在JavaFX8tabpane标头中显示选定选项卡前面的一些选项卡

Question

我试图修改JavaFX8中的TabPage控件，使其向视口显示当前选定选项卡前面（右边）的一些选项卡，或者如果选定选项卡位于标题的最左边，它会显示当前选项卡前面附近的选项卡。

现在怎么样了：

我想让它表现得像：

当用户选择索引X的选项卡时，选项卡窗格标题显示附近的另外2或3个选项卡。

import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.scene.control.Tab;
import javafx.scene.control.TabPane;

public class TabSelectionListener implements ChangeListener<Tab> {

    protected TabPane owner;
    protected boolean lock;
    protected int nextItems;

    TabSelectionListener(TabPane listenTo){
        owner = listenTo;
        lock = false;
        nextItems = 2;
    }

    TabSelectionListener(TabPane listenTo, int minimalInFront){
        owner = listenTo;
        lock = false;
        nextItems = minimalInFront;
    }

    @Override
    public void changed(ObservableValue<? extends Tab> list, Tab old, Tab newT) {
        int maxTab;
        int curTab;
        int i;

        // Locks this listener, because the selections owner.getSelectionModel().select(X)
        // will call this listener again, and we are calling those from here.
        if(!lock){
            lock = true;
            maxTab = owner.getTabs().size() - 1;
            curTab = owner.getSelectionModel().getSelectedIndex();

            for(i = 0; i < nextItems && curTab + i < maxTab; i++);
            owner.getSelectionModel().select(i); // int overload
            owner.getSelectionModel().select(newT);

            lock = false;
        }
    }
}

tabPane.getSelectionModel().selectedItemProperty().addListener(new TabSelectionListener(tabPane,3));

StackPane region = (StackPane) tabPane.lookup(".headers-region");

谢谢你的阅读。

Answer 1

我终于做到了。

发现我要找的类是[e-mail]，它有一个方法使选定的选项卡可见，每次选项卡上选定的选项卡不完全可见时它都会运行，我覆盖了它。

TabPaneSkin是TabPane的默认外观，它将一些行为应用于TabPane控件。

tabPane.setSkin(new TabPaneNewSkin(tabPane));

...用我编写的显示附近选项卡的选项卡覆盖Oracle默认的TabPaneSkin。

Oracle的原始代码，用于在选择标签以使其可见时重新定位标签：

    private void ensureSelectedTabIsVisible() {
            // work out the visible width of the tab header
            double tabPaneWidth = snapSize(isHorizontal() ? getSkinnable().getWidth() : getSkinnable().getHeight());
            double controlTabWidth = snapSize(controlButtons.getWidth());
            double visibleWidth = tabPaneWidth - controlTabWidth - firstTabIndent() - SPACER;

            // and get where the selected tab is in the header area
            double offset = 0.0;
            double selectedTabOffset = 0.0;
            double selectedTabWidth = 0.0;
            for (Node node : headersRegion.getChildren()) {
                TabHeaderSkin tabHeader = (TabHeaderSkin)node;

                double tabHeaderPrefWidth = snapSize(tabHeader.prefWidth(-1));

                if (selectedTab != null && selectedTab.equals(tabHeader.getTab())) {
                    selectedTabOffset = offset;
                    selectedTabWidth = tabHeaderPrefWidth;
                }
                offset += tabHeaderPrefWidth;
            }

            final double scrollOffset = getScrollOffset();
            final double selectedTabStartX = selectedTabOffset;
            final double selectedTabEndX = selectedTabOffset + selectedTabWidth;

            final double visibleAreaEndX = visibleWidth;

            if (selectedTabStartX < -scrollOffset) {
                setScrollOffset(-selectedTabStartX);
            } else if (selectedTabEndX > (visibleAreaEndX - scrollOffset)) {
                setScrollOffset(visibleAreaEndX - selectedTabEndX);
            }
        }

我写到自定义TabPane皮肤中的代码：

    // This function was overwritten
    private void ensureSelectedTabIsVisible() {
        // work out the visible width of the tab header
        double tabPaneWidth = snapSize(isHorizontal() ? getSkinnable().getWidth() : getSkinnable().getHeight());
        double controlTabWidth = snapSize(controlButtons.getWidth());
        double visibleWidth = tabPaneWidth - controlTabWidth - firstTabIndent() - SPACER;


        // and get where the selected tab is in the header area
        double offset = 0.0;
        double selectedTabOffset = 0.0;
        double selectedTabWidth = 0.0;

        // OVERWRITE
        // Makes the nearby 3 tabs for each side of the selected tab visible.
        ObservableList<Node> headersRegionChildren = headersRegion.getChildren();
        boolean nextTabs = false;
        int nextTabsCount = 0;
        int current = 0;
        int numOfTabsToShowNext = 3;
        int numOfTabsToShowBefore = 3;
        double tabHeaderPrefWidth;       
        TabHeaderSkin tabHeader;

        for (Node node : headersRegionChildren) {
            tabHeader = (TabHeaderSkin)node;

            tabHeaderPrefWidth = snapSize(tabHeader.prefWidth(-1));

           if (selectedTab != null && selectedTab.equals(tabHeader.getTab())) {
                    selectedTabWidth = tabHeaderPrefWidth;

                // OVERWRITE: Finds the offset of the first tab in the limit numOfTabsToShowBefore before the selected one to be shown
                for(int i = current - 1; i >= 0 && numOfTabsToShowBefore > 1; i--, numOfTabsToShowBefore--){
                    tabHeader = (TabHeaderSkin)headersRegionChildren.get(i);
                    tabHeaderPrefWidth = snapSize(tabHeader.prefWidth(-1));
                    offset -= tabHeaderPrefWidth;
                    selectedTabWidth += tabHeaderPrefWidth;
                }

                selectedTabOffset = offset;
                // OVERWRITE: Sets the flag to start counting in the next 3 nearby tabs.  
                nextTabs = true;
            }
            // OVERWRITE: Sums the width of the next nearby tabs with the
            // width of the selected tab, so it will scroll enough to show
            // them too.
            if(nextTabs && nextTabsCount < numOfTabsToShowNext){
                selectedTabWidth += tabHeaderPrefWidth;
                nextTabsCount++;
            }else if(nextTabsCount == numOfTabsToShowNext){
                break;
            }

            offset += tabHeaderPrefWidth;
            current++;
        }
        // END OVERWRITE

        final double scrollOffset = getScrollOffset();
        final double selectedTabStartX = selectedTabOffset;
        final double selectedTabEndX = selectedTabOffset + selectedTabWidth;

        final double visibleAreaEndX = visibleWidth;

        if (selectedTabStartX < -scrollOffset) {
            setScrollOffset(-selectedTabStartX);
        } else if (selectedTabEndX > (visibleAreaEndX - scrollOffset)) {
            setScrollOffset(visibleAreaEndX - selectedTabEndX);
        }
    }