title: Cannot edit main.xml in Eclipse Android project
body: <p>I've created several Android applications with the ADT in Eclipse, but I'm now unable to edit res/layout/main.xml in new or old Android projects.  When I type in the main.xml tab, my keystrokes have no effect.  Similarly, I am unable to make changes in the Graphical Layout tab.  I can drag a widget onto the screen, but it does not remain when I let go of the mouse button.  I have checked that main.xml is not write-protected, both through Eclipse and the file system.  I am able to create another file in that directory, through either Eclipse or the file system, which shows that the directory is not write-protected.  I have no problem editing or adding files under the "src" directory.</p>
  
  <p>I am running Eclipse Classic 3.6.1 with version 10.0.1.v201103111512-110841 of the Android Development Tools on Windows 7.  FWIW, I recently installed plugins for some other Google tools (GWT and GAE), although I did not use them for any of the Android projects (obviously).</p>
  
  <p>Update: When I edit the xml in a different editor and then refresh it in Eclipse, I get the error "Error parsing XML: unbound prefix".  My file is correct, but I discovered that the standard URL "http://schemas.android.com/apk/res/android" is unreachable.  Specifically, the server is down.  I don't know if this is related to my original problem.</p>
  
  <p>Update2: Here is foo.xml, which I created outside of Eclipse but is showing the error  <strong>Error parsing XML: unbound prefix</strong> on the second line:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
      &lt;TextView xmlns:android="http://schemas.android.com/apk/res/android"
  android:text="TextView" 
  android:id="@+id/textView1" 
  android:layout_width="wrap_content" 
  android:layout_height="wrap_content" /&gt;
  </code></pre>
  
  <p>The site <a href="http://schemas.android.com" rel="nofollow">schemas.android.com</a> is still down.</p>
  
  <p>I tried running my program to get the compiler errors, but it build correctly, and the error went away from the .xml file.  Go figure.</p>
  
  <p>That still leaves the original problem of not being able to edit <em>any</em> .xml file within Eclipse.  When I tried to edit the above xml file, I got this error in a popup:</p>
  
  <pre><code>No grammar constraints (DTD or XML schema) detected for the document.
  </code></pre>
  
  <p>My guess is that this is due to <a href="http://schemas.android.com" rel="nofollow">schemas.android.com</a> being down.</p>
  
  <p><strong>Update 3 (in response to slund's comment):</strong></p>
  
  <p>Cleaning and rebuilding did not change anything.  I could build, but I still got the "No grammar constraints" error when I tried editing either .xml file.</p>
  
  <p>The directory of the xml files is <strong>C:\Users\Ellen\workspace\SqliteDemo\res\layout</strong>, just as it should be.  It contains no other files.  The Problem view showed no warnings or problems for this project (although there were some for other projects of mine).</p>
  
  <p><strong>Update 4</strong></p>
  
  <p>I also cannot edit the (default) AndroidManifest.xml from within Eclipse.</p>