我正在尝试使用现有代码滑动JPanel。但是当我尝试滑动时会出现此错误，
线程“ AWT-EventQueue-0”中的异常java.lang.NullPointerException 在 Library.PanelSlider.PanelSlider.nextSlidPanel（PanelSlider.java:44） 在FDB.Main.MainWindow.addSBMouseClicked（MainWindow.java:180） 在FDB.Main.MainWindow.access $ 000（MainWindow.java:18）在 FDB.Main.MainWindow $ 1.mouseClicked（MainWindow.java:70）在 java.awt.AWTEventMulticaster.mouseClicked（AWTEventMulticaster.java:270） 在java.awt.Component.processMouseEvent（Component.java:6536）在 javax.swing.JComponent.processMouseEvent（JComponent.java:3324）在 java.awt.Component.processEvent（Component.java:6298）在 java.awt.Container.processEvent（Container.java:2236）在 java.awt.Component.dispatchEventImpl（Component.java:4889）在 java.awt.Container.dispatchEventImpl（Container.java:2294）在 java.awt.Component.dispatchEvent（Component.java:4711）在 java.awt.LightweightDispatcher.retargetMouseEvent（Container.java:4888） 在 java.awt.LightweightDispatcher.processMouseEvent（Container.java:4534） 在java.awt.LightweightDispatcher.dispatchEvent（Container.java:4466） 在java.awt.Container.dispatchEventImpl（Container.java:2280）在 java.awt.Window.dispatchEventImpl（Window.java:2746）在 java.awt.Component.dispatchEvent（Component.java:4711）在 java.awt.EventQueue.dispatchEventImpl（EventQueue.java:758）在 java.awt.EventQueue.access $ 500（EventQueue.java:97）在 java.awt.EventQueue $ 3.run（EventQueue.java:709）在 java.awt.EventQueue $ 3.run（EventQueue.java:703）在 java.security.AccessController.doPrivileged（本机方法），位于 java.security.ProtectionDomain $ JavaSecurityAccessImpl.doIntersectionPrivilege（ProtectionDomain.java:76） 在 java.security.ProtectionDomain $ JavaSecurityAccessImpl.doIntersectionPrivilege（ProtectionDomain.java:86） 在java.awt.EventQueue $ 4.run（EventQueue.java:731）在 java.awt.EventQueue $ 4.run（EventQueue.java:729）在 java.security.AccessController.doPrivileged（本机方法），位于 java.security.ProtectionDomain $ JavaSecurityAccessImpl.doIntersectionPrivilege（ProtectionDomain.java:76） 在java.awt.EventQueue.dispatchEvent（EventQueue.java:728）在 java.awt.EventDispatchThread.pumpOneEventForFilters（EventDispatchThread.java:201） 在 java.awt.EventDispatchThread.pumpEventsForFilter（EventDispatchThread.java:116） 在 java.awt.EventDispatchThread.pumpEventsForHierarchy（EventDispatchThread.java:105） 在 java.awt.EventDispatchThread.pumpEvents（EventDispatchThread.java:101） 在 java.awt.EventDispatchThread.pumpEvents（EventDispatchThread.java:93） 在java.awt.EventDispatchThread.run（EventDispatchThread.java:82）
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这是我的PanelSlider代码，
package Library.PanelSlider;
import java.awt.Component;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JPanel;
import javax.swing.Timer;
public class PanelSlider extends JPanel
{
public enum direct {
Left,
Right,
Up,
Down
};
public PanelSlider() {
setBorder(javax.swing.BorderFactory.createEtchedBorder());
Dimension size = new Dimension(this.getWidth(), this.getHeight());
}
public void nextSlidPanel(Component ShowPanel, direct DirectionMove) {
nextSlidPanel(10, 40, ShowPanel, DirectionMove);
}
public void nextSlidPanel(int SpeedPanel, Component ShowPanel, direct DirectionMove) {
nextSlidPanel(SpeedPanel, 40, ShowPanel, DirectionMove);
}
public void nextSlidPanel(int SpeedPanel, int TimeSpeed, Component ShowPanel, direct DirectionMove) {
if (!ShowPanel.getName().equals(getCurrentComponentShow(this))) {
Component currentComp = getCurrentComponent(this);
ShowPanel.setVisible(true);
JPanelSlidingListener sl = new JPanelSlidingListener(SpeedPanel, currentComp, ShowPanel, DirectionMove);
Timer t = new Timer(TimeSpeed, sl);
sl.timer = t;
t.start();
}
refresh();
}
public void previous(direct direct) {
Component currentComp = getCurrentComponent(this);
Component previousComp = getPreviousComponent(this);
Rectangle b = currentComp.getBounds();
previousComp.setVisible(true);
JPanelSlidingListener sl = new JPanelSlidingListener(10, currentComp, previousComp, direct);
Timer t = new Timer(40, sl);
sl.timer = t;
t.start();
refresh();
}
public void next(direct direct) {
Component currentComp = getCurrentComponent(this);
Component nextComp = getNextComponent(this);
Rectangle b = currentComp.getBounds();
nextComp.setVisible(true);
JPanelSlidingListener sl = new JPanelSlidingListener(10, currentComp, nextComp, direct);
Timer t = new Timer(40, sl);
sl.timer = t;
t.start();
refresh();
}
public Component getCurrentComponent(Container parent) {
Component comp = null;
int n = parent.getComponentCount();
for (int i = 0 ; i < n ; i++) {
comp = parent.getComponent(i);
if (comp.isVisible()) {
return comp;
}
}
return comp;
}
public Component getNextComponent(Container parent) {
int n = parent.getComponentCount();
for (int i = 0 ; i < n ; i++) {
Component comp = parent.getComponent(i);
if (comp.isVisible()) {
int currentCard = (i + 1) % n;
comp = parent.getComponent(currentCard);
return comp;
}
}
return null;
}
public Component getPreviousComponent(Container parent) {
int n = parent.getComponentCount();
for (int i = 0 ; i < n ; i++) {
Component comp = parent.getComponent(i);
if (comp.isVisible()) {
int currentCard = ((i > 0) ? i - 1 : n - 1);
comp = parent.getComponent(currentCard);
return comp;
}
}
return null;
}
public String getCurrentComponentShow(Container parent) {
String PanelName = null;
Component comp = null;
int n = parent.getComponentCount();
for (int i = 0 ; i < n ; i++) {
comp = parent.getComponent(i);
if (comp.isVisible()) {
PanelName = comp.getName();
return PanelName;
}
}
return PanelName;
}
public class JPanelSlidingListener implements ActionListener {
Component HidePanel;
Component ShowPanel;
int steps;
int step = 0;
Timer timer;
direct direct;
public JPanelSlidingListener(int steps, Component HidePanel, Component ShowPanel, direct direct) {
this.steps = steps;
this.HidePanel = HidePanel;
this.ShowPanel = ShowPanel;
this.direct = direct;
}
@Override
public void actionPerformed(ActionEvent e)
{
Rectangle bounds = HidePanel.getBounds();
int shift = bounds.width/steps;
int shiftup = bounds.height/steps;
switch(direct)
{
case Left:
HidePanel.setLocation(bounds.x - shift, bounds.y);
ShowPanel.setLocation(bounds.x - shift + bounds.width, bounds.y);
break;
case Right:
HidePanel.setLocation(bounds.x + shift, bounds.y);
ShowPanel.setLocation(bounds.x + shift - bounds.width, bounds.y);
break;
case Up:
HidePanel.setLocation(bounds.x, bounds.y - shiftup);
ShowPanel.setLocation(bounds.x, bounds.y - shiftup + bounds.height);
break;
case Down:
HidePanel.setLocation(bounds.x, bounds.y + shiftup);
ShowPanel.setLocation(bounds.x, bounds.y + shiftup - bounds.height);
break;
}
repaint();
step++;
if (step == steps) {
timer.stop();
HidePanel.setVisible(false);
}
}
}
public void refresh() {
revalidate();
repaint();
}
}
当我单击前两个错误行时，它将向我显示这些代码。但是我 无法弄清楚出了什么问题。
public void nextSlidPanel(int SpeedPanel, Component ShowPanel, direct DirectionMove) {
nextSlidPanel(SpeedPanel, 40, ShowPanel, DirectionMove);
}
public void nextSlidPanel(int SpeedPanel, int TimeSpeed, Component ShowPanel, direct DirectionMove) {
if (!ShowPanel.getName().equals(getCurrentComponentShow(this))) {
Component currentComp = getCurrentComponent(this);
ShowPanel.setVisible(true);
JPanelSlidingListener sl = new JPanelSlidingListener(SpeedPanel, currentComp, ShowPanel, DirectionMove);
Timer t = new Timer(TimeSpeed, sl);
sl.timer = t;
t.start();
}
refresh();
}
有人可以帮助我吗？我非常感谢。预先感谢。