndex;
    }

    /**
     * Find the last row in the tableView which is visible on the display
     * @return -1 if none visible or the index of the last visible row (wholly or fully)
     */
    public int getLastVisibleIndex()
    {
        // com.sun.javafx: END
//        int jre8Index = -1;
//        if (flow != null)
//        {
//            IndexedCell<?> cell = flow.getLastVisibleCell();
//            if (cell != null)
//                jre8Index = cell.getIndex();
//        }
        // com.sun.javafx: END

        recomputeVisibleIndexes();

        System.out.println("getLastVisibleIndex "+lastIndex+" rows="+rows.size()/*com.sun.javafx:+" jre8Index="+jre8Index*/);

        return lastIndex;
    }

    /**
     * Ensure that some part of the current selection is visible in the display view
     */
    public void scrollToSelection()
    {
        ObservableList<Integer> seln = tableView.getSelectionModel().getSelectedIndices();
        int[] indices = new int[seln.size()];
        for (int i = 0; i < indices.length; i++)
        {
            indices[i] = seln.get(i).intValue();
        }
        scrollToIndex(indices);
    }
}

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