我正在做一个游戏,在其中我有一个主菜单。我希望从数组中加载菜单项,这样可以更有效地向菜单中添加新项目。我希望为for循环创建的每个JLabel都启用一个鼠标侦听器,这样我就可以检查鼠标是否悬停在它上面,并查看它何时被单击。我怎样才能做到这一点?
下面是我目前使用的代码,它可以创建JLabels,尽管鼠标侦听器不能工作。
private String[] items = { "Exit", "Mods", "Settings", "New Game", "Play Game" };
private String item_hover_left = "[";
private String item_hover_right = "]";
private void createItems() {
GameSound sound = new GameSound();
int initialY = 951;
JLabel[] item = new JLabel[items.length];
for (i = 0; i < items.length; i++) {
int y = initialY - (101 * i);
item[i] = new JLabel();
item[i].setText(items[i]);
item[i].setForeground(ui_colour);
item[i].setFont(new Font("Overseer", Font.PLAIN, 50));
item[i].setHorizontalAlignment(SwingConstants.CENTER);
item[i].setBounds(1582, y, 328, 99);
add(item[i]);
repaint();
item[i].addMouseListener(new MouseAdapter() {
public void mousePressed(MouseEvent pressed) {
if (pressed.getButton() == MouseEvent.BUTTON1) {
sound.playSound("menu_ok");
}
}
public void mouseEntered(MouseEvent entered) {
item[i].setText(item_hover_left + " " + items[i] + " " + item_hover_right);
sound.playSound("menu_hover");
}
public void mouseExited(MouseEvent exited) {
item[i].setText(items[i]);
}
});
}
}
线程"AWT-EventQueue-0“中的异常:5在net.fallout.menu.MainMenu$1.mouseEntered(MainMenu.java:87) at java.awt.Component.processMouseEvent(未知源) at javax.swing.JComponent.processMouseEvent(Unknown Source) at java.awt.Component.processEvent(未知源)在java.awt.Container.processEvent(未知源) at java.awt.Component.dispatchEventImpl(未知源) at java.awt.Container.dispatchEventImpl(未知源) at java.awt.Componentjava.awt.LightweightDispatcher.retargetMouseEvent(Unknown源(未知源)、java.awt.LightweightDispatcher.retargetMouseEnterExit(Unknown源( java.awt.LightweightDispatcher.trackMouseEnterExit(Unknown源)、java.awt.LightweightDispatcher.processMouseEvent(Unknown源(java.awt.LightweightDispatcher.processMouseEvent(Unknown源)、java.awt.Container.dispatchEventImpl(未知源)、java.awt.Window.dispatchEventImpl(未知源)、java.awt.Component.dispatchEvent(未知源)、java.awt.Component.dispatchEvent(未知源)(未知来源)在java.awt.EventQueue$3.运行(未知来源)在java.awt.EventQueue$3.运行(未知源)在java.security.AccessController.doPrivileged(Native方法上运行(未知来源)在java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown来源)在java.awt.EventQueue$4.运行(未知源)在java.awt.EventQueue$4.运行(未知源)在java.security.AccessController.doPrivileged(Native方法上运行(未知来源))在< java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown来源]在java.awt.EventQueue.dispatchEvent(未知来源)在java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown源)在java.awt.EventDispatchThread.pumpEventsForFilter(Unknown源)在java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown源)在java.awt.EventDispatchThread.pumpEvents(Unknown源)在java.awt.EventDispatchThread.pumpEvents(Unknown源)在java.awt.EventDispatchThread.run(未知源)
发布于 2018-06-15 06:57:53
我建议您为MouseListener
创建一个单独的类,比如内部类,而不是您正在使用的匿名类。
class YourMouseListener extends MouseAdapter {
JLabel label;
String text;
YourMouseListener(JLabel label, String text) {
this.label = label;
this.text = text;
}
// ...
// use this.label instead of item[i], like this
public void mouseEntered(MouseEvent entered) {
label.setText(item_hover_left + " " + text + " " + item_hover_right);
sound.playSound("menu_hover");
}
// ...
}
然后在循环中使用这个类。
JLabel[] item = new JLabel[items.length];
for (i = 0; i < items.length; i++) {
item[i] = new JLabel(items[i]);
// ...
add(item[i]);
item[i].addMouseListener(new YourMouseListener(item[i], items[i]));
repaint();
}
您甚至可能不需要label
成员,因为您只需使用事件的目标来将文本设置为。
发布于 2018-06-15 06:55:52
在您的匿名类中,您有以下方法:
public void mouseEntered(MouseEvent entered) {
item[i].setText(item_hover_left + " " + items[i] + " " + item_hover_right);
sound.playSound("menu_hover");
}
在它中,您使用的是i
,我可以说它是一个类成员变量,因为它只能是那个或一个final
局部变量,但是i
是循环中的增量,所以它只能是一个类成员。
问题是,当您创建完您的标签时,由于i
for (i = 0; i < items.length; i++) {
**.的原因,会发生变化。当事件发生时,** item[i]
将指向数组外,解释异常。
首先,不要为i
使用类成员,这对保持这个值没有意义,会给您带来问题(就像这个问题)。
我知道您这样做是因为它没有编译,因为您可以在您正在实现的侦听器的方法中使用它,但是您可以在循环中使用final
变量来解决这个问题:
//declare `i` here
for (int i = 0; i < items.length; i++) {
//declare `index` final and assign `i`, each MouseAdapter instance will use the correct `index`
final int index = i;
item[i].addMouseListener(new MouseAdapter() {
public void mouseEntered(MouseEvent entered) {
item[index].setText(item_hover_left + " " + items[index] + " " + item_hover_right);
sound.playSound("menu_hover");
}
}
daniu建议的另一种方法,因为我过于关注索引问题,所以应该声明标签为final。
for (int i = 0; i < items.length; i++) {
final JLabel label = new JLabel();
item[i] = label;
label.addMouseListener(new MouseAdapter() {
public void mouseEntered(MouseEvent entered) {
label.setText(item_hover_left + " " + label + " " + item_hover_right);
sound.playSound("menu_hover");
}
}
}
当然,还有另一种方法,您可以使用EventObject.getSource
获取事件的源。您知道它将是一个JLabel
,因为这是一个匿名类,不能在其他地方使用。
public void mouseEntered(MouseEvent entered) {
JLabel label = (JLabel)entered.getSource();
label.setText(item_hover_left + " " + label + " " + item_hover_right);
sound.playSound("menu_hover");
}
发布于 2018-06-15 07:35:18
这是我用过的解决方案。
私有空createItems() {
int initialY = 951;
JLabel[] item = new JLabel[items.length];
for (int i = 0; i < item.length; i++) {
final int selected = i;
int y = initialY - (101 * selected);
item[selected] = new JLabel();
item[selected].setText(items[selected]);
item[selected].setForeground(ui_colour);
item[selected].setFont(new Font("Overseer", Font.PLAIN, 50));
item[selected].setHorizontalAlignment(SwingConstants.CENTER);
item[selected].setBounds(1582, y, 328, 99);
add(item[selected]);
item[i].addMouseListener(new ItemListener(item[i], selected));
repaint();
}
}
class ItemListener extends MouseAdapter {
GameSound sound = new GameSound();
JLabel item_label;
Integer item_index;
ItemListener(JLabel label, int index) {
this.item_label = label;
this.item_index = index;
}
public void mousePressed(MouseEvent pressed) {
if (pressed.getButton() == MouseEvent.BUTTON1) {
sound.playSound("menu_ok");
item_selected = item_index;
checkItem();
}
}
public void mouseEntered(MouseEvent entered) {
item_label.setText(item_hover_left + " " + items[item_index] + " "
+ item_hover_right); sound.playSound("menu_hover");
}
public void mouseExited(MouseEvent exited) {
item_label.setText(items[item_index]);
}
}
https://stackoverflow.com/questions/50870320
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