Android studio library dependency not showing up

Question

I went to file -->app--> dependencies --> green plus sign and press on library dependency . Nothing show up. I trying to add the support v4 dependency so I can extend Fragment Activity . Now I having error cannot resolve symbol support.

import android.support.v4.app.FragmentActivity;

public class MainActivity extends FragmentActivity {
    ViewPager viewpager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        viewpager = (ViewPager) findViewById(R.id.pager);
        PagerAdapter padapter = new PagerAdapter(getSupportFragmentManager());
        viewpager.setAdapter(padapter);
    }
}

Answer 1

Open the build.gradle file for your application and add this line compile "com.android.support:support-v4:18.0.+"

Make sure you have downloaded the Android Support Repository using the SDK Manager.

ref here