I am facing error "NullPointExeption", while trying to detect the user's selection in the eclipse plugin development. I have attached the code for both the classes, first, DetectSelection which detects the user's choice in the project explorer and second, SampleView which makes the custom plugin
Question that I asked Before : Eclipse Plugin: Get the class name on user's click/selection
After that it was working properly, but now I am again facing some errors: Now, I made DetectSelection class :
public class DetectSelection
{
String classname ;
IPath packageName ;
private ISelection selection;
public void setSelection(ISelection iSelection)
{
this.selection = iSelection;
}
public void jk()
{
System.out.println(" HI!!!!");
IWorkbenchPage page =PlatformUI.getWorkbench().getActiveWorkbenchWindow().getActivePage();
IViewPart viewPart = page.findView("org.eclipse.jdt.ui.PackageExplorer");
ISelectionProvider selProvider = viewPart.getSite().getSelectionProvider();
selProvider.addSelectionChangedListener(new ISelectionChangedListener()
{
public void selectionChanged(SelectionChangedEvent event)
{
if (!event.getSelection().isEmpty())
{
Iterator ite = ((IStructuredSelection) event.getSelection()).iterator();
while (ite.hasNext())
{
Object obj = ite.next();
String testString="";
if (obj instanceof IJavaElement)
{
packageName= ((IJavaElement)obj).getPath();
System.out.println("getFileExtension() "+ packageName.getFileExtension() );
String s= packageName.toString();
String s1[]= s.split("/");
if ("java".equals(packageName.getFileExtension()))
{
System.out.println("package name "+ s1[1]);
System.out.println("project name"+ ((IJavaElement)obj).getElementName());
}
}
}
}
}
});
}
}
This was working fine previously, when I made an object of this in the SampleView class and used it like this:
public class SampleView extends ViewPart
{
public static final String ID = "typesview.views.SampleView";
private TableViewer viewer;
private Action action1;
private Action action2;
private Action doubleClickAction;
class ViewContentProvider implements IStructuredContentProvider
{
public void inputChanged(Viewer v, Object oldInput, Object newInput)
{
}
public void dispose()
{
}
public Object[] getElements(Object parent)
{
return new String[] { "One", "Two", "Three" };
}
}
class ViewLabelProvider extends LabelProvider implements ITableLabelProvider {
public String getColumnText(Object obj, int index) {
return getText(obj);
}
public Image getColumnImage(Object obj, int index) {
return getImage(obj);
}
public Image getImage(Object obj) {
return PlatformUI.getWorkbench().
getSharedImages().getImage(ISharedImages.IMG_OBJ_ELEMENT);
}
}
class NameSorter extends ViewerSorter {
}
public SampleView() {
}
public void createPartControl(Composite parent) {
**DetectSelection obj2 = new DetectSelection();
obj2.jk();**
viewer = new TableViewer(parent, SWT.MULTI | SWT.H_SCROLL | SWT.V_SCROLL);
viewer.setContentProvider(new ViewContentProvider());
viewer.setLabelProvider(new ViewLabelProvider());
viewer.setSorter(new NameSorter());
viewer.setInput(getViewSite());
PlatformUI.getWorkbench().getHelpSystem().setHelp(viewer.getControl(), "TYPESview.viewer");
makeActions();
hookContextMenu();
hookDoubleClickAction();
contributeToActionBars();
}
private void hookContextMenu() {
MenuManager menuMgr = new MenuManager("#PopupMenu");
menuMgr.setRemoveAllWhenShown(true);
menuMgr.addMenuListener(new IMenuListener() {
public void menuAboutToShow(IMenuManager manager) {
SampleView.this.fillContextMenu(manager);
}
});
Menu menu = menuMgr.createContextMenu(viewer.getControl());
viewer.getControl().setMenu(menu);
getSite().registerContextMenu(menuMgr, viewer);
}
private void contributeToActionBars() {
IActionBars bars = getViewSite().getActionBars();
fillLocalPullDown(bars.getMenuManager());
fillLocalToolBar(bars.getToolBarManager());
}
private void fillLocalPullDown(IMenuManager manager) {
manager.add(action1);
manager.add(new Separator());
manager.add(action2);
}
private void fillContextMenu(IMenuManager manager) {
manager.add(action1);
manager.add(action2);
manager.add(new Separator(IWorkbenchActionConstants.MB_ADDITIONS));
}
private void fillLocalToolBar(IToolBarManager manager) {
manager.add(action1);
manager.add(action2);
}
private void makeActions() {
action1 = new Action() {
public void run() {
showMessage("Action 1 executed");
}
};
action1.setText("Action 1");
action1.setToolTipText("Action 1 tooltip");
action1.setImageDescriptor(PlatformUI.getWorkbench().getSharedImages().
getImageDescriptor(ISharedImages.IMG_OBJS_INFO_TSK));
action2 = new Action() {
public void run() {
showMessage("Action 2 executed");
}
};
action2.setText("Action 2");
action2.setToolTipText("Action 2 tooltip");
action2.setImageDescriptor(PlatformUI.getWorkbench().getSharedImages().
getImageDescriptor(ISharedImages.IMG_OBJS_INFO_TSK));
doubleClickAction = new Action() {
public void run() {
ISelection selection = viewer.getSelection();
Object obj = ((IStructuredSelection)selection).getFirstElement();
showMessage("Double-click detected on "+obj.toString());
}
};
}
private void hookDoubleClickAction() {
viewer.addDoubleClickListener(new IDoubleClickListener() {
public void doubleClick(DoubleClickEvent event) {
doubleClickAction.run();
}
});
}
private void showMessage(String message) {
MessageDialog.openInformation(
viewer.getControl().getShell(),
"Sample View",
message);
}
public void setFocus() {
viewer.getControl().setFocus();
}
}
Now on running the plugin, I am getting the error:
java.lang.NullPointerException
at typesview.views.DetectSelection.jk(DetectSelection.java:40)
at typesview.views.SampleView.createPartControl(SampleView.java:58)
at org.eclipse.ui.internal.ViewReference.createPartHelper(ViewReference.java:375)
at org.eclipse.ui.internal.ViewReference.createPart(ViewReference.java:229)
at org.eclipse.ui.internal.WorkbenchPartReference.getPart(WorkbenchPartReference.java:595)
at org.eclipse.ui.internal.WorkbenchPage$ActivationList.setActive(WorkbenchPage.java:4317)
at org.eclipse.ui.internal.WorkbenchPage$18.runWithException(WorkbenchPage.java:3359)
at org.eclipse.ui.internal.StartupThreading$StartupRunnable.run(StartupThreading.java:31)
at org.eclipse.swt.widgets.RunnableLock.run(RunnableLock.java:35)
at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:135)
at org.eclipse.swt.widgets.Display.runAsyncMessages(Display.java:4140)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3757)
at org.eclipse.ui.application.WorkbenchAdvisor.openWindows(WorkbenchAdvisor.java:803)
at org.eclipse.ui.internal.Workbench$33.runWithException(Workbench.java:1600)
at org.eclipse.ui.internal.StartupThreading$StartupRunnable.run(StartupThreading.java:31)
at org.eclipse.swt.widgets.RunnableLock.run(RunnableLock.java:35)
at org.eclipse.swt.widgets.Synchronizer.runAsyncMessages(Synchronizer.java:135)
at org.eclipse.swt.widgets.Display.runAsyncMessages(Display.java:4140)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3757)
at org.eclipse.ui.internal.Workbench.runUI(Workbench.java:2609)
at org.eclipse.ui.internal.Workbench.access$4(Workbench.java:2499)
at org.eclipse.ui.internal.Workbench$7.run(Workbench.java:679)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:668)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:123)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:344)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:622)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:577)
at org.eclipse.equinox.launcher.Main.run(Main.java:1410)
at org.eclipse.equinox.launcher.Main.main(Main.java:1386)
Images to get the line numbers:
DetectSelection:
SampleView:
The line numbers in the stacktrace and the screen-shot don't line up properly.
But in fact, the exception can only be thrown by the first five lines of the jk
method anyway. (The rest is defining a callback method / object, and if an NPE was thrown by that code, the classname in the stack trace would be different.)
I suggest that you add some more trace-prints, or use the debugger to figure out which statement is actually throwing the exception ... and work backwards to the source of the null
.
The javadoc for that method says:
Returns the view in this page with the specified id. There is at most one view in the page with the specified id.
Returns: the view, or null if none is found
If you are getting a null
from the cause, it follows that the id parameter is not correct.
This may or may not be relevant, but you are passing "org.eclipse.jdt.ui.PackageExplorer"
to find
, but the ID
for your SampleView
class is "typesview.views.SampleView"
.
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