java - 编译从Java中的Swing的JFrame类返回缺少的方法和包

Question

这段代码将在NetBeans上针对这些行返回三个错误:

leftPanel.setLayout (leftBox );
leftPanel.add (optionBar);
leftPanel.add (tabBar);
leftPanel.add (paintArea);
rightPanel.setLayout (rightBox);
rightPanel.add (toolbar);
rightPanel.add (toolArea);

它返回:

package rightPanel does not exist

<identifier> expected

missing method body, or declare abstract

<identifier> expected
----

该程序还存在以下问题:

setLayout(flo);

add(leftPanel);

add(rightPanel);

并返回:

方法声明无效；需要返回类型

我尝试搜索并找到所有类型问题的信息，但找不到与我的个人问题直接相关的任何信息。

这是完整的代码:

package level.builder;

import javax.swing.*;
import java.awt.*;

public class LevelBuilderGUI extends JFrame {

    //Version For the Title
    private static String version = "Alpha";

    //Creating leftmost panel
    JPanel leftPanel = new JPanel();
    BoxLayout leftBox = new BoxLayout(leftPanel, BoxLayout.Y_AXIS);

    leftPanel.setLayout (leftBox );
    JPanel optionBar = new JPanel();

    leftPanel.add (optionBar);
    JPanel tabBar = new JPanel();

    leftPanel.add (tabBar);
    JPanel paintArea = new JPanel();

    leftPanel.add (paintArea);

    //Creating rightmost panel
    JPanel rightPanel = new JPanel();
    BoxLayout rightBox = new BoxLayout(rightPanel, BoxLayout.Y_AXIS);

    rightPanel.setLayout (rightBox);
    JPanel toolBar = new JPanel();

    rightPanel.add (toolbar);
    JPanel toolArea = new JPanel();

    rightPanel.add (toolArea);

    //Putting it all together
    FlowLayout flo = new FlowLayout();

    setLayout(flo);

    add(leftPanel);

    add(rightPanel);

    public LevelBuilderGUI() {
        super();
        setTitle("Level Builder version" + version);
        setLookAndFeel();
        setSize(512, 128);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        setVisible(true);

    }

    private void setLookAndFeel() {
        try {
            UIManager.setLookAndFeel(
                "com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel);");
        } catch (Exception e) {
        }
    }
}

请帮助我理解我的错误。

编辑:感谢所有的帮助，我看到我遇到的问题是将所有代码放在方法之外。现在，将代码移入构造函数后即可运行。

Answer 1

尝试将所有这些行放入构造函数中，以获取错误信息。之所以会出现这些错误，是因为您在类的“主体”中调用任何封装之外的属性的方法。

此处的建议是:检查属性的可见性，从来没有一个好的习惯让它们像这样自由。 ;)