JTabbedPane组件何时获得其大小? [英] When does a JTabbedPane component get its size?

问题描述

将JPanel的大小添加到JTabbedPane中以计算其他值时，我需要知道它的大小.如果我调用add(Component)方法，什么时候Component会得到它的大小?

I need to know the size of a JPanel when I add it to a JTabbedPane to compute other values. If I call the add(Component) method, when does the Component get its size?

例如，

JTabbedPane tabbedPane = new JTabbedPane();
JPanel panel = new JPanel();
panel.setBackGround(Color.RED); // pretty colors!
tabbedPane.add(panel);

int newTabIndex = tabbedPane.indexOfComponent(panel);
tabbedPane.setSelectedIndex(newTabIndex);

提前谢谢！

修改 @mKorbel建议将JPanel的可见性设置为true:

Edit @mKorbel suggested setting the visibility of the JPanel to true:

JTabbedPane tabbedPane = new JTabbedPane();
JPanel panel = new JPanel();
panel.setBackGround(Color.RED);
tabbedPane.add(panel);
panel.setVisible(true); // NEW LINE


int newTabIndex = tabbedPane.indexOfComponent(panel);
tabbedPane.setSelectedIndex(newTabIndex);

不幸的是，当我将此更改应用于自己的程序时，JPanel的宽度和高度分别为0和0.我还能尝试什么?

Unfortunately, when I applied this change to my own program, the JPanel still had a width and height of 0 and 0, respectively. What else can I try?

推荐答案

JTabbedPane在调整大小之前，除非将其附加到能够放置它的容器上.

JTabbedPane won't be sized until it is attached to a container that is capable of laying it out.

Window#pack的工作是确定子组件的首选大小，并根据布局管理器的要求确定子组件的大小.

Window#packs job is to determine the preferred size of the child components and size them based on the requirements of the layout manager.

目前仅对组件(和您的JTabbedPane)进行大小调整.

Only at this time would a component (and your JTabbedPane) be sized.

也可以根据容器层次结构的更改来调整组件的大小，但是基本过程是相同的. JTabbedPane父容器将决定何时需要更新其内容并执行新的布局操作，并根据需要调整组件的大小

Components may be resized in response to changes in the container hierarchy as well, but the basic process is the same. The JTabbedPanes parent container will decide when it needs to update it's contents and perform a new layout operation, resizing the components based on it's needs

您的所有示例均未显示该选项卡式窗格已添加到父容器中...

None of your examples show the tabbed pane been added to a parent container...

下面的示例基本上演示了何时调整组件的大小.

The following example basically demonstrates when a component would be resized.

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.event.ComponentAdapter;
import java.awt.event.ComponentEvent;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTabbedPane;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;

public class TestTabSize {

    public static void main(String[] args) {
        new TestTabSize();
    }

    public TestTabSize() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                JPanel panel = new JPanel() {
                    @Override
                    public Dimension getPreferredSize() {
                        return new Dimension(200, 200);
                    }
                };

                panel.addComponentListener(new ComponentAdapter() {
                    @Override
                    public void componentResized(ComponentEvent e) {
                        System.out.println("Resized to " + e.getComponent().getSize());
                    }

                    @Override
                    public void componentMoved(ComponentEvent e) {
                        System.out.println("Moved to " + e.getComponent().getLocation());
                    }
                });

                System.out.println("Before been added = " + panel.getSize());

                JTabbedPane tabbedPane = new JTabbedPane();
                tabbedPane.addTab("test", panel);

                System.out.println("Before been added to tab = " + panel.getSize());

                JFrame frame = new JFrame("Test");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setLayout(new BorderLayout());
                System.out.println("Before been added to frame = " + panel.getSize());
                frame.add(tabbedPane);
                System.out.println("After been added to frame = " + panel.getSize());
                frame.pack();
                System.out.println("After been packed = " + panel.getSize());
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
                System.out.println("After been visible = " + panel.getSize());
            }
        });
    }

}

输出...

从输出中可以看到，直到帧为packed为止，没有任何尺寸

As you can see from the output, until the frame is packed, nothing is sized

Before been added = java.awt.Dimension[width=0,height=0]
Before been added to tab = java.awt.Dimension[width=0,height=0]
Before been added to frame = java.awt.Dimension[width=0,height=0]
After been added to frame = java.awt.Dimension[width=0,height=0]
After been packed = java.awt.Dimension[width=200,height=200]
After been visible = java.awt.Dimension[width=200,height=200]
Resized to java.awt.Dimension[width=200,height=200]
Moved to java.awt.Point[x=11,y=33]

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