package net.wequick.example.small.app.mine;

import android.app.Activity;
import android.os.Bundle;

/**
 * Created by galen on 15/11/11.
 */
public class MainActivity extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
}

package net.wequick.example.small.app.mine;

import android.app.Activity;
import android.os.Bundle;
import android.support.annotation.Nullable;

/**
 * Created by galen on 15/11/11.
 */
public class MainActivity extends Activity {
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
}

Add using support-annotation sample