Android app won't open after i install. But it can run in emulator

I found the problem! I had declared the activity 2 times in the manifest with different properties, like:

<activity android:name=".myclass"></activity> 

and

<activity android:name=".myclass" android:label="@string/app_name">
  <intent-filter>   
     <action android:name="android.intent.action.MAIN" /> 
     <category android:name="android.intent.category.LAUNCHER" /> 
  </intent-filter>
</activity> 

Remove the unwanted one from the manifest and it will work.

Check your android emulator version and the firmware version of the phone. If firmware version is not supported for that app you will be install from adb, but you cant start the app.

Check the settings to be able to install the unknown apps in
Settings->Applications and check box "Unknown Sources"