Question

我有一个JTable，我正在使用互联网上的数据插入行。当我运行直接从main函数填充列表的代码时，我可以看到在调用'fireTableRowsInserted'的同时插入每一行 - 这就是我想要的行为。但是，当我从JButton的ActionListener运行相同的代码时（在'ActionPreformed（）'期间，表在线程/事件完成之前不会更新）。我认为这个问题与线程有关，但我不太熟悉线程的工作方式，也不确定从哪里开始。以下是问题的一个示例：

public class Main { 
    static TestModel myTestModel = new TestModel(); 

    public static void main(String[] args) {
        JFrame  testFrame   = new JFrame();
        JTable  table       = new JTable(myTestModel);
        JButton button      = new JButton("Load");

        testFrame.getContentPane().add(new JScrollPane(table), BorderLayout.CENTER);
        testFrame.getContentPane().add(button, BorderLayout.PAGE_END);
        testFrame.pack();
        testFrame.setVisible(true);
        testFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        button.addActionListener(new ActionListener(){
            @Override public void actionPerformed(ActionEvent e) {
                //When openURLStr is called here, the table in the JFrame doesn't add rows until
                // the function has exited.
                openURLStr("http://download.oracle.com/javase/1.4.2/docs/api/java/awt/Component.html", true);               
            }           
        });

        //When openURLStr is called here, the table in the JFrame adds rows at the same time the 
        // list in the table-model adds a row. (the desired behavoir)
        openURLStr("http://download.oracle.com/javase/1.4.2/docs/api/java/awt/Component.html", true);
        myTestModel.myArrayList.clear();
        myTestModel.fireTableDataChanged();
    }

    static class TestModel extends AbstractTableModel {
        ArrayList<String> myArrayList = new ArrayList<String>();

        @Override public int    getColumnCount()    { return(3);                    }
        @Override public int    getRowCount()       { return(myArrayList.size());   }
        @Override public Object getValueAt(int row, int col) {
            char c = '*';
            String rowStr = myArrayList.get(row);
            if ( rowStr.length() > col ) c = rowStr.charAt(col);
            return(c);
        }

        public boolean add(String line) {
            int row = myArrayList.size();
            if ( row < 100 ) {
                myArrayList.add(line);
                this.fireTableRowsInserted(row, row);               
                return(true);
            }
            else {
                return(false);
            }
        }       
    }

    private static void openURLStr(String urlStr, boolean lookForLinks) {
        try {
            URL                 url         = new URL(urlStr);
            InputStreamReader   isr         = new InputStreamReader(url.openConnection().getInputStream());
            BufferedReader      br          = new BufferedReader(isr);
            ArrayList<String>   linksFound  = new ArrayList<String>();

            if ( br != null ) {
                String strLine = br.readLine();
                //row added to table-model here: 
                boolean continueParse = myTestModel.add(strLine);

                //this code is mainly to induce more time between each addition of a line.
                while ( strLine != null && continueParse ) {
                    if ( lookForLinks && strLine != null ) {
                        String ahrefStr = "a href=\"";
                        int start_i = strLine.indexOf(ahrefStr) + ahrefStr.length();
                        if ( start_i > -1 ) {
                            int end_i = strLine.indexOf("\"", start_i+1);
                            if ( end_i > -1 && end_i > start_i ) {
                                linksFound.add(strLine.substring(start_i, end_i));
                            }
                        }
                    }
                    strLine = br.readLine();
                }
                br.close();
            }

            for ( String link : linksFound ) {
                openURLStr(link, false);
            }

        } catch (IOException e) {
        }
    }
}

Answer 1

ActionListener的actionPerformed在event dispatch thread上执行，这将被您的代码阻止。因此，GUI暂时冻结，根本不会显示任何更新。

尝试将“长时间运行”的URL调用分开，例如在SwingWorker。

从Action Listener调用fireTableRowsInserted（）时，JTable不会立即更新

1 个答案: