ui/views/EffectiveNavigation/app/src/main/java/com/example/android/effectivenavigation/MainActivity.java

/*
 * Copyright 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.effectivenavigation;

import android.content.Intent;
import android.os.Build;
import android.os.Bundle;
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.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    /**
     * An {@link Intent} flag to be used for launching an external activity. This ensures that
     * relaunching the application from device home screen does not return to the external
     * activity. We can use {@link Intent#FLAG_ACTIVITY_NEW_DOCUMENT} or
     * {@link Intent#FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET} depending on the API level.
     */
    private static final int INTENT_FLAG_ACTIVITY_NEW_DOCUMENT;

    static {
        if (Build.VERSION.SDK_INT >= 21) {
            INTENT_FLAG_ACTIVITY_NEW_DOCUMENT = Intent.FLAG_ACTIVITY_NEW_DOCUMENT;
        } else {
            //noinspection deprecation
            INTENT_FLAG_ACTIVITY_NEW_DOCUMENT = Intent.FLAG_ACTIVITY_CLEAR_WHEN_TASK_RESET;
        }
    }

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Create the adapter that will return a fragment for each of the three primary sections
        // of the app.
        AppSectionsPagerAdapter appSectionsPagerAdapter = new AppSectionsPagerAdapter(
                getSupportFragmentManager());

        // Set up the app bar.
        final Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        // Set up the ViewPager, attaching the adapter and setting up a listener for when the
        // user swipes between sections.
        final ViewPager viewPager = (ViewPager) findViewById(R.id.pager);
        viewPager.setAdapter(appSectionsPagerAdapter);

        // Set up the TabLayout, making it sync with the ViewPager.
        final TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
        tabLayout.setupWithViewPager(viewPager);
    }

    /**
     * A {@link FragmentPagerAdapter} that returns a fragment corresponding to one of the primary
     * sections of the app.
     */
    private static class AppSectionsPagerAdapter extends FragmentPagerAdapter {

        AppSectionsPagerAdapter(FragmentManager fm) {
            super(fm);
        }

        @Override
        public Fragment getItem(int i) {
            switch (i) {
                case 0:
                    // The first section of the app is the most interesting -- it offers
                    // a launchpad into the other demonstrations in this example application.
                    return new LaunchpadSectionFragment();

                default:
                    // The other sections of the app are placeholder placeholders.
                    Fragment fragment = new DummySectionFragment();
                    Bundle args = new Bundle();
                    args.putInt(DummySectionFragment.ARG_SECTION_NUMBER, i + 1);
                    fragment.setArguments(args);
                    return fragment;
            }
        }

        @Override
        public int getCount() {
            return 3;
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return "Section " + (position + 1);
        }

    }

    /**
     * A fragment that launches other parts of the demo application.
     */
    public static class LaunchpadSectionFragment extends Fragment {

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_section_launchpad, container, false);

            // Demonstration of a collection-browsing activity.
            rootView.findViewById(R.id.demo_collection_button)
                    .setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View view) {
                            Intent intent = new Intent(getActivity(), CollectionDemoActivity.class);
                            startActivity(intent);
                        }
                    });

            // Demonstration of navigating to external activities.
            rootView.findViewById(R.id.demo_external_activity)
                    .setOnClickListener(new View.OnClickListener() {
                        @Override
                        public void onClick(View view) {
                            // Create an intent that asks the user to pick a photo, but using
                            // FLAG_ACTIVITY_NEW_DOCUMENT, ensures that relaunching
                            // the application from the device home screen does not return
                            // to the external activity.
                            Intent externalActivityIntent = new Intent(Intent.ACTION_PICK);
                            externalActivityIntent.setType("image/*");
                            externalActivityIntent.addFlags(
                                    INTENT_FLAG_ACTIVITY_NEW_DOCUMENT);
                            startActivity(externalActivityIntent);
                        }
                    });

            return rootView;
        }

    }

    /**
     * A placeholder fragment representing a section of the app, but that simply displays placeholder text.
     */
    public static class DummySectionFragment extends Fragment {

        public static final String ARG_SECTION_NUMBER = "section_number";

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_section_dummy, container, false);
            Bundle args = getArguments();
            ((TextView) rootView.findViewById(android.R.id.text1)).setText(
                    getString(R.string.dummy_section_text, args.getInt(ARG_SECTION_NUMBER)));
            return rootView;
        }

    }

}