com.google.gwt.user.client.ui.AttachDetachException.java Source code

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Here is the source code for com.google.gwt.user.client.ui.AttachDetachException.java

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/*
 * Copyright 2009 Google Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * 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.gwt.user.client.ui;

import com.google.gwt.event.shared.UmbrellaException;

import java.util.HashSet;
import java.util.Set;

/**
 * An exception that is thrown when the panel fails to attach or detach its
 * children.
 */
public class AttachDetachException extends UmbrellaException {

    /**
     * The singleton command used to attach widgets.
     */
    static final AttachDetachException.Command attachCommand = new AttachDetachException.Command() {
        public void execute(Widget w) {
            w.onAttach();
        }
    };

    /**
     * The singleton command used to detach widgets.
     */
    static final AttachDetachException.Command detachCommand = new AttachDetachException.Command() {
        public void execute(Widget w) {
            w.onDetach();
        }
    };

    /**
     * The command to execute when iterating through child widgets.
     */
    public static interface Command {
        void execute(Widget w);
    }

    /**
     * <p>
     * Iterator through all child widgets, trying to perform the specified
     * {@link Command} for each. All widgets will be visited even if the Command
     * throws an exception. If one or more exceptions occur, they will be combined
     * and thrown as a single {@link AttachDetachException}.
     * </p>
     * <p>
     * Use this method when attaching or detaching a widget with children to
     * ensure that the logical and physical state of all children match the
     * logical and physical state of the parent.
     * </p>
     * 
     * @param hasWidgets children to iterate
     * @param c the {@link Command} to try on all children
     */
    public static void tryCommand(Iterable<Widget> hasWidgets, Command c) {
        Set<Throwable> caught = null;
        for (Widget w : hasWidgets) {
            try {
                c.execute(w);
            } catch (Throwable e) {
                // Catch all exceptions to prevent some children from being attached
                // while others are not.
                if (caught == null) {
                    caught = new HashSet<Throwable>();
                }
                caught.add(e);
            }
        }

        // Throw the combined exceptions now that all children are attached.
        if (caught != null) {
            throw new AttachDetachException(caught);
        }
    }

    /**
     * <p>
     * Iterator through all child widgets, trying to perform the specified
     * {@link Command} for each. All widgets will be visited even if the Command
     * throws an exception. If one or more exceptions occur, they will be combined
     * and thrown as a single {@link AttachDetachException}.
     * </p>
     * <p>
     * Use this method when attaching or detaching a widget with children to
     * ensure that the logical and physical state of all children match the
     * logical and physical state of the parent.
     * </p>
     * 
     * @param c the {@link Command} to try on all children
     * @param widgets children to iterate, null children are ignored
     */
    public static void tryCommand(Command c, IsWidget... widgets) {
        Set<Throwable> caught = null;
        for (IsWidget w : widgets) {
            try {
                if (w != null) {
                    c.execute(w.asWidget());
                }
            } catch (Throwable e) {
                // Catch all exceptions to prevent some children from being attached
                // while others are not.
                if (caught == null) {
                    caught = new HashSet<Throwable>();
                }
                caught.add(e);
            }
        }

        // Throw the combined exceptions now that all children are attached.
        if (caught != null) {
            throw new AttachDetachException(caught);
        }
    }

    /**
     * Construct a new {@link AttachDetachException}.
     * 
     * @param causes the causes of the exception
     */
    public AttachDetachException(Set<Throwable> causes) {
        super(causes);
    }
}