android Gallery之动画效果

Gallery是一款用PHP开发的基于WEB的相片管理系统，Gallery 非常易于使用，包括一个配置向导，对于相片的操作包括自动生成缩略图、相片的大小改变、选择、排序等

这个程序主要是加深对Gallery的进一步了解，

主程序有两大重点：第一，是ImageAdapter继承BaseAdapter class的未实现方法的重写构造；
　　　　　　　　　第二，则是动画效果

第一步，先写好main.xml文件，比较简单，贴上代码

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:asg="http://schemas.android.com/apk/res/org.pskink"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical"
>
    <org.pskink.AnimatedSizingGallery
        android:layout_width="fill_parent"
        android:layout_height="0dip"
        android:layout_weight="2"
        android:id="@+id/gallery0"
        asg:animationScale="2.5"
        asg:animationDuration="400"
        asg:animationOffsetY="-0.5"
    />
    <org.pskink.AnimatedSizingGallery
        android:layout_width="fill_parent"
        android:layout_height="0dip"
        android:layout_weight="1"
        android:id="@+id/gallery1"
    />
</LinearLayout>

第二步：修改strings.xml文件

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="app_name">Sizing Gallery</string>
</resources>

第三步：在values文件夹下添加atts.xml文件，具体代码如下

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="AnimatedSizingGallery">
        <!-- defaults to 2.0 -->
        <attr name="animationScale" format="float" />
        <!-- defaults to 0.0 - no vertical movement-->
        <attr name="animationOffsetY" format="float" />
        <!-- defaults to 500 -->
        <attr name="animationDuration" format="integer" />
    </declare-styleable>
</resources>

第四步:添加照片

第五步：修改GalleryTest.xml文件，具体代码如下

package org.pskink;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Gallery;
import android.widget.ImageView;

public class GalleryTest extends Activity {
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        Gallery g = (Gallery) findViewById(R.id.gallery0);
        ImageAdapter a = new ImageAdapter(this);
        g.setAdapter(a);

        g = (Gallery) findViewById(R.id.gallery1);
        g.setAdapter(a);
    }

    public static class ImageAdapter extends BaseAdapter {
        private Context mContext;
        public ImageAdapter(Context c) {
            mContext = c;
        }

        public int getCount() {
            return mThumbIds.length;
        }
      //获取图片在库中的位置  
        public Object getItem(int position) {
            return position;
        }

        public long getItemId(int position) {
            return position;
        }

        public View getView(int position, View convertView, ViewGroup parent) {
            ImageView imageView;
            if (convertView == null) {
                imageView = new ImageView(mContext);
                imageView.setLayoutParams(new Gallery.LayoutParams(100, 100));
                imageView.setAdjustViewBounds(false);
                imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
                imageView.setPadding(18, 18, 18, 18);
            } else {
                imageView = (ImageView) convertView;
            }
          //给ImageView设置资源 
            imageView.setImageResource(mThumbIds[position]);

            return imageView;
        }
      //定义整型数组 即图片源 
        private Integer[] mThumbIds = {
                R.drawable.shao1,
                R.drawable.shao2,
                R.drawable.shao3,
                R.drawable.shao4,
                R.drawable.shao5,
               R.drawable.accessories,
               R.drawable.development,
               R.drawable.education,
               R.drawable.engineering,

        };
    }
}

第六步：也是最难的，都是些算法，不过不懂也没事，不影响你实现功能，代码如下

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);
        }
    }
}

下面在看效果图：