问题
I looked around trying to resolve my issue but could not find anything to resolve this. I am really new to java and am trying to do projects from the book without using the console but here is what I have,
import javax.swing.JComponent;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
public class FutureInvestmentValue {
public static void main(String[] args) {
double investmentAmount = Double.parseDouble(JOptionPane.showInputDialog(null, "Enter in the investment amount as a double.", "Investment Amout",
JOptionPane.PLAIN_MESSAGE));
double monthlyInterestRate = Double.parseDouble(JOptionPane.showInputDialog(null, "Enter in the monthly interest rate as a double.", "Monthly Interest Rate",
JOptionPane.PLAIN_MESSAGE));
int years = 30;
final JComponent[] outputHeader = new JComponent[] {
new JLabel("The amount invested: " + investmentAmount),
new JLabel("Annual interest Rate: " + monthlyInterestRate),
new JLabel("Years Future Value"),
};
JOptionPane.showMessageDialog(null, outputHeader + futureInvestmentValue(investmentAmount, monthlyInterestRate, years), "Future Investment Value",
JOptionPane.INFORMATION_MESSAGE);
}
public static JComponent[] futureInvestmentValue(double investmentAmount, double monthlyInterestRate, int years) {
final JComponent[] investmentArray = new JComponent[years];
for (int i = 1; i <= years; i++) {
double investmentTotal = investmentAmount + (investmentAmount * ((monthlyInterestRate / 10) * i));
investmentArray[i] = new JLabel(i + " " + investmentTotal);
}
return investmentArray;
}
}
and it seems that I am getting errors that are telling to to change futureInvestmentValue(); to a Jcomponent and when I do that another error happens and it just runs me in circles with changing from JLabel to JLabel[] to Jcomponent to Jcomponent[] and what not. Any help that can explain it to me in terms that wouldnt be confusing to a newbie would be appreciated.
回答1:
- why do you create an array of JLabel, to use the JTable instead,
import java.awt.*;
import java.awt.event.ActionEvent;
import java.util.Random;
import java.util.concurrent.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.table.DefaultTableModel;
public class ChangeNotifiersOnEvent extends JFrame implements Runnable {
private static final long serialVersionUID = 1L;
private boolean runProcess = true;
private Random random = new Random();
private javax.swing.Timer timerRun;
private Executor executor = Executors.newCachedThreadPool();
private String[] columnNames = {"Source", "Hit", "Last", "Ur_Diff"};
private JTable table;
private Object[][] data = {{"Swing Timer", 2.99, 5, 1.01},
{"Swing Worker", 7.10, 5, 1.010}, {"TableModelListener", 25.05, 5, 1.01}};
private DefaultTableModel model = new DefaultTableModel(data, columnNames);
public ChangeNotifiersOnEvent() {
table = new JTable(model) {
private static final long serialVersionUID = 1L;
@Override
public Class getColumnClass(int column) {
return getValueAt(0, column).getClass();
}
};
model.addTableModelListener(new TableModelListener() {
@Override
public void tableChanged(TableModelEvent tme) {
if (tme.getType() == TableModelEvent.UPDATE) {
if (tme.getColumn() == 1 && tme.getLastRow() == 2) {
double dbl = ((Double) table.getModel().getValueAt(2, 1))
- ((Integer) table.getModel().getValueAt(2, 2));
table.getModel().setValueAt(dbl, 2, 3);
} else if (tme.getColumn() == 1 && tme.getLastRow() == 0) {
prepareUpdateTableCell();
} else if (tme.getColumn() == 1 && tme.getLastRow() == 1) {
executor.execute(new MyTask(MyTask.UPDATE_TABLE_COLUMN));
}
}
}
});
table.setRowHeight(30);
table.setFont(new Font("Serif", Font.BOLD, 20));
table.getColumnModel().getColumn(0).setPreferredWidth(180);
table.setPreferredScrollableViewportSize(table.getPreferredSize());
JScrollPane scrollPane = new JScrollPane(table);
add(scrollPane, BorderLayout.CENTER);
new Thread(this).start();
}
private void prepareUpdateTableCell() {
timerRun = new javax.swing.Timer(10, UpdateTableCell());
timerRun.setRepeats(false);
timerRun.start();
}
private Action UpdateTableCell() {
return new AbstractAction("Update Table Cell") {
private static final long serialVersionUID = 1L;
@Override
public void actionPerformed(ActionEvent e) {
double dbl = ((Double) table.getModel().getValueAt(0, 1))
- ((Integer) table.getModel().getValueAt(0, 2));
table.getModel().setValueAt(dbl, 0, 3);
}
};
}
@Override
public void run() {
while (runProcess) {
try {
Thread.sleep(330);
} catch (Exception e) {
e.printStackTrace();
}
changeTableValues();
}
}
private void changeTableValues() {
Runnable doRun = new Runnable() {
@Override
public void run() {
table.getModel().setValueAt(random.nextInt(128) + random.nextDouble(), 0, 1);
table.getModel().setValueAt(random.nextInt(256) + random.nextDouble(), 1, 1);
table.getModel().setValueAt(random.nextInt(512) + random.nextDouble(), 2, 1);
table.getModel().setValueAt(random.nextInt(128), 0, 2);
table.getModel().setValueAt(random.nextInt(128), 1, 2);
table.getModel().setValueAt(random.nextInt(128), 2, 2);
}
};
SwingUtilities.invokeLater(doRun);
}
private class MyTask extends SwingWorker<Void, Integer> {
private static final String UPDATE_TABLE_COLUMN = "update";
private String namePr;
private double dbl;
MyTask(String str) {
this.namePr = str;
}
@Override
protected Void doInBackground() throws Exception {
dbl = ((Double) table.getModel().getValueAt(1, 1))
- ((Integer) table.getModel().getValueAt(1, 2));
return null;
}
@Override
protected void done() {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
table.getModel().setValueAt(dbl, 1, 3);
}
});
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
@Override
public void run() {
ChangeNotifiersOnEvent frame = new ChangeNotifiersOnEvent();
frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
frame.setLocation(150, 150);
frame.pack();
frame.setVisible(true);
}
});
}
}
- you can to add / remove row(s) on runtime,
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
import javax.swing.table.*;
public class RemoveAddRows extends JFrame {
private static final long serialVersionUID = 1L;
private Object[] columnNames = {"Type", "Company", "Shares", "Price"};
private Object[][] data = {
{"Buy", "IBM", new Integer(1000), new Double(80.50)},
{"Sell", "MicroSoft", new Integer(2000), new Double(6.25)},
{"Sell", "Apple", new Integer(3000), new Double(7.35)},
{"Buy", "Nortel", new Integer(4000), new Double(20.00)}
};
private JTable table;
private DefaultTableModel model;
public RemoveAddRows() {
model = new DefaultTableModel(data, columnNames) {
private static final long serialVersionUID = 1L;
@Override
public Class getColumnClass(int column) {
return getValueAt(0, column).getClass();
}
};
table = new JTable(model) {
private static final long serialVersionUID = 1L;
@Override
public Component prepareRenderer(TableCellRenderer renderer, int row, int column) {
Component c = super.prepareRenderer(renderer, row, column);
int firstRow = 0;
int lastRow = table.getRowCount() - 1;
int width = 0;
if (row == lastRow) {
((JComponent) c).setBackground(Color.red);
} else if (row == firstRow) {
((JComponent) c).setBackground(Color.blue);
} else {
((JComponent) c).setBackground(table.getBackground());
}
/*if (!isRowSelected(row)) {
String type = (String) getModel().getValueAt(row, 0);
c.setBackground("Buy".equals(type) ? Color.GREEN : Color.YELLOW);
}
if (isRowSelected(row) && isColumnSelected(column)) {
((JComponent) c).setBorder(new LineBorder(Color.red));
}*/
return c;
}
};
table.setPreferredScrollableViewportSize(table.getPreferredSize());
JScrollPane scrollPane = new JScrollPane(table);
add(scrollPane);
JButton button1 = new JButton("Remove all rows");
button1.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
if (model.getRowCount() > 0) {
for (int i = model.getRowCount() - 1; i > -1; i--) {
model.removeRow(i);
}
}
System.out.println("model.getRowCount() --->" + model.getRowCount());
}
});
JButton button2 = new JButton("Add new rows");
button2.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
Object[] data0 = {"Buy", "IBM", new Integer(1000), new Double(80.50)};
model.addRow(data0);
Object[] data1 = {"Sell", "MicroSoft", new Integer(2000), new Double(6.25)};
model.addRow(data1);
Object[] data2 = {"Sell", "Apple", new Integer(3000), new Double(7.35)};
model.addRow(data2);
Object[] data3 = {"Buy", "Nortel", new Integer(4000), new Double(20.00)};
model.addRow(data3);
System.out.println("model.getRowCount() --->" + model.getRowCount());
}
});
JPanel southPanel = new JPanel();
southPanel.add(button1);
southPanel.add(button2);
add(southPanel, BorderLayout.SOUTH);
}
public static void main(String[] args) {
RemoveAddRows frame = new RemoveAddRows();
frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
}
来源：https://stackoverflow.com/questions/11335153/importing-a-jlabel-array-into-a-jcomponent