java有没有一种安全的方法可以使用Cleaner注销侦听器?
我有一个摇摆动作类,其工作原理如下:
package org.trypticon.hex.gui.datatransfer;
import java.awt.Toolkit;
import java.awt.datatransfer.Clipboard;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.FlavorListener;
import java.awt.event.ActionEvent;
import javax.annotation.Nonnull;
import javax.swing.Action;
import javax.swing.JComponent;
import javax.swing.TransferHandler;
import org.trypticon.hex.gui.Resources;
import org.trypticon.hex.gui.util.FinalizeGuardian;
import org.trypticon.hex.gui.util.FocusedComponentAction;
public class PasteAction extends FocusedComponentAction {
private final FlavorListener listener = (event) -> {
// this method in the superclass calls back `shouldBeEnabled`
updateEnabled();
};
@SuppressWarnings({"UnusedDeclaration"})
private final Object finalizeGuardian = new FinalizeGuardian(() -> {
Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
clipboard.removeFlavorListener(listener);
});
public PasteAction() {
Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
clipboard.addFlavorListener(listener);
}
@Override
protected boolean shouldBeEnabled(@Nonnull JComponent focusOwner) {
TransferHandler transferHandler = focusOwner.getTransferHandler();
if (transferHandler == null) {
return false;
}
Clipboard clipboard = Toolkit.getDefaultToolkit().getSystemClipboard();
DataFlavor[] flavorsInClipboard = clipboard.getAvailableDataFlavors();
return transferHandler.canImport(focusOwner, flavorsInClipboard);
}
@Override
protected void doAction(@Nonnull JComponent focusOwner) throws Exception {
Action action = TransferHandler.getPasteAction();
action.actionPerformed(new ActionEvent(
focusOwner, ActionEvent.ACTION_PERFORMED, (String) action.getValue(Action.NAME)));
}
}
这里提到的FinalizeGuardian
目前使用finalize()
实现:
package org.trypticon.hex.gui.util;
public final class FinalizeGuardian {
private final Runnable cleanupLogic;
public FinalizeGuardian(Runnable cleanupLogic) {
this.cleanupLogic = cleanupLogic;
}
@Override
protected final void finalize() throws Throwable {
try {
cleanupLogic.run();
} finally {
super.finalize();
}
}
}
因此,出于显而易见的原因,我想切换到使用Cleaner
来实现这一点
第一次尝试是这样的:
package org.trypticon.hex.gui.util;
import java.lang.ref.Cleaner;
public final class FinalizeGuardian {
private static final Cleaner cleaner = Cleaner.create();
public FinalizeGuardian(Runnable cleanupLogic) {
cleaner.register(this, cleanupLogic);
}
}
问题是,现在对象永远无法到达幻影,因为:
Cleaner
本身对cleanupLogic
cleanupLogic
保存对listener
的引用,以便删除侦听器listener
持有对action类的引用,以便对其调用updateEnabled
- action类持有对
FinalizeGuardian
的引用,这样就不会过早地收集它
因为FinalizeGuardian
本身永远无法访问幻影,所以永远不会调用清理器
所以我想知道的是,有没有一种方法来重组它,以遵循规则,使Cleaner
正确工作,不涉及通过将侦听器移动到我的action类之外来破坏封装
共 (0) 个答案