com.google.gdt.eclipse.core.ui.BackgroundInitiatedYesNoDialog.java Source code

Introduction

Here is the source code for com.google.gdt.eclipse.core.ui.BackgroundInitiatedYesNoDialog.java

Source

/*******************************************************************************
 * Copyright 2013 Google Inc. All Rights Reserved.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *******************************************************************************/
package com.google.gdt.eclipse.core.ui;

import org.eclipse.core.runtime.IProgressMonitor;
import org.eclipse.core.runtime.IStatus;
import org.eclipse.core.runtime.Status;
import org.eclipse.jface.dialogs.MessageDialog;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.ui.PlatformUI;
import org.eclipse.ui.progress.UIJob;

import java.util.concurrent.Semaphore;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * A yes/no dialog that can be opened from a non-UI thread by calling the {@link #userAnsweredYes()}
 * method. The method blocks until the user has responded, then returns a value indicating the
 * user's response. The dialog may be of any of the types described by the integer codes in
 * {@link MessageDialog}.
 */
public class BackgroundInitiatedYesNoDialog {

    private enum YesOrNo {
        YES, NO
    }

    private static final String[] LABELS = { "Yes", "No" };

    /**
     * Displays a yes/no dialog of a specified type with a specified title,a specified message, and a
     * specified default value, then blocks until the user responds or interrupts the dialog.
     * 
     * @param type the dialog type, specified by one of the int constants in {@link MessageDialog}
     * @param title the specified title
     * @param message the specified message
     * @param defaultIsYes
     *     {@link true} if the specified default value is <i>yes</i>, false if the specified default
     *      value is <i>no</i>
     * @return
     *     {@code true} if the user responded <i>yes</i>, {@code false} if the user responded
     *     <i>no</i>, or the value of {@code defaultValueIsYes} if the user interrupts the dialog
     */
    public boolean userAnsweredYes(final int type, final String title, final String message,
            final boolean defaultIsYes) {
        final int defaultPosition = defaultIsYes ? YesOrNo.YES.ordinal() : YesOrNo.NO.ordinal();
        if (Display.getCurrent() == null) {
            // This is not a UI thread. Schedule a UI job to call displayDialogAndGetAnswer, and block
            // this thread until the UI job is complete.
            final Semaphore barrier = new Semaphore(0);
            final AtomicBoolean responseContainer = new AtomicBoolean();
            UIJob dialogJob = new UIJob("background-initiated question dialog") {
                @Override
                public IStatus runInUIThread(IProgressMonitor monitor) {
                    boolean result = displayDialogAndGetAnswer(type, title, message, defaultPosition);
                    responseContainer.set(result);
                    barrier.release();
                    return Status.OK_STATUS;
                }
            };
            dialogJob.schedule();
            try {
                barrier.acquire();
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
                return defaultIsYes;
            }
            return responseContainer.get();
        } else {
            // This is the UI thread. Simply call displayDialogAndGetAnswer in this thread.
            // (Scheduling a UIJob and blocking until it completes would result in deadlock.)
            return displayDialogAndGetAnswer(type, title, message, defaultPosition);
        }
    }

    // This method must be run in the UI thread.
    private static boolean displayDialogAndGetAnswer(int type, String title, final String message,
            int defaultPosition) {
        Shell activeShell = PlatformUI.getWorkbench().getActiveWorkbenchWindow().getShell();
        MessageDialog dialog = new MessageDialog(activeShell, title, null, message, type, LABELS, defaultPosition);
        int selection = dialog.open();
        return selection == YesOrNo.YES.ordinal();
    }

}