【发布时间】：2013-03-29 05:08:23
【问题描述】：
我正在swing 中编写一个程序，它使用链接节点来存储一个值，然后以黄色条的形式将包含的值绘制到一个JPanel 中。这幅画最初是使用 AWT 完成的。我已经阅读了一些this 摇摆绘画教程，但我仍然不明白如何在 JPanel 上绘画。程序应该在按下“随机”按钮时绘制条形图，但目前什么都不画。
我已包含我认为相关的代码，但如果您需要任何其他部分，请告诉我。提前感谢您提供的任何帮助或您可以指出的任何教程。
public class DataOrganizer extends JPanel
{
private JFrame frame;
protected static final Color DEFAULT_COLOR = Color.YELLOW;
protected static final Color HIGHLIGHT_COLOR = Color.YELLOW.darker();
protected DataCollection<Item> collection; // To hold our items
protected DataCollection<Item> sortedCollection;
protected Item selected;
private final int COLLECTION_SIZE = 10, // Maximum number of items
MAXIMUM_ITEM_VALUE = 16; // Maximum value of an item
private int firstItemXCoord;
protected int firstItemYCoord;
/**
* Launch the application.
*/
public static void main(String[] args)
{
EventQueue.invokeLater(new Runnable() {
public void run()
{
try
{
DataOrganizer window = new DataOrganizer();
window.frame.setVisible(true);
}
catch (Exception e)
{
e.printStackTrace();
}
}
});
}
/**
* Create the application.
*/
public DataOrganizer()
{
initialize();
}
/**
* Initialize the contents of the frame.
*/
private void initialize()
{
/*
* Create and set-up the JFrame.
*/
frame = new JFrame();
frame.setPreferredSize(new Dimension(550, 450));
frame.setBounds(100, 100, 600, 400);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setLayout(null);
frame.setVisible(true);
/*
* Create btnRandom and add an action listener
* that calls randomAction().
*/
JButton btnRandom = new JButton("Random");
btnRandom.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
randomAction();
}
});
btnRandom.setBounds(6, 18, 117, 29);
frame.getContentPane().add(btnRandom);
/*
* Create btnMaximum and add an action listener
* that calls maximumAction().
*/
JButton btnMaximum = new JButton("Maximum");
btnMaximum.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
maximumAction();
}
});
btnMaximum.setBounds(6, 59, 117, 29);
frame.getContentPane().add(btnMaximum);
/*
* Create btnMinimum and add an action listener
* that calls minimumAction().
*/
JButton btnMinimum = new JButton("Minimum");
btnMinimum.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
minimumAction();
}
});
btnMinimum.setBounds(6, 100, 117, 29);
frame.getContentPane().add(btnMinimum);
/*
* Create btnRemove and add an action listener
* that calls removeAction().
*/
JButton btnRemove = new JButton("Remove");
btnRemove.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
removeAction();
}
});
btnRemove.setBounds(6, 141, 117, 29);
frame.getContentPane().add(btnRemove);
/*
* Create btnSort and add an action listener
* that calls sort().
*/
JButton btnSort = new JButton("Sort");
btnSort.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
sort();
}
});
btnSort.setBounds(6, 182, 117, 29);
frame.getContentPane().add(btnSort);
/*
* Create the JPanel, set the bounds,
* and add it to the frame.
*/
JPanel panel = new JPanel();
panel.setBounds(135, 0, 465, 378);
frame.getContentPane().add(panel);
//Initialize the unsorted collection
collection = new DataCollection<Item>(COLLECTION_SIZE);
//Initialize the sorted collection
sortedCollection = new DataCollection<Item>(COLLECTION_SIZE);
repaint();
}
public void paintComponent(Graphics panel) {
super.paintComponent(panel);
panel.drawString("Hello World", 140 , 10);
/*
* Display the Items when instantiated.
*/
if (collection != null)
{
Item item;
int xCoord = firstItemXCoord;
/*
* Reset the selected item to the start of the collection,
* ensuring it always starts at the first node
*/
collection.reset();
//While there is another node in the collection, loop through.
while (collection.hasNext())
{
/*
* Set the item to the selected node.
* Which since reset() was called on the
* collection, it should be the first node
* in the collection. Then set the next node in the
* collection a the selected one.
*/
item = collection.next();
/*
* Call the paint method in the item class
*/
item.paint(panel, xCoord, firstItemXCoord);
xCoord += Item.OVERALL_WIDTH;
}
}
/*
* Display the Items when instantiated.
*/
if (sortedCollection != null)
{
Item item;
int xCoord = firstItemXCoord + 200;
/*
* Reset the selected item to the start of the collection,
* ensuring it always starts at the first node
*/
sortedCollection.reset();
//While there is another node in the collection, loop through.
while (sortedCollection.hasNext())
{
/*
* Set the item to the selected node.
* Which since reset() was called on the
* sortedCollection, it should be the first node
* in the collection. Then set the next node in the
* collection a the selected one.
*/
item = sortedCollection.next();
/*
* Call the paint method in the item class
*/
item.paint(panel, xCoord, firstItemXCoord);
xCoord += Item.OVERALL_WIDTH;
}
}
}
//
// Random
//
public void randomAction()
{
collection.clear(); // We restart with nothing,
// then we add random items,
for (int i = 1; i <= COLLECTION_SIZE; i++)
{
collection.add(new Item((int) (1 + MAXIMUM_ITEM_VALUE
* Math.random()), DEFAULT_COLOR));
}
selected = null; // We make sure nothing is selected
}
【问题讨论】：
-
您是否检查过您的面板的尺寸是否足够大，可以看到上面的任何东西？您按照您应该做的那样覆盖
paintComponent，它确实需要一个Graphics对象，除此之外，只要您确定paintComponent中的所有代码都按照您认为应该执行的方式执行，一切都会检查出来. -
我相信面板的大小是正确的。如果我正确读取 API，
panel.setBounds(135, 0, 465, 378);应将左上角设置为 (135,0) 并将尺寸设置为 465 x 378。除非我应该使用setSize(int width, int height)。 -
实际上应用于 Panel 父级的布局管理器决定了绘制大小和位置。
-
@user2220927，不要使用 setBounds() 来调整面板上组件的大小和位置。使用布局管理器。