GWT lazy loading

Question

Does GWT has LazyPanel .I can not see it .Please let me know .If it got lazyPanel ,please lemme know version

Answer 1

I agree with rustyshelf on the principle of Google search, but since StackOverflow is also a reference in itself, here is a more detailed answer:

By default, the LazyPanel is not displayed. Only when setVisible(true) is called on the LazyPanel is the underlying widget created.

This class primarily should be used in conjunction with StackPanel, DisclosurePanel, and TabPanel when the child panels contain relatively heavy weight contents.
Using LazyPanel to wrap the creation of those contents can significantly improve user experience.

---

Using the LazyPanel is simple. All you need to do is add the widget that you want to lazily load in the lazy panel, and then call setVisible(true) on the lazy panel to actually have the widget load on demand. It's worth mentioning that the LazyPanel is mainly intended for use with widgets like the TabPanel and the StackPanel, and is not ideal in all cases.

Answer 2

Here is LazyPanel.java from "release candidate" GWT 1.6.2 So yes, simple, and a confirmation of the answer above.

/*
 * 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;

/**
 * Convenience class to help lazy loading. The bulk of a LazyPanel is not
 * instantiated until {@link #setVisible}(true) or {@link #ensureWidget} is
 * called.
 * <p>
 * <h3>Example</h3> {@example com.google.gwt.examples.LazyPanelExample}
 */
public abstract class LazyPanel extends SimplePanel {

  public LazyPanel() {
  }

  /**
   * Create the widget contained within the {@link LazyPanel}.
   * 
   * @return the lazy widget
   */
  protected abstract Widget createWidget();

  /**
   * Ensures that the widget has been created by calling {@link #createWidget}
   * if {@link #getWidget} returns <code>null</code>. Typically it is not
   * necessary to call this directly, as it is called as a side effect of a
   * <code>setVisible(true)</code> call.
   */
  public void ensureWidget() {
    Widget widget = getWidget();
    if (widget == null) {
      widget = createWidget();
      setWidget(widget);
    }
  }

  @Override
  /*
   * Sets whether this object is visible. If <code>visible</code> is
   * <code>true</code>, creates the sole child widget if necessary by calling
   * {@link #ensureWidget}.
   * 
   * @param visible <code>true</code> to show the object, <code>false</code> to
   * hide it
   */
  public void setVisible(boolean visible) {
    if (visible) {
      ensureWidget();
    }
    super.setVisible(visible);
  }
}