What I want: the icons ALL in the LEFT, not based on the Text Size

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选项卡的内容以典型的实现为中心,这是有道理的,因为在有效地渲染选项卡之前,适应此内容所需的区域是不可预测的.由于该区域取决于内容,并且不同的选项卡可能具有不同的标题长度,因此必须制定有关如何呈现这些选项卡的策略.标准是使标签内容居中,并使标签区域适合此内容.当我们有一个默认的选项卡式窗格,其顶部放置有选项卡时,我们不太在乎图标/文本的对齐方式：

唯一关心的可能是具有不同长度的标签,但是谁在乎呢？毕竟,图标和文本是可见的,并且选项卡式窗格看起来足够好.但是,将选项卡的位置设置为LEFT或RIGHT时,情况会有所不同,并且看起来不那么吸引人：

显然,这种默认行为是一个长期存在的问题,有一个非常有趣的讨论here.那里有一些SO成员：@ camickr,@ kleopatra,@ splungebob.如该文章中所讨论的,不可能有一个简单的解决方案,并且提出了几种解决方法：基本上是自定义UI实现或使用面板作为渲染器,并根据文本长度使用首选的宽度/高度进行播放.两种选择都涉及大量工作.

为了避免与UI委托打交道并利用setTabComponentAt(…)方法,我前段时间已开始在此处共享一个选项卡式窗格扩展.该方法基于Swing的renderer概念：必须生成一个组件以渲染另一个组件的零件的类,目标是提供一种灵活的机制来添加自定义选项卡组件.

我使用自定义选项卡式窗格在下面提供了一个示例,这是提供上述机制所需的所有接口/类的概述.

ITabRenderer界面

第一步是定义一个Iterface,以提供合同来渲染Tab组件.

AbstractTabRenderer类

提供基本方法以帮助实现getTabRendererComponent(…)方法的抽象类.该抽象类具有三个主要属性：

> prototypeText：用于定义原型文本以生成默认渲染器组件.

> prototypeIcon：用于定义原型图标以生成默认渲染器.

> horizo??ntalTextAlignment：制表符的文本水平对齐方式.

请注意,此类是抽象的,因为它没有实现getTabRendererComponent(…)方法.

DefaultTabRenderer类

通过扩展AbstractTabRenderer类的具体实现.请注意,如果您想包括一个如教程演示中所示的关闭按钮,那么在此类中进行一些工作就足够了.事实上,我已经这样做了,但是我不会包括不扩展此(已经很大)帖子的那一部分.

JXTabbedPane

最后,选项卡式窗格的扩展包括选项卡渲染器支持并覆盖addTab(…)方法.

例

我使用这些PLAF运行了这个示例,并获得了积极的结果：

> WindowsLookAndFeel

> WindowsClassicLookAndFeel

>雨云LookAndFeel

> MetalLookAndFeel

> SeaglassLookAndFeel

另外,如果将选项卡的位置从“左”切换到“顶部”(默认)或“底部”,则所有选项卡的宽度仍然相同,从而解决了此答案第二段中所述的问题.

import java.awt.Component;

import java.awt.Dimension;

import java.awt.GridBagConstraints;

import java.awt.GridBagLayout;

import java.awt.Insets;

import java.beans.PropertyChangeEvent;

import java.beans.PropertyChangeListener;

import java.beans.PropertyChangeSupport;

import javax.swing.Icon;

import javax.swing.JFrame;

import javax.swing.JLabel;

import javax.swing.JPanel;

import javax.swing.JTabbedPane;

import javax.swing.SwingConstants;

import javax.swing.SwingUtilities;

import javax.swing.UIManager;

public class Demo {

private void createAndShowGUI() {

JXTabbedPane tabbedPane = new JXTabbedPane(JTabbedPane.LEFT);

AbstractTabRenderer renderer = (AbstractTabRenderer)tabbedPane.getTabRenderer();

renderer.setPrototypeText("This text is a prototype");

renderer.setHorizontalTextAlignment(SwingConstants.LEADING);

tabbedPane.addTab("Short", UIManager.getIcon("OptionPane.informationIcon"), createEmptyPanel(), "Information tool tip");

tabbedPane.addTab("Long text", UIManager.getIcon("OptionPane.warningIcon"), createEmptyPanel(), "Warning tool tip");

tabbedPane.addTab("This is a really long text", UIManager.getIcon("OptionPane.errorIcon"), createEmptyPanel(), "Error tool tip");

JFrame frame = new JFrame("Demo");

frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

frame.add(tabbedPane);

frame.pack();

frame.setLocationByPlatform(true);

frame.setVisible(true);

}

private JPanel createEmptyPanel() {

JPanel dummyPanel = new JPanel() {

@Override

public Dimension getPreferredSize() {

return isPreferredSizeSet() ?

super.getPreferredSize() : new Dimension(400, 300);

}

};

return dummyPanel;

}

public static void main(String[] args) {

SwingUtilities.invokeLater(new Runnable() {

@Override

public void run() {

new Demo().createAndShowGUI();

}

});

}

class JXTabbedPane extends JTabbedPane {

private ITabRenderer tabRenderer = new DefaultTabRenderer();

public JXTabbedPane() {

super();

}

public JXTabbedPane(int tabPlacement) {

super(tabPlacement);

}

public JXTabbedPane(int tabPlacement, int tabLayoutPolicy) {

super(tabPlacement, tabLayoutPolicy);

}

public ITabRenderer getTabRenderer() {

return tabRenderer;

}

public void setTabRenderer(ITabRenderer tabRenderer) {

this.tabRenderer = tabRenderer;

}

@Override

public void addTab(String title, Component component) {

this.addTab(title, null, component, null);

}

@Override

public void addTab(String title, Icon icon, Component component) {

this.addTab(title, icon, component, null);

}

@Override

public void addTab(String title, Icon icon, Component component, String tip) {

super.addTab(title, icon, component, tip);

int tabIndex = getTabCount() - 1;

Component tab = tabRenderer.getTabRendererComponent(this, title, icon, tabIndex);

super.setTabComponentAt(tabIndex, tab);

}

}

interface ITabRenderer {

public Component getTabRendererComponent(JTabbedPane tabbedPane, String text, Icon icon, int tabIndex);

}

abstract class AbstractTabRenderer implements ITabRenderer {

private String prototypeText = "";

private Icon prototypeIcon = UIManager.getIcon("OptionPane.informationIcon");

private int horizontalTextAlignment = SwingConstants.CENTER;

private final PropertyChangeSupport propertyChangeSupport = new PropertyChangeSupport(this);

public AbstractTabRenderer() {

super();

}

public void setPrototypeText(String text) {

String oldText = this.prototypeText;

this.prototypeText = text;

firePropertyChange("prototypeText", oldText, text);

}

public String getPrototypeText() {

return prototypeText;

}

public Icon getPrototypeIcon() {

return prototypeIcon;

}

public void setPrototypeIcon(Icon icon) {

Icon oldIcon = this.prototypeIcon;

this.prototypeIcon = icon;

firePropertyChange("prototypeIcon", oldIcon, icon);

}

public int getHorizontalTextAlignment() {

return horizontalTextAlignment;

}

public void setHorizontalTextAlignment(int horizontalTextAlignment) {

this.horizontalTextAlignment = horizontalTextAlignment;

}

public PropertyChangeListener[] getPropertyChangeListeners() {

return propertyChangeSupport.getPropertyChangeListeners();

}

public PropertyChangeListener[] getPropertyChangeListeners(String propertyName) {

return propertyChangeSupport.getPropertyChangeListeners(propertyName);

}

public void addPropertyChangeListener(PropertyChangeListener listener) {

propertyChangeSupport.addPropertyChangeListener(listener);

}

public void addPropertyChangeListener(String propertyName, PropertyChangeListener listener) {

propertyChangeSupport.addPropertyChangeListener(propertyName, listener);

}

protected void firePropertyChange(String propertyName, Object oldValue, Object newValue) {

PropertyChangeListener[] listeners = getPropertyChangeListeners();

for (int i = listeners.length - 1; i >= 0; i--) {

listeners[i].propertyChange(new PropertyChangeEvent(this, propertyName, oldValue, newValue));

}

}

}

class DefaultTabRenderer extends AbstractTabRenderer implements PropertyChangeListener {

private Component prototypeComponent;

public DefaultTabRenderer() {

super();

prototypeComponent = generateRendererComponent(getPrototypeText(), getPrototypeIcon(), getHorizontalTextAlignment());

addPropertyChangeListener(this);

}

private Component generateRendererComponent(String text, Icon icon, int horizontalTabTextAlignmen) {

JPanel rendererComponent = new JPanel(new GridBagLayout());

rendererComponent.setOpaque(false);

GridBagConstraints c = new GridBagConstraints();

c.insets = new Insets(2, 4, 2, 4);

c.fill = GridBagConstraints.HORIZONTAL;

rendererComponent.add(new JLabel(icon), c);

c.gridx = 1;

c.weightx = 1;

rendererComponent.add(new JLabel(text, horizontalTabTextAlignmen), c);

return rendererComponent;

}

@Override

public Component getTabRendererComponent(JTabbedPane tabbedPane, String text, Icon icon, int tabIndex) {

Component rendererComponent = generateRendererComponent(text, icon, getHorizontalTextAlignment());

int prototypeWidth = prototypeComponent.getPreferredSize().width;

int prototypeHeight = prototypeComponent.getPreferredSize().height;

rendererComponent.setPreferredSize(new Dimension(prototypeWidth, prototypeHeight));

return rendererComponent;

}

@Override

public void propertyChange(PropertyChangeEvent evt) {

String propertyName = evt.getPropertyName();

if ("prototypeText".equals(propertyName) || "prototypeIcon".equals(propertyName)) {

this.prototypeComponent = generateRendererComponent(getPrototypeText(), getPrototypeIcon(), getHorizontalTextAlignment());

}

}

}

}

截图

MetalLookAndFeel

NimbusLookAndFeel

SeaglassLookAndFeel

WindowsLookAndFeel