在我的项目中，我正在使用gwt和libary gwt-connectors 2.4 ..下面的代码抛出一个NullPointer-Exception，如果有人可以帮我找到这个异常的原因，那就太好了！我该如何解决？
public class Projekt implements EntryPoint {
private RootPanel rootPanel;
Image img;
Shape shapei;
Connector con;
Widget connected;
Image logo;
Image logo2;
public void onModuleLoad() {
rootPanel = RootPanel.get("gwtContainer");
rootPanel.setSize("1902", "868");
final AbsolutePanel boundaryPanel = new AbsolutePanel();
boundaryPanel.setStyleName("frame1");
boundaryPanel.setSize("1455px", "600px");
final Diagram diagram = new Diagram(boundaryPanel);
RootPanel.get().add(boundaryPanel, 446, 242);
Button la = new Button("Push");
la.setSize("200", "200");
boundaryPanel.add(la);
Button la2 = new Button("Push2");
la2.setSize("200", "200");
boundaryPanel.add(la2);
Image img2 = new Image("images/variable.svg");
img2.setSize("200", "200");
boundaryPanel.add(img2, 200,200);
final Shape shapei2 = new Shape(img2);
shapei2.showOnDiagram(diagram);
la.addClickHandler(new ClickHandler(){
@Override
public void onClick(ClickEvent event) {
img = new Image("images/concrete.svg");
img.setSize("200", "200");
boundaryPanel.add(img, 200,200);
boundaryPanel.add(img, 100,100);
Shape shapei = new Shape(img);
shapei.showOnDiagram(diagram);
}}
);
la2.addClickHandler(new ClickHandler(){
@Override
public void onClick(ClickEvent event) {
con = new Connector(100, 300, 300, 500);
con.showOnDiagram(diagram);
}
});
diagram.addDiagramListener(new DiagramListener(){
public void onElementConnect(ElementConnectEvent event) {
if (con.startEndPoint.isGluedToConnectionPoint()) {
connected = con.startEndPoint.gluedConnectionPoint.parentWidget;
if(connected.equals(shapei.connectedWidget)){//line 97, think here is the problem
logo = new Image("images/xor.svg");
logo.setSize("100", "100");
boundaryPanel.add(logo);
}
else if(connected.equals(shapei2.connectedWidget)){
logo2 = new Image("images/and.svg");
logo2.setSize("100", "100");
boundaryPanel.add(logo2);
};
}}
@Override
public void onConnectorClick(ConnectorClickEvent event) {
// TODO Auto-generated method stub
}
@Override
public void onConnectorDoubleClick(ConnectorDoubleClickEvent event) {
// TODO Auto-generated method stub
}
@Override
public void onDiagramAdd(DiagramAddEvent event) {
// TODO Auto-generated method stub
}
@Override
public void onDiagramRemove(DiagramRemoveEvent event) {
// TODO Auto-generated method stub
}
@Override
public void onElementDrag(ElementDragEvent event) {
// TODO Auto-generated method stub
}
});
}}
这是日志：
09:11:25.249 [ERROR] [projekt] Uncaught exception escaped
com.google.gwt.event.shared.UmbrellaException: Exception caught: null
at com.google.gwt.event.shared.HandlerManager.fireEvent(HandlerManager.java:129)
at com.google.gwt.user.client.ui.Widget.fireEvent(Widget.java:129)
at com.google.gwt.event.dom.client.DomEvent.fireNativeEvent(DomEvent.java:116)
at com.google.gwt.user.client.ui.Widget.onBrowserEvent(Widget.java:177)
at com.google.gwt.user.client.DOM.dispatchEventImpl(DOM.java:1351)
at com.google.gwt.user.client.DOM.dispatchEvent(DOM.java:1307)
at sun.reflect.GeneratedMethodAccessor43.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:338)
at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:219)
at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:136)
at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:571)
at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:279)
at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeObject(JavaScriptHost.java:91)
at com.google.gwt.core.client.impl.Impl.apply(Impl.java)
at com.google.gwt.core.client.impl.Impl.entry0(Impl.java:242)
at sun.reflect.GeneratedMethodAccessor40.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:293)
at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:547)
at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:364)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException: null
at com.exa.projekt.client.Projekt$3.onElementConnect(Projekt.java:97)
at pl.tecna.gwt.connectors.client.Diagram.onElementConnect(Diagram.java:421)
at pl.tecna.gwt.connectors.client.elements.EndPoint.glueToConnectionPoint(EndPoint.java:71)
at pl.tecna.gwt.connectors.client.drop.DiagramWidgetDropController.onDrop(DiagramWidgetDropController.java:57)
at com.allen_sauer.gwt.dnd.client.PickupDragController.dragEnd(PickupDragController.java:130)
at com.allen_sauer.gwt.dnd.client.MouseDragHandler.drop(MouseDragHandler.java:529)
at com.allen_sauer.gwt.dnd.client.MouseDragHandler.onMouseUp(MouseDragHandler.java:277)
at com.google.gwt.event.dom.client.MouseUpEvent.dispatch(MouseUpEvent.java:56)
at com.google.gwt.event.dom.client.MouseUpEvent.dispatch(MouseUpEvent.java:1)
at com.google.gwt.event.shared.GwtEvent.dispatch(GwtEvent.java:1)
at com.google.web.bindery.event.shared.EventBus.dispatchEvent(EventBus.java:40)
at com.google.web.bindery.event.shared.SimpleEventBus.doFire(SimpleEventBus.java:193)
at com.google.web.bindery.event.shared.SimpleEventBus.fireEvent(SimpleEventBus.java:88)
at com.google.gwt.event.shared.HandlerManager.fireEvent(HandlerManager.java:127)
at com.google.gwt.user.client.ui.Widget.fireEvent(Widget.java:129)
at com.google.gwt.event.dom.client.DomEvent.fireNativeEvent(DomEvent.java:116)
at com.google.gwt.user.client.ui.Widget.onBrowserEvent(Widget.java:177)
at com.google.gwt.user.client.DOM.dispatchEventImpl(DOM.java:1351)
at com.google.gwt.user.client.DOM.dispatchEvent(DOM.java:1307)
at sun.reflect.GeneratedMethodAccessor43.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessagesWhileWaitingForReturn(BrowserChannelServer.java:338)
at com.google.gwt.dev.shell.BrowserChannelServer.invokeJavascript(BrowserChannelServer.java:219)
at com.google.gwt.dev.shell.ModuleSpaceOOPHM.doInvoke(ModuleSpaceOOPHM.java:136)
at com.google.gwt.dev.shell.ModuleSpace.invokeNative(ModuleSpace.java:571)
at com.google.gwt.dev.shell.ModuleSpace.invokeNativeObject(ModuleSpace.java:279)
at com.google.gwt.dev.shell.JavaScriptHost.invokeNativeObject(JavaScriptHost.java:91)
at com.google.gwt.core.client.impl.Impl.apply(Impl.java)
at com.google.gwt.core.client.impl.Impl.entry0(Impl.java:242)
at sun.reflect.GeneratedMethodAccessor40.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at com.google.gwt.dev.shell.MethodAdaptor.invoke(MethodAdaptor.java:103)
at com.google.gwt.dev.shell.MethodDispatch.invoke(MethodDispatch.java:71)
at com.google.gwt.dev.shell.OophmSessionHandler.invoke(OophmSessionHandler.java:172)
at com.google.gwt.dev.shell.BrowserChannelServer.reactToMessages(BrowserChannelServer.java:293)
at com.google.gwt.dev.shell.BrowserChannelServer.processConnection(BrowserChannelServer.java:547)
at com.google.gwt.dev.shell.BrowserChannelServer.run(BrowserChannelServer.java:364)
at java.lang.Thread.run(Thread.java:745)