import com.google.samples.apps.iosched.ui.widget.ObservableScrollView; //导入依赖的package包/类
@Override
protected void onCreate(Bundle savedInstanceState) {
    getWindow().requestFeature(Window.FEATURE_CONTENT_TRANSITIONS);
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_video_detail);

    mSelectedVideo = getIntent().getExtras().getParcelable(KEY_BUNDLE_VIDEO);
    mObservableScrollView = (ObservableScrollView) findViewById(R.id.activity_detail_scroller);

    loadImage();
    initToolbar();
    initContent(savedInstanceState);
    initContentHeader();
    initFAB();
    initParallaxEffect();
}
 

import com.google.samples.apps.iosched.ui.widget.ObservableScrollView; //导入依赖的package包/类
private void initViews() {
    mFABElevation = getResources().getDimensionPixelSize(R.dimen.fab_elevation);
    mMaxHeaderElevation = getResources().getDimensionPixelSize(
            R.dimen.session_detail_max_header_elevation);

    mScrollView = (ObservableScrollView) getActivity().findViewById(R.id.scroll_view);
    mScrollView.addCallbacks(this);
    ViewTreeObserver vto = mScrollView.getViewTreeObserver();
    if (vto.isAlive()) {
        vto.addOnGlobalLayoutListener(mGlobalLayoutListener);
    }

    mScrollViewChild = getActivity().findViewById(R.id.scroll_view_child);
    mScrollViewChild.setVisibility(View.INVISIBLE);

    mDetailsContainer = getActivity().findViewById(R.id.details_container);
    mHeaderBox = getActivity().findViewById(R.id.header_session);
    mTitle = (TextView) getActivity().findViewById(R.id.session_title);
    mSubtitle = (TextView) getActivity().findViewById(R.id.session_subtitle);
    mPhotoViewContainer = getActivity().findViewById(R.id.session_photo_container);
    mPhotoView = (ImageView) getActivity().findViewById(R.id.session_photo);

    mAbstract = (TextView) getActivity().findViewById(R.id.session_abstract);

    mPlusOneIcon = (ImageView) getActivity().findViewById(R.id.gplus_icon_box);
    mTwitterIcon = (ImageView) getActivity().findViewById(R.id.twitter_icon_box);

    //Find view that shows a Videocam icon if the session is being live streamed.
    mLiveStreamVideocamIconAndText = (TextView) getActivity().findViewById(
            R.id.live_stream_videocam_icon_and_text);

    // Find view that shows a play button and some text for the user to watch the session live stream.
    mLiveStreamPlayIconAndText = (TextView) getActivity().findViewById(
            R.id.live_stream_play_icon_and_text);

    mRequirements = (TextView) getActivity().findViewById(R.id.session_requirements);
    mTags = (LinearLayout) getActivity().findViewById(R.id.session_tags);
    mTagsContainer = (ViewGroup) getActivity().findViewById(R.id.session_tags_container);

    ViewCompat.setTransitionName(mPhotoView, SessionDetailConstants.TRANSITION_NAME_PHOTO);

    mAddScheduleButtonContainer = getActivity()
            .findViewById(R.id.add_schedule_button_container);
    mAddScheduleButton = (CheckableFloatingActionButton) getActivity()
            .findViewById(R.id.add_schedule_button);

    mNoPlaceholderImageLoader = new ImageLoader(getContext());
    mSpeakersImageLoader = new ImageLoader(getContext(), R.drawable.person_image_empty);
}
 

import com.google.samples.apps.iosched.ui.widget.ObservableScrollView; //导入依赖的package包/类
private void initParallaxEffect() {

        final View contentImage = mObservableScrollView.findViewById(R.id.content_image);
        final View contentHeader = mObservableScrollView.findViewById(R.id.content_header);
        final View contentHeaderShadow
                = mObservableScrollView.findViewById(R.id.content_header_shadow);
        final View fabPlayButton = mObservableScrollView.findViewById(R.id.content_play);

        mObservableScrollView.addCallbacks(new ObservableScrollView.Callbacks() {
            public static final String TAG = "ObservableScrollView";

            @Override
            public void onScrollChanged(int deltaX, int deltaY) {
                final int scrollY = mObservableScrollView.getScrollY();

                // relocate the position of contentHeader
                if (contentHeader.getY() < scrollY) {
                    mIsHeaderSticky = true;
                } else if (scrollY <= mInitialContentHeaderPos) {
                    mIsHeaderSticky = false;
                    contentHeader.setY(mInitialContentHeaderPos);
                    contentHeaderShadow.setY(mInitialContentHeaderPos
                            + contentHeader.getHeight());
                    fabPlayButton.setY(mInitialContentHeaderPos
                            + contentHeader.getHeight() - fabPlayButton.getHeight() / 2);
                }
                if (mIsHeaderSticky) {
                    contentHeader.setY(scrollY);
                    contentHeaderShadow.setY(scrollY + contentHeader.getHeight());
                    fabPlayButton.setY(scrollY + contentHeader.getHeight()
                            - fabPlayButton.getHeight() / 2);
                }

                // relocate the position of contentImage
                final float currPosY = contentImage.getY();
                final float futurePosY = currPosY + (deltaY / 2.f);

                if (futurePosY >= mMaxContentImagePos) {
                    contentImage.setY(mMaxContentImagePos);
                } else if (futurePosY <= 0) {
                    contentImage.setY(0.f);
                } else {
                    contentImage.setY(futurePosY);
                }
            }
        });

    }