自定义Gallery 滑动中图片自动突出显示

package org.pskink;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Matrix;
import android.os.Handler;
import android.os.Message;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.Transformation;
import android.widget.AdapterView;
import android.widget.Gallery;
import android.widget.ImageView;
import android.widget.AdapterView.OnItemSelectedListener;

public class AnimatedSizingGallery extends Gallery implements OnItemSelectedListener {
	public static final String TAG = "AnimatedSizingGallery";
	private static final int MSG_ZOOM_IN = 1;
	private  static final long DELAY = 100;

	private View mPrev;
	private float mAnimationScale;
	private float mAnimationOffsetY;
	private int mAnimationDuration;
	
	public AnimatedSizingGallery(Context context, AttributeSet attrs) {
		super(context, attrs);
		TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.AnimatedSizingGallery);
		mAnimationScale = a.getFloat(R.styleable.AnimatedSizingGallery_animationScale, 2);
		mAnimationOffsetY = a.getFloat(R.styleable.AnimatedSizingGallery_animationOffsetY, 0);
		mAnimationDuration = a.getInteger(R.styleable.AnimatedSizingGallery_animationDuration, 500);
		a.recycle();
		setOnItemSelectedListener(this);
	}

	public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
		if (mPrev != null) {
			zoomOut();
		}
		mPrev = view;
		mGalleryHandler.removeCallbacksAndMessages(view);
		Message msg = Message.obtain(mGalleryHandler, MSG_ZOOM_IN, view);
		mGalleryHandler.sendMessageDelayed(msg, DELAY);
	}

	public void onNothingSelected(AdapterView<?> parent) {
		Log.d(TAG, "onNothingSelected called !!!");
		if (mPrev != null) {
			zoomOut();
			mPrev = null;
		}
	}
	
	private void zoomOut() {
		if (mGalleryHandler.hasMessages(MSG_ZOOM_IN, mPrev)) {
			mGalleryHandler.removeCallbacksAndMessages(mPrev);
		} else {
			ZoomAnimation a = (ZoomAnimation) mPrev.getAnimation();
			a.resetForZoomOut();
			mPrev.startAnimation(a);
		}
	}

	Handler mGalleryHandler = new Handler() {
		@Override
		public void dispatchMessage(Message msg) {
			if (msg.what == MSG_ZOOM_IN) {
				ImageView view = (ImageView) msg.obj;
				Animation a = new ZoomAnimation(view, 1, mAnimationScale, mAnimationOffsetY, mAnimationDuration);
				view.startAnimation(a);
			}
		}
	};

	class ZoomAnimation extends Animation {
		private float mFrom;
		private float mTo;
		private float mOffsetY;
		private int mPivotX;
		private int mPivotY;
		private float mInterpolatedTime;

		public ZoomAnimation(View v, float from, float to, float offsetY, int duration) {
			super();
			mFrom = from;
			mTo = to;
			mOffsetY = offsetY * v.getHeight();
			setDuration(duration);
			setFillAfter(true);
			mPivotX = v.getWidth() / 2;
			mPivotY = v.getHeight() / 2;
		}
		
		public void resetForZoomOut() {
			reset();
			mOffsetY = 0;
			mFrom = mFrom + (mTo - mFrom) * mInterpolatedTime;
			mTo = 1;
		}

		@Override
		protected void applyTransformation(float interpolatedTime, Transformation t) {
			mInterpolatedTime = interpolatedTime;
	        float s = mFrom + (mTo - mFrom) * interpolatedTime;
	        Matrix matrix = t.getMatrix();
	        if (mOffsetY != 0) {
	        	matrix.preTranslate(0, mOffsetY * interpolatedTime);
	        }
	        if (mTo == 1) {
	        	matrix.preRotate(360 * interpolatedTime, mPivotX, mPivotY);
	        }
            matrix.preScale(s, s, mPivotX, mPivotY);
		}
	}
}