Jcombobox自定义渲染器通用物

Question

我已经为Jcomboboxes写了一个渲染器，以替换乳白色 残疾状态更加清晰。

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

public class RendererDemo extends JFrame {
  public static final long serialVersionUID = 100L;

  String[] items= {"one", "two", "three"};


  public RendererDemo() {
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setSize(300, 100);

    JComboBox<Object> cmb = new JComboBox<>(items);
//    JComboBox<String> cmb = new JComboBox<>(items);
    cmb.setRenderer(new DisabledDarkTextRenderer(cmb));
    add(cmb, BorderLayout.NORTH);

    JCheckBox check = new JCheckBox("Combo enabled", true);
    add(check, BorderLayout.SOUTH);
    check.addActionListener(e -> cmb.setEnabled(check.isSelected()));

    setVisible(true);
  }


  static public void main(String args[]) {
    EventQueue.invokeLater(RendererDemo::new);
  }


  class DisabledDarkTextRenderer extends DefaultListCellRenderer {
    public static final long serialVersionUID = 50378L;

    JComboBox<Object> cmb;
    ListCellRenderer<Object> origRenderer;
    Object defaultResource= UIManager.get("ComboBox.disabledForeground");

    public DisabledDarkTextRenderer(JComboBox<Object> cmb) {
      this.cmb= cmb;
      origRenderer= cmb.getRenderer();
    }

    public Component getListCellRendererComponent(JList<?> list, Object value,
                        int index, boolean isSelected, boolean cellHasFocus) {
      Component orig= origRenderer.getListCellRendererComponent(list, value,
                                            index, isSelected, cellHasFocus);
      if (cmb.isEnabled())
        UIManager.put("ComboBox.disabledForeground", defaultResource);
      else
        UIManager.put("ComboBox.disabledForeground", new ColorUIResource
                                                            (Color.GRAY));
      return orig;
    }
  }

}

但是，当我将jcombobox声明为类型时，由于“不兼容类型：ListCellRenderer＆lt; cap＃1＆gt;无法将其转换为ListCellRenderer＆lt; object＆gt; ...代码>

因此，我试图使渲染器更加通用。从我所有的尝试修改 通用类型，以下版本是仅剩下一个错误的版本。同样是上述错误，只有它现在读取：“不兼容类型：jlist＆lt; cap＃1＆gt;无法将其转换为jlist＆lt;？

如何解决这个问题？

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

public class RendererDemo2 extends JFrame {
  public static final long serialVersionUID = 100L;

  String[] items= {"one", "two", "three"};


  public RendererDemo2() {
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    setSize(300, 100);

    JComboBox<String> cmb = new JComboBox<>(items);
    cmb.setRenderer(new DisabledDarkTextRenderer2(cmb));
    add(cmb, BorderLayout.NORTH);

    JCheckBox check = new JCheckBox("Combo enabled", true);
    add(check, BorderLayout.SOUTH);
    check.addActionListener(e -> cmb.setEnabled(check.isSelected()));

    setVisible(true);
  }


  static public void main(String args[]) {
    EventQueue.invokeLater(RendererDemo2::new);
  }


  class DisabledDarkTextRenderer2 extends DefaultListCellRenderer {
    public static final long serialVersionUID = 50379L;

    JComboBox<?> cmb;
    ListCellRenderer<?> origRenderer;
    Object defaultResource= UIManager.get("ComboBox.disabledForeground");

    public DisabledDarkTextRenderer2(JComboBox<?> cmb) {
      this.cmb= cmb;
      origRenderer= cmb.getRenderer();
    }

    public Component getListCellRendererComponent(JList<?> list, Object value,
            int index, boolean isSelected, boolean cellHasFocus) {
      Component orig= origRenderer.getListCellRendererComponent(list, value,
                    index, isSelected, cellHasFocus);
      if (cmb.isEnabled())
        UIManager.put("ComboBox.disabledForeground", defaultResource);
      else
        UIManager.put("ComboBox.disabledForeground", new ColorUIResource
                                                            (Color.GRAY));
      return orig;
    }
  }

}

---

遵循madprogrammer的建议，我的渲染器现在看起来像这样：

  class DisabledDarkTextRenderer2<T> extends DefaultListCellRenderer {
    public static final long serialVersionUID = 50379L;

    JComboBox<T> cmb;
    ListCellRenderer<?> origRenderer;
    Object defaultResource= UIManager.get("ComboBox.disabledForeground");

    public DisabledDarkTextRenderer2(JComboBox<T> cmb) {
      this.cmb= cmb;
      origRenderer= cmb.getRenderer();
    }

    public Component getListCellRendererComponent(JList<?> list, Object value,
            int index, boolean isSelected, boolean cellHasFocus) {
      Component orig= origRenderer.getListCellRendererComponent(list, value,
                    index, isSelected, cellHasFocus);
      if (cmb.isEnabled())
        UIManager.put("ComboBox.disabledForeground", defaultResource);
      else
        UIManager.put("ComboBox.disabledForeground", new ColorUIResource
                                                            (Color.GRAY));
      return orig;
    }
  }

但是编译时间错误仍然存​​在。
我正在使用此渲染器进行连击，以在运行时改变其状态。因此，我没有关心每个程序时可以在需要时设置颜色，因为渲染器正在自动为我进行此操作。

Answer 1

您需要“通用”您的disableddarktextrenderer2为例...

class DisabledDarkTextRenderer2<T> implements ListCellRenderer<T> {
    public static final long serialVersionUID = 50379L;

    private JComboBox<T> combobox;
    private ListCellRenderer<? super T> origRenderer;

    public DisabledDarkTextRenderer2(JComboBox<T> combobox) {
        this.combobox = combobox;
        this.origRenderer = combobox.getRenderer();
    }
    
    public static <T> void install(JComboBox<T> combobox) {
        combobox.setRenderer(new DisabledDarkTextRenderer2<T>(combobox));
    }

    @Override
    public Component getListCellRendererComponent(JList<? extends T> list, T value, int index, boolean isSelected, boolean cellHasFocus) {
        Component orig = origRenderer.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus);
        if (combobox.isEnabled()) {
            orig.setForeground(null);
        } else {
            orig.setForeground(Color.GRAY);
        }
        return orig;
    }
}

现在，我会说，我会阻止您在渲染器中使用uimanager，因为这将影响这会影响更改后呈现的所有组件，这可能是您所需的目标，如果是的，则只需在应用程序开始时设置值即可。

下面的示例将使所有组合的默认禁用前景颜色<代码>红色，而无需您做其他任何事情。

import java.awt.Color;
import java.awt.EventQueue;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.UIManager;
import javax.swing.border.EmptyBorder;
import javax.swing.plaf.ColorUIResource;

public final class Main {
    public static void main(String[] args) {
        new Main();
    }

    public Main() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                UIManager.put("ComboBox.disabledForeground", new ColorUIResource(Color.RED));
                JFrame frame = new JFrame();
                frame.add(new TestPane());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TestPane extends JPanel {
        public TestPane() {
            setLayout(new GridBagLayout());
            setBorder(new EmptyBorder(32, 32, 32, 32));

            JComboBox<String> cmb = new JComboBox<>(new String[]{"Hello", "Goodbye"});
            cmb.setSelectedIndex(0);

            GridBagConstraints gbc = new GridBagConstraints();
            gbc.gridwidth = GridBagConstraints.REMAINDER;

            add(cmb, gbc);

            JButton toggle = new JButton("Toggle");
            toggle.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    cmb.setEnabled(!cmb.isEnabled());
                }
            });
            add(toggle, gbc);
        }
    }

}