原始解决方案存在许多问题.
下面是一个准备复制的代码剪切,它基于原始答案,但处理所有这些问题.
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Point;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.widgets.Control;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.ScrollBar;
import org.eclipse.swt.widgets.Scrollable;
/**
* The standard platform behavior on Windows is to scroll the widget with
* keyboard focus when the user turns the mouse wheel, instead of the widget
* currently under the mouse pointer. Many consider this annoying and Windows
* itself, as well as many popular Windows software, breaks this rule and
* implements the behavior seen on other platforms, which is to scroll the
* widget under the mouse.
*
* Win32MouseWheelFilter is a Listener implementation which will filter for
* SWT.MouseWheel events delivered to any Widget and try to redirect the event
* to the widget under the mouse or one of it's parents. The widget, or one of
* it's parents is considered a suitable target, if it either has Listeners for
* SWT.MouseWheel attached (assuming that those listeners would do something
* sensible with the event), or if its style bits contain SWT.H_SCROLL and/or
* SWT.V_SCROLL. In the later case a low level system event is generated, which
* is necessary to get the event handled by the native ScrollBar widgets. A
* vertical ScrollBar is preferred as the target, unless it is for some reason
* unsuitable for scrolling. In that case, horizontal scrolling would take
* place, if there is a suitable horizontal ScrollBar.
*
* Simply creating a new Win32MouseWheelFilter instance will install it as an
* event filter in the Display passed to the constructor. At an appropriate
* time, you may call dispose() to remove the filter again. On SWT platforms
* other than "win32", constructing an Win32MouseWheelFilter will have no effect.
*/
public class Win32MouseWheelFilter implements Listener {
private final Display fDisplay;
private int WM_VSCROLL;
private int WM_HSCROLL;
private int SB_LINEUP;
private int SB_LINEDOWN;
private Method fSendEventMethod32;
private Method fSendEventMethod64;
/**
* Creates a new Win32MouseWheelFilter instance and registers it as global
* event filter in the provided Display. Nothing will happen if the SWT
* platform is not "win32". If for some reason some SWT internals have
* changed since the writing of this class, and the Reflection-based
* extraction of some win32 specific fields of the SWT OS class fails,
* no filtering of wheel events will take place either.
*
* @param display
* The Display instance that the Win32MouseWheelFilter should install
* itself into as global event filter.
*/
public Win32MouseWheelFilter(Display display) {
fDisplay = display;
if (!SWT.getPlatform().equals("win32"))
return;
try {
Class<?> os = Class.forName("org.eclipse.swt.internal.win32.OS");
WM_VSCROLL = os.getDeclaredField("WM_VSCROLL").getInt(null);
WM_HSCROLL = os.getDeclaredField("WM_HSCROLL").getInt(null);
SB_LINEUP = os.getDeclaredField("SB_LINEUP").getInt(null);
SB_LINEDOWN = os.getDeclaredField("SB_LINEDOWN").getInt(null);
try {
// Try the 32-bit version first
fSendEventMethod32 = os.getDeclaredMethod("SendMessage",
int.class, int.class, int.class, int.class);
} catch (NoSuchMethodException e) {
// Fall back to the 64-bit version
fSendEventMethod64 = os.getDeclaredMethod("SendMessage",
long.class, int.class, long.class, long.class);
}
display.addFilter(SWT.MouseWheel, this);
return;
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (SecurityException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (NoSuchFieldException e) {
e.printStackTrace();
} catch (NoSuchMethodException e) {
e.printStackTrace();
}
System.out.println("Warning: Running on win32 SWT platform, "
+ "but unable to install Win32MouseWheelFilter filter.");
}
/**
* If the receiver had previously installed itself as global event filter,
* this method will remove it again from the display's filters.
*/
public final void dispose() {
fDisplay.removeFilter(SWT.MouseWheel, this);
}
public final void handleEvent(Event event) {
Control cursorControl = event.display.getCursorControl();
if (event.widget == cursorControl || cursorControl == null)
return;
if (event.widget instanceof Control) {
// If the original target control's bounds contain the mouse
// location, do not re-target the event, since it may indeed be the
// Control that needs to handle scrolling for an embedded Control
// that has focus.
Control control = (Control) event.widget;
Rectangle bounds = control.getBounds();
bounds.x = 0;
bounds.y = 0;
Point cursorPos = control.toControl(display.getCursorLocation());
if (bounds.contains(cursorPos))
return;
}
// Try to find the best target widget for the event, based on the
// cursorControl. A suitable target control is either one that has
// a listener for SWT.MouseWheel attached, or one that has either
// SWT.H_SCROLL or SWT.V_SCROLL in its style bits.
Control wheelControl = cursorControl;
int scrollStyle = SWT.H_SCROLL | SWT.V_SCROLL;
while (wheelControl != null
&& (wheelControl.getStyle() & scrollStyle) == 0
&& wheelControl.getListeners(SWT.MouseWheel).length == 0) {
wheelControl = wheelControl.getParent();
}
if (wheelControl == null) {
// The event would not be handled by anyone, bail out.
return;
}
int style = wheelControl.getStyle();
if ((style & scrollStyle) != 0 && wheelControl instanceof Scrollable) {
// Construct the data for the low level event based on which
// direction the target can scroll in. We need to use a low-level
// event since otherwise it won't be handled by the native
// ScrollBar widgets.
int msg;
// Prefer vertical scrolling. However, if the
// there is no vertical ScrollBar, or if it's somehow disabled,
// then switch to horizontal scrolling instead.
if ((style & SWT.V_SCROLL) != 0 ) {
ScrollBar vBar = ((Scrollable) wheelControl).getVerticalBar();
if (vBar == null
|| ((vBar.getMinimum() == 0
&& vBar.getMaximum() == 0
&& vBar.getSelection() == 0)
|| !vBar.isEnabled()
|| !vBar.isVisible())) {
// There is no vertical ScrollBar, or it can't be used.
msg = WM_HSCROLL;
} else
msg = WM_VSCROLL;
} else {
msg = WM_HSCROLL;
}
int count = event.count;
int wParam = SB_LINEUP;
if (event.count < 0) {
count = -count;
wParam = SB_LINEDOWN;
}
try {
// Obtain the control's handle via Reflection and
// deliver the event using the low level platform method.
// (64 and 32 bit versions)
if (fSendEventMethod32 != null) {
int handle = org.eclipse.swt.widgets.Control.class
.getDeclaredField("handle").getInt(wheelControl);
for (int i = 0; i < count; i++)
fSendEventMethod32.invoke(null, handle, msg, wParam, 0);
} else {
long handle = org.eclipse.swt.widgets.Control.class
.getDeclaredField("handle").getLong(wheelControl);
for (int i = 0; i < count; i++)
fSendEventMethod64.invoke(null, handle, msg, wParam, 0);
}
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InvocationTargetException e) {
e.printStackTrace();
} catch (SecurityException e) {
e.printStackTrace();
} catch (NoSuchFieldException e) {
e.printStackTrace();
}
} else {
// It makes no sense using the low-level OS event delivery, since
// Widgets without the scrolling style bits won't receive this
// event. Since we selected this widget based on the fact that it
// has SWT.MouseWheel listeners attached, use the regular SWT event
// notification system.
// Convert mouse location, since the event contains it in the wrong
// coordinate space (the one of the original event target).
Point cursorPos = wheelControl.toControl(
event.display.getCursorLocation());
event.x = cursorPos.x;
event.y = cursorPos.y;
event.widget = wheelControl;
wheelControl.notifyListeners(event.type, event);
}
// We re-targeted the event, or re-posted a new event to another widget,
// so prevent this event from being processed any further.
event.type = SWT.None;
event.doit = false;
}
}
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