java - 显示 'Loading'帧直到后台进程完成

Question

我有一个打印 iReport 的按钮，但显示报告需要时间，因此我创建了一个名为 Loading 的加载框架类当我按下按钮时，我试图调用这个类，但它不能正常工作。

我的按钮 ActionListener 代码是:

private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                         
     loading.setVisible(true);// show frame before trying to connect to database and load report
    try {
        String reportquery = "Select * from invoices ";
        JasperDesign jasperdesign = JRXmlLoader.load("StatementReport.jrxml");
        JRDesignQuery designquery = new JRDesignQuery();
        designquery.setText(reportquery);
        jasperdesign.setQuery(designquery);
        JasperReport jasperreport = JasperCompileManager.compileReport(jasperdesign);
        JasperPrint jasperprint = JasperFillManager.fillReport(jasperreport, null, con);

        JasperViewer.viewReport(jasperprint, false);

    } catch (JRException e) {
        JOptionPane.showMessageDialog(this, e);
    } finally {
        try {
            rs.close();
            pst.close();
            loading.dispose(); // dispose loading frame when finish
        } catch (SQLException ex) {
            Logger.getLogger(showAllInvoices.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}  `

Answer 1

与所有与在 Swing 中执行长时间运行或阻塞任务相关的问题一样，以 Concurrency in Swing 开头更好地理解您要解决的问题。接下来看看Worker Threads and SwingWorker最常见的解决方案

例如:

public static class JasperReportsWorker extends SwingWorker<JasperReport, JasperReport> {

    @Override
    protected JasperReport doInBackground() throws Exception {
        JasperReport report = null;
        try {
            String reportquery = "Select * from invoices ";
            JasperDesign jasperdesign = JRXmlLoader.load("StatementReport.jrxml");
            JRDesignQuery designquery = new JRDesignQuery();
            designquery.setText(reportquery);
            jasperdesign.setQuery(designquery);
            report = JasperCompileManager.compileReport(jasperdesign);
        } finally {
            try {
                rs.close();
                pst.close();
            } catch (SQLException ex) {
                ex.printStackTrace();
            }
        }
        return report;
    }

}

然后可以使用如下内容:

JasperReportsWorker worker = new JasperReportsWorker();
JDialog dialog = new JDialog();
dialog.setModal(true);
dialog.add(new JLabel("Working..."));
dialog.pack();
dialog.setLocationRelativeTo(null);
worker.addPropertyChangeListener(new PropertyChangeListener() {
    @Override
    public void propertyChange(PropertyChangeEvent evt) {
        String name = evt.getPropertyName();
        JasperReportsWorker worker = (JasperReportsWorker) evt.getSource();
        if ("state".equalsIgnoreCase(name)) {
            switch (worker.getState()) {
                case DONE:
                    if (dialog != null) {
                        dialog.setVisible(false);
                    }
                    try {
                        JasperReport report = worker.get();
                        JasperPrint jasperprint = JasperFillManager.fillReport(jasperreport, null, con);
                        JasperViewer.viewReport(jasperprint, false);
                    } catch (InterruptedException | ExecutionException ex) {
                        ex.printStackTrace();
                    }
                    break;
            }
        }
    }
});
worker.execute();
dialog.setVisible(true);

围绕基本思想有许多变体，因此请随意尝试