java android.support.v4.widget.DrawerLayout not being found

Question

android.support.v4.widget.DrawerLayout; is not being found on my phone when I test the app. why is this happening and how do I fix it?

I don't know yet but I think I may be having the same problem with android.support.v4.view.GravityCompat; and android.support.v4.app.ActionBarDrawerToggle; if they do cause any problems.

I have never had any problems with android.support.v4.*; before but now it's not working. I have android.support.v4 lib (the may one).

Edit: better error message

my error

05-27 19:46:21.230: E/jdwp(11659): Failed sending reply to debugger: Broken pipe
05-27 19:46:21.290: W/dalvikvm(11659): VFY: unable to resolve virtual method 30: Landroid/support/v4/widget/DrawerLayout;.closeDrawer (Landroid/view/View;)V
05-27 19:46:21.290: W/dalvikvm(11659): VFY: unable to resolve virtual method 27: Landroid/support/v4/app/ActionBarDrawerToggle;.onConfigurationChanged (Landroid/content/res/Configuration;)V
05-27 19:46:21.290: E/dalvikvm(11659): Could not find class 'android.support.v4.widget.DrawerLayout', referenced from method com.MainActivity.onCreate
05-27 19:46:21.290: W/dalvikvm(11659): VFY: unable to resolve check-cast 16 (Landroid/support/v4/widget/DrawerLayout;) in Lcom/MainActivity;
05-27 19:46:21.290: W/dalvikvm(11659): VFY: unable to resolve virtual method 28: Landroid/support/v4/app/ActionBarDrawerToggle;.onOptionsItemSelected (Landroid/view/MenuItem;)Z
05-27 19:46:21.290: W/dalvikvm(11659): VFY: unable to resolve virtual method 29: Landroid/support/v4/app/ActionBarDrawerToggle;.syncState ()V
05-27 19:46:21.290: W/dalvikvm(11659): VFY: unable to resolve virtual method 31: Landroid/support/v4/widget/DrawerLayout;.isDrawerOpen (Landroid/view/View;)Z
05-27 19:46:21.290: W/dalvikvm(11659): Unable to resolve superclass of Lcom/MainActivity$1; (14)
05-27 19:46:21.290: W/dalvikvm(11659): Link of class 'Lcom/MainActivity$1;' failed
05-27 19:46:21.340: W/dalvikvm(11659): threadid=1: thread exiting with uncaught exception (group=0x40bc71f8)
05-27 19:16:42.404: E/dalvikvm(10623): Could not find class 'android.support.v4.widget.DrawerLayout', referenced from method com.MainActivity.onCreate
05-27 19:16:42.464: E/AndroidRuntime(10623): FATAL EXCEPTION: main
05-27 19:16:42.464: E/AndroidRuntime(10623): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.MainActivity}: android.view.InflateException: Binary XML file line #3: Error inflating class android.support.v4.widget.DrawerLayout

Solution

If you recently updated your ADT your Library Build Paths might have been messed up. Try the following:

1. Right click on Project
2. Build Path -> Configure Build Path
3. Tab: Order and Export
4. Make sure your Android and Android Dependencies libraries are checked
5. Clean & Build your Project

During my last ADT update all of them became unchecked and I had similar errors.