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

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

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/*
 * Copyright 2008 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.core.client.GWT;
import com.google.gwt.dom.client.Document;
import com.google.gwt.dom.client.Element;
import com.google.gwt.dom.client.InputElement;
import com.google.gwt.event.dom.client.ChangeEvent;
import com.google.gwt.event.dom.client.ChangeHandler;
import com.google.gwt.event.dom.client.HasChangeHandlers;
import com.google.gwt.event.shared.HandlerRegistration;
import com.google.gwt.user.client.Event;

/**
 * A widget that wraps the HTML <input type='file'> element. This widget
 * must be used with {@link com.google.gwt.user.client.ui.FormPanel} if it is to
 * be submitted to a server.
 * 
 * <p>
 * <h3>Example</h3>
 * {@example com.google.gwt.examples.FormPanelExample}
 * </p>
 */
public class FileUpload extends Widget implements HasName, HasChangeHandlers {
    /**
     * Implementation class for {@link FileUpload}.
     */
    private static class FileUploadImpl {
        /**
         * Initialize the impl class.
         * 
         * @param fileUpload the {@link FileUpload} to handle
         */
        public void init(FileUpload fileUpload) {
        }

        /**
         * Handle the browser event.
         * 
         * @param event the native event
         * @return true to fire the event normally, false to ignore it
         */
        public boolean onBrowserEvent(Event event) {
            return true;
        }
    }

    /**
     * Opera fires an onChange event every time a character is typed, but we only
     * want to fire one when the input element is blurred.
     */
    @SuppressWarnings("unused")
    private static class FileUploadImplOpera extends FileUploadImpl {
        private FileUpload fileUpload;
        private boolean eventPending;
        private boolean allowEvent;

        @Override
        public void init(FileUpload fileUpload) {
            this.fileUpload = fileUpload;
            fileUpload.sinkEvents(Event.ONBLUR);
        }

        @Override
        public boolean onBrowserEvent(Event event) {
            switch (event.getTypeInt()) {
            case Event.ONCHANGE:
                // When we fire the change event onBlur, we allow it to pass to
                // Widget#onBrowserEvent().
                if (!allowEvent) {
                    eventPending = true;
                    return false;
                }
                break;
            case Event.ONBLUR:
                // Trigger a change event now.
                if (eventPending) {
                    allowEvent = true;
                    fileUpload.getElement().dispatchEvent(Document.get().createChangeEvent());
                    allowEvent = false;
                    eventPending = false;
                }
                break;
            }
            return true;
        }
    }

    /**
     * Creates a FileUpload widget that wraps an existing &lt;input
     * type='file'&gt; element.
     * 
     * This element must already be attached to the document. If the element is
     * removed from the document, you must call
     * {@link RootPanel#detachNow(Widget)}.
     * 
     * @param element the element to be wrapped
     */
    public static FileUpload wrap(Element element) {
        // Assert that the element is attached.
        assert Document.get().getBody().isOrHasChild(element);

        FileUpload fileUpload = new FileUpload(element);

        // Mark it attached and remember it for cleanup.
        fileUpload.onAttach();
        RootPanel.detachOnWindowClose(fileUpload);

        return fileUpload;
    }

    private FileUploadImpl impl;

    /**
     * Constructs a new file upload widget.
     */
    public FileUpload() {
        setElement(Document.get().createFileInputElement());
        setStyleName("gwt-FileUpload");
        impl = GWT.create(FileUploadImpl.class);
        impl.init(this);
    }

    /**
     * This constructor may be used by subclasses to explicitly use an existing
     * element. This element must be an &lt;input&gt; element whose type is
     * 'file'.
     * 
     * @param element the element to be used
     */
    protected FileUpload(Element element) {
        assert InputElement.as(element).getType().equalsIgnoreCase("file");
        setElement(element);
    }

    public HandlerRegistration addChangeHandler(ChangeHandler handler) {
        return addDomHandler(handler, ChangeEvent.getType());
    }

    /**
     * Gets the filename selected by the user. This property has no mutator, as
     * browser security restrictions preclude setting it.
     * 
     * @return the widget's filename
     */
    public String getFilename() {
        return getInputElement().getValue();
    }

    public String getName() {
        return getInputElement().getName();
    }

    /**
     * Gets whether this widget is enabled.
     * 
     * @return <code>true</code> if the widget is enabled
     */
    public boolean isEnabled() {
        return !getElement().getPropertyBoolean("disabled");
    }

    @Override
    public void onBrowserEvent(Event event) {
        if (impl.onBrowserEvent(event)) {
            super.onBrowserEvent(event);
        }
    }

    /**
     * Sets whether this widget is enabled.
     * 
     * @param enabled <code>true</code> to enable the widget, <code>false</code>
     *          to disable it
     */
    public void setEnabled(boolean enabled) {
        getElement().setPropertyBoolean("disabled", !enabled);
    }

    public void setName(String name) {
        getInputElement().setName(name);
    }

    private InputElement getInputElement() {
        return getElement().cast();
    }
}