[英]Adding a JTabbedPane to a JTabbedPane error
收到此错误:
Project.reportpane.addComponent(reportpane.java:69)处的线程“ AWT-EventQueue-0”中的异常java.lang.NullPointerException
我无法将rptinvestment tabbedPane添加到面板tabinvestment
公共类reportpane扩展了JPanel {
JTabbedPane rpt;
JPanel tabcashflow;
JPanel tabinvestment;
JPanel tabexchangerates;
JTabbedPane rptinvestment;
JPanel tabofficial;
JPanel tabdem;
JPanel tabcommodities;
public reportpane() {
rpt = new JTabbedPane();
tabcashflow = new JPanel();
tabinvestment = new JPanel();
tabexchangerates = new JPanel();
tabofficial = new JPanel();
tabdem = new JPanel();
tabcommodities = new JPanel();
rpt.add("Cashflow", tabcashflow);
rpt.add("Investement", tabinvestment);
rpt.add("Exchange rates", tabexchangerates);
rpt.setBackground(new Color(255, 255, 255));
rpt.setFont(new Font("sansserif", Font.PLAIN, 14));
rpt.setTabPlacement(javax.swing.JTabbedPane.TOP);
rpt.setBorder(BorderFactory.createEmptyBorder());
rpt.setSize(750, 500);
rptinvestment = new JTabbedPane();
rptinvestment.add("Official", tabofficial);
rptinvestment.add("DEM", tabdem);
rptinvestment.add("Commodities", tabcommodities);
rptinvestment.setBackground(new Color(255, 255, 255));
rptinvestment.setFont(new Font("sansserif", Font.PLAIN, 14));
rptinvestment.setTabPlacement(JTabbedPane.TOP);
rptinvestment.setBorder(BorderFactory.createEmptyBorder());
rptinvestment.setSize(750, 500);
addComponent(tabinvestment, rptinvestment, 0, 0, 675, 570);
addComponent(this, rpt, 10, 10, 675, 570);
this.setLayout(new BorderLayout());
this.setBackground(Color.WHITE);
this.setBorder(null);
this.revalidate();
this.repaint();
}
public void addComponent(Container container, Component c, int x, int y, int width, int height) {
c.setBounds(x, y, width, height);
container.add(c);
}
}
您永远不会初始化tabinvestment。 您将其声明为实例变量,但从未在构造函数中对其进行初始化。 在某些时候,您需要调用JTabbedPane tabinvestment = new JTabbedPane()
。
您尝试使用绝对定位添加组件,而布局管理器已覆盖该绝对定位
JTabbedPane使用其自己的布局逻辑,除非您真的曾经创建过自己的UI类,否则无法更改。
同样,您已将框架布局管理器设置为BorderLayout,它将覆盖可能已设置的任何定位值(以前为其他设置)
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