java - 在 JavaFx 8 TabPane 标题中显示所选选项卡前面的一些选项卡

Question

我正在尝试修改 JavaFx 8 中的 TabPage 控件，使其向视口(viewport)显示当前所选选项卡前面(右侧)的一些选项卡，或者所选选项卡是否位于标题的最左侧, 它会在当前选项卡之前显示附近的选项卡。

现在怎么样了:

我是如何让它表现得像这样的:

当用户选择索引 X 的选项卡时，选项卡 Pane 标题会显示另外 2 或 3 个附近的选项卡。

这是我到目前为止尝试的方法，但没有成功，显然下面的代码太快了，无法使界面线程按时同步选项卡选择(我的想法是先选择一个选项卡，然后回退到由用户，使标题显示所选选项卡之后的选项卡):

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 为每个选项卡选择调用它:

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

我在这里阅读了一些主题，在我看来，标题实际上是一个 StackPane，可以通过执行以下命令获得:

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

它有效，但在那之后我不知道如何访问实现默认行为的属性。

有什么建议吗？

感谢阅读。

Answer 1

我终于做到了。

发现我正在寻找的类是 com.sun.javafx.scene.control.skin.TabPaneSkin @ jfxrt.jar，它有一种方法可以使所选选项卡可见，每次在 TabPane 中选择一个选项卡时它都会运行不完全可见，我覆盖了它。

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

/*
* Copyright (c) 2011, 2014, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*

希望甲骨文不要介意...

选择您的 TabPane，然后...

tabPane.setSkin(new TabPaneNewSkin(tabPane));

...用我写的显示附近选项卡的这个覆盖 Oracle 的默认 TabPaneSkin。

原始 Oracle 的代码，用于在选择一个选项卡以使其可见时重新定位选项卡:

    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);
            }
        }

我写入自定义 TabPane 皮肤的代码:

    // 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);
        }
    }

对于每个选项卡选择，上面的代码会在所选选项卡的每一侧显示 3 个最近的选项卡(如果其中一个在屏幕之外并且存在)。

原来如此。 com.sun.javafx.scene.control.skin.TabPaneSkin本来就不应该扩展的，几乎每个方法都是私有(private)的，所以我复制了一份，只改了上面提到的功能，改名为TabPaneNewSkin，就这样了在我的包裹里。