AutoViewHelper.java

package com.smartandroid.sa.view;

import android.app.Activity;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewGroup.LayoutParams;
import android.view.ViewParent;
import android.widget.AbsListView;
import android.widget.AbsListView.OnScrollListener;
import android.widget.FrameLayout;
import android.widget.ListView;
import android.widget.ScrollView;

import com.smartandroid.sa.animation.ViewPropertyAnimator;

public class AutoViewHelper {

	public enum AutoViewPosition {
		TOP, BOTTOM
	};

	private static final int SCROLL_TO_TOP = -1;

	private static final int SCROLL_TO_BOTTOM = 1;

	private static final int SCROLL_DIRECTION_CHANGE_THRESHOLD = 5;

	private Activity mActivity;

	private LayoutInflater mLayoutInflater;

	private View mPoppyView;

	private int mScrollDirection = 0;

	private int mPoppyViewHeight = -1;

	private AutoViewPosition mPoppyViewPosition;

	public AutoViewHelper(Activity activity, AutoViewPosition position) {
		mActivity = activity;
		mLayoutInflater = LayoutInflater.from(activity);
		mPoppyViewPosition = position;
	}

	public AutoViewHelper(Activity activity) {
		this(activity, AutoViewPosition.BOTTOM);
	}

	// for scrollview

	public View createAutoViewOnScrollView(int scrollViewId, int autoViewResId) {
		mPoppyView = mLayoutInflater.inflate(autoViewResId, null);
		final SmartingScrollView scrollView = (SmartingScrollView) mActivity.findViewById(scrollViewId);
		initAutoViewOnScrollView(scrollView);
		return mPoppyView;
	}

	// for ListView

	public View createAutoViewOnListView(int listViewId, int autoViewResId, OnScrollListener onScrollListener) {
		final ListView listView = (ListView) mActivity.findViewById(listViewId);
		if (listView.getHeaderViewsCount() != 0) {
			throw new IllegalArgumentException("use createAutoViewOnListView with headerResId parameter");
		}
		if (listView.getFooterViewsCount() != 0) {
			throw new IllegalArgumentException("autoview library doesn't support listview with footer");
		}
		mPoppyView = mLayoutInflater.inflate(autoViewResId, null);
		initAutoViewOnListView(listView, onScrollListener);
		return mPoppyView;
	}

	public View createAutoViewOnListView(int listViewId, int autoViewResId) {
		return createAutoViewOnListView(listViewId, autoViewResId, null);
	}

	// common

	private void setAutoViewOnView(View view) {
		LayoutParams lp = view.getLayoutParams();
		ViewParent parent = view.getParent();
		ViewGroup group = (ViewGroup) parent;
		int index = group.indexOfChild(view);
		final FrameLayout newContainer = new FrameLayout(mActivity);
		group.removeView(view);
		group.addView(newContainer, index, lp);
		newContainer.addView(view);
		final FrameLayout.LayoutParams layoutParams = new FrameLayout.LayoutParams(LayoutParams.MATCH_PARENT,
				LayoutParams.WRAP_CONTENT);
		layoutParams.gravity = mPoppyViewPosition == AutoViewPosition.BOTTOM ? Gravity.BOTTOM : Gravity.TOP;
		newContainer.addView(mPoppyView, layoutParams);
		group.invalidate();
	}

	private void onScrollPositionChanged(int oldScrollPosition, int newScrollPosition) {
		int newScrollDirection;

		System.out.println(oldScrollPosition + " ->" + newScrollPosition);

		if (newScrollPosition < oldScrollPosition) {
			newScrollDirection = SCROLL_TO_TOP;
		} else {
			newScrollDirection = SCROLL_TO_BOTTOM;
		}

		if (newScrollDirection != mScrollDirection) {
			mScrollDirection = newScrollDirection;
			translateYAutoView();
		}
	}

	private void translateYAutoView() {
		mPoppyView.post(new Runnable() {

			@Override
			public void run() {
				if (mPoppyViewHeight <= 0) {
					mPoppyViewHeight = mPoppyView.getHeight();
				}

				int translationY = 0;
				switch (mPoppyViewPosition) {
				case BOTTOM:
					translationY = mScrollDirection == SCROLL_TO_TOP ? 0 : mPoppyViewHeight;
					break;
				case TOP:
					translationY = mScrollDirection == SCROLL_TO_TOP ? -mPoppyViewHeight : 0;
					break;
				}

				ViewPropertyAnimator.animate(mPoppyView).setDuration(300).translationY(translationY);
			}
		});
	}

	// for ScrollView

	private void initAutoViewOnScrollView(SmartingScrollView scrollView) {
		setAutoViewOnView(scrollView);
		scrollView.setOnScrollChangedListener(new SmartingScrollView.OnScrollChangedListener() {

			int mScrollPosition;

			public void onScrollChanged(ScrollView who, int l, int t, int oldl, int oldt) {
				if (Math.abs(t - mScrollPosition) >= SCROLL_DIRECTION_CHANGE_THRESHOLD) {
					onScrollPositionChanged(mScrollPosition, t);
				}

				mScrollPosition = t;
			}
		});
	}

	// for ListView

	private void initAutoViewOnListView(ListView listView, final OnScrollListener onScrollListener) {
		setAutoViewOnView(listView);
		listView.setOnScrollListener(new OnScrollListener() {

			int mScrollPosition;

			@Override
			public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
				if (onScrollListener != null) {
					onScrollListener.onScroll(view, firstVisibleItem, visibleItemCount, totalItemCount);
				}
				View topChild = view.getChildAt(0);

				int newScrollPosition = 0;
				if (topChild == null) {
					newScrollPosition = 0;
				} else {
					newScrollPosition = -topChild.getTop() + view.getFirstVisiblePosition() * topChild.getHeight();
				}

				if (Math.abs(newScrollPosition - mScrollPosition) >= SCROLL_DIRECTION_CHANGE_THRESHOLD) {
					onScrollPositionChanged(mScrollPosition, newScrollPosition);
				}

				mScrollPosition = newScrollPosition;
			}

			@Override
			public void onScrollStateChanged(AbsListView view, int scrollState) {
				if (onScrollListener != null) {
					onScrollListener.onScrollStateChanged(view, scrollState);
				}
			}
		});
	}
}