title: Error with setAlpha
body: <p>hi guys i need your help because of this error:</p>
  
  <p>here is the logcat:</p>
  
  <pre><code>07-30 16:12:33.823: E/AndroidRuntime(21283): java.lang.NoSuchMethodError: android.widget.LinearLayout.setAlpha
  07-30 16:12:33.823: E/AndroidRuntime(21283):    at it.bisemanuDEV.piano.livello1$1.onClick(livello1.java:393)
  07-30 16:12:33.823: E/AndroidRuntime(21283):    at android.view.View.performClick(View.java:2408)
  07-30 16:12:33.823: E/AndroidRuntime(21283):    at android.view.View$PerformClick.run(View.java:8819)
  07-30 16:12:33.823: E/AndroidRuntime(21283):    at android.os.Handler.handleCallback(Handler.java:603)
  07-30 16:12:33.823: E/AndroidRuntime(21283):    at android.os.Handler.dispatchMessage(Handler.java:92)
  07-30 16:12:33.823: E/AndroidRuntime(21283):    at android.os.Looper.loop(Looper.java:123)
  07-30 16:12:33.823: E/AndroidRuntime(21283):    at android.app.ActivityThread.main(ActivityThread.java:4627)
  07-30 16:12:33.823: E/AndroidRuntime(21283):    at java.lang.reflect.Method.invokeNative(Native Method)
  07-30 16:12:33.823: E/AndroidRuntime(21283):    at java.lang.reflect.Method.invoke(Method.java:521)
  07-30 16:12:33.823: E/AndroidRuntime(21283):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
  07-30 16:12:33.823: E/AndroidRuntime(21283):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
  07-30 16:12:33.823: E/AndroidRuntime(21283):    at dalvik.system.NativeStart.main(Native Method)
  </code></pre>