Question

我有一个JTable。当用户选择列时，想法是将浮点数据添加到ArrayList。我稍后会尝试在arrayList上做一些统计数据。

目前我正在设法将所需数据添加到ArrayList，并且当我从侦听器中打印到控制台时可以看到数据。但是，即使从侦听器外部声明ArrayList，数据也无法从侦听器外部获得。

        TableColumnModel columnModelCompareL = table_CompareL.getColumnModel();
         ArrayList<Float> statsCompareL=new ArrayList<Float>();
         columnModelCompareL.addColumnModelListener(new TableColumnModelListener() {
                    public void columnSelectionChanged(ListSelectionEvent e) {
                          Object[] data = columnToArray(table_CompareL,table_CompareL.getSelectedColumn());
                        System.out.println("MY data length"+data.length);
                        try {
                            for(int i = 0; i < data.length; i++){
                                if (data[i]!=null){
                                try {
                                    statsCompareL.add(Float.parseFloat((data[i]).toString().trim()));
                                } catch (Exception e1) {
                                    System.out.println("nought to add here");
                                }
                                }
                            }
                        } catch (NumberFormatException e1) {
                            System.out.println("You haven't selected a numeric column. Please select again");
                        }
                    }
                    @Override
                    public void columnAdded(TableColumnModelEvent e) {
                    }

                    @Override
                    public void columnRemoved(TableColumnModelEvent e) {
                    }

                    @Override
                    public void columnMoved(TableColumnModelEvent e) {
                    }

                    @Override
                    public void columnMarginChanged(ChangeEvent e) {
                    }
                });

        System.out.println("statsCompareL"+statsCompareL);

Answer 1

更新的ArrayList在UI构造代码中不可见（因为此代码在更新ArrayList之前很久就结束了。）

但是在其他事件监听器中可用：

     TableColumnModel columnModelCompareL = table_CompareL.getColumnModel();
     ArrayList<Float> statsCompareL=new ArrayList<Float>();
     columnModelCompareL.addColumnModelListener(new TableColumnModelListener() {
         // implementation left out for brevity
     });

     // this runs during construction time, long before statsCompareL is updated
     System.out.println("statsCompareL"+statsCompareL);

     JButton testButton = new JButton("Test ArrayList");
     testButton.addActionListener(new ActionListener() {
         @Override
         public void actionPerformed(ActionEvent e) {
             // this runs after the button is clicked, so it will see the changes statsCompareL
             System.out.println("statsCompareL"+statsCompareL);
         }
     });
     // add the button somewhere convenient for testing purposes

ArrayList在侦听器外部不可用

1 个答案: