[英]java SwingWorker dialog is not shown
在Netbeans中,我創建了一個GUI項目,該項目使用框架前端,可以添加組件並雙擊以編輯其事件。 我指的是具有“源”,“設計”和“歷史”選項卡的窗口。
以下是組件和關系:
1-打開文件選擇器的按鈕。
2-一個TextArea以顯示文件選擇器的結果。 如果用戶選擇一個文件,它將在TextArea中顯示文件名; 否則會寫“被用戶取消”。
3-同時,如果用戶選擇一個文件,我想打開一個“請稍候”對話框,打開SwingWorker
並在后台做一些工作。
問題是,當用戶選擇文件時,我看不到“請稍候”對話框! Netbeans生成的完整代碼可從pastebin獲得 。 部分代碼如下所示:
private void OpenSongFileActionPerformed(java.awt.event.ActionEvent evt) {
// TODO add your handling code here:
JFileChooser fileChooser = new JFileChooser();
fileChooser.setAcceptAllFileFilterUsed(false);
FileNameExtensionFilter filter = new FileNameExtensionFilter("MP3 files", "mp3");
fileChooser.addChoosableFileFilter(filter);
fileChooser.setCurrentDirectory(new File(System.getProperty("user.dir")));
int result = fileChooser.showOpenDialog(this);
if (result != JFileChooser.APPROVE_OPTION) {
//ReadInfo.setText("No song has been selected");
System.out.println("OpenSongFile canceled by user");
return;
}
final JDialog loading = new JDialog(this);
JPanel p1 = new JPanel(new BorderLayout());
p1.add(new JLabel("Please wait..."), BorderLayout.CENTER);
loading.setUndecorated(true);
loading.getContentPane().add(p1);
loading.pack();
loading.setLocationRelativeTo(this);
loading.setDefaultCloseOperation(JDialog.DO_NOTHING_ON_CLOSE);
loading.setModal(true);
SwingWorker<String, Void> worker = new SwingWorker<String, Void>() {
@Override
protected String doInBackground() throws InterruptedException {
for (int i = 0; i < 10000; i++)
for (int j = 0; j < 10000; j++)
;
return "hello";
}
@Override
protected void done() {
loading.dispose();
}
};
worker.execute();
loading.setVisible(true);
try {
worker.get();
} catch (Exception e1) {
e1.printStackTrace();
}
File selectedFile = fileChooser.getSelectedFile();
ReadInfo.setText("Selected file: " + selectedFile.getAbsolutePath());
}
PS:我使用了此處解釋的SwingWorker代碼。
worker.get();
將一直阻塞,直到SwingWorker
返回為止,這意味着您正在阻塞EDT,從而阻止顯示對話框。
相反,請使用SwingWorker
的PropertyChangeListener
支持並監視START
和DONE
事件
SwingWorker<String, Void> worker = new SwingWorker<String, Void>() {
@Override
protected String doInBackground() throws InterruptedException {
Thread.sleep(5000);
return "hello";
}
@Override
protected void done() {
loading.dispose();
}
};
worker.addPropertyChangeListener(new PropertyChangeListener() {
@Override
public void propertyChange(PropertyChangeEvent evt) {
System.out.println(evt.getPropertyName());
Object value = evt.getNewValue();
if (value instanceof SwingWorker.StateValue) {
SwingWorker.StateValue state = (SwingWorker.StateValue) value;
switch (state) {
case DONE: {
try {
String result = worker.get();
JOptionPane.showMessageDialog(null, result);
} catch (InterruptedException | ExecutionException ex) {
ex.printStackTrace();
}
}
break;
}
}
}
});
worker.execute();
loading.setVisible(true);
另一個問題是您的循環可能運行得如此之快,以至於窗口在屏幕上實現之前就已關閉。
例如,我只是使用Thread.sleep
將doInBackground
方法暫停5秒鍾...
import java.awt.BorderLayout;
import java.beans.PropertyChangeEvent;
import java.beans.PropertyChangeListener;
import java.util.concurrent.ExecutionException;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.swing.JDialog;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.SwingWorker;
public class Memory extends JFrame {
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
makeItSo();
}
});
}
public static void makeItSo() {
final JDialog loading = new JDialog();
JPanel p1 = new JPanel(new BorderLayout());
p1.add(new JLabel("Please wait..."), BorderLayout.CENTER);
loading.setUndecorated(true);
loading.getContentPane().add(p1);
loading.pack();
loading.setLocationRelativeTo(null);
loading.setDefaultCloseOperation(JDialog.DO_NOTHING_ON_CLOSE);
loading.setModal(true);
SwingWorker<String, Void> worker = new SwingWorker<String, Void>() {
@Override
protected String doInBackground() throws InterruptedException {
Thread.sleep(5000);
return "hello";
}
@Override
protected void done() {
loading.dispose();
}
};
worker.addPropertyChangeListener(new PropertyChangeListener() {
@Override
public void propertyChange(PropertyChangeEvent evt) {
System.out.println(evt.getPropertyName());
Object value = evt.getNewValue();
if (value instanceof SwingWorker.StateValue) {
SwingWorker.StateValue state = (SwingWorker.StateValue) value;
switch (state) {
case DONE: {
try {
String result = worker.get();
JOptionPane.showMessageDialog(null, result);
} catch (InterruptedException | ExecutionException ex) {
ex.printStackTrace();
}
}
break;
}
}
}
});
worker.execute();
loading.setVisible(true);
}
}
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