PullScrollView.java

package com.smartandroid.sa.view;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.animation.TranslateAnimation;
import android.widget.ScrollView;

public class PullScrollView extends ScrollView {
	/** ����ϵ��,ԽС������Խ��. */
	private static final float SCROLL_RATIO = 0.5f;

	/** ��������ת�ľ���. */
	private static final int TURN_DISTANCE = 100;

	/** ͷ��view. */
	private View mHeader;

	/** ͷ��view�߶�. */
	private int mHeaderHeight;

	/** ͷ��view��ʾ�߶�. */
	private int mHeaderVisibleHeight;

	/** ScrollView��content view. */
	private View mContentView;

	/** ScrollView��content view����. */
	private Rect mContentRect = new Rect();

	/** �״ε����Y����. */
	private float mTouchDownY;

	/** �Ƿ�ر�ScrollView�Ļ���. */
	private boolean mEnableTouch = false;

	/** �Ƿ�ʼ�ƶ�. */
	private boolean isMoving = false;

	/** �Ƿ��ƶ�������λ��. */
	private boolean isTop = false;

	/** ͷ��ͼƬ��ʼ�����͵ײ�. */
	private int mInitTop, mInitBottom;

	/** ͷ��ͼƬ�϶�ʱ�����͵ײ�. */
	private int mCurrentTop, mCurrentBottom;

	/** ״̬�仯ʱ�ļ�����. */
	private OnTurnListener mOnTurnListener;

	private enum State {
		/** ���� */
		UP,
		/** �ײ� */
		DOWN,
		/** ���� */
		NORMAL
	}

	/** ״̬. */
	private State mState = State.NORMAL;

	public PullScrollView(Context context) {
		super(context);
		init(context, null);
	}

	public PullScrollView(Context context, AttributeSet attrs) {
		super(context, attrs);
		init(context, attrs);
	}

	public PullScrollView(Context context, AttributeSet attrs, int defStyle) {
		super(context, attrs, defStyle);
		init(context, attrs);
	}

	int[] PullScrollView = { 0x7f010000, 0x7f010001, 0x7f010002 };
	int PullScrollView_headerHeight = 1;
	int PullScrollView_headerVisibleHeight = 2;

	private void init(Context context, AttributeSet attrs) {
		// set scroll mode
		setOverScrollMode(OVER_SCROLL_NEVER);

		if (null != attrs) {
			TypedArray ta = context.obtainStyledAttributes(attrs,
					PullScrollView);
			// R.styleable.PullScrollView);
			if (ta != null) {
				mHeaderHeight = (int) ta.getDimension(
						PullScrollView_headerHeight, -1);
				// R.styleable.PullScrollView_headerHeight, -1);
				mHeaderVisibleHeight = (int) ta.getDimension(
						PullScrollView_headerVisibleHeight, -1);
				// R.styleable.PullScrollView_headerVisibleHeight, -1);
				ta.recycle();
			}
		}
	}

	/**
	 * ����Header
	 * 
	 * @param view
	 */
	public void setHeader(View view) {
		mHeader = view;
	}

	/**
	 * ����״̬�ı�ʱ�ļ�����
	 * 
	 * @param turnListener
	 */
	public void setOnTurnListener(OnTurnListener turnListener) {
		mOnTurnListener = turnListener;
	}

	@Override
	protected void onFinishInflate() {
		if (getChildCount() > 0) {
			mContentView = getChildAt(0);
		}
	}

	@Override
	protected void onScrollChanged(int l, int t, int oldl, int oldt) {
		super.onScrollChanged(l, t, oldl, oldt);

		if (getScrollY() == 0) {
			isTop = true;
		}
	}

	@Override
	public boolean onInterceptTouchEvent(MotionEvent ev) {
		if (ev.getAction() == MotionEvent.ACTION_DOWN) {
			mTouchDownY = ev.getY();
			mCurrentTop = mInitTop = mHeader.getTop();
			mCurrentBottom = mInitBottom = mHeader.getBottom();
		}
		return super.onInterceptTouchEvent(ev);
	}

	@Override
	public boolean onTouchEvent(MotionEvent ev) {
		if (mContentView != null) {
			doTouchEvent(ev);
		}

		// ��ֹ�ؼ�����Ļ���.
		return mEnableTouch || super.onTouchEvent(ev);
	}

	/**
	 * �����¼�����
	 * 
	 * @param event
	 */
	private void doTouchEvent(MotionEvent event) {
		int action = event.getAction();

		switch (action) {
		case MotionEvent.ACTION_MOVE:
			doActionMove(event);
			break;

		case MotionEvent.ACTION_UP:
			// �ع�����
			if (isNeedAnimation()) {
				rollBackAnimation();
			}

			if (getScrollY() == 0) {
				mState = State.NORMAL;
			}

			isMoving = false;
			mEnableTouch = false;
			break;

		default:
			break;
		}
	}

	/**
	 * ִ���ƶ�����
	 * 
	 * @param event
	 */
	private void doActionMove(MotionEvent event) {
		// ������������ʱ����״̬����Ϊ�����������������϶��������϶������˺��״δ�������Ӧ������
		if (getScrollY() == 0) {
			mState = State.NORMAL;

			// ��������������ʼλ��ʱ������Touch down������Ϊ��ǰTouch�������
			if (isTop) {
				isTop = false;
				mTouchDownY = event.getY();
			}
		}

		float deltaY = event.getY() - mTouchDownY;

		// �����״�Touch����Ҫ�жϷ�λ��UP OR DOWN
		if (deltaY < 0 && mState == State.NORMAL) {
			mState = State.UP;
		} else if (deltaY > 0 && mState == State.NORMAL) {
			mState = State.DOWN;
		}

		if (mState == State.UP) {
			deltaY = deltaY < 0 ? deltaY : 0;

			isMoving = false;
			mEnableTouch = false;

		} else if (mState == State.DOWN) {
			if (getScrollY() <= deltaY) {
				mEnableTouch = true;
				isMoving = true;
			}
			deltaY = deltaY < 0 ? 0 : deltaY;
		}

		if (isMoving) {
			// ��ʼ��content view����
			if (mContentRect.isEmpty()) {
				// ���������IJ����
				mContentRect.set(mContentView.getLeft(), mContentView.getTop(),
						mContentView.getRight(), mContentView.getBottom());
			}

			// ����header�ƶ�����(�����ƶ��ľ���*����ϵ��*0.5)
			float headerMoveHeight = deltaY * 0.5f * SCROLL_RATIO;
			mCurrentTop = (int) (mInitTop + headerMoveHeight);
			mCurrentBottom = (int) (mInitBottom + headerMoveHeight);

			// ����content�ƶ�����(�����ƶ��ľ���*����ϵ��)
			float contentMoveHeight = deltaY * SCROLL_RATIO;

			// ����content�ƶ��ľ��룬���ⳬ��header�ĵױ�Ե
			int headerBottom = mCurrentBottom - mHeaderVisibleHeight;
			int top = (int) (mContentRect.top + contentMoveHeight);
			int bottom = (int) (mContentRect.bottom + contentMoveHeight);

			if (top <= headerBottom) {
				// �ƶ�content view
				mContentView.layout(mContentRect.left, top, mContentRect.right,
						bottom);

				// �ƶ�header view
				mHeader.layout(mHeader.getLeft(), mCurrentTop,
						mHeader.getRight(), mCurrentBottom);
			}
		}
	}

	private void rollBackAnimation() {
		TranslateAnimation tranAnim = new TranslateAnimation(0, 0,
				Math.abs(mInitTop - mCurrentTop), 0);
		tranAnim.setDuration(200);
		mHeader.startAnimation(tranAnim);

		mHeader.layout(mHeader.getLeft(), mInitTop, mHeader.getRight(),
				mInitBottom);

		// �����ƶ�����
		TranslateAnimation innerAnim = new TranslateAnimation(0, 0,
				mContentView.getTop(), mContentRect.top);
		innerAnim.setDuration(200);
		mContentView.startAnimation(innerAnim);
		mContentView.layout(mContentRect.left, mContentRect.top,
				mContentRect.right, mContentRect.bottom);

		mContentRect.setEmpty();

		// �ص�������
		if (mCurrentTop > mInitTop + TURN_DISTANCE && mOnTurnListener != null) {
			mOnTurnListener.onTurn();
		}
	}

	/**
	 * �Ƿ���Ҫ��������
	 */
	private boolean isNeedAnimation() {
		return !mContentRect.isEmpty() && isMoving;
	}

	/**
	 * ��ת�¼�������
	 * 
	 * @author markmjw
	 */
	public interface OnTurnListener {
		/**
		 * ��ת�ص�����
		 */
		public void onTurn();
	}
}