silvermyth

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              在開發Java Swing應用程序的過程中,有兩個原則是必須要牢記的:
              1.耗時的操作(例如從數據庫查詢大量數據,讀取URI資源等)一定不能運行在EDT(事件派發線程)上,否則會導致Swing用戶界面失去響應。
              2.只能在EDT線程上對Swing Components進行訪問。
              基于上面兩點原因,在一個Java Swing程序中,要想使用戶界面響應靈敏,至少應該有兩個線程;一個線程用來執行耗時操作,EDT線程用來執行所有與Swing Components的交互,例如更新文本,重繪圖形等等。這就要求兩個線程之間要相互通訊,給程序的開發帶來了不少的難度,Swing Worker的出現從根本上解決了這個問題,使程序員快速開發反應靈敏的的Swing程序成為可能。SwingWoker被設計應用在此種場景下,你有一個耗時操作需要運行在后臺,在該操作完成或部分完成時,你要利用操作返回的結果去更新用戶界面。
              讓我們假想有這樣一個應用場景,我有一個保存聯系人的文件,我需要從中讀取并解析出所有聯系人的信息,并及時更新在一個JTable中;假設這個文件非常的大,解析出所有聯系人的信息需要花費幾分鐘的時間,如果不能很好的協調這個任務和EDT線程,則很有可能會造成用戶在幾分鐘時間里得不到結果,而Swing界面處于無響應狀態。在這種情況下,SwingWorker就是一個絕佳的選擇。我們首先看一下SwingWorker的定義:
              public abstract class SwingWorker<T,V> extends Object implements RunnableFuture<T>
          顯然,這時一個抽象的模板類,在應用的時候,我們需要繼承SwingWorker并實例化模板參數。那么,這兩個模板類型究竟是什么意思呢,T參數代表的是你的耗時任務執行完成時返回的結果類型,V代表的是你的耗時任務部分完成時返回的結果類型。在我們的場景中,假設任務完成時我們需要一個List<BeanContact>(BeanContact是一個保存聯系人信息的JavaBean),每當從文件中解析出一個聯系人信息時,我們會新建一個BeanContact并需要更新到JTable中。那么我們的T就是List<BeanContact>,而V就是BeanContact,則應該定義如下的類:
               public class LoadContactsTask extends SwingWorker<List<BeanContact>, BeanContact> {
                      

               @Override
              protected List<BeanContact> doInBackground() throws Exception {

                  //To do the task and return the result
              }


               }
              從上面可以看到,我們還必須覆蓋SwingWorker的doInBackground方法,該方法執行我們的耗時操作,并且返回模板實例化時的T類型結果。下面是具體的代碼實現:
               

              @Override
              protected List<BeanContact> doInBackground() throws Exception {
                  BufferedReader reader = new BufferedReader(new FileReader("c:/contacts.cff"));
                  String line = null;
                  while ((line = reader.readLine()) != null) {
                      String[] strContacts = line.split(",");
                      BeanContact contact = new BeanContact();
                      contact.setName(strContacts[0]);
                      contact.setSex(strContacts[1]);
                      contact.setPhone(strContacts[2]);
                      contact.setEmail(strContacts[3]);

                      lineCnt++;
                      publish(contact);/*********/
                     contacts.add(contact);
                     
                      Thread.sleep(100);
                  }
                  return contacts;
              }

               該方法很簡單,就是從文件中讀取一個聯系人的記錄并且新建一個BeanContact實例添加到結果集中。我們需要注意的是其中的publish方法,該方法用來發布部分執行結果,每讀取一個聯系人信息,我們就用該方法把新建的BeanContact發布出去。我們需要知道的是,在publish若干個結果后(可能是一個或多個,由SwingWorker類實現)SwingWorker類的process方法會被自動回調,而我們可以在其中去更新用戶界面,SwingWorker保證process方法中所有操作都運行在EDT線程中。下面是我們的具體實現:
              @Override
              protected void process(List<BeanContact> chunks) {
                  if (progressHandle != null) {
                      progressHandle.processInProgress(chunks, lineCnt * 100 / 10000);
                  }
              }

              我們的實現中,process中會調用IProgressHandle(自定義的一個接口,用來更新用戶界面,詳見后面代碼)的processInProgress方法來更新用戶界面,大家會注意到process方法的參數是一個List<BeanContact>,為什么不是一個BeanContact呢,答案就是我們在上面講過的,有可能publish若干次后才調用process方法。
              與此類似,在doInBackground完成后,SwingWorker會自動調用done方法,下面是我們的實現:
              @Override
              protected void done() {
                  if (progressHandle != null) {
                      progressHandle.processComplete(contacts);
                  }
              }
              客戶端如何來使用用SwingWork呢,很簡單,只需要新建一個實例并且調用它的execute方法即可,他會自動調用doInBackground方法來完成操作;以下是完整的代碼實現:
              
              

          /*
           * To change this template, choose Tools | Templates
           * and open the template in the editor.
           */
          package swingworkertest;

          /**
           *
           * @author Administrator
           */
          public class BeanContact {
              private String name=null;
              private String sex=null;
              private String phone=null;
              private String email=null;

              /**
               * @return the name
               */
              public String getName() {
                  return name;
              }

              /**
               * @param name the name to set
               */
              public void setName(String name) {
                  this.name = name;
              }

              /**
               * @return the sex
               */
              public String getSex() {
                  return sex;
              }

              /**
               * @param sex the sex to set
               */
              public void setSex(String sex) {
                  this.sex = sex;
              }

              /**
               * @return the phone
               */
              public String getPhone() {
                  return phone;
              }

              /**
               * @param phone the phone to set
               */
              public void setPhone(String phone) {
                  this.phone = phone;
              }

              /**
               * @return the email
               */
              public String getEmail() {
                  return email;
              }

              /**
               * @param email the email to set
               */
              public void setEmail(String email) {
                  this.email = email;
              }
             
          }


          /*
           * To change this template, choose Tools | Templates
           * and open the template in the editor.
           */

          /*
           * Contacts.java
           *
           * Created on 2011-6-25, 10:40:13
           */
          package swingworkertest;

          import javax.swing.JFileChooser;

          /**
           *
           * @author Administrator
           */
          public class Contacts extends javax.swing.JFrame {

              /** Creates new form Contacts */
              public Contacts() {
                  initComponents();
                  handle = new DefaultProgressHandle();
                  handle.setTable(jTable1);
                  handle.setProgressBar(jProgressBar1);
              }

              /** This method is called from within the constructor to
               * initialize the form.
               * WARNING: Do NOT modify this code. The content of this method is
               * always regenerated by the Form Editor.
               */
              @SuppressWarnings("unchecked")
              // <editor-fold defaultstate="collapsed" desc="Generated Code">                         
              private void initComponents() {

                  jButton1 = new javax.swing.JButton();
                  jTextField1 = new javax.swing.JTextField();
                  jScrollPane1 = new javax.swing.JScrollPane();
                  jTable1 = new javax.swing.JTable();
                  jButton2 = new javax.swing.JButton();
                  jProgressBar1 = new javax.swing.JProgressBar();

                  setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

                  jButton1.setText("瀏覽");
                  jButton1.addActionListener(new java.awt.event.ActionListener() {
                      public void actionPerformed(java.awt.event.ActionEvent evt) {
                          jButton1ActionPerformed(evt);
                      }
                  });

                  jTextField1.setEditable(false);

                  jTable1.setModel(new javax.swing.table.DefaultTableModel(
                      new Object [][] {

                      },
                      new String [] {
                          "姓名", "性別", "電話", "電子郵件"
                      }
                  ) {
                      Class[] types = new Class [] {
                          java.lang.String.class, java.lang.String.class, java.lang.String.class, java.lang.String.class
                      };

                      public Class getColumnClass(int columnIndex) {
                          return types [columnIndex];
                      }
                  });
                  jScrollPane1.setViewportView(jTable1);

                  jButton2.setText("加載聯系人");
                  jButton2.addActionListener(new java.awt.event.ActionListener() {
                      public void actionPerformed(java.awt.event.ActionEvent evt) {
                          jButton2ActionPerformed(evt);
                      }
                  });

                  javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
                  getContentPane().setLayout(layout);
                  layout.setHorizontalGroup(
                      layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                      .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, layout.createSequentialGroup()
                          .addContainerGap()
                          .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING)
                              .addComponent(jScrollPane1, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, 557, Short.MAX_VALUE)
                              .addComponent(jProgressBar1, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, 557, Short.MAX_VALUE)
                              .addComponent(jButton2, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, 557, Short.MAX_VALUE)
                              .addGroup(layout.createSequentialGroup()
                                  .addComponent(jButton1, javax.swing.GroupLayout.DEFAULT_SIZE, 97, Short.MAX_VALUE)
                                  .addGap(18, 18, 18)
                                  .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, 442, javax.swing.GroupLayout.PREFERRED_SIZE)))
                          .addContainerGap())
                  );
                  layout.setVerticalGroup(
                      layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                      .addGroup(layout.createSequentialGroup()
                          .addContainerGap()
                          .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                              .addComponent(jButton1)
                              .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                          .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                          .addComponent(jButton2)
                          .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                          .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 120, javax.swing.GroupLayout.PREFERRED_SIZE)
                          .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                          .addComponent(jProgressBar1, javax.swing.GroupLayout.PREFERRED_SIZE, 22, javax.swing.GroupLayout.PREFERRED_SIZE)
                          .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))
                  );

                  layout.linkSize(javax.swing.SwingConstants.VERTICAL, new java.awt.Component[] {jButton1, jButton2, jTextField1});

                  pack();
              }// </editor-fold>                       

              private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                        

                  ContactsFileFilter filter = new ContactsFileFilter();
                 
                  JFileChooser chooser = new JFileChooser();
                  chooser.setFileFilter(filter);
                  int returnVal = chooser.showOpenDialog(null);
                  if(returnVal == JFileChooser.APPROVE_OPTION){
                      jTextField1.setText(chooser.getSelectedFile().getAbsolutePath());
                  }
              }                                       

              private void jButton2ActionPerformed(java.awt.event.ActionEvent evt) {                                        
                  // TODO add your handling code here:
                  LoadContactsTask task = new LoadContactsTask(jTextField1.getText());
                  task.setProgressHandle(handle);
                  task.execute();
              }                                       

              /**
               * @param args the command line arguments
               */
              public static void main(String args[]) {
                  java.awt.EventQueue.invokeLater(new Runnable() {

                      public void run() {
                          Contacts contacts = new Contacts();
                          contacts.setTitle("Contacts");;
                          contacts.setVisible(true);
                      }
                  });
              }
              DefaultProgressHandle handle = null;
              // Variables declaration - do not modify                    
              private javax.swing.JButton jButton1;
              private javax.swing.JButton jButton2;
              private javax.swing.JProgressBar jProgressBar1;
              private javax.swing.JScrollPane jScrollPane1;
              private javax.swing.JTable jTable1;
              private javax.swing.JTextField jTextField1;
              // End of variables declaration                  
          }


          /*
           * To change this template, choose Tools | Templates
           * and open the template in the editor.
           */
          package swingworkertest;

          import java.io.File;
          import javax.swing.filechooser.FileFilter;

          /**
           *
           * @author Administrator
           */
          public class ContactsFileFilter extends FileFilter{

              public boolean accept(File pathname) {
                  if(pathname.isDirectory()){
                      return true;
                  }else{
                      return pathname.getName().endsWith(".cff");
                  }
              }

              @Override
              public String getDescription() {
                  return "Text Files";
              }
             
          }


          /*
           * To change this template, choose Tools | Templates
           * and open the template in the editor.
           */
          package swingworkertest;

          import java.util.List;
          import javax.swing.JProgressBar;
          import javax.swing.JTable;
          import javax.swing.table.DefaultTableModel;

          /**
           *
           * @author Administrator
           */
          public class DefaultProgressHandle implements IProgressHandle {

              private JTable table = null;
              private JProgressBar progressBar = null;

              public void processInProgress(List<BeanContact> contacts, int progress) {
                  DefaultTableModel model = (DefaultTableModel) table.getModel();
                  for (BeanContact contact : contacts) {
                      String[] strArray = {contact.getName(), contact.getSex(), contact.getPhone(), contact.getEmail()};
                      model.addRow(strArray);
                  }
                  progressBar.setValue(progress);
              }

              public void processComplete(List<BeanContact> contacts) {
                  progressBar.setValue(progressBar.getMaximum());
              }

              /**
               * @param table the table to set
               */
              public void setTable(JTable table) {
                  this.table = table;
              }

              /**
               * @param progressBar the progressBar to set
               */
              public void setProgressBar(JProgressBar progressBar) {
                  this.progressBar = progressBar;
              }
          }


          /*
           * To change this template, choose Tools | Templates
           * and open the template in the editor.
           */
          package swingworkertest;

          import java.util.List;

          /**
           *
           * @author Administrator
           */
          public interface IProgressHandle {
              public abstract void processInProgress(List<BeanContact> contacts,int progress);
              public abstract void processComplete(List<BeanContact> contacts);
          }


          /*
           * To change this template, choose Tools | Templates
           * and open the template in the editor.
           */
          package swingworkertest;

          import java.io.BufferedReader;
          import java.io.FileReader;
          import java.util.ArrayList;
          import java.util.List;
          import javax.swing.SwingWorker;

          /**
           *
           * @author Administrator
           */
          public class LoadContactsTask extends SwingWorker<List<BeanContact>, BeanContact> {

              private String fileName = null;
              private IProgressHandle progressHandle = null;
              private List<BeanContact> contacts = null;
              private int lineCnt = 0;

              public LoadContactsTask(String fileName) {
                  this.fileName = fileName;
                  contacts = new ArrayList<BeanContact>();
              }

              @Override
              protected List<BeanContact> doInBackground() throws Exception {
                  BufferedReader reader = new BufferedReader(new FileReader("c:/contacts.cff"));
                  String line = null;
                  while ((line = reader.readLine()) != null) {
                      String[] strContacts = line.split(",");
                      BeanContact contact = new BeanContact();
                      contact.setName(strContacts[0]);
                      contact.setSex(strContacts[1]);
                      contact.setPhone(strContacts[2]);
                      contact.setEmail(strContacts[3]);

                      lineCnt++;
                      publish(contact);
                      contacts.add(contact);
                     
                      Thread.sleep(100);
                  }
                  return contacts;
              }

              /**
               * @param progressHandle the progressHandle to set
               */
              public void setProgressHandle(IProgressHandle progressHandle) {
                  this.progressHandle = progressHandle;
              }

              @Override
              protected void process(List<BeanContact> chunks) {
                  if (progressHandle != null) {
                      progressHandle.processInProgress(chunks, lineCnt * 100 / 10000);
                  }
              }

              @Override
              protected void done() {
                  if (progressHandle != null) {
                      progressHandle.processComplete(contacts);
                  }
              }
          }

          posted on 2011-06-26 11:10 Gavin Li 閱讀(3762) 評論(0)  編輯  收藏 所屬分類: Java

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