Clockplus/app/src/main/java/com/philliphsu/clock2/MainActivity.java

package com.philliphsu.clock2;

import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.TabLayout;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentPagerAdapter;
import android.support.v4.view.ViewPager;
import android.view.LayoutInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import com.philliphsu.clock2.alarms.AlarmsFragment;
import com.philliphsu.clock2.settings.SettingsActivity;
import com.philliphsu.clock2.timers.TimersFragment;

import butterknife.Bind;

public class MainActivity extends BaseActivity {
    private static final String TAG = "MainActivity";

    /**
     * The {@link android.support.v4.view.PagerAdapter} that will provide
     * fragments for each of the sections. We use a
     * {@link FragmentPagerAdapter} derivative, which will keep every
     * loaded fragment in memory. If this becomes too memory intensive, it
     * may be best to switch to a
     * {@link android.support.v4.app.FragmentStatePagerAdapter}.
     */
    private SectionsPagerAdapter mSectionsPagerAdapter;

    @Bind(R.id.container)
    ViewPager mViewPager;

    @Bind(R.id.fab)
    FloatingActionButton mFab;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // Create the adapter that will return a fragment for each of the three
        // primary sections of the activity.
        mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
        mViewPager.setAdapter(mSectionsPagerAdapter);

        TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
        tabLayout.setupWithViewPager(mViewPager);

        // TODO: @OnCLick instead.
        mFab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
//                Intent intent = new Intent(MainActivity.this, EditAlarmActivity.class);
//                // Call Fragment#startActivityForResult() instead of Activity#startActivityForResult()
//                // because we want the result to be handled in the Fragment, not in this Activity.
//                // FragmentActivity does NOT deliver the result to the Fragment, i.e. your
//                // Fragment's onActivityResult() will NOT be called.
//                mSectionsPagerAdapter.getCurrentFragment()
//                        .startActivityForResult(intent, AlarmsFragment.REQUEST_CREATE_ALARM);
                Fragment f;
                if ((f = mSectionsPagerAdapter.getCurrentFragment()) instanceof RecyclerViewFragment) {
                    ((RecyclerViewFragment) f).onFabClick();
                }
            }
        });
    }

    @Override
    protected int layoutResId() {
        return R.layout.activity_main;
    }

    @Override
    protected int menuResId() {
        return R.menu.menu_main;
    }

    @Override
    protected boolean isDisplayHomeUpEnabled() {
        return false;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            startActivity(new Intent(this, SettingsActivity.class));
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {
        /**
         * The fragment argument representing the section number for this
         * fragment.
         */
        private static final String ARG_SECTION_NUMBER = "section_number";

        public PlaceholderFragment() {
        }

        /**
         * Returns a new instance of this fragment for the given section
         * number.
         */
        public static PlaceholderFragment newInstance(int sectionNumber) {
            PlaceholderFragment fragment = new PlaceholderFragment();
            Bundle args = new Bundle();
            args.putInt(ARG_SECTION_NUMBER, sectionNumber);
            fragment.setArguments(args);
            return fragment;
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                                 Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main, container, false);
            TextView textView = (TextView) rootView.findViewById(R.id.section_label);
            textView.setText(getString(R.string.section_format, getArguments().getInt(ARG_SECTION_NUMBER)));
            return rootView;
        }
    }

    /**
     * A {@link FragmentPagerAdapter} that returns a fragment corresponding to
     * one of the sections/tabs/pages.
     */
    private static class SectionsPagerAdapter extends FragmentPagerAdapter {

        private Fragment mCurrentFragment;

        public SectionsPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int position) {
            // getItem is called to instantiate the fragment for the given page.
            switch (position) {
                case 0:
                    return AlarmsFragment.newInstance(1);
                case 1:
                    return new TimersFragment();
                default:
                    return PlaceholderFragment.newInstance(position + 1);
            }
        }

        @Override
        public void setPrimaryItem(ViewGroup container, int position, Object object) {
            super.setPrimaryItem(container, position, object);
            if (mCurrentFragment != object) {
                mCurrentFragment = (Fragment) object;
            }
        }

        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            if (mCurrentFragment == object) {
                mCurrentFragment = null;
            }
            super.destroyItem(container, position, object);
        }

        @Override
        public int getCount() {
            // Show 3 total pages.
            return 3;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            switch (position) {
                case 0:
                    return "SECTION 1";
                case 1:
                    return "SECTION 2";
                case 2:
                    return "SECTION 3";
            }
            return null;
        }

        public Fragment getCurrentFragment() {
            return mCurrentFragment;
        }
    }
}