Android: actionShareProvider doesn't show applications

Question

I have some problems with the implementation of an actionShareProvider in my Android app. I set it up like this:

XML-File action_share

<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<item android:id="@+id/action_share"
    android:title="action_detail_share"
    app:showAsAction="always"
    app:actionProviderClass="android.support.v7.widget.ShareActionProvider"></item>

In Main Activity:

public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.menu_main, menu);
    MenuItem item = menu.findItem(R.id.action_share);
    mShareActionProvider = (ShareActionProvider) MenuItemCompat.getActionProvider(item);
    if (mShareActionProvider != null) {
        mShareActionProvider.setShareIntent(getDefaultShareIntent());
    }
    return true;
}

private Intent getDefaultShareIntent(){
    Intent intent = new Intent(Intent.ACTION_SEND);
    intent.setType("text/plain");
    intent.putExtra(Intent.EXTRA_SUBJECT, "SUBJECT");
    intent.putExtra(Intent.EXTRA_TEXT,dbHandler.databaseToString());

    System.out.println(dbHandler.databaseToString());
    return intent;
}

If i start the emulator it shows correctly with 3 dots arranged vertically. But if i click on it, it only displays the "settings-item". Do you have any suggestions what could be wrong ? I also tested my app on an S4 and there the shareActionprovider didn't even show up...

Edit:

My imports for this are: import android.support.v4.view.MenuItemCompat; import android.support.v7.app.ActionBarActivity; import android.support.v7.widget.ShareActionProvider; import android.support.v4.view.MenuItemCompat; import android.support.v7.app.ActionBarActivity; import android.support.v7.widget.ShareActionProvider;

Edit 2: I also have the problem, that mShareActionProvider seems to be null ... I tried, to add -keep class android.support.v7.widget.SearchView { *; } -keep class android.support.v7.widget.SearchView { *; } in my proguard-projext.txt but it doesn't seem to work.

**Question is solved by myself**