ViewPagerTabListViewActivity.java

/*
 * Copyright 2014 Soichiro Kashima
 *
 * 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.marshalchen.common.demoofui.observablescrollview;

import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentStatePagerAdapter;
import android.support.v4.view.ViewCompat;
import android.support.v4.view.ViewPager;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.widget.Toolbar;
import android.util.SparseArray;
import android.view.View;
import android.view.ViewGroup;

import com.github.ksoichiro.android.observablescrollview.ObservableListView;
import com.github.ksoichiro.android.observablescrollview.ObservableScrollViewCallbacks;
import com.github.ksoichiro.android.observablescrollview.ScrollState;
import com.marshalchen.common.demoofui.R;
import com.marshalchen.common.demoofui.observablescrollview.ui.widget.SlidingTabLayout;
import com.nineoldandroids.view.ViewHelper;
import com.nineoldandroids.view.ViewPropertyAnimator;

/**
 * SlidingTabLayout and SlidingTabStrip are from google/iosched:
 * https://github.com/google/iosched
 */
public class ViewPagerTabListViewActivity extends ActionBarActivity implements ObservableScrollViewCallbacks {

    private View mHeaderView;
    private View mToolbarView;
    private int mBaseTranslationY;
    private ViewPager mPager;
    private NavigationAdapter mPagerAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.observable_scroll_view_activity_viewpagertabscrollview);

        setSupportActionBar((Toolbar) findViewById(R.id.toolbar));

        mHeaderView = findViewById(R.id.header);
        ViewCompat.setElevation(mHeaderView, getResources().getDimension(R.dimen.toolbar_elevation));
        mToolbarView = findViewById(R.id.toolbar);
        mPagerAdapter = new NavigationAdapter(getSupportFragmentManager());
        mPager = (ViewPager) findViewById(R.id.pager);
        mPager.setAdapter(mPagerAdapter);

        SlidingTabLayout slidingTabLayout = (SlidingTabLayout) findViewById(R.id.sliding_tabs);
        slidingTabLayout.setCustomTabView(R.layout.observable_scroll_view_tab_indicator, android.R.id.text1);
        slidingTabLayout.setSelectedIndicatorColors(getResources().getColor(R.color.accent));
        slidingTabLayout.setDistributeEvenly(true);
        slidingTabLayout.setViewPager(mPager);

        // When the page is selected, other fragments' scrollY should be adjusted
        // according to the toolbar status(shown/hidden)
        slidingTabLayout.setOnPageChangeListener(new ViewPager.OnPageChangeListener() {
            @Override
            public void onPageScrolled(int i, float v, int i2) {
            }

            @Override
            public void onPageSelected(int i) {
                propagateToolbarState(toolbarIsShown());
            }

            @Override
            public void onPageScrollStateChanged(int i) {
            }
        });

        propagateToolbarState(toolbarIsShown());
    }

    @Override
    public void onScrollChanged(int scrollY, boolean firstScroll, boolean dragging) {
        if (dragging) {
            int toolbarHeight = mToolbarView.getHeight();
            float currentHeaderTranslationY = ViewHelper.getTranslationY(mHeaderView);
            if (firstScroll) {
                if (-toolbarHeight < currentHeaderTranslationY) {
                    mBaseTranslationY = scrollY;
                }
            }
            int headerTranslationY = Math.min(0, Math.max(-toolbarHeight, -(scrollY - mBaseTranslationY)));
            ViewPropertyAnimator.animate(mHeaderView).cancel();
            ViewHelper.setTranslationY(mHeaderView, headerTranslationY);
        }
    }

    @Override
    public void onDownMotionEvent() {
    }

    @Override
    public void onUpOrCancelMotionEvent(ScrollState scrollState) {
        mBaseTranslationY = 0;

        Fragment fragment = getCurrentFragment();
        if (fragment == null) {
            return;
        }
        View view = fragment.getView();
        if (view == null) {
            return;
        }

        int toolbarHeight = mToolbarView.getHeight();
        final ObservableListView listView = (ObservableListView) view.findViewById(R.id.list);
        if (scrollState == ScrollState.UP) {
            if (toolbarHeight < listView.getCurrentScrollY()) {
                hideToolbar();
            } else if (listView.getCurrentScrollY() < toolbarHeight) {
                showToolbar();
            }
        } else if (scrollState == ScrollState.DOWN) {
            if (toolbarHeight < listView.getCurrentScrollY()) {
                showToolbar();
            }
        }
    }

    private Fragment getCurrentFragment() {
        return mPagerAdapter.getItemAt(mPager.getCurrentItem());
    }

    private void propagateToolbarState(boolean isShown) {
        int toolbarHeight = mToolbarView.getHeight();

        // Set scrollY for the fragments that are not created yet
        mPagerAdapter.setScrollY(isShown ? 0 : toolbarHeight);

        // Set scrollY for the active fragments
        for (int i = 0; i < mPagerAdapter.getCount(); i++) {
            // Skip current item
            if (i == mPager.getCurrentItem()) {
                continue;
            }

            // Skip destroyed or not created item
            Fragment f = mPagerAdapter.getItemAt(i);
            if (f == null) {
                continue;
            }

            ObservableListView listView = (ObservableListView) f.getView().findViewById(R.id.list);
            if (isShown) {
                // Scroll up
                if (0 < listView.getCurrentScrollY()) {
                    listView.setSelection(0);
                }
            } else {
                // Scroll down (to hide padding)
                if (listView.getCurrentScrollY() < toolbarHeight) {
                    listView.setSelection(1);
                }
            }
        }
    }

    private boolean toolbarIsShown() {
        return ViewHelper.getTranslationY(mHeaderView) == 0;
    }

    private void showToolbar() {
        float headerTranslationY = ViewHelper.getTranslationY(mHeaderView);
        if (headerTranslationY != 0) {
            ViewPropertyAnimator.animate(mHeaderView).cancel();
            ViewPropertyAnimator.animate(mHeaderView).translationY(0).setDuration(200).start();
        }
        propagateToolbarState(true);
    }

    private void hideToolbar() {
        float headerTranslationY = ViewHelper.getTranslationY(mHeaderView);
        int toolbarHeight = mToolbarView.getHeight();
        if (headerTranslationY != -toolbarHeight) {
            ViewPropertyAnimator.animate(mHeaderView).cancel();
            ViewPropertyAnimator.animate(mHeaderView).translationY(-toolbarHeight).setDuration(200).start();
        }
        propagateToolbarState(false);
    }

    private static class NavigationAdapter extends FragmentStatePagerAdapter {

        private static final String[] TITLES = new String[]{"Applepie", "Butter Cookie", "Cupcake", "Donut", "Eclair", "Froyo", "Gingerbread", "Honeycomb", "Ice Cream Sandwich", "Jelly Bean", "KitKat", "Lollipop"};

        private SparseArray<Fragment> mPages;
        private int mScrollY;

        public NavigationAdapter(FragmentManager fm) {
            super(fm);
            mPages = new SparseArray<Fragment>();
        }

        public void setScrollY(int scrollY) {
            mScrollY = scrollY;
        }

        @Override
        public Fragment getItem(int position) {
            Fragment f = new ViewPagerTabListViewFragment();
            if (0 < mScrollY) {
                Bundle args = new Bundle();
                args.putInt(ViewPagerTabListViewFragment.ARG_INITIAL_POSITION, 1);
                f.setArguments(args);
            }
            mPages.put(position, f);
            return f;
        }

        public Fragment getItemAt(int position) {
            return mPages.get(position);
        }

        @Override
        public int getCount() {
            return TITLES.length;
        }

        @Override
        public void destroyItem(ViewGroup container, int position, Object object) {
            if (0 <= mPages.indexOfKey(position)) {
                mPages.remove(position);
            }
            super.destroyItem(container, position, object);
        }

        @Override
        public CharSequence getPageTitle(int position) {
            return TITLES[position];
        }
    }
}