我创建了一个窗口,并希望使用windowStateChanged方法拦截出口,以便在应用程序关闭之前保存数据.但是,它似乎没有在数据关闭之前保存数据.我怎么能纠正这个？
见下面的代码:
public class InventoryMainFrame extends JFrame implements WindowStateListener{
//set up the main window - instantiate the application
private InventoryInterface inventoryInterface; //panel that contains menu choices and buttons
public InventoryMainFrame(){ //main window
setTitle("Inventory System");
setSize (500,500);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLayout(new BorderLayout());
//setLocationRelativeTo(null); //center window on the screen
inventoryInterface = new InventoryInterface(); //set up the panel that contains menu choices and buttons
add(inventoryInterface.getMainPane()); //add that panel to this window
pack();
setVisible(true);
//display window on the screen
}
public static void main(String[] args) { …当我使用JLabel.setText()时如何插入换行符？我试图使用Html,但似乎可以使它适用于setText,仅用于jLabel的初始声明
最初声明jlabel时的方法是:
label = new JLabel("<html>Hello World!<br>blahblahblah</html>");
我的代码:
textString += "<html> quantityTextField.getText() +
theInventory.findItem(UPCTextField.getText()).toString() + <br> </html>";
purchaseInfo.setText( textString);
它显示html标签和方法名称,而不是方法返回的字符串
下面是我创建JList的代码.当它在独立的JFrame中创建时,JList会填充整个框架.但是,当我将其创建为JPanel并将其添加到JFrame时,它没有填充组件的大小,为什么？
public class ListBranchesInterface extends JPanel {
private Library theLibrary; // reference to back end
private ArrayList<LibraryBranch> branches;
private DefaultListModel dlm;
private JList list;
private JScrollPane scroll;
public ListBranchesInterface(Library theLibrary) {
this.theLibrary = theLibrary;
branches = new ArrayList<LibraryBranch>();
branches.addAll(theLibrary.getLibraryBranches());
Iterator<LibraryBranch> iter = branches.iterator();
dlm = new DefaultListModel();
while (iter.hasNext()) {
dlm.addElement(iter.next().toString());
}
list = new JList(dlm); // create a JList from the default list model
scroll = new JScrollPane(list, JScrollPane.VERTICAL_SCROLLBAR_ALWAYS,
JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS); // add a scroll pane
// to the JList …我有一个应用程序,允许用户选择一个选项,并根据用户选择从组件中删除JPanel,添加新的JPanel并重新验证组件
看代码:
if (c != null) {
contentPane.remove(c);
}
c = new AddBookInterface(theLibrary);
contentPane.add(c);
contentPane.revalidate();
break;
c是一个组件
我有几个JPanels,用户可以切换,交换机正常工作.但是,当我在用户选择时添加此JPanel时,之后添加的JPanel无法正确加载.是什么造成的？
public class RemoveBookInterface extends JPanel {
private Library theLibrary;
public RemoveBookInterface(Library theLibrary) {
this.theLibrary = theLibrary;
setSize(400, 400);
setLayout(new BorderLayout());
setVisible(true);
removeBook(theLibrary);
}
public void removeBook(Library theLibrary) {
// prompt user for book id of book to remove
Long ID = Long
.parseLong(JOptionPane
.showInputDialog("Enter the library book ID for the book you want to remove"));
try {
// get library book info …我想在我的应用程序中添加一个功能,允许用户通过在起始位置单击鼠标并在结束位置释放它来绘制直线.当鼠标移动直到最终释放时,线应该移动; 类似于使用Microsoft Paint应用程序绘制线条的方式.
如何实现这一点,以便线条在移动时重新绘制,而不重新绘制可能已在该矩形区域中绘制的其他内容？
我有很多矩形,我试图生成一个不在任何一个内部的随机点.我创建了一个方法来执行此操作,但似乎这导致我的应用程序冻结,因为它必须在生成有效点之前经过大量的点:
public Point getLegalPoint() {
Random generator = new Random();
Point point;
boolean okPoint = true;
do {
point = new Point(generator.nextInt(975), generator.nextInt(650));
for (int i = 0; i < buildingViews.size(); i++) {
if (buildingViews.get(i).getBuilding().getRectangle()
.contains(point)) {
okPoint = false;
break;
}
}
} while (okPoint == false);
return point;
}
有什么我做错了,或者有更有效的方法来做它,以便它不会冻结我的应用程序？
java ×6
swing ×4
awt ×2
jframe ×2
jpanel ×2
components ×1
draw ×1
exit ×1
graphics2d ×1
jlabel ×1
jlist ×1
joptionpane ×1
mouseevent ×1
multiline ×1
newline ×1
point ×1
save ×1