corejava第9版

corejava第9版/v2ch06/progressBar/ProgressBarFrame.java

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+package progressBar;
+
+import java.awt.*;
+import java.awt.event.*;
+import java.util.List;
+import javax.swing.*;
+
+/**
+ * A frame that contains a button to launch a simulated activity, a progress bar, and a text area
+ * for the activity output.
+ */
+public class ProgressBarFrame extends JFrame
+{
+   public static final int TEXT_ROWS = 10;
+   public static final int TEXT_COLUMNS = 40;
+
+   private JButton startButton;
+   private JProgressBar progressBar;
+   private JCheckBox checkBox;
+   private JTextArea textArea;
+   private SimulatedActivity activity;
+
+   public ProgressBarFrame()
+   {
+      // this text area holds the activity output
+      textArea = new JTextArea(TEXT_ROWS, TEXT_COLUMNS);
+
+      // set up panel with button and progress bar
+
+      final int MAX = 1000;
+      JPanel panel = new JPanel();
+      startButton = new JButton("Start");
+      progressBar = new JProgressBar(0, MAX);
+      progressBar.setStringPainted(true);
+      panel.add(startButton);
+      panel.add(progressBar);
+
+      checkBox = new JCheckBox("indeterminate");
+      checkBox.addActionListener(new ActionListener()
+         {
+            public void actionPerformed(ActionEvent event)
+            {
+               progressBar.setIndeterminate(checkBox.isSelected());
+               progressBar.setStringPainted(!progressBar.isIndeterminate());
+            }
+         });
+      panel.add(checkBox);
+      add(new JScrollPane(textArea), BorderLayout.CENTER);
+      add(panel, BorderLayout.SOUTH);
+
+      // set up the button action
+
+      startButton.addActionListener(new ActionListener()
+         {
+            public void actionPerformed(ActionEvent event)
+            {
+               startButton.setEnabled(false);
+               activity = new SimulatedActivity(MAX);
+               activity.execute();
+            }
+         });
+      pack();
+   }
+   
+   class SimulatedActivity extends SwingWorker<Void, Integer>
+   {
+      private int current;
+      private int target;
+
+      /**
+       * Constructs the simulated activity that increments a counter from 0 to a
+       * given target.
+       * @param t the target value of the counter.
+       */
+      public SimulatedActivity(int t)
+      {
+         current = 0;
+         target = t;
+      }
+
+      protected Void doInBackground() throws Exception
+      {
+         try
+         {
+            while (current < target)
+            {
+               Thread.sleep(100);
+               current++;
+               publish(current);
+            }
+         }
+         catch (InterruptedException e)
+         {
+         }
+         return null;
+      }
+
+      protected void process(List<Integer> chunks)
+      {
+         for (Integer chunk : chunks)
+         {
+            textArea.append(chunk + "\n");
+            progressBar.setValue(chunk);
+         }
+      }
+      
+      protected void done()
+      {
+         startButton.setEnabled(true);
+      }     
+   }   
+}