當我想要時更改JList項目顏色

Question

我正在嘗試構建一個JList，其中某些項目的背景顏色與其他項目不同，但僅限於我需要時。

我一直在試圖做這樣的事情，它會產生錯誤。

static DefaultListModel<String> model = new DefaultListModel<>(); 

for(int K=0;K<Collectionsize();K++){ 
     Jlist.setForeground(Color.red); 
     model.addElement(type 1); 

     for(int I=0;I<(subcollection.size();I++){ 
      Jlist.setForeground(Color.white); 
      model.addElement(type 2); 
      } 
     } 

類型1和2之間沒有模式，所以我想在需要時更改顏色而不是依賴if語句。

我看到很多人在討論構建自定義渲染類的問題，但我正在瞄準一些更簡單的東西。

Answer 1

注意：每個項目包含兩條信息的項目列表更適合在表格中顯示而不是在列表中顯示，但如果需要的話，可以將其調整爲列表。適用相同的基本原則（使用渲染組件）。

因爲我感覺慈善，這是我的意思是：

這是通過這種渲染類實現：

class TrackCellRenderer extends DefaultTableCellRenderer { 

    HashMap<String, Color> colorMap = new HashMap<>(); 
    Random r = new Random(); 

    @Override 
    public Component getTableCellRendererComponent(
      JTable table, 
      Object value, 
      boolean isSelected, boolean hasFocus, 
      int row, int column) { 
     Component c = super.getTableCellRendererComponent(
       table, value, isSelected, hasFocus, row, column); 
     JLabel l = (JLabel) c; 

     String s = (String) value; 
     if (column == 0) { 
      if (!colorMap.containsKey(s)) { 
       Color clr = new Color(
         150 + r.nextInt(105), 
         150 + r.nextInt(105), 
         150 + r.nextInt(105)); 
       colorMap.put(s, clr); 
      } 
      Color color = colorMap.get(s); 
      l.setBackground(color); 
      l.setOpaque(true); 
     } else { 
      l.setOpaque(false); 
     } 

     return l; 
    } 
} 

注：它可能是最好使用枚舉，而不是隨機分配一種顏色，但有3張專輯和超過一百萬種可能的顏色，我們應該很安全。

在剛剛超過100行代碼本（二級）MCVE：

import java.awt.*; 
import javax.swing.*; 
import javax.swing.border.EmptyBorder; 
import javax.swing.table.*; 
import java.util.*; 

public class AlbumTrackTable { 

    private JComponent ui = null; 
    String[][] playList = { 
     {"The Will to Live", "Faded"}, 
     {"The Will to Live", "Homeless Child"}, 
     {"Oh Mercy", "Political Wrold"}, 
     {"Oh Mercy", "What Was it You Wanted?"}, 
     {"Red Sails in the Sunset", "Helps Me Helps You"}, 
     {"Red Sails in the Sunset", "Redneck Wonderland"} 
    }; 
    String[] columnNames = {"Album", "Track"}; 

    AlbumTrackTable() { 
     initUI(); 
    } 

    public void initUI() { 
     if (ui != null) { 
      return; 
     } 

     ui = new JPanel(new BorderLayout(4, 4)); 
     ui.setBorder(new EmptyBorder(4, 4, 4, 4)); 

     DefaultTableModel trackModel = new DefaultTableModel(playList, columnNames); 
     JTable table = new JTable(trackModel); 
     ui.add(new JScrollPane(table)); 
     TableCellRenderer renderer = new TrackCellRenderer(); 
     table.setDefaultRenderer(Object.class, renderer); 
     table.setAutoCreateRowSorter(true); 
    } 

    public JComponent getUI() { 
     return ui; 
    } 

    public static void main(String[] args) { 
     Runnable r = new Runnable() { 
      @Override 
      public void run() { 
       try { 
        UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); 
       } catch (Exception useDefault) { 
       } 
       AlbumTrackTable o = new AlbumTrackTable(); 

       JFrame f = new JFrame(o.getClass().getSimpleName()); 
       f.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE); 
       f.setLocationByPlatform(true); 

       f.setContentPane(o.getUI()); 
       f.pack(); 
       f.setMinimumSize(f.getSize()); 

       f.setVisible(true); 
      } 
     }; 
     SwingUtilities.invokeLater(r); 
    } 
} 

class TrackCellRenderer extends DefaultTableCellRenderer { 

    HashMap<String, Color> colorMap = new HashMap<>(); 
    Random r = new Random(); 

    @Override 
    public Component getTableCellRendererComponent(
      JTable table, 
      Object value, 
      boolean isSelected, boolean hasFocus, 
      int row, int column) { 
     Component c = super.getTableCellRendererComponent(
       table, value, isSelected, hasFocus, row, column); 
     JLabel l = (JLabel) c; 

     String s = (String) value; 
     if (column == 0) { 
      if (!colorMap.containsKey(s)) { 
       Color clr = new Color(
         150 + r.nextInt(105), 
         150 + r.nextInt(105), 
         150 + r.nextInt(105)); 
       colorMap.put(s, clr); 
      } 
      Color color = colorMap.get(s); 
      l.setBackground(color); 
      l.setOpaque(true); 
     } else { 
      l.setOpaque(false); 
     } 

     return l; 
    } 
}