SwingWorker

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SwingWorker

App.java:

import javax.swing.SwingUtilities;public class App {    /**     * @param args     */    public static void main(String[] args) {        SwingUtilities.invokeLater(new Runnable() {                        @Override            public void run() {                new MainFrame("SwingWorker Demo");            }        });    }}

MainFrame.java:

import java.awt.GridBagConstraints;import java.awt.GridBagLayout;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import java.util.List;import java.util.concurrent.ExecutionException;import javax.swing.JButton;import javax.swing.JFrame;import javax.swing.JLabel;import javax.swing.SwingWorker;public class MainFrame extends JFrame {    private JLabel countLabel1 = new JLabel("0");    private JLabel statusLabel = new JLabel("Task not completed.");    private JButton startButton = new JButton("Start");    public MainFrame(String title) {        super(title);        setLayout(new GridBagLayout());        GridBagConstraints gc = new GridBagConstraints();        gc.fill = GridBagConstraints.NONE;        gc.gridx = 0;        gc.gridy = 0;        gc.weightx = 1;        gc.weighty = 1;        add(countLabel1, gc);        gc.gridx = 0;        gc.gridy = 1;        gc.weightx = 1;        gc.weighty = 1;        add(statusLabel, gc);        gc.gridx = 0;        gc.gridy = 2;        gc.weightx = 1;        gc.weighty = 1;        add(startButton, gc);        startButton.addActionListener(new ActionListener() {            public void actionPerformed(ActionEvent arg0) {                start();            }        });        setSize(200, 400);        setDefaultCloseOperation(EXIT_ON_CLOSE);        setVisible(true);    }    private void start() {                // Use SwingWorker<void void=""> and return null from doInBackground if        // you don't want any final result and you don't want to update the GUI        // as the thread goes along.        // First argument is the thread result, returned when processing finished.        // Second argument is the value to update the GUI with via publish() and process()        SwingWorker<boolean integer=""> worker = new SwingWorker<boolean integer="">() {            @Override            /*             * Note: do not update the GUI from within doInBackground.             */            protected Boolean doInBackground() throws Exception {                                // Simulate useful work                for(int i=0; i<30; i++) {                    Thread.sleep(100);                    System.out.println("Hello: " + i);                                        // optional: use publish to send values to process(), which                    // you can then use to update the GUI.                    publish(i);                }                                return false;            }            @Override            // This will be called if you call publish() from doInBackground()            // Can safely update the GUI here.            protected void process(List<integer> chunks) {                Integer value = chunks.get(chunks.size() - 1);                                countLabel1.setText("Current value: " + value);            }            @Override            // This is called when the thread finishes.            // Can safely update GUI here.            protected void done() {                                try {                    Boolean status = get();                    statusLabel.setText("Completed with status: " + status);                } catch (InterruptedException e) {                    // TODO Auto-generated catch block                    e.printStackTrace();                } catch (ExecutionException e) {                    // TODO Auto-generated catch block                    e.printStackTrace();                }                            }                    };                worker.execute();    }}</integer></boolean></boolean></void>

SwingWorker的第一个template argument：doInBackground方法的返回类型，get方法的返回值类型
template argument中只能用Void（void对应的类）。如果用Void，doInBackground方法必须返回null。
template argument中只能用class，不能用primitive type。
SwingWorker的第二个template argument：publish方法的参数类型，process方法参数List的泛型类型。如果要再doInBackground方法执行的同时，update GUI，在doInBackground方法中调用publish方法，然后override process方法。
process方法的参数是一个List<第二个template argument>，因为并不是每一次在doInBackground方法中调用publish的时候process方法都会被调用。这个List保存了每次publish的内容。在process方法中，可以update GUI safely。process方法在EDT中被调度。
每一个SwingWorker对象只能execute一次，如果需要再执行一遍，只能再创建一个对象。
doInBackground方法中update GUI不安全。doInBackground方法可以throw exception。在done方法中可以catch。
done方法在这个thread结束的时候会被执行，done方法中可以update GUI safely。
get方法得到doInBackground方法的返回值，如果doInBackground还没有执行完，get方法wait。

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