这是我在这里发表的第一篇文章,如果内容很糟糕,请提前道歉......
我正在尝试使用自定义 ListCellRenderer 将自定义类列表中的项目添加到 JList 中。每个都有我想添加到一行的各种内容,并为列表中的每个内容添加一个新行:
public class MatchRecord {
private String player;
private Integer kills;
private Integer deaths;
private Integer assists;//getters + setters etc etc below}
private class GameStatistics{//this is the main class of the program
listModel = new DefaultListModel();
jList.setModel(listModel);
listModel.clear(); //get rid of any junk in the list before loading
recordJList.setLayoutOrientation(JList.VERTICAL);
//add the records to the JList
recordJList.setCellRenderer(new RecordListRenderer());
List<MatchRecord> list = new ArrayList();
list.addAll(recordSet); //recordSet is a Set<MatchRecord> which has been previously loaded from file
for(int i = 0; i < list.size(); i++){
System.out.println(list.get(i).getPlayer()); //this is NOT NULL!
listModel.addElement(list.get(i));
}
}
public class RecordListRenderer extends JPanel implements ListCellRenderer {
private JLabel[] labels = new JLabel[3];
public RecordListRenderer(){
setOpaque(true);
setLayout(new GridLayout(1, 4));
//set font size + colour here
}
public Component getListCellRendererComponent(JList list,
Object r,
int index,
boolean isSelected,
boolean hasFocus){
MatchRecord record = (MatchRecord) r;
labels[0].setText(record.getPlayer()); //This line returns a null pointer
labels[1].setText(record.getKills());
labels[2].setText(record.getDeaths());
labels[3].setText(record.getAssists());
return this}
我检查了列表的内容以确保它不为空,但上面突出显示的行返回一个空指针。
我对 Java 的了解仍然有限,因此任何(简单!)帮助将不胜感激。
最佳答案
您初始化 JLabel
数组:
private JLabel[] labels = new JLabel[3];
但是您永远不会用值填充该数组,因此当您想要访问它们时它们将为null
。使用 new JLabel()
设置每个元素,当您需要它们时,它们不会为 null
。
关于java - ListCellRenderer 返回空指针,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/16470967/