Issue compiling a GWT FeedReader Application

[Rakesh Chaudhary]

Hi Ranchers,

I am trying to compile a Ajax FeedReader Application on eclipse.I downloaded the code from

http://gwt-feed-reader.googlecode.com/svn/trunk

This link has two folders

1.ajaxfeed
2.sample

which I have copied in a New Project in eclipse as
two separate folders One for the sample and the other for the ajaxfeed like

com.feedReader for sample

com.feedReader.ajaxfeed

I am trying to run this application in Development Mode.

When I try to compile the application it gives me a

Internal Compiler Error Like

java.lang.IncompatibleClassChangeError: Found class com.google.gwt.core.ext.TreeLogger, but interface was expected

Its throwing this exception for the Loader.java class in the ajaxfeed source.The following is the source for Loader.java

   
/*
 * Copyright 2007 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.feedReader.client.ajaxfeed;

import com.google.gwt.core.client.GWT;
import com.google.gwt.core.client.JavaScriptObject;
import com.google.gwt.user.client.DOM;
import com.google.gwt.user.client.Element;
import com.google.gwt.user.client.Timer;

/**
 * This class must be invoked before any other class in the Google AJAX Feed API
 * is used. It is responsible for downloading and initializing the API. Because
 * the AJAX Feed API is external to the GWT application, the API may not be
 * immediately available, so a callback is used to notify the GWT code that the
 * API is ready for use.
 */
public final class Loader {
  /**
   * A callback interface used to signal state changes in the load process.
   */
  public static interface LoaderCallback {
    public void onError(Throwable t);

    public void onLoad();
  }

  /**
   * The callback to invoke.
   */
  private static LoaderCallback callback;

  /**
   * A reference to the iframe containing the AJAX Feed API.
   */
  private static final Element SANDBOX;

  static {
    SANDBOX = DOM.getElementById("LoaderSandbox");
    assert SANDBOX != null : "No LoaderSandbox iframe in host page.";
  }

  /**
   * Indicates whether or not the external JavaScript for the Google AJAX Feed
   * API has been installed into the JSVM.
   * 
   * @return <code>true</code> iff the API is ready for use.
   */
  public static native boolean apiReady()
  /*-{
   return Boolean($wnd.google_feed && $wnd.google_feed.feeds && $wnd.google_feed.feeds.Feed || false);
   }-*/;

  /**
   * Initialize the Google AJAX Feed API.
   * 
   * @param apiKey The developer's API key
   * @param apiCallback the callback to invoke when the Loader has finished
   */
  public static void init(final String apiKey, LoaderCallback apiCallback) {
    callback = apiCallback;
    registerSandboxCallback();

    setupDocument(getDocument(SANDBOX), apiKey);
  }

  /**
   * This is called from the sandbox iframe with the top-level google object.
   */
  static void ajaxFeedError(JavaScriptObject ex) {
    closeDocument(getDocument(SANDBOX));
    callback.onError(new RuntimeException("Unable to initialize ajax feed api "
        + ex.toString()));
  }

  /**
   * This is called from the sandbox iframe with the top-level google object.
   */
  static native void ajaxFeedLoad(JavaScriptObject google) /*-{
   $wnd.google_feed = google;
   @com.feedReader.client.ajaxfeed.Loader::startTimer()();
   }-*/;

  static void startTimer() {
    Timer t = new Timer() {
      public void run() {
        if (apiReady()) {
          cancel();
          closeDocument(getDocument(SANDBOX));
          callback.onLoad();
        }
      }
    };
    t.scheduleRepeating(10);
  }

  /**
   * Allow a Java exception to be thrown by a JSNI function.
   */
  static void throwRuntimeException(String msg) {
    throw new RuntimeException(msg);
  }

  /**
   * Because we're using document.write() to construct the sandbox iframe, we
   * must call document.close() or some browsers will contine to display the
   * spinner. It's also possible that a browser that does not use progressive
   * rendering would not evaluate the contents of the document until it's
   * closed.
   */
  private static native void closeDocument(Element doc) /*-{
   doc.close();
   }-*/;

  /**
   * Extract the document Element from a Frame.
   */
  private static native Element getDocument(Element elt) /*-{
   
   // FF || IE
   var doc = elt.contentDocument || elt.contentWindow;
   // Opera sometimes returns the window
   if (doc.document) {
   doc = doc.document;
   }
   
   if (!doc) {
   @com.feedReader.client.ajaxfeed.Loader::throwRuntimeException(Ljava/lang/String;)("Unable to obtain sandbox");
   }
   
   return doc;
   }-*/;

  private static native void openDocument(Element doc) /*-{
   doc.open();
   }-*/;

  /**
   * Registers a function that will be called from within the sandbox iframe to
   * indicate that the API download process has started.
   * 
   * @see #ajaxFeedLoad(JavaScriptObject)
   */
  private static native void registerSandboxCallback() /*-{
   $wnd.AjaxFeedError = @com.feedReader.client.ajaxfeed.Loader::ajaxFeedError(Lcom/google/gwt/core/client/JavaScriptObject;);
   $wnd.AjaxFeedLoad = @com.feedReader.client.ajaxfeed.Loader::ajaxFeedLoad(Lcom/google/gwt/core/client/JavaScriptObject;);
   }-*/;

  private static void setupDocument(Element doc, String apiKey) {
    Resources resources = (Resources) GWT.create(Resources.class);

    String docContents = resources.bootstrap().getText();
    docContents =
        docContents.replaceAll("KEY", (apiKey != null) ? "?key=" + apiKey : "");

    openDocument(doc);

    // IE can't handle having the document written as a single string
    String[] lines = docContents.split("\n");
    for (int i = 0 ; i < lines.length; i++) {
      write(doc, lines[i]);
    }
    
    // Don't close the document because the loader API will also perform
    // document.write calls, which would re-open and thus destoy the document
  }

  private static native void write(Element doc, String data) /*-{
   doc.write(data);
   }-*/;

  private Loader() {
  }
}

I am stuck since few days I know this is something very stupid...But

awating your replies experts..

[Rakesh Chaudhary]

Hi Ranchers,

The exception above was due to a unsupported Class built on Ajax...

Using sample package code only after removing the associations with ajaxfeed package..The application compiles successfully and gives the desired results.

I customized the application according to my organizations proprietary needs and gave it some look and feels according to the clients requirements

Its great to see that the application is very fast on Android and Blackberry phones... GWT Rocks..

What I was surprised to see was that the application fits the prescribed screen size without any change...

I would say it took me..some time...to figure it out ...But today after deploying it since last 3 months...I want to praise the effort of GWT FeedReader developers for writing such a application

Thanks