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Java example source code file (ContextAction.java)

This example Java source code file (ContextAction.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

awt, callablesystemaction, class, contextaction, contextawareaction, lookup, lookuplistener, override, runnable

The ContextAction.java Java example source code

/*
 * Copyright (c) 1998, 2007, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */
package com.sun.hotspot.igv.util;

import java.awt.EventQueue;
import org.openide.util.ContextAwareAction;
import org.openide.util.Lookup;
import org.openide.util.LookupEvent;
import org.openide.util.LookupListener;
import org.openide.util.Utilities;
import org.openide.util.actions.CallableSystemAction;

/**
 *
 * @author Thomas Wuerthinger
 */
public abstract class ContextAction<T> extends CallableSystemAction implements LookupListener, ContextAwareAction {

    private Lookup context = null;
    private Lookup.Result<T> result = null;

    public ContextAction() {
        this(Utilities.actionsGlobalContext());
    }

    public ContextAction(Lookup context) {
        init(context);
    }

    private void init(Lookup context) {
        this.context = context;
        result = context.lookupResult(contextClass());
        result.addLookupListener(this);
        resultChanged(null);
    }

    public void resultChanged(LookupEvent e) {
        if (result.allItems().size() != 0) {
            update(result.allInstances().iterator().next());
        } else {
            update(null);
        }
    }

    @Override
    public void performAction() {
        final T t = result.allInstances().iterator().next();

        // Ensure it's AWT event thread
        EventQueue.invokeLater(new Runnable() {

            public void run() {
                performAction(t);
            }
        });
    }

    public void update(T t) {
        if (t == null) {
            setEnabled(false);
        } else {
            setEnabled(isEnabled(t));
        }
    }

    public boolean isEnabled(T context) {
        return true;
    }

    public abstract Class<T> contextClass();

    public abstract void performAction(T context);
}

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