title: can't create folder in /mnt/sdcard
body: <p>I think I'm doing everything right to first create a folder
  that I can write to later in my app, but it doesn't seem to be working.
  Any clues as to how I've failed?</p>
  
  <p>It correctly tries to create /mnt/sdcard/gradebook</p>
  
  <p>I have uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"
  in my manifest. I'm running on a real device (Samsung Galaxy S) and I'm not using the
  sdcard as storage while its attached to my computer.</p>
  
  <pre><code>    boolean mExternalStorageAvailable = false;
      boolean mExternalStorageWriteable = false;
      String state = Environment.getExternalStorageState();
  
      if (Environment.MEDIA_MOUNTED.equals(state)) {
          // We can read and write the media
          mExternalStorageAvailable = mExternalStorageWriteable = true;
      } else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
          // We can only read the media
          mExternalStorageAvailable = true;
          mExternalStorageWriteable = false;
          Toast.makeText(this,"This Application needs a writable external storage (sdcard).",Toast.LENGTH_SHORT).show();
          finish();
      } else {
          // Something else is wrong. It may be one of many other states, but all we need
          //  to know is we can neither read nor write
          mExternalStorageAvailable = mExternalStorageWriteable = false;
          Toast.makeText(this,"This Application needs a mounted external storage (sdcard).",Toast.LENGTH_SHORT).show();
          finish();
  
      }
  
  
      File folder = new File(Environment.getExternalStorageDirectory () + "/gradeBook");
      boolean success = false;
      if(!folder.exists()){
           success = folder.mkdir();
      }
      if (!success) {
          Log.e("FILE", "can't create " + folder);
      }
      else 
      {
          Log.i("FILE", "directory is created"); 
      }
  </code></pre>
  
  <p>Here is the manifest</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
    &lt;manifest xmlns:android="http://schemas.android.com/apk/res/android" 
      package="com.ulsanonline.gradebook" 
      android:versionName="@string/version" 
      android:installLocation="auto" 
      android:versionCode="2"&gt;
      &lt;uses-sdk android:minSdkVersion="8"&gt;&lt;/uses-sdk&gt; 
      &lt;application 
          android:icon="@drawable/icon" 
          android:debuggable="true" 
          android:persistent="false" 
          android:hasCode="true"
          android:minSdkVersion="8"&gt;
          &lt;uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" /&gt;
          &lt;uses-permission android:name="android.permission.CAMERA" /&gt;
          &lt;activity 
              android:name=".CourseWork" 
              android:label="@string/app_name" 
              android:screenOrientation="portrait"&gt;
              &lt;intent-filter&gt;
                  &lt;action android:name="android.intent.action.MAIN" /&gt;
                  &lt;category android:name="android.intent.category.LAUNCHER" /&gt;
              &lt;/intent-filter&gt;
          &lt;/activity&gt;
  </code></pre>